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Volume 8
Issue 10
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Catalysts, Volume 8, Issue 10 (October 2018) – 80 articles

Cover Story (view full-size image): Colloidal Pd nanoparticles capped with octanethiolate ligands show good regio- and stereoselectivity toward the mono-hydrogenation of ester-conjugated allenes to either Z or E olefinic isomers depending on the substitution pattern around C=C bonds. Kinetic studies indicate that the reaction progresses through the hydrogenation of less hindered C=C bond to produce internal Z olefinic isomers. The high selectivity of Pd nanoparticles averting an additional hydrogenation is steered from the controlled electronic and geometric properties of the Pd surface, which are the result of thiolate-induced partial poisoning and surface crowding, respectively. View this paper.
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9 pages, 1721 KiB  
Article
Cu42Ge24Na4—A Giant Trimetallic Sesquioxane Cage: Synthesis, Structure, and Catalytic Activity
by Alena N. Kulakova, Alexey N. Bilyachenko, Victor N. Khrustalev, Yan V. Zubavichus, Pavel V. Dorovatovskii, Lidia S. Shul’pina, Xavier Bantreil, Frédéric Lamaty, Elena S. Shubina, Mikhail M. Levitsky and Georgiy B. Shul’pin
Catalysts 2018, 8(10), 484; https://doi.org/10.3390/catal8100484 - 22 Oct 2018
Cited by 15 | Viewed by 3743
Abstract
Unprecedented germanium-based sesquioxane exhibits an extremely high nuclearity (Cu42Ge24Na4) and unusual encapsulation features. The compound demonstrated a high catalytic activity in the oxidative amidation of alcohols, with cost-effective catalyst loading down to 400 ppm of copper, and [...] Read more.
Unprecedented germanium-based sesquioxane exhibits an extremely high nuclearity (Cu42Ge24Na4) and unusual encapsulation features. The compound demonstrated a high catalytic activity in the oxidative amidation of alcohols, with cost-effective catalyst loading down to 400 ppm of copper, and in the oxidation of cyclohexane and other alkanes with H2O2 in acetonitrile in the presence of nitric acid. Selectivity parameters and the mode of dependence of initial cyclohexane oxidation rate on initial concentration of the hydrocarbon indicate that the reaction occurs with the participation of hydroxyl radicals and alkyl hydroperoxides are formed as the main primary product. Alcohols have been transformed into the corresponding ketones by the catalytic oxidation with tert-butyl hydroperoxide. Full article
(This article belongs to the Section Catalytic Materials)
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Figure 1

Figure 1
<p>General scheme of synthesis and structure of coppersodiumgermsesquioxane <b>1</b>.</p> Full article ">Figure 2
<p>Top panel. The molecular structure of <b>1</b>. Central panel. A sketch of the cage’s building block in <b>1</b>. Bottom panel. The structure of acyclic germoxane ligands in <b>1</b>.</p> Full article ">Figure 3
<p>Accumulation of cyclohexanol and cyclohexanone in the oxidation of cyclohexane (0.46 M) with H<sub>2</sub>O<sub>2</sub> (0.5 M containing 0.94 M H<sub>2</sub>O) catalyzed by complex <b>1</b> (2.5 × 10<sup>−4</sup> M) in the presence of HNO<sub>3</sub> (0.05 M) at 40 °C. Concentrations of products were measured by GC after the reduction of the reaction sample with solid PPh<sub>3</sub>. The yield of oxygenates after 60 min was 22% (TON 400). Curves <span class="html-italic">a</span>: the same in the absence of HNO<sub>3</sub>.</p> Full article ">Figure 4
<p>The tentatively proposed catalytic cycle for alkane oxygenation with hydrogen peroxide.</p> Full article ">Scheme 1
<p>Catalytic properties of <b>1</b> in the oxidative amidation. Reaction conditions: ammonium chloride (0.5 mmol), benzyl alcohol (1.0 mmol), CaCO<sub>3</sub> (0.25 mmol), TBHP (5.5 M, 2.5 mmol), <b>1</b> (0.04 mol% of Cu), CH<sub>3</sub>CN (1 mL), 80 °C, 24 h.</p> Full article ">
21 pages, 3491 KiB  
Review
General and Prospective Views on Oxidation Reactions in Heterogeneous Catalysis
by Sabine Valange and Jacques C. Védrine
Catalysts 2018, 8(10), 483; https://doi.org/10.3390/catal8100483 - 22 Oct 2018
Cited by 45 | Viewed by 7502
Abstract
In this review paper, we have assembled the main characteristics of partial oxidation reactions (oxidative dehydrogenation and selective oxidation to olefins or oxygenates, as aldehydes and carboxylic acids and nitriles), as well as total oxidation, particularly for depollution, environmental issues and wastewater treatments. [...] Read more.
In this review paper, we have assembled the main characteristics of partial oxidation reactions (oxidative dehydrogenation and selective oxidation to olefins or oxygenates, as aldehydes and carboxylic acids and nitriles), as well as total oxidation, particularly for depollution, environmental issues and wastewater treatments. Both gas–solid and liquid–solid media have been considered with recent and representative examples within these fields. We have also discussed about their potential and prospective industrial applications. Particular attention has been brought to new raw materials stemming from biomass, as well as to liquid–solid catalysts cases. This review paper also summarizes the progresses made in the use of unconventional activation methods for performing oxidation reactions, highlighting the synergy of these technologies with heterogeneous catalysis. Focus has been centered on both usual catalysts activation methods and less usual ones, such as the use of ultrasounds, microwaves, grinding (mechanochemistry) and photo-activated processes, as well as their combined use. Full article
(This article belongs to the Special Issue New Developments in Heterogeneous Partial and Total Oxidation Catalysis)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Oxidation reactions performed on Cr-MIL-101 MOF catalysts [<a href="#B40-catalysts-08-00483" class="html-bibr">40</a>].</p> Full article ">Figure 2
<p>Comparison of the yields to vanillin and vanillic acid by microwave electric (E<sub>max</sub>) and magnetic (H<sub>max</sub>) effects and conventional heating (CH) in a cavity perturbation heating system, adapted from [<a href="#B50-catalysts-08-00483" class="html-bibr">50</a>].</p> Full article ">Figure 3
<p>Schematic representation of the principle of sonophotocatalysis combining sonocatalysis and photocatalysis [<a href="#B56-catalysts-08-00483" class="html-bibr">56</a>].</p> Full article ">Figure 4
<p>Schematic representation of advanced materials synthesized by a ball-milling route for catalytic and electrochemical energy storage applications [<a href="#B59-catalysts-08-00483" class="html-bibr">59</a>].</p> Full article ">Figure 5
<p>Schematic representation of the synthesis of materials by using the (1) sonoelectrodeposition and (2) sonophotodeposition processes, adapted from [<a href="#B61-catalysts-08-00483" class="html-bibr">61</a>].</p> Full article ">Figure 6
<p>Schematic representation of the IPC (Inside Plasma Catalysis) and PPC (Post Plasma Catalysis) configurations [<a href="#B85-catalysts-08-00483" class="html-bibr">85</a>].</p> Full article ">Figure 7
<p>Classification of advanced oxidation processes. The nature of the catalysts used in these AOPs has not been mentioned for the sake of clarity.</p> Full article ">Scheme 1
<p>Electrocatalytic oxidation of cellulose to gluconate [<a href="#B54-catalysts-08-00483" class="html-bibr">54</a>].</p> Full article ">
14 pages, 5003 KiB  
Article
A Buoyant, Microstructured Polymer Substrate for Photocatalytic Degradation Applications
by John R. Bertram and Matthew J. Nee
Catalysts 2018, 8(10), 482; https://doi.org/10.3390/catal8100482 - 22 Oct 2018
Cited by 5 | Viewed by 3784
Abstract
Microbubble fabrication of poly(dimethylsiloxane) (PDMS) beads with incorporated TiO2 provides a low-density, microstructured photocatalyst that is buoyant in water. This approach surmounts many of the challenges traditionally encountered in the generation of buoyant photocatalysts, an area which is critical for the implementation [...] Read more.
Microbubble fabrication of poly(dimethylsiloxane) (PDMS) beads with incorporated TiO2 provides a low-density, microstructured photocatalyst that is buoyant in water. This approach surmounts many of the challenges traditionally encountered in the generation of buoyant photocatalysts, an area which is critical for the implementation of widespread environmental cleaning of organic pollutants in water resources. Because the incorporation into the polymer bead surface is done at low temperatures, the crystal structure of TiO2 is unaltered, ensuring high-quality photocatalytic activity, while PDMS is well-established as biocompatible, temperature stable, and simple to produce. The photocatalyst is shown to degrade methylene blue faster than other buoyant, TiO2-based photocatalysts, and only an order of magnitude less than direct suspension of an equivalent amount of photocatalyst in solution, even though the photocatalyst is only present at the surface of the solution. The reusability of the TiO2/PDMS beads is also strong, showing no depreciation in photocatalytic activity after five consecutive degradation trials. Full article
(This article belongs to the Special Issue Catalysts for Oxidative Destruction of Volatile Organic Compounds)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>SEM images of representative poly(dimethylsiloxane) (PDMS) beads with (<b>a</b>) no TiO<sub>2</sub> and (<b>b</b>) with a mass ratio of 20% TiO<sub>2</sub> added to the emulsion. Red rectangles indicate the areas in which images of the magnified regions for (<b>c</b>) the inert PDMS bead and (<b>d</b>) the 20% TiO<sub>2</sub>/PDMS bead were measured. The convex porosity of the beads increases the surface area per bead, allowing a high density of available TiO<sub>2</sub> for photocatalytic degradation.</p> Full article ">Figure 2
<p>Raman spectrum of pure anatase TiO<sub>2</sub>, TiO<sub>2</sub>/PDMS after synthesis, TiO<sub>2</sub>/PDMS after three consecutive 3-h long degradation trials, and inert PDMS beads.</p> Full article ">Figure 3
<p>Visible absorption spectra of methylene blue (MB) solution during irradiation in the presence of photocatalytic beads, showing loss of MB from solution as a function of time. Inset plot shows the natural log of the peak area ratio as a function of time suggesting the removal rate of MB is first-order. The beads used are made with a 5% TiO<sub>2</sub>:PDMS mass ratio in the emulsion.</p> Full article ">Figure 4
<p>First-order kinetic plots (natural log of concentration relative to initial concentration) for MB solution using a series of beads with different TiO<sub>2</sub> loads. Also shown are inert PDMS beads (0% load) and photolysis of MB solution without any additives (MB Only). The slopes of the lines indicate the rate constant for loss of MB by adsorption, photolysis, and photocatalytic degradation. Two linear regions are observed for 20% and 10% loads due to MB adsorption equilibrium onto the beads resulting in a slight decrease in the removal rate; the value of <span class="html-italic">k<sub>TOT</sub></span> is based on the first region, indicated with a line in the plot.</p> Full article ">Figure 5
<p>Adsorption curves for MB to TiO<sub>2</sub>/PDMS beads. Visible absorbance spectra are collected in the absence of radiation capable of photolysis or photocatalytic activation to isolate the extent to which MB adsorbs to the beads as a function of time. Due to adsorption equilibrium, removal rates of MB for 10% and 20% loads began depreciating during the trial. Thus, the negative slope of the linear regions (indicated in the plot) are reported as <span class="html-italic">k<sub>ads</sub></span>.</p> Full article ">Figure 6
<p>Reuse data for photocatalytic TiO<sub>2</sub>/PDMS beads, showing <span class="html-italic">k<sub>TOT</sub></span> for three consecutive runs of 3 h each for several different loads of TiO<sub>2</sub>. The error bars represent the uncertainty for each value, as reported in <a href="#catalysts-08-00482-t003" class="html-table">Table 3</a>.</p> Full article ">
12 pages, 3557 KiB  
Article
Low Temperature Activation of Carbon Dioxide by Ammonia in Methane Dry Reforming—A Thermodynamic Study
by Anand Kumar
Catalysts 2018, 8(10), 481; https://doi.org/10.3390/catal8100481 - 22 Oct 2018
Cited by 8 | Viewed by 4367
Abstract
Methane dry reforming (MDR) is an attractive alternative to methane steam reforming for hydrogen production with low harmful environmental emissions on account of utilizing carbon dioxide in the feed. However, carbon formation in the product stream has been the most challenging aspect of [...] Read more.
Methane dry reforming (MDR) is an attractive alternative to methane steam reforming for hydrogen production with low harmful environmental emissions on account of utilizing carbon dioxide in the feed. However, carbon formation in the product stream has been the most challenging aspect of MDR, as it leads to catalyst deactivation by coking, prevalent in hydrocarbon reforming reactions. Common strategies to limit coking have mainly targeted catalyst modifications, such as by doping with rare earth metals, supporting on refractory oxides, adding oxygen/steam in the feed, or operating at reaction conditions (e.g., higher temperature), where carbon formation is thermodynamically restrained. These methods do help in suppressing carbon formation; nonetheless, to a large extent, catalyst activity and product selectivity are also adversely affected. In this study, the effect of ammonia addition in MDR feed on carbon suppression is presented. Based on a thermodynamic equilibrium analysis, the most significant observation of ammonia addition is towards low temperature carbon dioxide activation to methane, along with carbon removal. Results indicate that ammonia not only helps in removing carbon formation, but also greatly enriches hydrogen production. Full article
(This article belongs to the Special Issue Catalytic Reforming of Methane)
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<p>Product distribution in (<b>a</b>) methane dry reforming, (<b>b</b>) methane steam reforming, (<b>c</b>) methane partial oxidation, (<b>d</b>) total carbon formation in all the three reactions. All the calculations were performed at 1 atm pressure.</p> Full article ">Figure 2
<p>(<b>a</b>) Product distribution in ammonia-assisted methane dry reforming (CH<sub>4</sub> + CO<sub>2</sub> + NH<sub>3</sub>); (<b>b</b>) comparison in product amount at 800 K with and without NH<sub>3</sub> addition.</p> Full article ">Figure 3
<p>Effect of ammonia content on carbon formation in methane dry reforming; (<b>a</b>) at temperature 300–1000 K, (<b>b</b>) at temperature = 900 K.</p> Full article ">Figure 4
<p>(<b>a</b>) Effect of ammonia content in MDR on methane; (<b>b</b>) comparison in methane amount in presence of NH<sub>3</sub> at 300 K and 1000 K with regard to no NH<sub>3</sub> in DMR.</p> Full article ">Figure 5
<p>(<b>a</b>) Effect of ammonia content in DMR on CO<sub>2</sub> in product; (<b>b</b>) a decreasing trend in CO<sub>2</sub> amount in presence of NH<sub>3</sub> at 900 K.</p> Full article ">Figure 6
<p>(<b>a</b>) Effect of ammonia content in DMR on CO in product; (<b>b</b>) CO amount in presence of NH<sub>3</sub> at 1000 K.</p> Full article ">Figure 7
<p>(<b>a</b>) Effect of ammonia content in DMR on H<sub>2</sub> in product, and (<b>b</b>) H<sub>2</sub>O in product.</p> Full article ">Figure 8
<p>(<b>a</b>) Effect of ammonia content on syngas quality (H<sub>2</sub>/CO ratio) and carbon content at 1000 K; (<b>b</b>) distribution of carbon-containing products at 1000 K as a function of ammonia content.</p> Full article ">
14 pages, 8756 KiB  
Article
A New Tool in the Quest for Biocompatible Phthalocyanines: Palladium Catalyzed Aminocarbonylation for Amide Substituted Phthalonitriles and Illustrative Phthalocyanines Thereof
by Vanessa A. Tomé, Mário J. F. Calvete, Carolina S. Vinagreiro, Rafael T. Aroso and Mariette M. Pereira
Catalysts 2018, 8(10), 480; https://doi.org/10.3390/catal8100480 - 20 Oct 2018
Cited by 5 | Viewed by 3792
Abstract
The amide peptide bond type linkage is one of the most natural conjugations available, present in many biological synthons and pharmaceutical drugs. Hence, aiming the direct conjugation of potentially biologically active compounds to phthalocyanines, herein we disclose a new strategy for direct modulation [...] Read more.
The amide peptide bond type linkage is one of the most natural conjugations available, present in many biological synthons and pharmaceutical drugs. Hence, aiming the direct conjugation of potentially biologically active compounds to phthalocyanines, herein we disclose a new strategy for direct modulation of phthalonitriles, inspired by an attractive synthetic strategy for the preparation of carboxamides based on palladium-catalyzed aminocarbonylation of aryl halides in the presence of carbon monoxide (CO) which, to our knowledge, has never been used to prepare amide-substituted phthalonitriles, the natural precursors for the synthesis of phthalocyanines. Some examples of phthalocyanines prepared thereof are also reported, along with their full spectroscopic characterization and photophysical properties initial assessment. Full article
(This article belongs to the Special Issue Catalysis for Global Development. Contributions around the Iberoamerican Federation of Catalysis)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Simplified catalytic cycle describing the formation of 4-amide substituted phthalonitriles. L = PPh<sub>3.</sub></p> Full article ">Figure 2
<p>UV–VIS spectra of metallophthalocyanines <b>4a, 4c</b>, and <b>4d</b> in THF (<b>a</b>); normalized UV–Vis of studied phthalocyanines with absorption (black solid line) and emission spectra (red dashed line) in THF of: Zn(II)-<b>4a</b> (<b>b</b>); Zn(II)-<b>4c</b> (<b>c</b>); Zn(II)-<b>4d</b> (<b>d</b>). Fluorescence quantum yields (Φ<sub>F</sub>) of the zinc phthalocyanines <b>4a</b> and <b>4c</b>–<b>d,</b> are presented in <a href="#catalysts-08-00480-t003" class="html-table">Table 3</a>, were determined by the comparative method (Equation (1)) using the unsubstituted Zn phthalocyanine in DMSO as standard (Φ<sub>F</sub> = 0.18) [<a href="#B68-catalysts-08-00480" class="html-bibr">68</a>], and both the samples and the standard were excited at the same wavelength (640 nm). The Φ<sub>F</sub> were calculated as 0.26, 0.31 and 0.38 for <b>4a</b>, <b>4c</b> and <b>4d</b>, respectively. The Φ<sub>F</sub> value of zinc phthalocyanine complexes functionalized with the amino acid esters <b>4a</b> and <b>4c</b> have the same order of magnitude (Φ<sub>F</sub> = 0.26–0.31) and are lower than non-biocompatible zinc phthalocyanine <b>4d</b> (Φ<sub>F</sub> = 0.38).</p> Full article ">
23 pages, 3639 KiB  
Article
A Novel Method of Affinity Tag Cleavage in the Purification of a Recombinant Thermostable Lipase from Aneurinibacillus thermoaerophilus Strain HZ
by Malihe Masomian, Raja Noor Zaliha Raja Abd Rahman and Abu Bakar Salleh
Catalysts 2018, 8(10), 479; https://doi.org/10.3390/catal8100479 - 20 Oct 2018
Cited by 8 | Viewed by 5305
Abstract
The development of an efficient and economical purification method is required to obtain a pure and mature recombinant protein in a simple process with high efficiency. Hence, a new technique was invented to cleave the tags from the N-terminal region of recombinant fusion [...] Read more.
The development of an efficient and economical purification method is required to obtain a pure and mature recombinant protein in a simple process with high efficiency. Hence, a new technique was invented to cleave the tags from the N-terminal region of recombinant fusion HZ lipase in the absence of protease treatment. The recombinant pET32b/rHZ lipase was overexpressed into E. coli BL21 (DE3). Affinity chromatography was performed as the first step of purification. The stability of the protein was then tested in different temperatures. The fused Trx-His-S-tags to the rHZ lipase was cleaved by treatment of the fusion protein at 20 °C in 100 mM Tris-HCl buffer, pH 8.0. The precipitated tag was removed, and the mature recombinant enzyme was further characterized to specify its properties. A purification yield of 78.9% with 1.3-fold and 21.8 mg total purified mature protein was obtained from 50 mL starting a bacterial culture. N-terminal sequencing of purified recombinant HZ lipase confirmed the elimination of the 17.4 kDa tag from one amino acid before the native start codon (Methionine) of the protein. The mature rHZ lipase was highly active at 65 °C and a pH of 7.0, with a half-life of 2 h 15 min at 55 °C and 45 min at 60 °C. The rHZ lipase showed a preference for the hydrolysis of natural oil with a long carbon chain (C18) and medium-size acyl chain p-nitrophenyl esters (C10). The enzyme remained stable in the presence of nonpolar organic solvents, and its activity was increased by polar organic solvents. This study thus demonstrates a simple and convenient purification method which resulted in the high yield of mature enzyme along with unique and detailed biochemical characterization of rHZ lipase, making the enzyme favorable in various industrial applications. Full article
(This article belongs to the Special Issue Biocatalysis for Industrial Applications)
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Figure 1

Figure 1
<p>Affinity chromatography of fusion rHZ lipase using Ni Sepharose 6 Fast Flow resin. (<b>a</b>) Elution profile of the fusion rHZ lipase. A linear gradient up to 500 mM Imidazole was used. The optical density (OD) at 280 nm was recorded by the AKTA Explorer every 2.56 s. (<b>b</b>) Lipase activity profile of the fusion rHZ lipase. The lipase activity was measured at 65 °C for 30 min using olive oil as a substrate. (<b>c</b>) SDS-PAGE analysis of the fusion rHZ lipase after affinity chromatography. Lane M: Protein marker, lane 1: crude cell lysate, 2.5 µL sample loaded, lanes 2–4: fractions 1–3 (sample injection), 5 µL sample loaded, lanes 5–8: fractions 4–7 (wash unbound protein) 5 µL sample loaded, lanes 9–17: fractions 17–25 (Elution of bind protein), 1 µL sample loaded.</p> Full article ">Figure 2
<p>Effect of Recombinant Enterokinase and temperature on the fusion rHZ lipase tag-cleavage. (<b>a</b>) Optimization of minimum rEK concentrations to cleave the tags of the target protein. The mixtures were incubated at 20 °C for 16 h. Lane M: Protein marker, lane 1: 0.1 U rEK, lane 2: 0.2 U rEK, lane 3: 0.5 U rEk, lane 4: 0 U rEK (control). Note: After 16 h of incubation with different rEK concentrations, the lipase activity of the samples was tested to confirm the presence of rHZ lipase and all showed similar results (data not shown). (<b>b</b>) Optimization of maximum rEK concentrations to cleave the tags of the target protein. The mixtures were incubated at 20 °C for 16 h. Lane M: Protein marker, lane 1: 1 U rEK, lane 2: 1.5 U rEK. (<b>c</b>) Optimization on the effect of different temperatures on tag-cleavage in fusion rHZ lipase. The dialyzed protein against 100 mM Tris-HCl buffer, pH 8.0 were incubated at 4, 10, 20, RT (room temperature) and 37 °C for 48 h. The samples were loaded on an SDS-PAGE gel before centrifugation. Lane M: Protein marker, lane 1: 4 °C, lane 2: 10 °C, lane 3: 20 °C, lane 4: RT, lane 5: 37 °C. (<b>d</b>) Lipase activity of treated rHZ lipase after 48 h incubation at different temperatures.</p> Full article ">Figure 3
<p>Gel electrophoresis analysis of mature rHZ lipase. (<b>a</b>) SDS-PAGE analysis of rHZ lipase after treatment at 20 °C and centrifugation. Lane M: Protein marker, lane 1: fraction no. 12 of affinity chromatography, lane 2: fraction no. 13 of affinity chromatography. (<b>b</b>) Native-PAGE analysis of purified rHZ lipase.</p> Full article ">Figure 4
<p>N-terminal sequencing situation of purified mature rHZ lipase. The seven amino acids detected in N-terminal sequencing are bracketed and the His<sub>6</sub>-tag is underlined. The red arrow indicates the cleavage point.</p> Full article ">Figure 5
<p>Effect of temperature on the mature rHZ lipase. (<b>a</b>) The optimum temperature of mature rHZ lipase. The enzyme was incubated with substrate (olive oil) at various temperatures for 30 min. (<b>b</b>) Effect of temperature on mature rHZ lipase stability. The rHZ lipase was pre-incubated at various temperatures ranging from 50 to 60 °C at 5 °C intervals for 4 h. The residual activity was measured at 65 °C (optimum temperature) every 1 h. Data are means ± standard deviations of three determinations (<span class="html-italic">n</span> = 3) and the standard deviations are indicated as error bars.</p> Full article ">Figure 6
<p>Effects of pH on the mature rHZ lipase. (<b>a</b>) The optimum pH of mature rHZ lipase activity. The enzyme was incubated with substrate (olive oil) emulsion prepared in various buffers with pHs from 4 to 12 at 65 °C for 30 min. The activities of the rHZ lipase against different buffer are shown as values relative to the optimum pH (pH 7.0). (<b>b</b>) Effect of pH on the mature rHZ lipase stability. The enzyme was pre-incubated in various buffers with pHs ranging from 4 to 12 at 50 °C for 30 min. Lipase assay was done at 65 °C for 30 min using the substrate emulsion of olive oil and Tris-HCl, pH (65 °C) 7.0. The relative activities of the rHZ lipase against different buffer are shown as values relative to the optimum pH (pH 7.0). The buffers used were at 50 mM concentration. Data are means ± standard deviations of three determinations (<span class="html-italic">n</span> = 3) and the standard deviations are indicated as error bars. When the error bar cannot be seen, the deviation is less than the size of the symbol.</p> Full article ">Figure 7
<p>Effect of substrate on the mature rHZ lipase activity. The mature rHZ lipase was assayed with different oil emulsion (<span class="html-italic">v</span>/<span class="html-italic">v</span>, 1:1) as substrate at 65 °C for 30 min. Data are means ± standard deviations of three determinations (<span class="html-italic">n</span> = 3) and the standard deviations are indicated as error bars. When the error bar cannot be seen, the deviation is less than the size of the symbol.</p> Full article ">Figure 8
<p>Effect of substrate specificities toward different <span class="html-italic">p</span>-nitrophenyl esters on mature rHZ lipase activity. Data are means ± standard deviations of three determinations (<span class="html-italic">n</span> = 3) and the standard deviations are indicated as error bars. When the error bar cannot be seen, the deviation is less than the size of the symbol.</p> Full article ">Figure 9
<p>The binding mode of the complexes between rHZ lipase and <span class="html-italic">p</span>-NP decanoate (C10) (<b>a</b>)and <span class="html-italic">p</span>-NP butyrate (C4) (<b>b</b>). The catalytic residues contained Ser113, Asp308, and His350.</p> Full article ">
20 pages, 2965 KiB  
Review
Active Sites in Heterogeneous Catalytic Reaction on Metal and Metal Oxide: Theory and Practice
by Yanbo Pan, Xiaochen Shen, Libo Yao, Abdulaziz Bentalib and Zhenmeng Peng
Catalysts 2018, 8(10), 478; https://doi.org/10.3390/catal8100478 - 20 Oct 2018
Cited by 66 | Viewed by 18486
Abstract
Active sites play an essential role in heterogeneous catalysis and largely determine the reaction properties. Yet identification and study of the active sites remain challenging owing to their dynamic behaviors during catalysis process and issues with current characterization techniques. This article provides a [...] Read more.
Active sites play an essential role in heterogeneous catalysis and largely determine the reaction properties. Yet identification and study of the active sites remain challenging owing to their dynamic behaviors during catalysis process and issues with current characterization techniques. This article provides a short review of research progresses in active sites of metal and metal oxide catalysts, which covers the past achievements, current research status, and perspectives in this research field. In particular, the concepts and theories of active sites are introduced. Major experimental and computational approaches that are used in active site study are summarized, with their applications and limitations being discussed. An outlook of future research direction in both experimental and computational catalysis research is provided. Full article
(This article belongs to the Special Issue Active Sites in Catalytic Reaction)
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Figure 1
<p>Structure sensitivity in alkane isomerization reactions catalyzed over platinum single-crystal surfaces. Adapted with permission from [<a href="#B28-catalysts-08-00478" class="html-bibr">28</a>], Elsevier, 2001.</p> Full article ">Figure 2
<p>Schematic illustration of CO preferential oxidation (PROX) pathways on Pt-M alloy catalyst. Reprinted with permission from [<a href="#B45-catalysts-08-00478" class="html-bibr">45</a>], American Chemical Society, 2018.</p> Full article ">Figure 3
<p>Characterization of Ni<sub>3</sub>N nanosheets. (<b>a</b>) XRD pattern; (<b>b</b>) SEM image; (<b>c</b>) HRTEM image. Inset: corresponding FFT pattern and TEM image; (<b>d</b>) AFM image. Reprinted with permission from [<a href="#B85-catalysts-08-00478" class="html-bibr">85</a>], American Chemical Society, 2015.</p> Full article ">Figure 4
<p>The Cu(111), Cu(211), and CuZn(211) facets as viewed from perspective (<b>a</b>); Gibbs free energy diagram obtained from DFT calculations for CO<sub>2</sub> (<b>b</b>) and CO (<b>c</b>) hydrogenation on close-packed (black), stepped (blue), and Zn substituted steps (red Intermediates marked with a star are adsorbed on the surface. Reprinted with permission from [<a href="#B102-catalysts-08-00478" class="html-bibr">102</a>], AAAS, 2012.</p> Full article ">Figure 5
<p>Schematic cross section view of the assembled gas cell with sample loaded for in situ STEM (<b>a</b>) and in situ FTIR (<b>b</b>). Reprinted with permission from [<a href="#B108-catalysts-08-00478" class="html-bibr">108</a>], American Chemical Society, 2017.</p> Full article ">Figure 6
<p>Catalysts design for selective acetylene hydrogenation. (<b>a</b>) Heats of adsorption for acetylene (C<sub>2</sub>H<sub>2</sub>) and ethylene (C<sub>2</sub>H<sub>4</sub>) plotted against the heat of adsorption for methyl (CH<sub>3</sub>). The solid lines show the predicted acetylene (red line) and ethylene (blue line) adsorption energies from scaling. The dotted lines define the region of interest; (<b>b</b>) Price (in 2006) of 70 binary intermetallic compounds plotted against the calculated methyl binding energies. The smooth transition between regions of low and high selectivity (blue) and high and low reactivity (red) is indicated; (<b>c</b>) Modeling of the NiZn catalyst in the bcc-B2 (110) structure. The Ni atoms are shown as blue and Zn as gray. The adsorption of acetylene (left) and ethylene (right) is shown (small black and white structures); (<b>d</b>) Measured concentration of ethane at the reactor outlet as a function of acetylene conversion for seven catalysts. Ethane production is a measure of the selectivity of acetylene hydrogenation, and zero ethane corresponds to the most-selective catalyst. Experimental details are given in the corresponding reference. Adapted with permission from [<a href="#B86-catalysts-08-00478" class="html-bibr">86</a>], Springer Nature, 2009.</p> Full article ">Figure 7
<p>Dynamic changes of a small Au particle supported on activated carbon under electron beam irradiation at various observation times. Electron doses: (<b>a</b>) 1.1×10<sup>6</sup>, (<b>b</b>) 6.6×10<sup>6</sup>, (<b>c</b>) 31.9×10<sup>6</sup>, (<b>d</b>) 44×10<sup>6</sup>, (<b>e</b>) 48.4×10<sup>6</sup>, (<b>f</b>) 59.4×10<sup>6</sup>, (<b>g</b>) 73.7×10<sup>6</sup>, (<b>h</b>) 84.7×10<sup>6</sup>, (<b>i</b>) 102.3×10<sup>6</sup>, (<b>j</b>) 110×10<sup>6</sup> e<sup>−</sup>nm<sup>−2</sup>. Adapted with permission from [<a href="#B119-catalysts-08-00478" class="html-bibr">119</a>], John Wiley and Sons, 2011.</p> Full article ">
10 pages, 2999 KiB  
Article
Facile Synthesis of Bi2MoO6 Microspheres Decorated by CdS Nanoparticles with Efficient Photocatalytic Removal of Levfloxacin Antibiotic
by Shijie Li, Yanping Liu, Yunqian Long, Liuye Mo, Huiqiu Zhang and Jianshe Liu
Catalysts 2018, 8(10), 477; https://doi.org/10.3390/catal8100477 - 19 Oct 2018
Cited by 16 | Viewed by 4599
Abstract
Developing high-efficiency and stable visible-light-driven (VLD) photocatalysts for removal of toxic antibiotics is still a huge challenge at present. Herein, a novel CdS/Bi2MoO6 heterojunction with CdS nanoparticles decorated Bi2MoO6 microspheres has been obtained by a simple solvothermal-precipitation-calcination [...] Read more.
Developing high-efficiency and stable visible-light-driven (VLD) photocatalysts for removal of toxic antibiotics is still a huge challenge at present. Herein, a novel CdS/Bi2MoO6 heterojunction with CdS nanoparticles decorated Bi2MoO6 microspheres has been obtained by a simple solvothermal-precipitation-calcination method. 1.0CdS/Bi2MoO6 has stronger light absorption ability and highest photocatalytic activity with levofloxacin (LEV) degradation efficiency improving 6.2 or 12.6 times compared to pristine CdS or Bi2MoO6. CdS/Bi2MoO6 is very stable during cycling tests, and no appreciable activity decline and microstructural changes are observed. Results signify that the introduction of CdS could enhance the light absorption ability and dramatically boost the separation of charge carriers, leading to the excellent photocatalytic performance of the heterojunction. This work demonstrates that flower-like CdS/ Bi2MoO6 is an excellent photocatalyst for the efficient removal of the LEV antibiotic. Full article
(This article belongs to the Special Issue Novel Heterogeneous Catalysts for Advanced Oxidation Processes (AOPs))
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<p>XRD patterns of Bi<sub>2</sub>MoO<sub>6</sub>, CdS, and 1.0CdS/Bi<sub>2</sub>MoO<sub>6</sub>.</p> Full article ">Figure 2
<p>(<b>a</b>,<b>b</b>) SEM images, (<b>c</b>) EDX spectrum, and (<b>d</b>) TEM image of 1.0CdS/Bi<sub>2</sub>MoO<sub>6.</sub></p> Full article ">Figure 3
<p>UV-vis absorbance spectra of bare Bi<sub>2</sub>MoO<sub>6</sub>, CdS, and 1.0CdS/Bi<sub>2</sub>MoO<sub>6.</sub></p> Full article ">Figure 4
<p>(<b>a</b>) The photo-degradation efficiency against LEV (20 mg L<sup>−1</sup>, 100 mL) by different catalysts (35 mg). (<b>b</b>) Kinetic modeling for LEV removal over different catalysts.</p> Full article ">Figure 5
<p>TOC removal profile of LEV (40 mg L<sup>−1</sup>, 200 mL) over 1.0CdS/Bi<sub>2</sub>MoO<sub>6</sub> (200 mg).</p> Full article ">Figure 6
<p>(<b>a</b>) Recycling tests of 1.0CdS/Bi<sub>2</sub>MoO<sub>6</sub> for LEV degradation; (<b>b</b>) XRD patterns of 1.0CdS/Bi<sub>2</sub>MoO<sub>6</sub> before and after six cycles.</p> Full article ">Figure 7
<p>Photo-degradation of LEV (20 mg L<sup>−1</sup>, 100 mL) by1.0CdS/Bi<sub>2</sub>MoO<sub>6</sub> (35 mg) under visible light in the presence of isopropyl alcohol (IPA), ammonium oxalate (AO), and benzoquinone (BQ).</p> Full article ">Figure 8
<p>Photocatalytic mechanism scheme over CdS/Bi<sub>2</sub>MoO<sub>6</sub>.</p> Full article ">
15 pages, 2782 KiB  
Article
Characterization of a New Glyoxal Oxidase from the Thermophilic Fungus Myceliophthora thermophila M77: Hydrogen Peroxide Production Retained in 5-Hydroxymethylfurfural Oxidation
by Marco Antonio Seiki Kadowaki, Mariana Ortiz de Godoy, Patricia Suemy Kumagai, Antonio José da Costa-Filho, Andrew Mort, Rolf Alexander Prade and Igor Polikarpov
Catalysts 2018, 8(10), 476; https://doi.org/10.3390/catal8100476 - 19 Oct 2018
Cited by 21 | Viewed by 4653
Abstract
Myceliophthora thermophyla is a thermophilic industrially relevant fungus that secretes an assortment of hydrolytic and oxidative enzymes for lignocellulose degradation. Among them is glyoxal oxidase (MtGLOx), an extracellular oxidoreductase that oxidizes several aldehydes and α-hydroxy carbonyl substrates coupled to the reduction [...] Read more.
Myceliophthora thermophyla is a thermophilic industrially relevant fungus that secretes an assortment of hydrolytic and oxidative enzymes for lignocellulose degradation. Among them is glyoxal oxidase (MtGLOx), an extracellular oxidoreductase that oxidizes several aldehydes and α-hydroxy carbonyl substrates coupled to the reduction of O2 to H2O2. This copper metalloprotein belongs to a class of enzymes called radical copper oxidases (CRO) and to the “auxiliary activities” subfamily AA5_1 that is based on the Carbohydrate-Active enZYmes (CAZy) database. Only a few members of this family have been characterized to date. Here, we report the recombinant production, characterization, and structure-function analysis of MtGLOx. Electron Paramagnetic Resonance (EPR) spectroscopy confirmed MtGLOx to be a radical-coupled copper complex and small angle X-ray scattering (SAXS) revealed an extended spatial arrangement of the catalytic and four N-terminal WSC domains. Furthermore, we demonstrate that methylglyoxal and 5-hydroxymethylfurfural (HMF), a fermentation inhibitor, are substrates for the enzyme. Full article
(This article belongs to the Special Issue Recent Advances in Biocatalysis and Metabolic Engineering for Biomanufacturing)
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<p>Domain organization of glyoxal oxidases. Phylogenetic tree of predicted AA5 domains of glyoxal oxidase (GLOx) enzymes. The N-terminal Wall Stress-responsive Component (WSC)/Chtb domains were removed to avoid alignment bias. Muscle alignment and tree constructed using MEGA are shown. The GLOx domains were annotated using the CDD (Conserved Domain Database) tool in NCBI. The bootstrap values are indicated on the nodes based on 1000 trials. The asterisk indicates the characterized GLOxes.</p> Full article ">Figure 2
<p>Pathway followed by <span class="html-italic">Mt</span>GLOx for hydroxymethylfurfural (HMF) oxidation. (<b>A</b>) Representation of possible pathways of hydroxymethylfurfural (HMF) oxidation and products. <span class="html-italic">Mt</span>GLOx oxidizes HMF only to 2,5-dimormylfuran (DFF) (black path). (<b>B</b>) High Performance Liquid Chromatography (HPLC) chromatograms of the products generated from HMF oxidation. Blue line: product generated from HMF oxidation. Red and black lines: DFF and HMF standards, respectively. Reaction mixture were incubated for 24 h (blue). (<b>C</b>) Time course reactions were monitored for oxidation of 1 mM HMF to DFF by 0.5 µM <span class="html-italic">Mt</span>GLOx. Standard deviations are shown by error bars (n = 3).</p> Full article ">Figure 3
<p>Effect of pH and temperature on enzymatic activity. Effect of temperature (<b>A</b>) and pH (<b>B</b>) on enzymatic activity of <span class="html-italic">Mt</span>GLOx. Values calculated as a percentage of the activity at the maximum. (<b>C</b>) The enzyme residual activity after incubation at different temperature is represented as a percentage with respect to the enzyme initial activity at different incubation times.</p> Full article ">Figure 4
<p>Structural model and spectroscopy of the <span class="html-italic">Mt</span>GLOx Cu center. (<b>A</b>) Cartoon representation of the model of the catalytic domain of <span class="html-italic">Mt</span>GLOx. (<b>B</b>) Stick model of the substrate pocket showing the conserved residues coordinating the copper ion (blue sphere). Sections of the sequence from the characterized glyoxal oxidases from <span class="html-italic">P. chrysosporium</span> (Pch) and <span class="html-italic">Pycnoporus cinnabarinus</span> (Pci1 and 2), alcohol oxidase from <span class="html-italic">Colletotrichum graminicola</span> (Cgr), galactose oxidase from <span class="html-italic">Fusarium graminearum</span> (Fgr) and cuproenzyme from <span class="html-italic">Streptomyces lividans</span> (Sli) showing conserved amino acids. (<b>C</b>) Cu(II)-<span class="html-italic">Mt</span>GLOx EPR spectrum (black) with simulation (red).</p> Full article ">Figure 5
<p>Solution structure of <span class="html-italic">Mt</span>GLOx. (<b>A</b>) Small Angle X-ray Scattering (SAXS) data. Raw data: plot of scattered intensity vs. scattering angle q. Experimental SAXS curve is shown in black filled circles. The fit of the molecular envelope (red line) and molecular dynamic model (blue line). Exp: experimental raw data. DRM: dammy residue modelling fit. MD: molecular dynamic model fit. (<b>B</b>) Pair distribution function P(r). (<b>C</b>) Kratky plot. (<b>D</b>) Ab initio envelope models based on SAXS data. Molecular envelope superimposed on the three-dimensional model of each domain. The Ab initio envelope is represented in gray. Each domain is represented in stick form. The blue sphere highlights the position of the copper co-factor center.</p> Full article ">
9 pages, 4055 KiB  
Article
Heteroatom (Nitrogen/Sulfur)-Doped Graphene as an Efficient Electrocatalyst for Oxygen Reduction and Evolution Reactions
by Jian Zhang, Jia Wang, Zexing Wu, Shuai Wang, Yumin Wu and Xien Liu
Catalysts 2018, 8(10), 475; https://doi.org/10.3390/catal8100475 - 19 Oct 2018
Cited by 19 | Viewed by 4072
Abstract
Carbon nanomaterials are potential materials with their intrinsic structure and property in energy conversion and storage. As the electrocatalysts, graphene is more remarkable in electrochemical reactions. Additionally, heteroatoms doping with metal-free materials can obtain unique structure and demonstrate excellent electrocatalytic performance. In this [...] Read more.
Carbon nanomaterials are potential materials with their intrinsic structure and property in energy conversion and storage. As the electrocatalysts, graphene is more remarkable in electrochemical reactions. Additionally, heteroatoms doping with metal-free materials can obtain unique structure and demonstrate excellent electrocatalytic performance. In this work, we proposed a facile method to prepare bifunctional electrocatalyst which was constructed by nitrogen, sulfur doped graphene (NSG), which demonstrate superior properties with high activity and excellent durability compared with Pt/C and IrO2 for oxygen reduction (OR) and oxygen evolution (OE) reactions. Accordingly, these phenomena are closely related to the synergistic effect of doping with nitrogen and sulfur by rationally regulating the polarity of carbon in graphene. The current work expands the method towards carbon materials with heteroatom dopants for commercialization in energy-related reactions. Full article
(This article belongs to the Special Issue Immobilized Non-Precious Electrocatalysts for Advanced Energy Devices)
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<p>Transmission electron microscopy (TEM) (<b>a</b>), scanning electron microscopy (SEM) (<b>b</b>,<b>c</b>) and mapping (<b>d</b>) of C, N, O, S for NSG.</p> Full article ">Figure 2
<p>(<b>a</b>) Full range XPS spectra of NSG; (<b>b</b>–<b>d</b>) XPS spectrum of C 1s, N 1s and S 2p for NSG.</p> Full article ">Figure 3
<p>Raman spectra (<b>a</b>) and X-ray diffraction (XRD) (<b>b</b>) of NSG, NG and SG.</p> Full article ">Figure 4
<p>(<b>a</b>) Oxygen reduction reaction (ORR) polarization curves of Pt/C, NSG, SG, NG in O<sub>2</sub>-saturated 0.1 M KOH solution, respectively (rotation speed 1600 rpm, sweep rate 10 mV s<sup>−1</sup>); (<b>b</b>) Half-wave potential of NSG, SG, NG and Pt/C; (<b>c</b>) ORR polarization curves of NSG at the various rotation speeds (sweep rate 10 mV s<sup>−1</sup>) (inset: Corresponding K-L plots at different electrode potentials); (<b>d</b>) The electron transfer number n of NSG, NG, SG and Pt/C at different potentials (left), and percentage (%) of peroxide with respect to the total oxygen reduction products (right); (<b>e</b>) Chronoamperometric response of NSG and 20% Pt/C at 0.57 V in O<sub>2</sub>-saturated 0.1 mol L<sup>−1</sup> KOH solution. The arrows indicate the addition of methanol; (<b>f</b>) Durability evaluation of NSG and 20% Pt/C at 0.57 V for 30,000 s with a rotating rate of 1600 rpm.</p> Full article ">Figure 5
<p>(<b>a</b>) OER linear sweeping voltammetrys (LSVs) of NG, SG, IrO<sub>2</sub> and NSG at a sweep rate of 10 mV s<sup>−1</sup>; (<b>b</b>) OER Tafel plots.</p> Full article ">Scheme 1
<p>Schematic illustration of the preparation of NSG.</p> Full article ">
12 pages, 6191 KiB  
Article
Water: Friend or Foe in Catalytic Hydrogenation? A Case Study Using Copper Catalysts
by Alisa Govender, Abdul S. Mahomed and Holger B. Friedrich
Catalysts 2018, 8(10), 474; https://doi.org/10.3390/catal8100474 - 19 Oct 2018
Cited by 7 | Viewed by 3421
Abstract
Copper oxide supported on alumina and copper chromite were synthesized, characterized, and subsequently tested for their catalytic activity toward the hydrogenation of octanal. Thereafter, the impact of water addition on the conversion and selectivity of the catalysts were investigated. The fresh catalysts were [...] Read more.
Copper oxide supported on alumina and copper chromite were synthesized, characterized, and subsequently tested for their catalytic activity toward the hydrogenation of octanal. Thereafter, the impact of water addition on the conversion and selectivity of the catalysts were investigated. The fresh catalysts were characterized using X-ray diffraction (XRD), BET surface area and pore volume, SEM, TEM, TGA-DSC, ICP, TPR, and TPD. An initial catalytic testing study was carried out using the catalysts to optimize the temperature and the hydrogen-to-aldehyde ratio—which were found to be 160 °C and 2, respectively—to obtain the best conversion and selectivity to octanol prior to water addition. Water impact studies were carried out under the same conditions. The copper chromite catalyst showed no deactivation or change in octanol selectivity when water was added to the feed. The alumina-supported catalyst showed no change in conversion, but the octanol selectivity improved marginally when water was added. Full article
(This article belongs to the Special Issue Catalysts Deactivation, Poisoning and Regeneration)
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<p>TPR profile of (<b>a</b>) CuO/Al<sub>2</sub>O<sub>3</sub>; (<b>b</b>) CuCr<sub>2</sub>O<sub>4</sub>; and (<b>c</b>) unsupported CuO.</p> Full article ">Figure 2
<p>(<b>a</b>) Backscattered SEM images of CuO/Al<sub>2</sub>O<sub>3</sub>; (<b>b</b>) backscattered SEM image of CuCr<sub>2</sub>O<sub>4</sub>.</p> Full article ">Figure 3
<p>(<b>a</b>) TEM images of CuO/Al<sub>2</sub>O<sub>3</sub>; (<b>b</b>) TEM image for CuCr<sub>2</sub>O<sub>4</sub>.</p> Full article ">Figure 4
<p>Conversion of octanal and the selectivity to octanol for the hydrogenation of octanal using the fresh feed and the water-spiked feed over CuO/Al<sub>2</sub>O<sub>3</sub>. (60 bars, 160 °C, H<sub>2</sub>:octanal ratio of 2:1).</p> Full article ">Figure 5
<p>Conversion of octanal and selectivity to octanol for the hydrogenation of octanal using fresh feed and water-spiked feed over CuCr<sub>2</sub>O<sub>4</sub>. (60 bars, 160 °C, H<sub>2</sub>:octanal ratio of 2:1).</p> Full article ">Figure 6
<p>Diffractogram of the used Cu/Al<sub>2</sub>O<sub>3</sub> after the reaction with fresh feed only and water-spiked feed.</p> Full article ">Figure 7
<p>Diffractogram of the used CuCr<sub>2</sub>O<sub>4</sub> after the reaction with fresh feed only and water-spiked feed.</p> Full article ">Figure 8
<p>SEM image of Cu/Al<sub>2</sub>O<sub>3</sub> after (<b>a</b>) the reaction with fresh feed and (<b>b</b>) reaction with the water-spiked feed.</p> Full article ">Figure 9
<p>SEM image of CuCr<sub>2</sub>O<sub>4</sub> after (<b>a</b>) the reaction with fresh feed and (<b>b</b>) reaction with the water-spiked feed.</p> Full article ">
11 pages, 2578 KiB  
Review
α-Glucan Phosphorylase-Catalyzed Enzymatic Reactions Using Analog Substrates to Synthesize Non-Natural Oligo- and Polysaccharides
by Jun-ichi Kadokawa
Catalysts 2018, 8(10), 473; https://doi.org/10.3390/catal8100473 - 19 Oct 2018
Cited by 18 | Viewed by 4526
Abstract
As natural oligo- and polysaccharides are important biomass resources and exhibit vital biological functions, non-natural oligo- and polysaccharides with a well-defined structure can be expected to act as new functional materials with specific natures and properties. α-Glucan phosphorylase (GP) is one of the [...] Read more.
As natural oligo- and polysaccharides are important biomass resources and exhibit vital biological functions, non-natural oligo- and polysaccharides with a well-defined structure can be expected to act as new functional materials with specific natures and properties. α-Glucan phosphorylase (GP) is one of the enzymes that have been used as catalysts for practical synthesis of oligo- and polysaccharides. By means of weak specificity for the recognition of substrates by GP, non-natural oligo- and polysaccharides has precisely been synthesized. GP-catalyzed enzymatic glycosylations using several analog substrates as glycosyl donors have been carried out to produce oligosaccharides having different monosaccharide residues at the non-reducing end. Glycogen, a highly branched natural polysaccharide, has been used as the polymeric glycosyl acceptor and primer for the GP-catalyzed glycosylation and polymerization to obtain glycogen-based non-natural polysaccharide materials. Under the conditions of removal of inorganic phosphate, thermostable GP-catalyzed enzymatic polymerization of analog monomers occurred to give amylose analog polysaccharides. Full article
(This article belongs to the Section Biocatalysis)
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<p>Typical reversible reactions catalyzed by phosphorylases.</p> Full article ">Figure 2
<p>α-Glucan phosphorylase (GP)-catalyzed (<b>a</b>) phosphorolysis, (<b>b</b>) glycosylation, and (<b>c</b>) polymerization.</p> Full article ">Figure 3
<p>GP-catalyzed enzymatic glycosylations using analog substrates (monosaccharide 1-phosphates) as glycosyl donors to produce non-natural oligosaccharides.</p> Full article ">Figure 4
<p>GP-catalyzed (<b>a</b>) polymerization to produce glycogen hydrogel, (<b>b</b>) glucuronylation and subsequent glucosaminylation to produce amphoteric glycogen, and (<b>c</b>) following polymerization to produce amphoteric glycogen hydrogel.</p> Full article ">Figure 5
<p>Matrix assisted laser desorption/ionization-time of flight (MALDI-TOF) mass spectrum of crude product from thermostable GP-catalyzed glucosaminylations using GlcN-1-P in acetate buffer (10:1 donor/acceptor feed ratio).</p> Full article ">Figure 6
<p>Thermostable GP-catalyzed enzymatic polymerization of GlcN-1-P with removal of Pi to produce amylosamine.</p> Full article ">Figure 7
<p>Thermostable GP-catalyzed synthesis of amphoteric block polysaccharide.</p> Full article ">
14 pages, 769 KiB  
Article
Bacterial Biodegradation of 4-Monohalogenated Diphenyl Ethers in One-Substrate and Co-Metabolic Systems
by Amanda Pacholak, Wojciech Smułek, Agata Zdarta, Agnieszka Zgoła-Grześkowiak and Ewa Kaczorek
Catalysts 2018, 8(10), 472; https://doi.org/10.3390/catal8100472 - 19 Oct 2018
Cited by 10 | Viewed by 2677
Abstract
The use of diphenyl ether (DE) and its 4-monohalogenated derivatives (4-HDE) as flame retardants, solvents, and substrates in biocide production significantly increases the risk of ecosystem contamination. Their removal is important from the point of view of environmental protection. The aim of this [...] Read more.
The use of diphenyl ether (DE) and its 4-monohalogenated derivatives (4-HDE) as flame retardants, solvents, and substrates in biocide production significantly increases the risk of ecosystem contamination. Their removal is important from the point of view of environmental protection. The aim of this study was to evaluate the degradation processes of DE and 4-HDE by enzymes of the environmental bacterial strains under one-substrate and co-metabolic conditions. The study is focused on the biodegradation of DE and 4-HDE, the enzymatic activity of microbial strains, and the cell surface properties after contact with compounds. The results show that the highest biodegradation (96%) was observed for 4-chlorodiphenyl ether in co-metabolic culture with P. fluorescens B01. Moreover, the activity of 1,2-dioxygenase during degradation of 4-monohalogenated diphenyl ethers was higher than that of 2,3-dioxygenase for each strain tested. The presence of a co-substrate provoked changes in dioxygenase activity, resulting in the increased activity of 1,2-dioxygenase. Moreover, the addition of phenol as a co-substrate allowed for increased biodegradation of the diphenyl ethers and noticeable modification of the cell surface hydrophobicity during the process. All observations within the study performed have led to a deeper understanding of the contaminants’ biodegradation processes catalyzed by environmental bacteria. Full article
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<p>Levels of removal of phenol as a sole carbon source and in co-metabolism (examined by HPLC/FD analysis) and diphenyl ether and its derivatives as sole carbon sources and in co-metabolism (examined by GC/MC analysis) measured in cultures of (<b>a</b>) <span class="html-italic">P. fluorescens</span> B01 after seven days; (<b>b</b>) <span class="html-italic">P. fluorescens</span> B01 after 14 days; (<b>c</b>) <span class="html-italic">P. plecoglossicida</span> IsA after seven days and (<b>d</b>) <span class="html-italic">P. plecoglossicida</span> IsA after 14 days. Letters on the x-axis refer to different carbon sources: Ph—phenol; DE—diphenyl ether; BDE—4-bromodiphenyl ether; CDE—4-chlorodiphenyl ether. All measurements were made in triplicate and the values are presented as a mean ± standard deviation.</p> Full article ">Figure 2
<p>Changes in relative cell metabolic activity during biodegradation of phenol (Ph), diphenyl ether (DE), 4-bromodiphenyl ether (BDE), 4-chlorodiethylether (CDE) and their mixtures by (<b>a</b>) <span class="html-italic">P. plecoglossicida</span> IsA and (<b>b</b>) <span class="html-italic">P. fluorescens</span> B01.</p> Full article ">
23 pages, 6711 KiB  
Article
Rice Husk as an Inexpensive Renewable Immobilization Carrier for Biocatalysts Employed in the Food, Cosmetic and Polymer Sectors
by Marco Cespugli, Simone Lotteria, Luciano Navarini, Valentina Lonzarich, Lorenzo Del Terra, Francesca Vita, Marina Zweyer, Giovanna Baldini, Valerio Ferrario, Cynthia Ebert and Lucia Gardossi
Catalysts 2018, 8(10), 471; https://doi.org/10.3390/catal8100471 - 19 Oct 2018
Cited by 36 | Viewed by 5666
Abstract
The high cost and environmental impact of fossil-based organic carriers represent a critical bottleneck to their use in large-scale industrial processes. The present study demonstrates the applicability of rice husk as inexpensive renewable carrier for the immobilization of enzymes applicable sectors where the [...] Read more.
The high cost and environmental impact of fossil-based organic carriers represent a critical bottleneck to their use in large-scale industrial processes. The present study demonstrates the applicability of rice husk as inexpensive renewable carrier for the immobilization of enzymes applicable sectors where the covalent anchorage of the protein is a pre-requisite for preventing protein contamination while assuring the recyclability. Rice husk was oxidized and then functionalized with a di-amino spacer. The morphological characterization shed light on the properties that affect the functionalization processes. Lipase B from Candida antarctica (CaLB) and two commercial asparaginases were immobilized covalently achieving higher immobilization yield than previously reported. All enzymes were immobilized also on commercial epoxy methacrylic resins and the CaLB immobilized on rice husk demonstrated a higher efficiency in the solvent-free polycondensation of dimethylitaconate. CaLB on rice husk appears particularly suitable for applications in highly viscous processes because of the unusual combination of its low density and remarkable mechanical robustness. In the case of the two asparaginases, the biocatalyst immobilized on rice husk performed in aqueous solution at least as efficiently as the enzyme immobilized on methacrylic resins, although the rice husk loaded a lower amount of protein. Full article
(This article belongs to the Special Issue Immobilization of Enzymes)
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<p>Scanning electron micrographs of rice husk fibers at different orders of magnification: (<b>A</b>) View of the external and internal surface; (<b>B</b>) internal section exposing the tracheids.</p> Full article ">Figure 2
<p>SEM images of: (<b>a</b>–<b>c</b>) Milled rice husk with particle size 200–400 μm; (<b>d</b>–<b>f</b>) milled rice husk with particle size 100–200 μm.</p> Full article ">Figure 3
<p>Bright field light microscopy images highlighting the tubular structure of tracheids (red arrows): (<b>a</b>,<b>b</b>) Milled rice husk (RH) with average size of 200–400 μm; (<b>c</b>,<b>d</b>) milled RH with average size of 100–200 μm; (<b>e</b>) detail of the external siliceous layer of a fragment of milled RH.</p> Full article ">Figure 4
<p>Milled RH (fragments with average size of 200–400 μm): (<b>a</b>,<b>b</b>) Fluorescence microscopy, (<b>c</b>) phase contrast image.</p> Full article ">Figure 5
<p>Comparison of the content (mmol·g<sup>−1</sup>) of carbonyl (light gray) and carboxylic groups (black) in samples of milled RH before and after different oxidative treatment.</p> Full article ">Figure 6
<p>Analysis of the 3D structure of lipase B from <span class="html-italic">Candida antarctica</span> (CaLB, PDB: 1TCA). (<b>A</b>) The active site entrance is indicated by a cyan arrow while the superficial Lys are highlighted in blue spheres on the secondary structure of the enzyme. (<b>B</b>) The color of designates the hydrophobicity of the surface, going from white (hydrophilic) to red (hydrophobic).</p> Full article ">Figure 7
<p>Schematic illustration of the oxidation and functionalization of the cellulosic fraction of RH for the covalent immobilization of CaLB.</p> Full article ">Figure 8
<p>SEM images of: (<b>a</b>) Milled rice husk with average particle size 200–400 μm; (<b>b</b>) Sepabeads EC-EP epoxy methacrylic resin beads with average particle size 100–300 μm.</p> Full article ">Figure 9
<p>Solvent-free polycondensation catalyzed by CaLB covalently immobilized on RH.</p> Full article ">Figure 10
<p>Electron Spry Ionization Mass Spectrometry (ESI-MS) positive ion mass spectra of the solvent-free enzymatic polycondensation products of dimethyl itaconate (DMI) with 1,4-butandiol (BDO) after 72 h. Top: Reaction catalyzed by CaLB on rice husk. Bottom: Reaction catalyzed by CaLB on EC-EP/S. A = BDO; B = DMI.</p> Full article ">Figure 11
<p>Analysis of the 3D structure of asparaginase from <span class="html-italic">Erwinia chrysantemi</span> in tetrameric form (PDB 1O7J). (<b>A</b>) The superficial Lys of the enzyme are highlighted in blue spheres on the secondary structure of the enzyme. (<b>B</b>) The colors of the enzyme surface indicate hydrophilic areas (white) and hydrophobic regions (red). (<b>C</b>) The tetrameric structure with each monomer colored differently while the glycosylation sites are highlighted in orange sphere mode.</p> Full article ">
12 pages, 2745 KiB  
Article
Development of Biotransamination Reactions towards the 3,4-Dihydro-2H-1,5-benzoxathiepin-3-amine Enantiomers
by Daniel González-Martínez, Nerea Fernández-Sáez, Carlos Cativiela, Joaquín M. Campos and Vicente Gotor-Fernández
Catalysts 2018, 8(10), 470; https://doi.org/10.3390/catal8100470 - 19 Oct 2018
Cited by 5 | Viewed by 3391
Abstract
The stereoselective synthesis of chiral amines is an appealing task nowadays. In this context, biocatalysis plays a crucial role due to the straightforward conversion of prochiral and racemic ketones into enantiopure amines by means of a series of enzyme classes such as amine [...] Read more.
The stereoselective synthesis of chiral amines is an appealing task nowadays. In this context, biocatalysis plays a crucial role due to the straightforward conversion of prochiral and racemic ketones into enantiopure amines by means of a series of enzyme classes such as amine dehydrogenases, imine reductases, reductive aminases and amine transaminases. In particular, the stereoselective synthesis of 1,5-benzoxathiepin-3-amines have attracted particular attention since they possess remarkable biological profiles; however, their access through biocatalytic methods is unexplored. Amine transaminases are applied herein in the biotransamination of 3,4-dihydro-2H-1,5-benzoxathiepin-3-one, finding suitable enzymes for accessing both target amine enantiomers in high conversion and enantiomeric excess values. Biotransamination experiments have been analysed, trying to optimise the reaction conditions in terms of enzyme loading, temperature and reaction times. Full article
(This article belongs to the Special Issue Biocatalysis and Pharmaceuticals: A Smart Tool for Sustainable Development)
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<p>Benzo-fused seven-membered rings with oxygen and sulphur atoms in 1,5 relative positions (<b>1</b>–<b>5</b>) with interesting biological properties [<a href="#B1-catalysts-08-00470" class="html-bibr">1</a>,<a href="#B2-catalysts-08-00470" class="html-bibr">2</a>,<a href="#B3-catalysts-08-00470" class="html-bibr">3</a>,<a href="#B4-catalysts-08-00470" class="html-bibr">4</a>,<a href="#B5-catalysts-08-00470" class="html-bibr">5</a>]. The (3<span class="html-italic">R</span>)-3,4-dihydro-2<span class="html-italic">H</span>-1,5-benzoxathiepin-3-amine core appears in red in compounds <b>3</b>–<b>5</b>.</p> Full article ">Figure 2
<p>Optimised geometry of 3,4-dihydro-2<span class="html-italic">H</span>-1,5-benzoxathiepin-3-one (<b>6</b>): electronic isodensity contour (<b>left</b>); colour-mapped with the electrostatic potential (<b>right</b>), where red and blue zones are related to the electrophilic and nucleophilic zones of the molecule, respectively.</p> Full article ">Figure 3
<p>Study of the enzymatic transamination of ketone <b>6</b> with TA-P1-G05 over time employing: (<span class="html-fig-inline" id="catalysts-08-00470-i001"> <img alt="Catalysts 08 00470 i001" src="/catalysts/catalysts-08-00470/article_deploy/html/images/catalysts-08-00470-i001.png"/></span>) 90% of enzyme loading (<span class="html-italic">w</span>/<span class="html-italic">w</span>) or (<span class="html-fig-inline" id="catalysts-08-00470-i002"> <img alt="Catalysts 08 00470 i002" src="/catalysts/catalysts-08-00470/article_deploy/html/images/catalysts-08-00470-i002.png"/></span>) 45% of enzyme loading (<span class="html-italic">w</span>/<span class="html-italic">w</span> vs. <b>6</b>).</p> Full article ">Figure 4
<p>Structures of (<span class="html-italic">R</span>)- and (<span class="html-italic">S</span>)-<b>10</b>.</p> Full article ">Scheme 1
<p>Chemical synthesis of 3,4-dihydro-2<span class="html-italic">H</span>-1,5-benzoxathiepin-3-one <b>6</b>.</p> Full article ">Scheme 2
<p>Biotransamination of 3,4-dihydro-2<span class="html-italic">H</span>-1,5-benzoxathiepin-3-one (<b>6</b>) into amine <b>9</b>, using ATAs.</p> Full article ">Scheme 3
<p>Scale-up of the biotransamination towards the (3<span class="html-italic">R</span>)-3,4-dihydro-2<span class="html-italic">H</span>-1,5-benzoxathiepin-3-amine (<span class="html-italic">R</span>-<b>9</b>).</p> Full article ">
18 pages, 5074 KiB  
Article
Catalytic Performance of Gold Supported on Mn, Fe and Ni Doped Ceria in the Preferential Oxidation of CO in H2-Rich Stream
by Shuna Li, Huaqing Zhu, Zhangfeng Qin, Yagang Zhang, Guofu Wang, Zhiwei Wu, Weibin Fan and Jianguo Wang
Catalysts 2018, 8(10), 469; https://doi.org/10.3390/catal8100469 - 18 Oct 2018
Cited by 10 | Viewed by 3890
Abstract
Ceria supported metal catalysts often exhibit high activity in the preferential oxidation (PROX) of CO in H2-rich stream and doping the ceria support with other metals proves to be rather effective in further enhancing their catalytic performance. Therefore, in this work, [...] Read more.
Ceria supported metal catalysts often exhibit high activity in the preferential oxidation (PROX) of CO in H2-rich stream and doping the ceria support with other metals proves to be rather effective in further enhancing their catalytic performance. Therefore, in this work, a series of ceria materials doped with Mn, Fe and Ni (CeM, where M = Mn, Fe and Ni; M/Ce = 1/8) were synthesized by a modified hydrothermal method; with the doped ceria materials (CeM) as the support, various supported gold catalysts (Au/CeM) were prepared by the colloidal deposition method. The influence of metal dopant on the performance of these ceria materials supported with gold catalysts in CO PROX was then investigated in detail with the help of various characterization measures such as N2 sorption, XRD, TEM, Raman spectroscopy, H2-TPR, XPS and XAS. The results indicate that the incorporation of Mn, Fe and Ni metal ions into ceria can remarkably increase the amount of oxygen vacancies in the doped ceria support, which is beneficial for enhancing the reducibility of ceria, the metal-support interaction and the dispersion of gold species. Although the gold catalysts supported on various doped ceria are similar in the size and state of Au nanoparticles, the CO conversions for CO PROX over Au/CeMn, Au/CeFe and Au/CeNi catalysts are 65.6%, 93.0% and 48.2%, respectively, much higher than the value of 33.6% over the undoped Au/CeO2 catalyst at ambient temperature. For CO PROX over the Au/CeNi catalyst, the conversion of CO remains near 100% at 60–130 °C, with a PROX selectivity to CO2 of higher than 50%. The excellent performance of Au/CeNi catalyst can be ascribed to its large amount of oxygen vacancies and high reducibility on account of Ni incorporation. The insight shown in this work helps to clarify the doping effect of other metals on the physicochemical properties of ceria, which is then beneficial to building a structure-performance relation for ceria supported gold catalyst as well as developing a better catalyst for removing trace CO in the hydrogen stream and producing high purity hydrogen. Full article
(This article belongs to the Special Issue Heterogeneous Catalysis for Energy Conversion)
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<p>XRD patterns of CeO<sub>2</sub>, CeM mixed oxides with different dopants and corresponding supported Au/CeM catalysts: (<b>a</b>) CeO<sub>2</sub>; (<b>b</b>) CeMn; (<b>c</b>) CeFe; (<b>d</b>) CeNi; (<b>e</b>) Au/CeO<sub>2</sub>; (<b>f</b>) Au/CeMn; (<b>g</b>) Au/CeFe; (<b>h</b>) Au/CeNi.</p> Full article ">Figure 2
<p>TEM images of Au catalysts supported on CeO<sub>2</sub> and CeM mixed oxides with different dopants (Au/CeO<sub>2</sub>; Au/CeMn; Au/CeFe; Au/CeNi).</p> Full article ">Figure 3
<p>HRTEM images of Au catalysts supported on CeO<sub>2</sub> and CeM mixed oxides with different dopants (Au/CeO<sub>2</sub>; Au/CeMn; Au/CeFe; Au/CeNi).</p> Full article ">Figure 4
<p>Raman spectra of CeO<sub>2</sub>, CeM mixed oxides with different dopants and corresponding supported Au/CeM catalysts: (<b>a</b>) CeO<sub>2</sub>; (<b>b</b>) CeMn; (<b>c</b>) CeFe; (<b>d</b>) CeNi; (<b>e</b>) Au/CeO<sub>2</sub>; (<b>f</b>) Au/CeMn; (<b>g</b>) Au/CeFe; (<b>h</b>) Au/CeNi.</p> Full article ">Figure 5
<p>H<sub>2</sub>-TPR profiles of CeO<sub>2</sub>, CeM mixed oxides with different dopants and corresponding supported Au/CeM catalysts: (<b>a</b>) CeO<sub>2</sub>; (<b>b</b>) CeMn; (<b>c</b>) CeFe; (<b>d</b>) CeNi; (<b>e</b>) Au/CeO<sub>2</sub>; (<b>f</b>) Au/CeMn; (<b>g</b>) Au/CeFe; (<b>h</b>) Au/CeNi.</p> Full article ">Figure 6
<p>Ce 3<span class="html-italic">d</span> XPS spectra of CeO<sub>2</sub>, CeM mixed oxides with different dopants and corresponding supported Au/CeM catalysts: (<b>a</b>) CeO<sub>2</sub>; (<b>b</b>) CeMn; (<b>c</b>) CeFe; (<b>d</b>) CeNi; (<b>e</b>) Au/CeO<sub>2</sub>; (<b>f</b>) Au/CeMn; (<b>g</b>) Au/CeFe; (<b>h</b>) Au/CeNi.</p> Full article ">Figure 7
<p>Au 4<span class="html-italic">f</span> XPS spectra of Au catalysts supported on CeO<sub>2</sub> and CeM mixed oxides with different dopants: (<b>a</b>) Au/CeO<sub>2</sub>; (<b>b</b>) Au/CeMn; (<b>c</b>) Au/CeFe; (<b>d</b>) Au/CeNi.</p> Full article ">Figure 8
<p>O 1<span class="html-italic">s</span> XPS spectra of Au catalysts supported on CeO<sub>2</sub> and CeM mixed oxides with different dopants: (<b>a</b>) CeO<sub>2</sub>; (<b>b</b>) CeMn; (<b>c</b>) CeFe; (<b>d</b>) CeNi; (<b>e</b>) Au/CeO<sub>2</sub>; (<b>f</b>) Au/CeMn; (<b>g</b>) Au/CeFe; (<b>h</b>) Au/CeNi.</p> Full article ">Figure 9
<p>Au L<sub>III</sub>-edge XANES spectra of the Au catalysts supported on CeO<sub>2</sub> and CeM mixed oxides with different dopants: (<b>a</b>) Au foil; (<b>b</b>) Au/CeO<sub>2</sub>; (<b>c</b>) Au/CeMn; (<b>d</b>) Au/CeFe; (<b>e</b>) Au/CeNi.</p> Full article ">Figure 10
<p>Light-off profiles (temperature-programmed reaction) of CO PROX in H<sub>2</sub>-rich stream over CeO<sub>2</sub> and doped CeM mixed oxides with different dopants: (<b>a</b>) CeO<sub>2</sub>; (<b>b</b>) CeMn; (<b>c</b>) CeFe; (<b>d</b>) CeNi.</p> Full article ">Figure 11
<p>Light-off profiles (temperature-programmed reaction) of CO PROX in H<sub>2</sub>-rich stream over CeO<sub>2</sub> and doped CeM supported gold catalysts: (<b>a</b>) Au/CeO<sub>2</sub>; (<b>b</b>) Au/CeMn; (<b>c</b>) Au/CeFe; (<b>d</b>) Au/CeNi.</p> Full article ">Figure 12
<p>Long-term test of CO PROX over Au/CeFe (<b>a1</b>,<b>a2</b>) and Au/CeNi (<b>b1</b>,<b>b2</b>) catalysts at 80 °C.</p> Full article ">
10 pages, 3239 KiB  
Article
Preparation of a Flower-Like Immobilized D-Psicose 3-Epimerase with Enhanced Catalytic Performance
by Lu Zheng, Yining Sun, Jing Wang, He Huang, Xin Geng, Yi Tong and Zhi Wang
Catalysts 2018, 8(10), 468; https://doi.org/10.3390/catal8100468 - 18 Oct 2018
Cited by 38 | Viewed by 5173
Abstract
In this present study, we proposed a smart biomineralization method for creating hybrid organic–inorganic nanoflowers using a Co2+-dependent enzyme (D-psicose 3-epimerase; DPEase) as the organic component and cobalt phosphate as the inorganic component. The prepared nanoflowers have many separated [...] Read more.
In this present study, we proposed a smart biomineralization method for creating hybrid organic–inorganic nanoflowers using a Co2+-dependent enzyme (D-psicose 3-epimerase; DPEase) as the organic component and cobalt phosphate as the inorganic component. The prepared nanoflowers have many separated petals that have a nanometer size. Under optimum conditions (60 °C and pH of 8.5), the nanoflower can display its maximum activity (36.2 U/mg), which is about 7.2-fold higher than free DPEase. Furthermore, the immobilized DPEase presents enhanced pH and thermal stabilities. The DPEase-nanoflower maintained about 90% of its activity after six reaction cycles, highlighting its excellent reusability. Full article
(This article belongs to the Special Issue Immobilization of Enzymes)
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<p>(<b>A</b>) Morphology of nanoflower; (<b>B</b>) EDAX analysis and (<b>C</b>) the possible mechanism of nanoflower formation.</p> Full article ">Figure 2
<p>FTIR spectrum of the nanoflower (curve b) and its raw materials (curve a, cobalt phosphate; and curve c, DPEase).</p> Full article ">Figure 3
<p>Effect of temperature on nanoflower and free DPEase. The enzyme activities of nanoflower (36.2 U/mg) and free DPEase (5.0 U/mg) at 60 °C were both 100%.</p> Full article ">Figure 4
<p>Thermal stability of nanoflower and free DPEase. The residual activities were determined at different given time intervals. The enzyme activities of the nanoflower (36.2 U/mg at 60 °C and 35.4 U/mg at 55 °C) and free DPEase (5.0 U/mg at 60 °C and 4.6 U/mg at 55 °C) were both 100%.</p> Full article ">Figure 5
<p>Effect of pH on nanoflower and free DPEase. The pH range was 6.0–9.5. The enzyme activities at a pH of 8.5 for nanoflower (36.2 U/mg) and at a pH of 8.0 for free DPEase (5.0 U/mg) were both 100%.</p> Full article ">Figure 6
<p>pH stability of nanoflower and free DPEase. Both the free DPEase and the nanoflower were pre-incubated at 4 °C and different pH values for 2.0 h. After this, the residual activity was measured. The DPEase activities at a pH of 8.5 for nanoflower (36.2 U/mg) and at a pH of 8.0 for free DPEase (5.0 U/mg) were both 100%, respectively.</p> Full article ">Figure 7
<p>The reusability of the prepared DPEase nanoflower. The assay mixture contained D-fructose (500.0 mg/mL, 100.0 µL), Co<sup>2+</sup> (10.0 mM, 10.0 µL), nanoflower (0.17 mg, containing 20.0 µg of DPEase) and Tris-HCl buffer (50.0 mM, pH 8.5, 890.0 µL). The reaction was performed at 60 °C for 10 min. After each reaction cycle, the nanoflower was recycled by centrifugation and reused for the next run.</p> Full article ">Scheme 1
<p>D-psicose production catalyzed by DPEase or DTEase.</p> Full article ">
12 pages, 1847 KiB  
Article
Selective Dehydration of Glucose into 5-Hydroxymethylfurfural by Ionic Liquid-ZrOCl2 in Isopropanol
by Yubo Ma, Lei Wang, Hongyi Li, Tianfu Wang and Ronghui Zhang
Catalysts 2018, 8(10), 467; https://doi.org/10.3390/catal8100467 - 18 Oct 2018
Cited by 8 | Viewed by 4225
Abstract
In this work, a heterogeneous catalytic system consisting of [HO2CMMIm]Cl and ZrOCl2 in isopropanol is demonstrated to be effective for 5-hydroxymethylfurfural (HMF) synthesis with glucose as the feedstock. Various reaction conditions for HMF synthesis by glucose dehydration were investigated systematically. [...] Read more.
In this work, a heterogeneous catalytic system consisting of [HO2CMMIm]Cl and ZrOCl2 in isopropanol is demonstrated to be effective for 5-hydroxymethylfurfural (HMF) synthesis with glucose as the feedstock. Various reaction conditions for HMF synthesis by glucose dehydration were investigated systematically. Under optimized reaction conditions, as high as 43 mol% HMF yield could be achieved. Increasing the water content to a level below 3.17% led to the production of HMF with a higher yield, while a lower HMF yield was observed when the water content was increased above 3.17%. In addition, the data also showed that ZrOCl2 could not only effectively convert glucose into intermediate species (which were not fructose, in contrast to the literature) but also catalyze the intermediate species’ in situ dehydration into HMF. [HO2CMMIm]Cl was used to catalyze the intermediate species’ in situ conversion to HMF. The kinetics data showed that a temperature increase accelerated the intermediate species’ dehydration reaction rate. The reaction of glucose dehydration was a strong endothermal reaction. Full article
(This article belongs to the Special Issue Catalytic Conversion of Biomass-Derived Molecules to Chemicals and Fuels)
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<p>Effect of IL [HO<sub>2</sub>CMMIm]Cl loading on glucose dehydration.Experimental conditions: 0.15 g ZrOCl<sub>2</sub>, 0.1 g glucose, 3.0 g isopropanol, 3 h reaction time, 150 °C reaction temperature.</p> Full article ">Figure 2
<p>Influence of ZrOCl<sub>2</sub> loading on glucose conversion.Reaction conditions: 0.05 g [HO<sub>2</sub>CMMIm]Cl, 0.1 g glucose, 3.0 g isopropanol, 3 h reaction time, 150 °C reaction temperature.</p> Full article ">Figure 3
<p>Effect of reaction time on glucose dehydration Reaction conditions: 0.15 ZrOCl<sub>2</sub>, 0.15 g [HO<sub>2</sub>CMMIm]Cl, 0.1 g glucose, 3.0 g isopropanol, 150 °C reaction temperature.</p> Full article ">Figure 4
<p>Effect of the reaction temperature on HMF yield, during glucose conversion.Experimental conditions: 0.15 g ZrOCl<sub>2</sub>, 0.05 g [HO<sub>2</sub>CMMIm]Cl, 0.1 g glucose, 3.0 g isopropanol, 3 h reaction time.</p> Full article ">Figure 5
<p>Effect of Substrate loading on glucose conversion.Reaction conditions: 0.15 g ZrOCl<sub>2</sub>, 0.05 g [HO<sub>2</sub>CMMIm]Cl, 3.0 g isopropanol, 3 h reaction time, 150 °C reaction temperature.</p> Full article ">Figure 6
<p>Effect of water content% on glucose dehydration.Experimental conditions: 0.1 g glucose, 0.15 g ZrOCl<sub>2</sub>, 0.05 g [HO<sub>2</sub>CMMIm]Cl, 3.0 g isopropanol, 3 h reaction time, and 150 °C reaction temperature.</p> Full article ">Figure 7
<p>Arrhenius plot for glucose dehydration in isopropanol over [HO<sub>2</sub>CMMIm]Cl–ZrOCl<sub>2.</sub></p> Full article ">Scheme 1
<p>Dehydration of glucose into 5-hydroxymethylfurfural (HMF).</p> Full article ">Scheme 2
<p>Glucose dehydration by [HO<sub>2</sub>CMMIm]Cl ionic liquid (IL)–ZrOCl<sub>2</sub> in isopropanol.</p> Full article ">
19 pages, 7438 KiB  
Article
Comparing Photocatalytic Degradation of Gaseous Ethylbenzene Using N-doped and Pure TiO2 Nano-Catalysts Coated on Glass Beads under Both UV and Visible Light Irradiation
by Morteza Kamaei, Hamid Rashedi, Seyed Mohammad Mehdi Dastgheib and Saeideh Tasharrofi
Catalysts 2018, 8(10), 466; https://doi.org/10.3390/catal8100466 - 18 Oct 2018
Cited by 31 | Viewed by 3974
Abstract
Volatile Organic Compounds (VOCs) are within the main industrial air pollutants whose release into the atmosphere is harmful to the ecosystem and human health. Gas-phase photocatalytic degradation of ethylbenzene, an aromatic VOC emitted from various sources, has been investigated in this study using [...] Read more.
Volatile Organic Compounds (VOCs) are within the main industrial air pollutants whose release into the atmosphere is harmful to the ecosystem and human health. Gas-phase photocatalytic degradation of ethylbenzene, an aromatic VOC emitted from various sources, has been investigated in this study using TiO2 nanoparticle-coated glass beads in an annular photoreactor. To use visible light irradiation, TiO2 nanoparticles were doped by nitrogen using urea. The results showed that nitrogen doping significantly increased the removal efficiency of ethylbenzene under visible light irradiation compared with the pure TiO2, so that the removal efficiencies between 75–100% could be yielded for the initial ethylbenzene concentrations up to 0.13 g/m3 under visible light which could be useful for improving indoor air quality. The UV irradiated reactor needed less residence time and much higher removal efficiencies could be yielded at high initial concentrations. When the residence time under UV irradiation was one third of the same under visible light, the removal efficiency was more than 80% for the inlet concentrations up to 0.6 g/m3, whereas the removal efficiency under visible light was about 25% at this inlet concentration. Langmuir-Hinshelwood kinetic model could be well fitted to the photocatalytic reaction in both irradiation systems. Full article
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<p>X-ray diffraction (XRD) pattern of the prepared N-doped TiO<sub>2</sub>.</p> Full article ">Figure 2
<p>Nitrogen adsorption-desorption isotherms of as-prepared N-doped P25. The inset shows the Barrett-Joyner-Halenda (BJH) pore size distribution curve.</p> Full article ">Figure 3
<p>Field emission scanning electron microscope (FE-SEM) images of the as-prepared N-doped TiO<sub>2</sub> catalyst.</p> Full article ">Figure 4
<p>Energy dispersive X-ray spectroscopy (EDS) pattern of the as-prepared N-doped TiO<sub>2</sub> catalyst.</p> Full article ">Figure 5
<p>SEM images of the surface of (<b>a</b>) uncoated glass beads; (<b>b</b>) the glass beads coated by N-doped TiO<sub>2</sub> catalyst in different magnitudes.</p> Full article ">Figure 6
<p>XPS spectra of (<b>a</b>) Ti2p, (<b>b</b>) O1s, (<b>c</b>) N1s and (<b>d</b>) C1s for the prepared N-doped TiO<sub>2</sub>. The colored dashed lines stand for the deconvoluted scan of the elements which show all the obtained peaks for each element.</p> Full article ">Figure 6 Cont.
<p>XPS spectra of (<b>a</b>) Ti2p, (<b>b</b>) O1s, (<b>c</b>) N1s and (<b>d</b>) C1s for the prepared N-doped TiO<sub>2</sub>. The colored dashed lines stand for the deconvoluted scan of the elements which show all the obtained peaks for each element.</p> Full article ">Figure 7
<p>(<b>a</b>) UV-Vis diffuse reflectance spectra and, (<b>b</b>) plots of the transformed Kubelka-Munk function vs the photon energy for N-doped TiO<sub>2</sub> and pristine P25-TiO<sub>2</sub>.</p> Full article ">Figure 8
<p>Effect of inlet concentration on removal efficiency at 1 min residence time under UV irradiation for N-doped and pristine TiO<sub>2</sub>.</p> Full article ">Figure 9
<p>Effect of inlet concentration on removal efficiency at 3 min residence time under visible light irradiation for N-doped and pristine TiO<sub>2</sub>.</p> Full article ">Figure 10
<p>Ethylbenzene removal efficiency using N-doped TiO<sub>2</sub> under (<b>a</b>) UV irradiation and inlet concentration of 0.66 g/m<sup>3</sup> at different residence times; (<b>b</b>) visible light and inlet concentration of 0.13 g/m<sup>3</sup> at different residence times.</p> Full article ">Figure 11
<p>CO<sub>2</sub> production against the ethlylbenzene inlet load in photocatalytic reactions using N-doped TiO<sub>2</sub> catalyst under (<b>a</b>) UV and (<b>b</b>) visible light irradiation.</p> Full article ">Figure 12
<p>The relationship between the inverse of reaction rates and ethylbenzene initial concentrations using N-doped TiO<sub>2</sub> catalyst under (<b>a</b>) UV and (<b>b</b>) visible light irradiation.</p> Full article ">Figure 13
<p>Schematics of the photocatalytic reaction system: (<b>1</b>) air pump, (<b>2</b>) rotameters, (<b>3</b>) humidifier, (<b>4</b>) ethylbenzene saturator, (<b>5</b>) mixing tank, (<b>6</b>) photoreactor, (<b>7</b>) power supply, (<b>8</b>) light source.</p> Full article ">
15 pages, 5854 KiB  
Article
The Modification of Pt/Graphene Composites with Oxophilic Metal Bi (Bi2O3) and Its Dual-Functional Electro-Photo Catalytic Performance
by Yingli Wu, Xiuyun Duan, Zhongshui Li, Shuhong Xu, Yixin Xie, Yufei Lai and Shen Lin
Catalysts 2018, 8(10), 465; https://doi.org/10.3390/catal8100465 - 17 Oct 2018
Cited by 7 | Viewed by 3964
Abstract
The Pt-Bi (Bi2O3)/GNs (PVP) composite was synthesized using aqueous solution synthesis and characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and Raman spectroscopy. It was found that the [...] Read more.
The Pt-Bi (Bi2O3)/GNs (PVP) composite was synthesized using aqueous solution synthesis and characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), inductively coupled plasma-atomic emission spectroscopy (ICP-AES) and Raman spectroscopy. It was found that the water-soluble polyvinyl pyrrolidone (PVP) helped to tune the particles’ morphology, resulting in a uniform distribution of Pt-Bi nanoclusters on the surface of graphene. Cyclic voltammetry, chronoamperometry and linear scanning voltammetry (LSV) were used to study the electrocatalytic properties towards a methanol oxidation reaction (MOR) and an oxygen reduction reaction (ORR). The results show that Pt-Bi (Bi2O3)/GNs (PVP) exhibits superior bifunctional electrocatalytic properties for both MOR and ORR, mainly due to the introduction of oxophilic Bi species and the better dispersion of the Pt-Bi nanoclusters. In particular, the electro-photo catalysis for both MOR and ORR occurred under simulated sunlight irradiation due to the existence of photo-responsive Bi species, which is helpful for converting solar energy into electric energy during a traditional electrocatalytic process. Full article
(This article belongs to the Special Issue Recent Advances in Pt-Based Catalysts: Theoretical and Experimental Results)
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<p>(<b>A</b>) X-ray diffraction (XRD) patterns: Pt-Bi (Bi<sub>2</sub>O<sub>3</sub>)/GNs (PVP) (<b>a</b>), Pt/GNs (PVP) (<b>b</b>), and Pt-Bi (Bi<sub>2</sub>O<sub>3</sub>)/GNs (<b>c</b>); (<b>B</b>) Pt 4f X-ray photoelectron spectroscopy (XPS) for Pt-Bi (Bi<sub>2</sub>O<sub>3</sub>)/GNs (PVP); (<b>C</b>) Pt 4f XPS for Pt/GNs (PVP); (<b>D</b>) Pt 4f XPS for Pt-Bi (Bi<sub>2</sub>O<sub>3</sub>)/GNs; (<b>E</b>) Bi 4f XPS for Pt-Bi (Bi<sub>2</sub>O<sub>3</sub>)/GNs (PVP); (<b>F</b>) Bi 4f XPS for Pt-Bi (Bi<sub>2</sub>O<sub>3</sub>)/GNs.</p> Full article ">Figure 2
<p>Transmission electron microscopy (TEM) images: Pt-Bi (Bi<sub>2</sub>O<sub>3</sub>)/GNs (PVP) (<b>A</b>,<b>B</b>), Pt/GNs (PVP) (<b>D</b>,<b>E</b>) and Pt-Bi (Bi<sub>2</sub>O<sub>3</sub>)/GNs (<b>G</b>,<b>H</b>); The inset in panel B is magnified TEM images of Pt-Bi (Bi<sub>2</sub>O<sub>3</sub>)/GNs (PVP); High-resolution transmission electron microscopy (HRTEM) images: Pt-Bi(Bi<sub>2</sub>O<sub>3</sub>)/GNs (PVP) (<b>C</b>), Pt/GNs (PVP) (<b>F</b>) and Pt-Bi (Bi<sub>2</sub>O<sub>3</sub>)/GNs (<b>I</b>).</p> Full article ">Figure 3
<p>The high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) images: Pt-Bi (Bi<sub>2</sub>O<sub>3</sub>)/GNs (PVP) (<b>A</b>), Pt-Bi (Bi<sub>2</sub>O<sub>3</sub>)/GNs (<b>E</b>); Elemental mapping images: Pt (<b>B</b>) and Bi (<b>C</b>) for Pt-Bi (Bi<sub>2</sub>O<sub>3</sub>)/GNs (PVP), Pt (<b>F</b>) and Bi (<b>G</b>) for Pt-Bi (Bi<sub>2</sub>O<sub>3</sub>)/GNs; The distribution of Pt and Bi (<b>D</b>) and Pt and Bi (<b>H</b>) atoms along the corresponding cross-sectional line shown in (<b>A</b>,<b>E</b>) respectively.</p> Full article ">Figure 4
<p>Raman spectra: Pt-Bi (Bi<sub>2</sub>O<sub>3</sub>)/GNs (PVP) (<b>a</b>), Pt/GNs (PVP) (<b>b</b>), Pt-Bi (Bi<sub>2</sub>O<sub>3</sub>)/GNs (<b>c</b>).</p> Full article ">Figure 5
<p>Cyclic voltammetry in 1.0 M CH<sub>3</sub>OH + 1.0 M NaOH: Pt-Bi (Bi<sub>2</sub>O<sub>3</sub>)/GNs (PVP) (<b>a</b>), 30% PtRu/C-JM (<b>b</b>), Pt/GNs (PVP) (<b>c</b>) and Pt-Bi (Bi<sub>2</sub>O<sub>3</sub>)/GNs (<b>d</b>), at 10 mV s<sup>−1</sup>.</p> Full article ">Figure 6
<p>Chronoamperometric curves in 1.0 M CH<sub>3</sub>OH + 1.0 M NaOH: Pt-Bi (Bi<sub>2</sub>O<sub>3</sub>)/GNs (PVP) (<b>a</b>), 30% PtRu/C-JM (<b>b</b>), Pt/GNs (PVP) (<b>c</b>), and Pt-Bi (Bi<sub>2</sub>O<sub>3</sub>)/GNs (<b>d</b>), at 100 mV s<sup>−1</sup>.</p> Full article ">Figure 7
<p>Cyclic voltammetry in 1.0 M NaOH: Pt-Bi (Bi<sub>2</sub>O<sub>3</sub>)/GNs (PVP) (<b>A</b>), 30% PtRu/C-JM (<b>B</b>), Pt/GNs (PVP) (<b>C</b>) and Pt-Bi (Bi<sub>2</sub>O<sub>3</sub>)/GNs (<b>D</b>), at 10 mV s<sup>−1</sup>, curve a: saturated with oxygen, curve b: saturated with nitrogen.</p> Full article ">Figure 8
<p>Linear scanning voltammetry (LSV) curves for the Pt-Bi (Bi<sub>2</sub>O<sub>3</sub>)/GNs (PVP) (<b>A</b>), 30% PtRu/C-JM (<b>B</b>), Pt/GNs (PVP) (<b>C</b>), Pt-Bi (Bi<sub>2</sub>O<sub>3</sub>)/GNs (<b>D</b>) in an O<sub>2</sub> saturated 1.0 M NaOH solution at different rotation rates.</p> Full article ">Figure 9
<p>Cyclic voltammetry in 1.0 M CH<sub>3</sub>OH + 1.0 M NaOH: Pt-Bi (Bi<sub>2</sub>O<sub>3</sub>)/GNs (PVP) (<b>A</b>), 30% PtRu/C-JM (<b>B</b>), Pt/GNs (PVP) (<b>C</b>), Pt-Bi (Bi<sub>2</sub>O<sub>3</sub>)/GNs (<b>D</b>); curve a: with simulator sunlight irradiation, curve b: without irradiation.</p> Full article ">Figure 10
<p>Cyclic voltammetry in 1.0 M NaOH saturated with oxygen: Pt-Bi (Bi<sub>2</sub>O<sub>3</sub>)/GNs (PVP) (<b>A</b>), 30% PtRu/C-JM (<b>B</b>), Pt/GNs (PVP) (<b>C</b>) and Pt-Bi (Bi<sub>2</sub>O<sub>3</sub>)/GNs (<b>D</b>), curve a: under simulated sunlight irradiation, curve b: without irradiation.</p> Full article ">Figure 11
<p>The electro-photo catalytic mechanism for the methanol oxidation reaction (MOR) and the oxygen reduction reaction (ORR).</p> Full article ">
17 pages, 1448 KiB  
Perspective
Oxidative Cleavage of Fatty Acid Derivatives for Monomer Synthesis
by Ana Soutelo-Maria, Jean-Luc Dubois, Jean-Luc Couturier and Giancarlo Cravotto
Catalysts 2018, 8(10), 464; https://doi.org/10.3390/catal8100464 - 17 Oct 2018
Cited by 30 | Viewed by 10917
Abstract
Oxidative cleavage of fatty acids and fatty acid derivatives is a practical way to obtain bifunctional molecules that can be used in polycondensation reactions. Diacids, hydroxyacids, and amino acids can then be used to produce polyesters or polyamides and also a large range [...] Read more.
Oxidative cleavage of fatty acids and fatty acid derivatives is a practical way to obtain bifunctional molecules that can be used in polycondensation reactions. Diacids, hydroxyacids, and amino acids can then be used to produce polyesters or polyamides and also a large range of other products, such as lubricants and plasticizers. Ozonolysis has long been the sole industrial process for oxidative cleavage, but recently, routes using hydrogen peroxide as a clean oxidant have regained interest. Hydrogen peroxide is easier to use, but the kinetics of the catalyzed reactions are still slow. Although several catalytic systems have been described in the literature, tungsten-based catalysts are still the preferred choices. Different catalysts can trigger different mechanisms, such as a radical mechanism instead of a catalytic reaction. In addition, some side products and co-products often disregarded in the literature, such as shorted cleavage products, indicate the presence of side reactions that affect the quality of the final products. The oxidative cleavages in continuous and batch processes have significant differences, which are discussed with an illustration of our understanding of the process used by Matrica S.p.A. Full article
(This article belongs to the Special Issue New Developments in Heterogeneous Partial and Total Oxidation Catalysis)
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<p>Chemical structure of (<b>a</b>) polyamide 11 (Rilsan) [<a href="#B3-catalysts-08-00464" class="html-bibr">3</a>] and (<b>b</b>) polyamide 10.10 (Rilsan T) [<a href="#B5-catalysts-08-00464" class="html-bibr">5</a>].</p> Full article ">Figure 2
<p>Oxidative cleavage intermediate steps with hydrogen peroxide and tungstic acid.</p> Full article ">Figure 3
<p>Complex formed between the anionic tungsten peroxo specie and the diol intermediate.</p> Full article ">Figure 4
<p>Proposed mechanism adapted from the study by Venturello et al. [<a href="#B67-catalysts-08-00464" class="html-bibr">67</a>].</p> Full article ">Figure 5
<p>Epoxidation of the C=C bond mechanism.</p> Full article ">Figure 6
<p>Oxidative cleavage of linoleic acid.</p> Full article ">Figure 7
<p>Representation of our interpretation of the continuous oxidative cleavage process described in <span class="html-italic">Novamont’s</span> patents [<a href="#B60-catalysts-08-00464" class="html-bibr">60</a>,<a href="#B64-catalysts-08-00464" class="html-bibr">64</a>,<a href="#B77-catalysts-08-00464" class="html-bibr">77</a>].</p> Full article ">
13 pages, 1757 KiB  
Article
Interface-Controlled Pd Nanodot-Au Nanoparticle Colloids for Efficient Visible-Light-Induced Photocatalytic Suzuki-Miyaura Coupling Reaction
by Eunmi Kang, Hyeon Ho Shin and Dong-Kwon Lim
Catalysts 2018, 8(10), 463; https://doi.org/10.3390/catal8100463 - 17 Oct 2018
Cited by 13 | Viewed by 4418
Abstract
Plasmonic nanostructures can be employed for performing photocatalytic reactions with visible-light illumination involving two different possible mechanisms, namely, the near-field enhancement and/or direct hot-electron transfer to the conduction band of an active catalyst. In this study, we demonstrate the significant contribution of a [...] Read more.
Plasmonic nanostructures can be employed for performing photocatalytic reactions with visible-light illumination involving two different possible mechanisms, namely, the near-field enhancement and/or direct hot-electron transfer to the conduction band of an active catalyst. In this study, we demonstrate the significant contribution of a graphene interface layer present between plasmonic nanoparticles and active catalysts (Pd nanodots) in enhancing the photocatalytic efficiency of Pd nanodots through an accelerated electron transfer process. The well-defined Pd-nanodot-modified gold nanoparticles with or without a graphene interface layer were prepared using a wet-chemical synthetic method. The role of the graphene interface was investigated by performing wavelength-dependent reduction studies using potassium hexacyanoferrate (III) in the presence of Pd-nanodot-modified cysteamine-modified AuNPs (Pd-cys-AuNPs), Pd-nanodot-modified graphene oxide (GO)-coated AuNPs (Pd-GO-AuNPs), and Pd-nanodot-modified reduced GO (rGO)-coated AuNPs (Pd-rGO-AuNPs). The fastest rate for the reduction of Fe3+ to Fe2+ was obtained with Pd-rGO-AuNPs because of the fast electron transfer achieved in the presence of the reduced graphene oxide layer. The highest catalytic activity for the visible-light induced C-C coupling reaction was obtained with Pd-rGO-AuNPs, indicating the role of the graphene interface layer. These results indicate that the design and use of engineered interfaces are of importance to achieve enhanced catalytic activity with plasmonic hybrid nanomaterials. Full article
(This article belongs to the Special Issue Catalysts for Suzuki–Miyaura Coupling Reaction)
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<p>(<b>a</b>) Schematic representation of the Suzuki-Miyaura cross-coupling reaction of Pd-nanodot-decorated AuNPs with graphene interface, (<b>b</b>) synthetic scheme of Pd-cys-AuNPs, Pd-GO-AuNPs, and Pd-rGO-AuNPs.</p> Full article ">Figure 2
<p>UV-visible spectra (inset: photograph of the solutions of as prepared catalysts), Raman spectra, and TEM images of ① Pd-cys-AuNPs, ② Pd-GO-AuNPs, and ③ Pd-rGO-AuNPs. (<b>a</b>) UV-Visible Spectra and (<b>b</b>) Raman spectra of Pd-cys-AuNPs (red line), Pd-GO-AuNPs (green line), and Pd-rGO-AuNPs (blue line). (<b>c</b>–<b>e</b>) TEM images and energy dispersive X-ray mapping of (<b>c</b>) Pd-cys-AuNPs, (<b>d</b>) Pd-GO-AuNPs, and (<b>e</b>) Pd-rGO-AuNPs.</p> Full article ">Figure 3
<p>Kinetic study of Fe<sup>3+</sup> reduction with Pd-modified AuNPs performed with two different light sources (Xe-lamp and NIR (808 nm)) and three different wavelengths. (<b>a</b>) UV-Visible spectra of potassium hexacyanoferrate (III) (orange line, 500 μM) in the presence of Pd-cys-AuNPs, Pd-GO-AuNPs, and Pd-rGO-AuNPs (Abs 1.0 or 1.2 at 540 nm). (<b>b</b>,<b>c</b>) Time-dependent transformation of Fe<sup>3+</sup> to Fe<sup>2+</sup> monitored at 420 nm by illuminating with (b) Xe-lamp or with (c) NIR laser (808 nm). (<b>d</b>) Wavelength-dependent transformation of Fe<sup>3+</sup> to Fe<sup>2+</sup> in the presence of Pd-rGO-AuNPs (purple square, 450 nm; green circle, 500 nm; red triangle, 630 nm).</p> Full article ">Figure 4
<p>Comparison of the catalytic performances of Pd-cys-AuNPs, Pd-GO-AuNPs, and Pd-rGO-AuNPs for the Suzuki C-C coupling reaction at various conditions. (<b>a</b>) Xe-lamp illumination without controlling the reaction temperature, (<b>b</b>) Xe-lamp illumination by maintaining the reaction temperature of 25 °C.</p> Full article ">Figure 5
<p>Catalytic performances of Pd-rGO-AuNPs for the Suzuki C-C coupling reaction at various conditions. (<b>a</b>) UV-Vis spectrum of Pd-rGO-AuNPs for excitation wavelength-dependent Suzuki-coupling reaction, (<b>b</b>) Wavelength-dependent Suzuki-coupling reaction (blue square, 460 nm; green circle, 575 nm; red triangle, 630 nm), (<b>c</b>) Mechanism study in the presence of Pd-rGO-AuNPs with TEA, KBrO<sub>3</sub> under Xe-lamp, 25 °C, (<b>d</b>) Suzuki-Miyaura cross-coupling reaction under sunlight illumination (black line: Changes of light intensity with time (mW/cm<sup>2</sup>)).</p> Full article ">
15 pages, 4784 KiB  
Article
Atmospheric Air Plasma Treated SnS Films: An Efficient Electrocatalyst for HER
by Po-Chia Huang, Sanjaya Brahma, Po-Yen Liu, Jow-Lay Huang, Sheng-Chang Wang, Shao-Chieh Weng and Muhammad Omar Shaikh
Catalysts 2018, 8(10), 462; https://doi.org/10.3390/catal8100462 - 17 Oct 2018
Cited by 7 | Viewed by 3712
Abstract
Here, we demonstrate the enhanced water-splitting performance (I = 10 mA/cm2, Tafel slope = 60 mV/dec, onset potential = −80 mV) of atmospheric air plasma treated (AAPT) SnS thin films by the hydrogen evolution reaction (HER). The as prepared SnS films [...] Read more.
Here, we demonstrate the enhanced water-splitting performance (I = 10 mA/cm2, Tafel slope = 60 mV/dec, onset potential = −80 mV) of atmospheric air plasma treated (AAPT) SnS thin films by the hydrogen evolution reaction (HER). The as prepared SnS films were subjected to Atmospheric Air Plasma Treatment (AAPT) which leads to formation of additional phases of Sn and SnO2 at plasma powers of 150 W and 250 W, respectively. The AAPT treatment at 150 W leads to the evaporation of the S atoms as SO2 generates a number of S-vacancies and Sn active edge sites over the surface of the SnS thin film. S-vacancies also create Sn active edge sites, surface p-type pinning that tunes the suitable band positions, and a hydrophilic surface which is beneficial for hydrogen adsorption/desorption. At high plasma power (250 W), the surface of the SnS films becomes oxidized and degrades the HER performance. These results demonstrate that AAPT (150 W) is capable of improving the HER performance of SnS thin films and our results indicate that SnS thin films can work as efficient electrocatalysts for HER. Full article
(This article belongs to the Special Issue Platinum-Free Electrocatalysts)
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<p>X-ray diffraction (XRD) patterns of the SnS thin film (<b>a</b>) without, and with (<b>b</b>) 150 W, and (<b>c</b>) 250 W atmospheric air plasma treatment.</p> Full article ">Figure 2
<p>SEM images of the SnS thin films (<b>a</b>) without, and with (<b>b</b>) 150 W, and (<b>c</b>) 250 W atmospheric air plasma treatment.</p> Full article ">Figure 3
<p>(<b>a</b>) TEM images of the SnS nanocrystals consisting of orthorhombic phase hexagonal SnS nanosheets and cubic phase SnS nanoparticles. (<b>b</b>) HRTEM image showing the crystal planes of cubic phase SnS. (<b>c</b>) TEM image showing the top view of the SnS nanosheet (Inset: selected area electron diffraction (SAED) patterns indexed to orthorhombic-SnS). (<b>d</b>) HRTEM top-view image of the SnS nanosheet showing crystal planes of orthorhombic SnS. (<b>e</b>) TEM image showing the cross-sectional view of the SnS nanosheet. (<b>f</b>) HRTEM image of SnS nanosheet cross-section showing stacked crystal planes of orthorhombic SnS.</p> Full article ">Figure 4
<p>TEM bright field image and high-resolution image of SnS nanocrystals under (<b>a</b>,<b>b</b>) 150 W and (<b>c</b>,<b>d</b>) 250 W atmospheric air plasma treatment, respectively. The samples were prepared by stripping from different watt-treated SnS thin films.</p> Full article ">Figure 5
<p>Water contact angle (WCA) images of SnS thin films surface (<b>a</b>) without, and with (<b>b</b>) 150 W and (<b>c</b>) 250 W atmospheric air plasma treatment (AAPT).</p> Full article ">Figure 6
<p>Electron spectroscopy for chemical analysis (ESCA) core level spectra analysis of the (<b>a</b>) Sn3d<sub>5/2</sub> peak, (<b>b</b>) S 2p<sub>1/2</sub> peak and (<b>c</b>) O1s peak for the untreated SnS thin films and with 150 W and 250 W AAPT.</p> Full article ">Figure 7
<p>(<b>a</b>) Valence band maxima (VBM) fitting; and, (<b>b</b>) O atomic percentage and S/Sn atomic ratio plot for the SnS thin films before and after AAPT.</p> Full article ">Figure 8
<p>(<b>a</b>) Linear sweep voltammetry curves at the scan rate of 5 mV/s for the SnS thin films without treatment, and with 150 W and 250 W AAPT. (<b>b</b>) The corresponding Tafel plots for the SnS thin films without treatment, and with 150 W and 250 W AAPT.</p> Full article ">Figure 9
<p>Schematic energy band diagrams of SnS (<b>a</b>) without, and with (<b>b</b>) 150 W and (<b>c</b>) 250 W AAPT.</p> Full article ">Figure 10
<p>Schematic diagram of the atmospheric air plasma treatment for the SnS thin films used in this work.</p> Full article ">
15 pages, 3234 KiB  
Article
Oxygen Reduction Reaction Electrocatalysis in Alkaline Electrolyte on Glassy-Carbon-Supported Nanostructured Pr6O11 Thin-Films
by Rakesh K. Sharma, Verónica Müller, Marian Chatenet and Elisabeth Djurado
Catalysts 2018, 8(10), 461; https://doi.org/10.3390/catal8100461 - 17 Oct 2018
Cited by 7 | Viewed by 4117
Abstract
In this work, hierarchical nanostructured Pr6O11 thin-films of brain-like morphology were successfully prepared by electrostatic spray deposition (ESD) on glassy-carbon substrates. These surfaces were used as working electrodes in the rotating disk electrode (RDE) setup and characterized in alkaline electrolyte [...] Read more.
In this work, hierarchical nanostructured Pr6O11 thin-films of brain-like morphology were successfully prepared by electrostatic spray deposition (ESD) on glassy-carbon substrates. These surfaces were used as working electrodes in the rotating disk electrode (RDE) setup and characterized in alkaline electrolyte (0.1 M NaOH at 25 ± 2 °C) for the hydrogen evolution reaction (HER), the oxygen evolution reaction (OER), and the oxygen reduction reaction (ORR) for their potential application in alkaline electrolyzers or in alkaline fuel cells. The electrochemical performances of these electrodes were investigated as a function of their crystallized state (amorphous versus crystalline). Although none of the materials display spectacular HER and OER activity, the results show interesting performances of the crystallized sample towards the ORR with regards to this class of non-Pt group metal (non-PGM) electrocatalysts, the activity being, however, still far from a benchmark Pt/C electrocatalyst. Full article
(This article belongs to the Special Issue Catalysts for Polymer Membrane Fuel Cells)
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<p>SEM micrographs of Pr<sub>6</sub>O<sub>11</sub>/GC ESD films obtained with a EtOH:BC (1:2) solution with a concentration of 0.02 M at <span class="html-italic">T</span><sub>s</sub> = 230 °C for a nozzle to substrate distance of <span class="html-italic">d</span><sub>ns</sub> = 20 mm, a flow rate of <span class="html-italic">Q</span> = 1.5 mL h<sup>−1</sup>, and a deposition time of <span class="html-italic">t</span> = 3 h. (<b>A</b>–<b>C</b>) surface view and (<b>D</b>) cross-section of amorphous (as-prepared) Pr<sub>6</sub>O<sub>11</sub>/GC; (<b>E</b>–<b>G</b>) surface view; (<b>H</b>) cross-section of crystalline (sintered at <span class="html-italic">T</span> = 550 °C for 2 h in air) Pr<sub>6</sub>O<sub>11</sub>/GC.</p> Full article ">Figure 2
<p>Typical X-EDS spectra of the Pr<sub>6</sub>O<sub>11</sub>/GC film deposited on the glassy-carbon substrate: (<b>A</b>) amorphous; (<b>B</b>) crystalline, sintered for 2 h in air at <span class="html-italic">T</span> = 550 °C.</p> Full article ">Figure 3
<p>X-ray diffraction patterns of Pr<sub>6</sub>O<sub>11</sub> ESD film deposited on vitreous carbon substrate: (<b>A</b>) as-deposited (amorphous); (<b>B</b>) sintered for 2 h in air at <span class="html-italic">T</span> = 550 °C (crystalline).</p> Full article ">Figure 4
<p>TEM, HRTEM, and SAED pattern of powder scratched from the brain-like type Pr<sub>6</sub>O<sub>11</sub> ESD film sintered in air for 2 h at <span class="html-italic">T</span> = 550 °C (crystalline Pr<sub>6</sub>O<sub>11</sub>): (<b>A</b>) TEM, (<b>B</b>) HRTEM, (<b>C</b>) SAED pattern.</p> Full article ">Figure 5
<p>Voltamperogram in 0.1 M NaOH-supporting electrolyte of amorphous Pr<sub>6</sub>O<sub>11</sub> (Ar atmosphere), with incursions in the HER and OER regions of Pr<sub>6</sub>O<sub>11</sub>; <span class="html-italic">T</span> = 25 ± 2 °C, <span class="html-italic">v</span> = 20 mV s<sup>−1</sup>.</p> Full article ">Figure 6
<p>Oxygen reduction reaction voltamperogram in 0.1 M NaOH electrolyte of amorphous Pr<sub>6</sub>O<sub>11</sub> (O<sub>2</sub> atmosphere); <span class="html-italic">T</span> = 25 ± 2 °C, <span class="html-italic">v</span> = 5 mV s<sup>−1</sup>.</p> Full article ">Figure 7
<p>Oxygen reduction reaction voltamperogram in 0.1 M NaOH + 0.01 M NaBH<sub>4</sub> electrolyte of amorphous Pr<sub>6</sub>O<sub>11</sub> (O<sub>2</sub> atmosphere); <span class="html-italic">T</span> = 25 ± 2 °C, <span class="html-italic">v</span> = 5 mV s<sup>−1</sup>.</p> Full article ">Figure 8
<p>Voltamperogram in 0.1 M NaOH-supporting electrolyte of crystalline Pr<sub>6</sub>O<sub>11</sub> annealed at <span class="html-italic">T</span> = 550 °C (Ar atmosphere), with incursions in the HER and OER regions; <span class="html-italic">T</span> = 25 ± 2 °C, <span class="html-italic">v</span> = 20 mV s<sup>−1</sup>.</p> Full article ">Figure 9
<p>(<b>A</b>) Oxygen reduction reaction voltamperogram in 0.1 M NaOH electrolyte of crystalline Pr<sub>6</sub>O<sub>11</sub> annealed at <span class="html-italic">T</span> = 550 °C (O<sub>2</sub> atmosphere), (<b>B</b>) comparison with amorphous Pr<sub>6</sub>O<sub>11</sub> (not-annealed, data set in dashed lines), and (<b>C</b>) comparison of amorphous and crystalline Pr<sub>6</sub>O<sub>11</sub> with a state-of-the-art Pt/C electrocatalyst at Ω = 900 rpm; <span class="html-italic">T</span> = 25 ± 2 °C, <span class="html-italic">v</span> = 5 mV s<sup>−1</sup>.</p> Full article ">Figure 10
<p>Oxygen reduction reaction voltamperogram in 0.1 M NaOH + 0.01 M NaBH<sub>4</sub> electrolyte of crystalline Pr<sub>6</sub>O<sub>11</sub> annealed at <span class="html-italic">T</span> = 550 °C (O<sub>2</sub> atmosphere); <span class="html-italic">T</span> = 25 ± 2 °C, <span class="html-italic">v</span> = 5 mV s<sup>−1</sup>.</p> Full article ">
20 pages, 2202 KiB  
Review
Combined Cross-Linked Enzyme Aggregates as Biocatalysts
by Meng-Qiu Xu, Shuang-Shuang Wang, Li-Na Li, Jian Gao and Ye-Wang Zhang
Catalysts 2018, 8(10), 460; https://doi.org/10.3390/catal8100460 - 17 Oct 2018
Cited by 71 | Viewed by 7625
Abstract
Enzymes are efficient biocatalysts providing an important tool in many industrial biocatalytic processes. Currently, the immobilized enzymes prepared by the cross-linked enzyme aggregates (CLEAs) have drawn much attention due to their simple preparation and high catalytic efficiency. Combined cross-linked enzyme aggregates (combi-CLEAs) including [...] Read more.
Enzymes are efficient biocatalysts providing an important tool in many industrial biocatalytic processes. Currently, the immobilized enzymes prepared by the cross-linked enzyme aggregates (CLEAs) have drawn much attention due to their simple preparation and high catalytic efficiency. Combined cross-linked enzyme aggregates (combi-CLEAs) including multiple enzymes have significant advantages for practical applications. In this review, the conditions or factors for the preparation of combi-CLEAs such as the proportion of enzymes, the type of cross-linker, and coupling temperature were discussed based on the reaction mechanism. The recent applications of combi-CLEAs were also reviewed. Full article
(This article belongs to the Special Issue Recent Advances in Biocatalysis and Metabolic Engineering for Biomanufacturing)
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<p>The reaction of polymeric glutaraldehyde with lysine residues protein in alkaline conditions (<b>A</b>) and acidic conditions (<b>B</b>).</p> Full article ">Figure 2
<p>The one-step bioconversion of sucrose to trehalose with combi-CLEAs of AS, MTS, and MTH.</p> Full article ">Figure 3
<p>The Biocatalytic (<b>A</b>) and Chemical (<b>B</b>) synthesis of mandelic acid from benzaldehyde.</p> Full article ">Figure 4
<p>The combi-CLEAs of amylase, glucoamylase, and pullulanase for hydrolyzing of starch.</p> Full article ">Figure 5
<p>The combi-CLEAs of L-arabinose and β--glucosidase involved in aroma release in wine.</p> Full article ">Figure 6
<p>The combi-CLEAs of PepX and PepN.</p> Full article ">Figure 7
<p>The combi-CLEAs of eductases and glucose dehydrogenase for cofactor regeneration system.</p> Full article ">Figure 8
<p>The combi-CLEAs of glucose oxidase and horseradish peroxidase.</p> Full article ">Figure 9
<p>Combi-CLEAs of ADH and GDH for cofactor regeneration system.</p> Full article ">Figure 10
<p>The combi-CLEAs of ketoreductase and <sub>D</sub>-glucose dehydrogenase for the cofactor regeneration system.</p> Full article ">
4 pages, 155 KiB  
Editorial
Selective Catalytic Reduction of NOx
by Oliver Kröcher
Catalysts 2018, 8(10), 459; https://doi.org/10.3390/catal8100459 - 17 Oct 2018
Cited by 21 | Viewed by 3567
Abstract
n/a Full article
(This article belongs to the Special Issue Selective Catalytic Reduction of NOx)
64 pages, 21630 KiB  
Review
Recent Progress in the Transition Metal Catalyzed Synthesis of Indoles
by Raffaella Mancuso and Renato Dalpozzo
Catalysts 2018, 8(10), 458; https://doi.org/10.3390/catal8100458 - 16 Oct 2018
Cited by 56 | Viewed by 8410
Abstract
Indole is the most frequently found heterocyclic core structures in pharmaceuticals, natural products, agrochemicals, dyes and fragrances. For about 150 years, chemists were absorbed in finding new and easier synthetic strategies to build this nucleus. Many books and reviews have been written, but [...] Read more.
Indole is the most frequently found heterocyclic core structures in pharmaceuticals, natural products, agrochemicals, dyes and fragrances. For about 150 years, chemists were absorbed in finding new and easier synthetic strategies to build this nucleus. Many books and reviews have been written, but the number of new syntheses that appear in the literature, make necessary continuous updates. This reviews aims to give a comprehensive overview on indole synthesis catalyzed by transition metals appeared in the literature in the years 2016 and 2017. Full article
(This article belongs to the Section Catalytic Materials)
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Graphical abstract
Full article ">Scheme 1
<p>Accepted mechanism for C–H activation reaction with traceless directing group.</p> Full article ">Scheme 2
<p>Cobalt(III)-catalyzed indolization with nitrones.</p> Full article ">Scheme 3
<p>Cobalt(III)-catalyzed indolization from ureas and alkynes.</p> Full article ">Scheme 4
<p>Cobalt(III) catalyzed indolization with <span class="html-italic">N</span>-nitrosoanilines.</p> Full article ">Scheme 5
<p>Cobalt(III) catalyzed indolization with Boc-arylhydrazines.</p> Full article ">Scheme 6
<p>Cobalt(III) catalyzed indolization with <span class="html-italic">N</span>-alkyl-<span class="html-italic">N</span>-arylhydrazines.</p> Full article ">Scheme 7
<p>Cobalt catalyzed cross-dehydrogenative coupling.</p> Full article ">Scheme 8
<p>Synthesis of 3-imine indole derivatives.</p> Full article ">Scheme 9
<p>Synthesis of indoles from α-aminonitriles and 2-halobenzyl halides.</p> Full article ">Scheme 10
<p>Synthesis of 3-cyanoindoles.</p> Full article ">Scheme 11
<p>Reaction of <span class="html-italic">ortho</span>-iodoanilines and β-ketoesters or β-diketones.</p> Full article ">Scheme 12
<p>Synthesis of indole and imidazo[1,2-<span class="html-italic">a</span>]pyridine by cross-dehydrogenative coupling.</p> Full article ">Scheme 13
<p>Oxidative cyclization of <span class="html-italic">N</span>-arylenamines.</p> Full article ">Scheme 14
<p>Synthesis of 3-arylsulfonyl-2-trifluoromethyl-1<span class="html-italic">H</span>-indoles.</p> Full article ">Scheme 15
<p>Cu-catalyzed intramolecular C–H amination.</p> Full article ">Scheme 16
<p>Cyclization of 2-alkenylanilines.</p> Full article ">Scheme 17
<p>Synthesis of indoloindoles.</p> Full article ">Scheme 18
<p>1,2-Disubstituted indoles from 2-iodobenzamide derivatives.</p> Full article ">Scheme 19
<p>3-Arylindoles from nitroalkanes.</p> Full article ">Scheme 20
<p>Copper-catalyzed aerobic [<a href="#B1-catalysts-08-00458" class="html-bibr">1</a>,<a href="#B3-catalysts-08-00458" class="html-bibr">3</a>]-nitrogen shift.</p> Full article ">Scheme 21
<p>2-Arylindoles by gold nanoparticles catalysis.</p> Full article ">Scheme 22
<p>Indoles by photoredox/gold catalysis.</p> Full article ">Scheme 23
<p>Hydroamination reaction catalyzed by NHC–gold complexes.</p> Full article ">Scheme 24
<p>Gold catalysts for the cascade reaction of 2-(phenylethynyl)aniline and cyclohexanone.</p> Full article ">Scheme 25
<p>Indoles by gold-catalyzed cyclization of 2-alkynylarylazides.</p> Full article ">Scheme 26
<p>Indoles from 2-alkynylnitroarenes with diboron as reductant.</p> Full article ">Scheme 27
<p>7-Acylindoles from annulation of anthranils with alkynes.</p> Full article ">Scheme 28
<p>Pd-NHC catalyzed α-arylation of imines.</p> Full article ">Scheme 29
<p>Three-component synthesis of 3-[2-(phenylsulfonyl)ethyl]indoles.</p> Full article ">Scheme 30
<p>Unexpected formation of indoles.</p> Full article ">Scheme 31
<p>Synthesis of 1,2,3-trisubstituted indoles from α-diketones and <span class="html-italic">N</span>-substituted anilines.</p> Full article ">Scheme 32
<p>Palladium-catalyzed tandem addition/cyclization in aqueous medium.</p> Full article ">Scheme 33
<p>Some derivatives prepared with the reaction described in <a href="#catalysts-08-00458-t001" class="html-table">Table 1</a> entry 2 [<a href="#B50-catalysts-08-00458" class="html-bibr">50</a>].</p> Full article ">Scheme 34
<p>One-pot synthesis of indoles from electron-withdrawing substituted alkynes and anilines.</p> Full article ">Scheme 35
<p>Palladium-catalyzed regioselective synthesis of 3-arylindoles.</p> Full article ">Scheme 36
<p>Surmised mechanism for the reaction described in <a href="#catalysts-08-00458-t002" class="html-table">Table 2</a> entry 1 [<a href="#B56-catalysts-08-00458" class="html-bibr">56</a>].</p> Full article ">Scheme 37
<p>Synthesis of indoles from in situ generated phosphinimine.</p> Full article ">Scheme 38
<p>Continuous flow synthesis of indoles by reduction of <span class="html-italic">o</span>-vinylnitroarenes.</p> Full article ">Scheme 39
<p>Double palladium catalyzed reductive cyclization.</p> Full article ">Scheme 40
<p>Mechanism of the cyclization of aniline-tethered alkylidenecyclopropanes.</p> Full article ">Scheme 41
<p>Remote C–H alkylation and C–C bond cleavage.</p> Full article ">Scheme 42
<p>2-(Trifluoromethyl)indoles via Pd(0)-catalysis.</p> Full article ">Scheme 43
<p>Palladium-catalyzed intramolecular arylative carboxylation of allenes.</p> Full article ">Scheme 44
<p>Reaction between <span class="html-italic">N</span>-tosylhydrazones and bromonitrobenzenes.</p> Full article ">Scheme 45
<p>Pd(0)-catalyzed cascade formation of indoles from furans.</p> Full article ">Scheme 46
<p>Cyclization of 2-alknylanilines in the presence of isocyanates.</p> Full article ">Scheme 47
<p>Rhodium(III)-catalyzed for the synthesis of 3-amidoindoles.</p> Full article ">Scheme 48
<p>Mechanochemical synthesis of indoles.</p> Full article ">Scheme 49
<p>Rhodium-catalyzed annulation of tertiary aniline <span class="html-italic">N</span>-oxides.</p> Full article ">Scheme 50
<p>Synthesis of indoles with amino traceless directing group.</p> Full article ">Scheme 51
<p>Synthesis of <span class="html-italic">N</span>-substituted indole derivatives from phenidones.</p> Full article ">Scheme 52
<p>Indole derivatives from pyrimidyl-substituted anilines and diazo compounds.</p> Full article ">Scheme 53
<p>Oxindole derivatives from pyridyl-substituted anilines and diazo compounds.</p> Full article ">Scheme 54
<p>1-Aminoindoles via Rh(III)-catalyzed three-component annulation.</p> Full article ">Scheme 55
<p>Synthesis of unprotected 1-aminoindoles.</p> Full article ">Scheme 56
<p>Indole derivatives from <span class="html-italic">N</span>-arylureas and α-diazo-β-keto esters.</p> Full article ">Scheme 57
<p>Rh(III)-catalyzed indolization of imidamides and diazo ketoesters.</p> Full article ">Scheme 58
<p>Rh(III)-catalyzed synthesis of indoles from nitrones and diazo-acetoacetate.</p> Full article ">Scheme 59
<p>Rh(III)-catalyzed synthesis of indoles from <span class="html-italic">N</span>-nitrosoanilines and diazo ketoesters.</p> Full article ">Scheme 60
<p>Rh(III)-catalyzed reaction of azobenzenes with vinyl ketones or <span class="html-italic">N</span>,<span class="html-italic">N</span>-dimethyl acrylamides.</p> Full article ">Scheme 61
<p>Rh(II)-catalyzed synthesis of indoles from 2-tetrazoleanilines.</p> Full article ">Scheme 62
<p>Rh(I)-catalyzed annulation of pyrrole propargylic esters.</p> Full article ">Scheme 63
<p>Rh(I)/H<sub>8</sub>−BINAP catalyzed cycloisomerization of 2-(2-silylethynyl)anilines.</p> Full article ">Scheme 64
<p>Ruthenium-catalyzed cycloisomerization of 2-alkynylanilides.</p> Full article ">Scheme 65
<p>Ruthenium-catalyzed synthesis of indole from arylhydrazines.</p> Full article ">Scheme 66
<p>Ruthenium-catalyzed synthesis of indoles from imidamides and diazo ketoesters.</p> Full article ">Scheme 67
<p>Ruthenium-catalyzed dehydrative C−H coupling of arylamines with 1,2-diols.</p> Full article ">Scheme 68
<p>Ruthenium-catalyzed 1,6-aromatic enamide−silylalkyne cycloisomerization.</p> Full article ">Scheme 69
<p>Synthesis of 3-phosphinoylindoles.</p> Full article ">Scheme 70
<p>Synthesis of indolo[1,2-<span class="html-italic">c</span>]quinazolin-6(5<span class="html-italic">H</span>)-ones.</p> Full article ">Scheme 71
<p>Indole synthesis under visible light irradiation.</p> Full article ">Scheme 72
<p>Iridium(III)-catalyzed coupling of anilines with α-diazoesters.</p> Full article ">Scheme 73
<p>Iron catalyzed cyclization of styrylazides.</p> Full article ">Scheme 74
<p>Mn-catalyzed synthesis of indoles from aromatic amines and diazo compounds.</p> Full article ">Scheme 75
<p>Polystyrene-stabilized Pt nanoparticles catalyzed indole synthesis.</p> Full article ">Scheme 76
<p>Indole synthesis by platinum catalyzed annulation.</p> Full article ">
9 pages, 2329 KiB  
Article
Ultrasonic-Assisted Synthesis of 2D α-Fe2O3@g-C3N4 Composite with Excellent Visible Light Photocatalytic Activity
by Huoli Zhang, Changxin Zhu, Jianliang Cao, Qingjie Tang, Man Li, Peng Kang, Changliang Shi and Mingjie Ma
Catalysts 2018, 8(10), 457; https://doi.org/10.3390/catal8100457 - 16 Oct 2018
Cited by 30 | Viewed by 4859
Abstract
In this study, α-Fe2O3@g-C3N4 photocatalyst was synthesized using an ultrasonic assisted self-assembly preparation method. The α-Fe2O3@g-C3N4 photocatalyst had a stronger optical absorption in the visible light region than pure [...] Read more.
In this study, α-Fe2O3@g-C3N4 photocatalyst was synthesized using an ultrasonic assisted self-assembly preparation method. The α-Fe2O3@g-C3N4 photocatalyst had a stronger optical absorption in the visible light region than pure graphitic carbon nitride (g-C3N4). The Z-Scheme heterojunction between α-Fe2O3 and g-C3N4 significantly inhibited the recombination of electrons and holes. The photocatalytic performances of α-Fe2O3@g-C3N4 photocatalyst were excellent in degradation of Rhodamine B (RhB) under visible light irradiation. The results indicated that 5 wt.% α-Fe2O3/g-C3N4 had the optimal photocatalytic activity because two-dimension (2D) α-Fe2O3 nanosheets can be well-dispersed on the surface of g-C3N4 layers by ultrasonic assisted treatment. A possible photocatalytic mechanism is also discussed. Full article
(This article belongs to the Special Issue Semiconductor Catalysis)
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Figure 1
<p>XRD patterns of different samples.</p> Full article ">Figure 2
<p>SEM images of different samples: (<b>a</b>) 2D α-Fe<sub>2</sub>O<sub>3</sub>, (<b>b</b>) 2D g-C<sub>3</sub>N<sub>4</sub>, (<b>c</b>) 5 wt.% α-Fe<sub>2</sub>O<sub>3</sub>@g-C<sub>3</sub>N<sub>4</sub> photocatalyst and (<b>d</b>) EDS of 5 wt.% α-Fe<sub>2</sub>O<sub>3</sub>@g-C<sub>3</sub>N<sub>4</sub> photocatalyst.</p> Full article ">Figure 3
<p>(<b>a</b>) UV-vis diffuse reflectance spectra (UV–vis DRS) of different samples, (<b>b</b>) plots of the (ahν)<sup>1/2</sup> versus photon energy (hv) for g-C<sub>3</sub>N<sub>4</sub> and 5 wt.% α-Fe<sub>2</sub>O<sub>3</sub>@g-C<sub>3</sub>N<sub>4</sub> photocatalyst; plots of the (ahν)<sup>2</sup> versus photon energy (hv) for α-Fe<sub>2</sub>O<sub>3</sub>.</p> Full article ">Figure 4
<p>(<b>A</b>) Photocatalytic performances of different samples, (<b>B</b>) kinetic curves of the as-prepared samples, (<b>C</b>) rate constant k of the samples: (a) P-25, (b) α-Fe<sub>2</sub>O<sub>3</sub>, (c) g-C<sub>3</sub>N<sub>4</sub>, (d) 5 wt.% α-Fe<sub>2</sub>O<sub>3</sub>@g-C<sub>3</sub>N<sub>4</sub> photocatalyst, (e) 10 wt.% α-Fe<sub>2</sub>O<sub>3</sub>@g-C<sub>3</sub>N<sub>4</sub> photocatalyst, (f) 20 wt.% α-Fe<sub>2</sub>O<sub>3</sub>@g-C<sub>3</sub>N<sub>4</sub> photocatalyst and (<b>D</b>) recycling runs of 5 wt.% α-Fe<sub>2</sub>O<sub>3</sub>@g-C<sub>3</sub>N<sub>4</sub> photocatalyst.</p> Full article ">Figure 5
<p>SEM images of (<b>a</b>) 10 wt.% α-Fe<sub>2</sub>O<sub>3</sub>@g-C<sub>3</sub>N<sub>4</sub> photocatalyst and (<b>b</b>) 20 wt.% α-Fe<sub>2</sub>O<sub>3</sub>@g-C<sub>3</sub>N<sub>4</sub> photocatalyst.</p> Full article ">Figure 6
<p>Schematic illustration of the charge carrier separation and transfer on α-Fe<sub>2</sub>O<sub>3</sub>@g-C<sub>3</sub>N<sub>4</sub> photocatalyst.</p> Full article ">Figure 7
<p>Schematic illustration for the 2D α-Fe<sub>2</sub>O<sub>3</sub>@g-C<sub>3</sub>N<sub>4</sub> photocatalyst synthesis.</p> Full article ">
13 pages, 3395 KiB  
Article
Oligomerization of Butene Mixture over NiO/Mesoporous Aluminosilicate Catalyst
by Donggun Lee, Hyeona Kim, Young-Kwon Park and Jong-Ki Jeon
Catalysts 2018, 8(10), 456; https://doi.org/10.3390/catal8100456 - 16 Oct 2018
Cited by 5 | Viewed by 3814
Abstract
This study is aimed at preparing C8–C16 alkene through oligomerization of a butene mixture using nickel oxide supported on mesoporous aluminosilicate. Mesoporous aluminosilicate with an ordered structure was successfully synthesized from HZSM-5 zeolite by combining a top-down and a bottom-up [...] Read more.
This study is aimed at preparing C8–C16 alkene through oligomerization of a butene mixture using nickel oxide supported on mesoporous aluminosilicate. Mesoporous aluminosilicate with an ordered structure was successfully synthesized from HZSM-5 zeolite by combining a top-down and a bottom-up method. MMZZSM-5 catalyst showed much higher butene conversion and C8–C16 yield in the butene oligomerization reaction than those with HZSM-5. This is attributed to the pore geometry of MMZZSM-5, which is more beneficial for internal diffusion of reactants, reaction intermediates, and products. The ordered channel-like mesopores were maintained after the nickel-loading on MMZZSM-5. The yield for C8–C16 hydrocarbons over NiO/MMZZSM-5 was higher than that of MMZZSM-5 catalyst, which seemed to be due to higher acid strength from a higher ratio of Lewis acid to Brønsted acid. The present study reveals that a mesoporous NiO/MMZZSM-5 catalyst with a large amount of Lewis acid sites is one of the potential catalysts for efficient generation of aviation fuel through the butene oligomerization. Full article
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Figure 1
<p>N<sub>2</sub> adsorption–desorption isotherms of various catalysts.</p> Full article ">Figure 2
<p>Pore size distribution of various catalysts.</p> Full article ">Figure 3
<p>Low-angle XRD patterns of MMZ<sub>ZSM-5</sub> and NiO/MMZ<sub>ZSM-5.</sub></p> Full article ">Figure 4
<p>High angle XRD patterns of HZSM-5, MMZ<sub>ZSM-5</sub>, and NiO/MMZ<sub>ZSM-5.</sub></p> Full article ">Figure 5
<p>TEM image of (<b>a</b>) MMZ<sub>ZSM-5</sub> and (<b>b</b>) NiO/MMZ<sub>ZSM-5</sub>.</p> Full article ">Figure 6
<p>NH<sub>3</sub>-TPD profiles of various catalysts.</p> Full article ">Figure 7
<p>Pyridine-FTIR spectra over NiO/MMZ<sub>ZSM-5</sub> under a vacuum (a: room temperature, b: 100 °C, c: 150 °C, d: 200 °C, e: 250 °C, and f: 300 °C).</p> Full article ">Figure 8
<p>Pyridine-FTIR spectra at 200 °C under a vacuum over various catalysts.</p> Full article ">Figure 9
<p>Conversion of butene through the oligomerization of a butene mixture over various catalysts (Reaction condition: pressure 1.5 MPa, temperature 350 °C, WHSV 10 h<sup>−1</sup>).</p> Full article ">Figure 10
<p>Conversion of butene, selectivity to C<sub>8</sub>–C<sub>16</sub> fraction, and yield of C<sub>8</sub>–C<sub>16</sub> fraction over various catalysts (reaction condition: pressure 1.5 MPa, temperature 350 °C, WHSV 10 h<sup>−1</sup>, and T-O-S 6 h).</p> Full article ">Figure 11
<p>Product distribution of the C<sub>8</sub>–C<sub>16</sub> range through the oligomerization of a butene mixture over various catalysts (reaction condition: pressure 1.5 MPa, temperature 350 °C, WHSV 10 h<sup>−1</sup>, T-O-S 6 h).</p> Full article ">Figure 12
<p>Conversion of butene, selectivity to C<sub>8</sub>–C<sub>16</sub> fraction, and yield of C<sub>8</sub>–C<sub>16</sub> fraction over NiO/MMZ<sub>ZSM-5</sub> catalyst for TOS up to 30 h (reaction condition: pressure 1.5 MPa, temperature 350 °C, and WHSV 10 h<sup>−1</sup>).</p> Full article ">Figure 13
<p>Degradation temperature measurement of the spent NiO/MMZ<sub>ZSM-5</sub> catalyst.</p> Full article ">
10 pages, 1806 KiB  
Article
Photoelectrocatalytic vs. Photocatalytic Degradation of Organic Water Born Pollutants
by Ioannis Papagiannis, Georgia Koutsikou, Zacharias Frontistis, Ioannis Konstantinou, George Avgouropoulos, Dionissios Mantzavinos and Panagiotis Lianos
Catalysts 2018, 8(10), 455; https://doi.org/10.3390/catal8100455 - 15 Oct 2018
Cited by 24 | Viewed by 4033
Abstract
The azo dye Basic Blue 41 was subjected to photocatalytic and photoelectrocatalytic degradation using nanopararticulate titania films deposited on either glass slides or Fluorine doped Tin Oxide (FTO) transparent electrodes. The degradation was carried out by irradiating titania films with weak ultraviolet (UVA) [...] Read more.
The azo dye Basic Blue 41 was subjected to photocatalytic and photoelectrocatalytic degradation using nanopararticulate titania films deposited on either glass slides or Fluorine doped Tin Oxide (FTO) transparent electrodes. The degradation was carried out by irradiating titania films with weak ultraviolet (UVA) radiation. The degradation was faster when using FTO as a titania support even without bias and was further accelerated under forward electric bias. This result was explained by enhanced electron-hole separation even in the case of the unbiased titania/FTO combination. This system for organic material photocatalytic degradation was also successfully applied to the degradation of the anti-inflammatory drug piroxicam, which demonstrated a well distinguished degradation behavior in going from a plain glass support to unbiased and biased FTO. The degradation pathway of piroxicam has been additionally studied using liquid chromatography-accurate mass spectrometry analysis. Full article
(This article belongs to the Special Issue New Trends in the Photocatalytic Removal of Organic Dyes)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Chemical structure of Basic Blue 41 (BB41) and Piroxicam.</p> Full article ">Figure 2
<p>Variation of the absorption spectrum of 2 × 10<sup>−5</sup> Μ (~10 ppm) aqueous solution of BB41 by photocatalytic degradation in the presence of a titania film supported on Fluorine doped Tin Oxide (FTO) glass under black-light radiation.</p> Full article ">Figure 3
<p>Degradation curves for BB41 for various types of photocatalyst supports and operation conditions: (<b>1</b>) plain glass slide; (<b>2</b>) FTO; (<b>3</b>) FTO plus supporting electrolyte without electric bias; (<b>4</b>) +1 V bias vs. Ag/AgCl; and (<b>5</b>) −1 V bias vs Ag/AgCl.</p> Full article ">Figure 4
<p>Variation of the absorption spectrum of 40 ppm aqueous solution of piroxicam by photocatalytic degradation in the presence of a titania film supported on FTO glass under black-light radiation.</p> Full article ">Figure 5
<p>Degradation curves for piroxicam for various types of photocatalyst supports and operation conditions: (<b>1</b>) plain glass slide; (<b>2</b>) FTO plus supporting electrolyte without electric bias; and (<b>3</b>) +1 V bias.</p> Full article ">Figure 6
<p>Photocatalytic degradation pathway of piroxicam.</p> Full article ">
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