The effect of oxidative and reductive delignification processes on the hydrolysis of pine sawdust... more The effect of oxidative and reductive delignification processes on the hydrolysis of pine sawdust at mild conditions (200-1000 ppm of HCl and 140-220 °C) is studied in this work. Dimers and reduced sugars are the main products obtained with the fresh sawdust (>82%), reaching a maximum liquid phase yield of 17% after 8 h, at the strongest conditions. This conversion increases up to almost 40% with the pretreated sawdust, obtaining selectivities higher than 87% of levulinic acid and a well-defined distribution of the relevant platform molecules (sugars, HMF, furfural, levulinic acid) as function of the severity of the reaction, decreasing the humins formation and being possible to define different conditions to maximize each yield. These conclusions were corroborated by the kinetic analysis, obtaining a clear decrease in the energy activation for all the individual steps involved in this process.
Abstract Benzofuran (BZF) is produced during the biomass and waste pyrolysis, playing a key role ... more Abstract Benzofuran (BZF) is produced during the biomass and waste pyrolysis, playing a key role in the catalytic deactivation in the processing of the resulting fractions, as well as in catalytic pyrolysis reactions. The transformation of this chemical over a typical pyrolysis catalyst (ZSM-5) is studied in this article. When this compound is processed alone, it presents a very high reactivity. At low temperature, the formation of large amount of coke precursors leads to a fast catalyst deactivation. As temperature increases, the weight of cracking reactions (yielding benzenes or naphtalenes) becomes more important, increasing the catalyst’s stability, although new polyaromatic carbon species are detected. A new strategy to minimize the deactivation caused by this compound, consisting of co-feeding propylene, is proposed. The presence of an alkene leads to the formation of alkylated derivatives of Diels-Alder condensation products, hindering their oligomerization capacity and minimizing the formation of polyaromatic coke deposits. Different temperatures and alkene/BZF ratios were tested, concluding that increasing the alkene concentration and the reaction temperature monotonously increase the catalyst’s stability in presence of BZF.
Different possible applications of ion exchange resins in the framework of biorefinery catalytic ... more Different possible applications of ion exchange resins in the framework of biorefinery catalytic applications are discussed in this article. Three case studies were selected for this approach, connected to three main routes for biomass upgrading: syngas upgrading to high-value chemicals, biomass hydrolysate upgrading, and direct upgrading of oily fraction. The tailored acidic properties of these materials, as well as their stability in the presence of water, have made them promising catalysts for applications such as obtaining biodiesel from activated sludge wastes in batch reactors and obtaining polyoxymethylene methyl ether from syngas (via formaldehyde and methylal, and working in a continuous fixed bed reactor). However, the acidity of these materials may still be too low for acid-catalyzed aldol condensation reactions in the aqueous phase.
Abstract After testing different mixed oxides, a very promising catalyst to obtain γ-valerolacton... more Abstract After testing different mixed oxides, a very promising catalyst to obtain γ-valerolactone from levulinic acid and formic acid is proposed in this work: a ZnAl hydrotalcite-derived material. Optimum conditions (T = 140 °C, FA/LA = 5/1, aqueous phase stirred batch reactor) excel results previously proposed in the literature, combining high activity (>87%) and selectivity (90% GVL yield) with remarkable stability, the reaction being performed at mild conditions and using a highly available and cheap catalyst. A detailed mechanistic with its kinetic study was accomplished for this optimum catalyst, considering that formic acid decomposition is the limiting step following a second–order kinetic, and the FA dehydration to AL is a pseudo-first–order reversible step. Angelica-lactone is identified as the main by–product and the precursor for the formation of light organic deposits, the main responsible for the slight deactivation observed during the experiments in absence of reactivation procedure.
The potential of biomass as a source of chemical products is presented in this work. The concept ... more The potential of biomass as a source of chemical products is presented in this work. The concept of biorefinery is analyzed, considering that the integration of biofuels and chemicals is necessary to guarantee the technical and economic viability. Two main platform molecules are evaluated: the ethanol and the acetone, analyzing the most promising processes to obtain a high variety of products with high value in chemical, pharmaceutical and food industries. Despite most of these processes were firstly proposed more than 50 years ago , the need of petroleum replacement as raw material for most of the chemicals has motivated new researches to focus on some parameters that limit their implementation in an industrial scale. The optimization of heterogeneous catalysts is one of the key parameters in these studies.
The development of a hydrogen-based economy is the perfect nexus between the need of discontinuin... more The development of a hydrogen-based economy is the perfect nexus between the need of discontinuing the use of fossil fuels (trying to mitigate climate change), the development of a system based on renewable energy (with the use of hydrogen allowing us to buffer the discontinuities produced in this generation) and the achievement of a local-based robust energy supply system [...]
Abstract Benzofuran (BZF) is produced during the biomass and waste pyrolysis, playing a key role ... more Abstract Benzofuran (BZF) is produced during the biomass and waste pyrolysis, playing a key role in the catalytic deactivation in the processing of the resulting fractions, as well as in catalytic pyrolysis reactions. The transformation of this chemical over a typical pyrolysis catalyst (ZSM-5) is studied in this article. When this compound is processed alone, it presents a very high reactivity. At low temperature, the formation of large amount of coke precursors leads to a fast catalyst deactivation. As temperature increases, the weight of cracking reactions (yielding benzenes or naphtalenes) becomes more important, increasing the catalyst’s stability, although new polyaromatic carbon species are detected. A new strategy to minimize the deactivation caused by this compound, consisting of co-feeding propylene, is proposed. The presence of an alkene leads to the formation of alkylated derivatives of Diels-Alder condensation products, hindering their oligomerization capacity and minimizing the formation of polyaromatic coke deposits. Different temperatures and alkene/BZF ratios were tested, concluding that increasing the alkene concentration and the reaction temperature monotonously increase the catalyst’s stability in presence of BZF.
Journal of Environmental Chemical Engineering, 2021
Abstract The hydrogenation of furfural-cyclopentanone (C15) condensation adduct is studied in thi... more Abstract The hydrogenation of furfural-cyclopentanone (C15) condensation adduct is studied in this work. Three different metals (Pt, Pd, Ni) supported on two materials (Al2O3 and Nb2O5) were compared, highlighting the good results obtained with Pd/Al2O3. The kinetic analysis of the reaction results suggests a parallel route in which the hydrogenation of cyclic unsaturation can occur simultaneously with the hydrogenation of aliphatic C˭C. A key role of metal dispersion is discarded, concluding that this reaction is selective to the presence of Pd nanoparticles with a synergetic effect with the Al2O3 support, mainly due to the presence of strong acidic sites. Different organic solvents have been tested, including protic, polar and apolar ones. The best results are obtained with hexane and butanol, combining the absence of competitive adsorption and reactant solvation. At optimum conditions, more than 75% of yield to the fully hydrogenated molecules were obtained in less than two hours, obtaining a mixture with good properties as a fuel additive.
Abstract The production of biodiesel from waste activated sludge by the in-situ transesterificati... more Abstract The production of biodiesel from waste activated sludge by the in-situ transesterification of its lipid content is studied in this work, comparing both basic and acidic catalytic routes. The acid mechanism is chosen as the optimum one, considering that the high percentage of free fatty acids strongly limits the yields obtained by the basic route, due to the saponification competence. Different pre-treatments are proposed (sonication, microwaves, sieving) to enhance the extraction rate, identified as the limiting step of the process. Sludge drying requirements are also analysed, concluding that water contents below 20% (weight base) does not lead to significant decreases in the transesterification activity. The acidic reaction is also chosen once the quality of the final mixture as alternative biofuel is analysed. Almost all the biodiesel properties (higher heat value, iodine number, kinematic viscosity, density, and long-chain saturated factor and cetane number) are in the optimum ranges proposed by the international normative, concluding that pretreatments do not damage the final product. Optimum results were obtained applying microwaves, with a final yield of 46.7% of FAMEs, which is a clear improvement on the previous literature of biodiesel obtaining from sewage sludge.
Surface chemistry and pore topology affect mesitylene selectivity in acid-catalysed acetone conde... more Surface chemistry and pore topology affect mesitylene selectivity in acid-catalysed acetone condensation. Hydrogen improves both catalyst stability and condensation selectivity.
The effect of oxidative and reductive delignification processes on the hydrolysis of pine sawdust... more The effect of oxidative and reductive delignification processes on the hydrolysis of pine sawdust at mild conditions (200-1000 ppm of HCl and 140-220 °C) is studied in this work. Dimers and reduced sugars are the main products obtained with the fresh sawdust (>82%), reaching a maximum liquid phase yield of 17% after 8 h, at the strongest conditions. This conversion increases up to almost 40% with the pretreated sawdust, obtaining selectivities higher than 87% of levulinic acid and a well-defined distribution of the relevant platform molecules (sugars, HMF, furfural, levulinic acid) as function of the severity of the reaction, decreasing the humins formation and being possible to define different conditions to maximize each yield. These conclusions were corroborated by the kinetic analysis, obtaining a clear decrease in the energy activation for all the individual steps involved in this process.
Abstract Benzofuran (BZF) is produced during the biomass and waste pyrolysis, playing a key role ... more Abstract Benzofuran (BZF) is produced during the biomass and waste pyrolysis, playing a key role in the catalytic deactivation in the processing of the resulting fractions, as well as in catalytic pyrolysis reactions. The transformation of this chemical over a typical pyrolysis catalyst (ZSM-5) is studied in this article. When this compound is processed alone, it presents a very high reactivity. At low temperature, the formation of large amount of coke precursors leads to a fast catalyst deactivation. As temperature increases, the weight of cracking reactions (yielding benzenes or naphtalenes) becomes more important, increasing the catalyst’s stability, although new polyaromatic carbon species are detected. A new strategy to minimize the deactivation caused by this compound, consisting of co-feeding propylene, is proposed. The presence of an alkene leads to the formation of alkylated derivatives of Diels-Alder condensation products, hindering their oligomerization capacity and minimizing the formation of polyaromatic coke deposits. Different temperatures and alkene/BZF ratios were tested, concluding that increasing the alkene concentration and the reaction temperature monotonously increase the catalyst’s stability in presence of BZF.
Different possible applications of ion exchange resins in the framework of biorefinery catalytic ... more Different possible applications of ion exchange resins in the framework of biorefinery catalytic applications are discussed in this article. Three case studies were selected for this approach, connected to three main routes for biomass upgrading: syngas upgrading to high-value chemicals, biomass hydrolysate upgrading, and direct upgrading of oily fraction. The tailored acidic properties of these materials, as well as their stability in the presence of water, have made them promising catalysts for applications such as obtaining biodiesel from activated sludge wastes in batch reactors and obtaining polyoxymethylene methyl ether from syngas (via formaldehyde and methylal, and working in a continuous fixed bed reactor). However, the acidity of these materials may still be too low for acid-catalyzed aldol condensation reactions in the aqueous phase.
Abstract After testing different mixed oxides, a very promising catalyst to obtain γ-valerolacton... more Abstract After testing different mixed oxides, a very promising catalyst to obtain γ-valerolactone from levulinic acid and formic acid is proposed in this work: a ZnAl hydrotalcite-derived material. Optimum conditions (T = 140 °C, FA/LA = 5/1, aqueous phase stirred batch reactor) excel results previously proposed in the literature, combining high activity (>87%) and selectivity (90% GVL yield) with remarkable stability, the reaction being performed at mild conditions and using a highly available and cheap catalyst. A detailed mechanistic with its kinetic study was accomplished for this optimum catalyst, considering that formic acid decomposition is the limiting step following a second–order kinetic, and the FA dehydration to AL is a pseudo-first–order reversible step. Angelica-lactone is identified as the main by–product and the precursor for the formation of light organic deposits, the main responsible for the slight deactivation observed during the experiments in absence of reactivation procedure.
The potential of biomass as a source of chemical products is presented in this work. The concept ... more The potential of biomass as a source of chemical products is presented in this work. The concept of biorefinery is analyzed, considering that the integration of biofuels and chemicals is necessary to guarantee the technical and economic viability. Two main platform molecules are evaluated: the ethanol and the acetone, analyzing the most promising processes to obtain a high variety of products with high value in chemical, pharmaceutical and food industries. Despite most of these processes were firstly proposed more than 50 years ago , the need of petroleum replacement as raw material for most of the chemicals has motivated new researches to focus on some parameters that limit their implementation in an industrial scale. The optimization of heterogeneous catalysts is one of the key parameters in these studies.
The development of a hydrogen-based economy is the perfect nexus between the need of discontinuin... more The development of a hydrogen-based economy is the perfect nexus between the need of discontinuing the use of fossil fuels (trying to mitigate climate change), the development of a system based on renewable energy (with the use of hydrogen allowing us to buffer the discontinuities produced in this generation) and the achievement of a local-based robust energy supply system [...]
Abstract Benzofuran (BZF) is produced during the biomass and waste pyrolysis, playing a key role ... more Abstract Benzofuran (BZF) is produced during the biomass and waste pyrolysis, playing a key role in the catalytic deactivation in the processing of the resulting fractions, as well as in catalytic pyrolysis reactions. The transformation of this chemical over a typical pyrolysis catalyst (ZSM-5) is studied in this article. When this compound is processed alone, it presents a very high reactivity. At low temperature, the formation of large amount of coke precursors leads to a fast catalyst deactivation. As temperature increases, the weight of cracking reactions (yielding benzenes or naphtalenes) becomes more important, increasing the catalyst’s stability, although new polyaromatic carbon species are detected. A new strategy to minimize the deactivation caused by this compound, consisting of co-feeding propylene, is proposed. The presence of an alkene leads to the formation of alkylated derivatives of Diels-Alder condensation products, hindering their oligomerization capacity and minimizing the formation of polyaromatic coke deposits. Different temperatures and alkene/BZF ratios were tested, concluding that increasing the alkene concentration and the reaction temperature monotonously increase the catalyst’s stability in presence of BZF.
Journal of Environmental Chemical Engineering, 2021
Abstract The hydrogenation of furfural-cyclopentanone (C15) condensation adduct is studied in thi... more Abstract The hydrogenation of furfural-cyclopentanone (C15) condensation adduct is studied in this work. Three different metals (Pt, Pd, Ni) supported on two materials (Al2O3 and Nb2O5) were compared, highlighting the good results obtained with Pd/Al2O3. The kinetic analysis of the reaction results suggests a parallel route in which the hydrogenation of cyclic unsaturation can occur simultaneously with the hydrogenation of aliphatic C˭C. A key role of metal dispersion is discarded, concluding that this reaction is selective to the presence of Pd nanoparticles with a synergetic effect with the Al2O3 support, mainly due to the presence of strong acidic sites. Different organic solvents have been tested, including protic, polar and apolar ones. The best results are obtained with hexane and butanol, combining the absence of competitive adsorption and reactant solvation. At optimum conditions, more than 75% of yield to the fully hydrogenated molecules were obtained in less than two hours, obtaining a mixture with good properties as a fuel additive.
Abstract The production of biodiesel from waste activated sludge by the in-situ transesterificati... more Abstract The production of biodiesel from waste activated sludge by the in-situ transesterification of its lipid content is studied in this work, comparing both basic and acidic catalytic routes. The acid mechanism is chosen as the optimum one, considering that the high percentage of free fatty acids strongly limits the yields obtained by the basic route, due to the saponification competence. Different pre-treatments are proposed (sonication, microwaves, sieving) to enhance the extraction rate, identified as the limiting step of the process. Sludge drying requirements are also analysed, concluding that water contents below 20% (weight base) does not lead to significant decreases in the transesterification activity. The acidic reaction is also chosen once the quality of the final mixture as alternative biofuel is analysed. Almost all the biodiesel properties (higher heat value, iodine number, kinematic viscosity, density, and long-chain saturated factor and cetane number) are in the optimum ranges proposed by the international normative, concluding that pretreatments do not damage the final product. Optimum results were obtained applying microwaves, with a final yield of 46.7% of FAMEs, which is a clear improvement on the previous literature of biodiesel obtaining from sewage sludge.
Surface chemistry and pore topology affect mesitylene selectivity in acid-catalysed acetone conde... more Surface chemistry and pore topology affect mesitylene selectivity in acid-catalysed acetone condensation. Hydrogen improves both catalyst stability and condensation selectivity.
Uploads
Papers