CN115377471A - Method for producing 5-hydroxymethylfurfural through selective oxidative coupling of electric energy - Google Patents

Abstract

The invention discloses a method for producing 5-hydroxymethylfurfural selective oxidative coupling electric energy, which comprises the following steps: adding the anolyte containing 5-hydroxymethylfurfural in the anode liquid storage tank into an anode discharge chamber of the flow fuel cell, and circulating the anolyte back to the anode liquid storage tank; adding the catholyte containing redox electrolyte in the cathode liquid storage tank into a cathode discharge chamber of the flow fuel cell, and circulating the catholyte back to the cathode liquid storage tank; introducing air into the cathode discharge chamber and the cathode liquid storage tank; connecting the cathode and the anode of the liquid flow fuel cell with an external load to form a loop, and oxidizing the 5-hydroxymethylfurfural while generating electric energy. Therefore, the oxidation reaction of the 5-hydroxymethylfurfural is carried out in a fuel cell mode, 5-hydroxymethylfurfural oxidation products can be generated under mild conditions, the method can also regulate and control product distribution, specifically, HMFCA or FDCA can be generated, and in addition, the co-production of electric energy can be realized.

Description

5-Hydroxymethylfurfural Selective Oxidative Coupling Method for Electric Energy Production

technical field

The invention belongs to the field of biomass chemical industry, and in particular relates to a method for selective oxidation coupling of 5-hydroxymethylfurfural to produce electric energy.

Background technique

5-Hydroxymethylfurfural (HMF) is an important platform compound derived from biomass. It has a furan ring, an aldehyde group and a hydroxyl group. It is a chemical intermediate with active chemical properties and can be produced by oxidation, hydrogenation and other reactions. A variety of derivatives are promising fine chemical raw materials. HMF can be oxidized to obtain various products, for example, 5-hydroxymethyl-2-furancarboxylic acid (HMFCA), 2,5-furandicarbaldehyde (DFF), 5-formyl-2-furancarboxylic acid (FFCA) and 2 ,5-furandicarboxylic acid (FDCA). These derivatives derived from HMF are of great economic value. DFF can be used to synthesize new polymer materials, pharmaceutical intermediates, fluorescent agents and macrocyclic ligands, and can also be used as fungicides, fluorescent materials, etc., and has high application value in medical, industrial and fine chemical fields; FDCA is listed as one of the 12 high value-added compounds by the U.S. Department of Energy. Various important chemicals can be derived through different chemical transformations. FDCA can be used to produce 2,5-diol furandicarboxylate (PEF). PEF is used as Recyclable bio-based polyester can replace petroleum-based plastic polyethylene terephthalate (PET) to produce daily plastic products such as bottles and outer packaging; HMFCA can be used as a synthetic precursor for various polyester materials, It can also be used to synthesize non-benzene-based bio-based plasticizers, and it has been reported to have certain anti-tumor activity and can be used as an interleukin inhibitor; FFCA is an intermediate oxidized to FDCA, and is used in the field of medicine and furan polyester All have good application prospects. It can be seen that the oxidation products of HMF have a wide range of applications, so how to oxidize HMF efficiently and greenly has always been a key issue in the utilization of biomass resources.

At present, there have been many studies on the production of FDCA by oxidation of HMF. As early as 2001, foreign scholars reported that under the conditions of 125 ° C and 70 bar, the chemical oxidation of HMF was realized in a homogeneous system with air as the oxidant and Co(OAc) ₂ , Mn(OAc) ₂ and HBr as the catalyst. , obtain 60.9% FDCA yield (Walt Partenheimer, VladimirV.Grushin.Synthesis of 2,5-Diformylfuran and Furan-2,5-Dicarboxylic Acid by Catalytic Air-Oxidation of 5-Hydroxymethylfurfural.Unexpectedly SelectiveAerobic Oxidation of Benzyl Benzyl Alcohol Metal=Bromide Catalysts [J]. Advanced Synthesis & Catalysis, 2001, 343(1): 102-111.). People such as Hansen use copper salt and tetramethyl piperidine oxide (TEMPO) as catalyzer, t-BuOOH is oxidant, can obtain 45% FDCA yield (Hansen TS, Sádaba I, Garcia-Suarez EJ , Riisager A.Cu catalyzedoxidation of 5-hydroxymethylfurfural to 2,5-diformylfuran and 2,5-furandicarboxylic acid under benign reaction conditions[J].Applied CatalysisA:General,2013,456:44-50.). Origin Materials and Eastman Chemical Company jointly designed the commercial production FDCA route in 2017, and then applied for a patent, using Co/Mn/Br catalyst, at 132 ° C, 8.96 bar air, the FDCA yield of 89.4% was obtained (Janka M ,Lange D,Morrow M,Bowers B,Parker K,Shaikh A,Partin L,Jenkins J,Moody P,Shanks T,Sumner C,US Pat,20150011783A1,Eastman Chemical Company,Kingsport,TN(US),2015.) . Zhang Junhua and others applied for a patent in 2018, using potassium ferrate as an oxidant to directly catalyze the oxidation of HMF in an alkaline solution to prepare FDCA (Zhang Junhua, Xie Wenxing, Liang Qidi. The preparation method and application of catalysts for the catalytic oxidation of HMF to prepare FDCA , CN108043409A[P].2018.). However, there are still great challenges in the homogeneous catalytic system, not only the yield of FDCA products is very low, but also the separation of products and the recovery and regeneration of catalysts are difficult. In order to solve these two problems, heterogeneous catalysts have gradually become the main research direction at present.

In recent years, the preparation of FDCA by the oxidation of HMF in heterogeneous catalytic systems has been extensively studied. Heterogeneous catalysts are easy to recover and regenerate, and can even use cheap and readily available oxygen and air as oxidants, which is in line with the mainstream trend of green environmental protection. Due to the difficult activation of oxygen molecules, highly active noble metal catalysts, such as platinum, gold, palladium, rhodium, etc., are mainly used for the preparation of FDCA by oxidation of HMF. Air Rass et al. optimized the Bi-Pt/C catalyst to obtain a 98% FDCA yield at 100°C and 40 bar of air (Ait Rass H; Essayem N, Besson M. Selective aqueous phase oxidation of 5-hydroxymethylfurfural to 2 ,5-furandicarboxylic acid over Pt/C catalysts: influence of the base and effect of bismuth promotion[J]. Green Chemistry, 2013). In order to avoid the use of a large amount of alkali, some researchers coated MgO with carbon to prepare an alkaline carrier, and then loaded Pt by impregnation. Under the optimal conditions (110°C, 1MPa O ₂ ) and no alkali The rate can reach 97% (Base-freeaerobic oxidation of 5-hydroxymethylfurfural to 2,5-furandicarboxylic acid over a Pt/C–O–Mg catalyst[J].Green Chemistry,2015,18.). With the deepening of the research, the researchers found that the supported gold catalyst can exhibit excellent performance of HMF selective oxidation to prepare FDCA, and gold can be supported on TiO ₂ and CeO ₂ , and the yield of FDCA can reach more than 99% ( Casanova O, Iborra S, Corma A. Biomassinto chemicals: aerobic oxidation of 5-hydroxymethyl-2-furfural into 2,5-furandicarboxylic acid with gold nanoparticles catalysts[J].Chemsuschem,2010,2(12):1138-1144. ). Villa et al. found that the Au-Pd alloy catalyst has a synergistic effect, and the Au ₈ -Pd ₂ /AC catalyst obtained by optimizing the molar ratio of the two exhibits the highest catalytic activity. It can be reacted for 2 hours at 60°C and 30bar oxygen atmosphere. Obtain more than 99% FDCA yield (Villa A, Schiavoni M, Campisi S, et al.Pd-modified Au on Carbon as an Effective and Durable Catalyst for the Direct Oxidation of HMFto 2,5-Furandicarboxylic Acid[J].Chemsuschem, 2013, 6(4):609-612.). Avantium Company in the Netherlands has established a 40t annual HMF oxidative synthesis FDCA commercial device, which has been officially put into production in 2011. Under 100°C and 100bar air conditions, Pt/C was selected as the catalyst for HMF oxidative synthesis of FDCA. NOVAMONT also used Pt/C as a catalyst to synthesize FDCA by oxidation of HMF in a weak base sodium bicarbonate solution at 100°C and 5bar oxygen pressure, and obtained a yield of 95% of FDCA (Sajid M, Zhao X, Liu D. Production of 2,5-furandicarboxylic acid (FDCA) from 5-hydroxymethylfurfural (HMF): recent progress focusing on the chemical-catalytic routes [J]. Green Chemistry, 2018, 20(24): 5427-5453.). Although the research on the heterogeneous system has made outstanding progress and has been applied to commercial production, there are still some obvious deficiencies, the most notable being that almost all chemical oxidation synthesis methods for FDCA require harsh conditions of high temperature and high pressure. Conditions, and the used supported noble metal catalyst will gradually deactivate during the reaction process, resulting in a significant increase in the cost of the catalyst.

In general, using existing methods to oxidize 5-hydroxymethylfurfural requires relatively harsh reaction conditions, for example, the oxidation reaction needs to be carried out at high temperature and/or high pressure.

Therefore, it is necessary to improve the oxidation method of 5-hydroxymethylfurfural.

Contents of the invention

The present invention aims to improve at least one of the above technical problems at least to a certain extent.

In order to improve the above technical problems, the present invention provides a method for the selective oxidation coupling of 5-hydroxymethylfurfural to produce electric energy, the method comprising: adding the anolyte containing 5-hydroxymethylfurfural in the anode liquid storage tank to the liquid The anode discharge chamber of the flow fuel cell, and circulates back to the anode liquid storage tank; the catholyte containing the redox electrolyte in the cathode liquid storage tank is added to the cathode discharge chamber of the liquid flow fuel cell, and circulated back to the Cathode liquid storage tank; air is passed into the cathode discharge chamber and cathode liquid storage tank; wherein, the redox electrolyte includes vanadyl sulfate, ferric chloride, ferric nitrate, ferric citrate, phosphomolybdic acid, phosphomolybdenum vanadium At least one of acid, copper chloride, and potassium ferricyanide; the cathode and anode of the liquid flow fuel cell are connected to an external load to form a loop, and 5-hydroxymethylfurfural is oxidized while generating electric energy. Thus, the present invention carries out the oxidation reaction of 5-hydroxymethylfurfural in the form of a fuel cell, and can oxidize 5-hydroxymethylfurfural to generate corresponding products under mild conditions. Specifically, the method of the present invention can be adjusted by adjusting The electron transfer rate is used to conveniently regulate the product distribution, and the selective oxidation of 5-hydroxymethylfurfural can be made to generate 5-hydroxymethylfuroic acid (HMFCA) or 2,5-furandicarboxylic acid (FDCA). In addition, the method of the present invention can be used in While generating 5-hydroxymethylfurfural oxidation products, electric energy can also be obtained, and cogeneration of electric energy can be realized.

According to an embodiment of the present invention, the method further includes the step of assembling a liquid flow fuel cell, and the liquid flow fuel cell includes an anode liquid storage tank, an anode discharge chamber, an anode, an anode graphite bipolar plate, an ion exchange membrane, cathode graphite bipolar plate, cathode, cathode discharge chamber, external load and cathode liquid storage tank; the ion exchange membrane is located between the anode graphite bipolar plate and the cathode graphite bipolar plate; the anode graphite bipolar plate The plate is located on the side of the ion exchange membrane close to the anode discharge chamber, and the cathode graphite bipolar plate is located on the side of the ion exchange membrane close to the cathode discharge chamber; the anode graphite bipolar plate is provided with The first groove, the anode is arranged in the first groove, the anode is located on the side of the anode graphite bipolar plate close to the anode discharge chamber; the cathode graphite bipolar plate is provided with the first Two grooves, the cathode is arranged in the second groove, the cathode is located on the side of the cathode graphite bipolar plate close to the cathode discharge chamber; the anode liquid storage tank and the anode discharge chamber The cathode liquid storage tank is connected to the cathode discharge chamber through pipelines; the external load is arranged outside the liquid flow fuel cell, and the cathode and the anode are respectively connected to the external load . Thus, the 5-hydroxymethylfurfural in the anode discharge chamber can be selectively oxidized to generate the target product, and in the cathode discharge chamber, the oxygen molecules in the air undergo a reduction reaction to generate water, and at the same time, electricity can be generated.

According to an embodiment of the present invention, the anode is formed by loading an anode electron carrier on the first conductive substrate; the anode electron carrier is selected from silver oxide, copper oxide, nickel oxide, manganese dioxide, cobalt oxide, iron oxide , nickel phosphide, cobalt phosphide, nickel sulfide, cobalt sulfide, nickel boride, nickel nitride, tricobalt tetroxide, nickel hydroxide, cobalt hydroxide, nickel oxyhydroxide, cobalt oxyhydroxide; A conductive substrate is selected from one of copper foam, nickel foam, carbon felt, carbon paper, and carbon cloth; optionally, the loading amount of the anode electron carrier is 0.001-10 mg/cm ² . Thus, 5-hydroxymethylfurfural can undergo an oxidation reaction on the surface of the anode, and lose electrons to generate oxidation products, specifically, FDCA or HMFCA can be generated.

According to an embodiment of the present invention, the cathode is formed by loading a cathode electron carrier on a second conductive substrate; the cathode electron carrier is selected from metal platinum, metal ruthenium, carbon black, iron phthalocyanine, iron-nitrogen-carbon One of compound, cobalt-nitrogen-carbon compound, graphene; the second conductive substrate is selected from one of foamed copper, foamed nickel, carbon felt, carbon paper, carbon cloth; optionally, the The loading capacity of the cathode electron carrier is 0.001-10 mg/cm ² . As a result, oxygen in the air can undergo a reduction reaction on the surface of the cathode to generate water.

According to an embodiment of the present invention, the ion exchange membrane is selected from an anion exchange membrane or a cation exchange membrane.

According to an embodiment of the present invention, the method further includes: controlling the temperature of the anolyte in the anode storage tank and the temperature of the catholyte in the cathode storage tank to 20-100°C by means of a heating device . Thus, the method of the present invention can have a higher yield of 5-hydroxymethylfurfural oxidation products.

According to an embodiment of the present invention, the concentration of the 5-hydroxymethylfurfural is 0.001-5 mol/L. Thus, a higher concentration of 5-hydroxymethylfurfural oxidation products can be obtained.

According to an embodiment of the present invention, the anolyte contains a first supporting electrolyte; optionally, the first supporting electrolyte is an inorganic base; the concentration of the first supporting electrolyte is 0.01-6 mol/L. Thus, the conductivity of the solution can be increased, and the reaction rate can be accelerated.

According to an embodiment of the present invention, the concentration of the redox electrolyte is 0.001-4 mol/L; thus, the conductivity of the catholyte can be increased, and electrons can be further transferred to the oxygen in the air.

According to an embodiment of the present invention, the catholyte further includes a second supporting electrolyte; the second supporting electrolyte includes an inorganic acid or an inorganic base; the concentration of the second supporting electrolyte is 0.01-6 mol/L. Thereby, the electrical conductivity can be improved and the reaction rate can be increased.

According to an embodiment of the present invention, the resistance of the external load is 0-2000 ohms, and the output voltage of the liquid flow fuel cell is 0-1V; optionally, the 5-hydroxymethylfurfural is fed batch The form of the formula is added to the anode discharge chamber. Thus, good electricity generation and HMF oxidation effects can be obtained.

Description of drawings

Fig. 1 is a schematic structural view of a liquid flow fuel cell in an embodiment of the present invention.

Explanation of reference signs

1-anode liquid storage tank, 2-anode discharge chamber, 3-anode graphite bipolar plate, 4-ion exchange membrane, 5-cathode graphite bipolar plate, 6-cathode discharge chamber, 7-external load, 8-cathode storage liquid tank.

Detailed ways

Embodiments of the present application are described in detail below. The embodiments described below are exemplary and are only used for explaining the present application, and should not be construed as limiting the present application. If no specific technique or condition is indicated in the examples, it shall be carried out according to the technique or condition described in the literature in this field or according to the product specification. The reagents used were not indicated by the manufacturer, but were commercially available conventional products.

The invention provides a novel 5-hydroxymethylfurfural selective oxidation coupling method for producing electric energy, the method comprising: adding the anolyte containing 5-hydroxymethylfurfural in the anode liquid storage tank to the liquid flow The anode discharge chamber of the liquid flow fuel cell, and circulated back to the anode liquid storage tank; the catholyte containing the redox electrolyte in the cathode liquid storage tank is added to the cathode discharge chamber of the liquid flow fuel cell, and circulated back to the cathode Liquid storage tank; air is passed into the cathode discharge chamber and cathode liquid storage tank; wherein, the redox electrolyte includes vanadyl sulfate, ferric chloride, ferric nitrate, ferric citrate, phosphomolybdic acid, phosphomolybdovanadic acid At least one of copper chloride and potassium ferricyanide; the cathode and anode of the liquid flow fuel cell are connected to an external load to form a loop, and 5-hydroxymethylfurfural is oxidized while generating electric energy. Thus, in the present invention, the oxidation reaction of 5-hydroxymethylfurfural is carried out in the form of a fuel cell, and 5-hydroxymethylfurfural can be oxidized to generate corresponding products under mild conditions, specifically, 5-hydroxymethylfurfural can be generated Furoic acid (HMFCA) or 2,5-furandicarboxylic acid (FDCA), and at the same time realize the cogeneration of electric energy.

For ease of understanding, the principles of the present invention are briefly described below:

The oxidation reaction of 5-hydroxymethylfurfural (HMF) involves electron transfer, usually as long as the oxidation-reduction potential of the oxidant is higher than that of the HMF aldehyde group and hydroxyl group, the oxidation reaction can occur, that is, the reaction is thermodynamically feasible . However, the speed of the reaction depends on the kinetics of electron transfer. In order to increase the electron transfer rate, electron carriers can be used to construct an electron transfer chain to realize the step-by-step transfer of electrons, thereby increasing the kinetic rate of electron transfer. On the other hand, the directional movement of electrons can form a current, so the electron carrier-mediated oxidation reaction of HMF can be carried out in the form of a fuel cell, not only can realize the oxidation of HMF, but also can be regulated by adjusting the cathode electron carrier and external load Oxidation driving force and electron transfer rate to better control the oxidation process. In particular, the selective oxidation of HMF, such as the oxidation of hydroxyl groups, aldehyde groups or both, can be achieved by regulating the oxidation driving force by selecting the anode electron carrier and electrolyte, the cathode electron carrier and electrolyte, and the battery output voltage (by adjusting the external load). Oxidation to carboxyl groups, so as to obtain different oxidation products, can also regulate the oxidation rate of HMF through the above method, and realize the cogeneration of electric energy at the same time.

According to an embodiment of the present invention, the method further includes the step of assembling a liquid flow fuel cell. Referring to FIG. , ion exchange membrane 4, cathode graphite bipolar plate 5, cathode, cathode discharge chamber 6, external load 7 and cathode liquid storage tank 8; ion exchange membrane 4 is located between the anode graphite bipolar plate 3 and the cathode graphite bipolar plate 5 The anode graphite bipolar plate 3 is located at the side of the ion exchange membrane 4 close to the anode discharge chamber 2, and the cathode graphite bipolar plate 5 is located at the side of the ion exchange membrane 4 close to the cathode discharge chamber 6; the anode graphite bipolar plate 3 is provided with The first groove, the anode is arranged in the first groove, and the anode is positioned at the side of the anode graphite bipolar plate 3 close to the anode discharge chamber 2; the cathode graphite bipolar plate 5 is provided with a second groove, and the cathode is arranged at the second In the groove, the cathode is located on the side of the cathode graphite bipolar plate 5 close to the cathode discharge chamber 6; the anode liquid storage tank 1 is connected to the anode discharge chamber 2 through pipelines, and the cathode liquid storage tank 8 is connected to the cathode discharge chamber 6 through pipelines; The load 7 is arranged outside the liquid flow fuel cell, and the cathode and the anode are respectively connected to the external load 7 . Thus, the 5-hydroxymethylfurfural in the anode discharge chamber 2 can be selectively oxidized to generate the target product, and in the cathode discharge chamber 6, the oxygen molecules in the air undergo a reduction reaction to generate water and generate electricity at the same time.

According to an embodiment of the present invention, the anode is formed by loading the anode electron carrier on the first conductive substrate; thus, the anolyte containing 5-hydroxymethylfurfural can undergo an oxidation reaction on the surface of the anode, and lose electrons to generate oxidation product.

According to an embodiment of the present invention, the anode electron carrier is selected from silver oxide, copper oxide, nickel oxide, manganese dioxide, cobalt oxide, iron oxide, nickel phosphide, cobalt phosphide, nickel sulfide, cobalt sulfide, nickel boride , nickel nitride, cobalt tetroxide, nickel hydroxide, cobalt hydroxide, nickel oxyhydroxide, cobalt oxyhydroxide; thus, these compounds have a certain redox potential and can oxidize aldehyde groups and/or hydroxyl groups, Moreover, it is hardly soluble in water, which can avoid the problem of separation of the product and the catalyst. Specifically, in the anode discharge chamber of the liquid flow fuel cell, the high-valence anode electron carrier oxidizes HMF to generate HMFCA or FDCA, which itself is reduced and quickly transfers electrons to the oxidized cathode electron carrier in the cathode discharge chamber through an external circuit, Electrical energy is thus generated, at which point the anode electron carrier returns to its high valence state and continues to participate in the catalytic cycle.

According to an embodiment of the present invention, the first conductive substrate is selected from one of foamed copper, foamed nickel, carbon felt, carbon paper, and carbon cloth; thus, these substrate materials have good conductivity and porosity, It can provide abundant reaction sites for the loading and reaction of anode electron carriers. In addition, the choice of the material for the first conductive base also needs to take into account the acidity and alkalinity of the electrolyte. Using the above materials as the first conductive base can avoid dissolution and corrosion of the first conductive base.

According to some embodiments of the present invention, the loading capacity of the anode electron carrier is 0.001-10 mg/cm ² . Thus, a high electron transfer rate can be ensured, which is conducive to the generation of HMF oxidation products. If the load is too small, the electron transfer rate will be too slow and the current will be too low, which is not conducive to the oxidation of HMF and the production of electric energy; if the load is too large, the raw materials will be wasted, and there will be obvious shedding phenomenon after long-term operation.

In the process of loading the anode electron carrier on the first conductive substrate to form the anode, the present invention does not limit the loading method, such as coating, electrodeposition, in-situ growth, etc.

According to an embodiment of the present invention, the cathode is formed by carrying cathode electron carriers on the second conductive substrate; thus, electrons are transferred to the cathode through an external circuit and received by the cathode electron carriers. Both the cathode discharge chamber and the cathode liquid storage tank are continuously fed with air to oxidize and regenerate the cathode electron carrier and redox electrolyte. By screening the cathode electron carrier, the oxygen in the air can be reduced to water. By adjusting the size of the external load, the output voltage and power of the battery can be adjusted, thereby adjusting the transfer rate of electrons. Therefore, the method provided by the invention can selectively oxidize 5-hydroxymethylfurfural and simultaneously convert chemical energy into electrical energy.

According to some embodiments of the present invention, the cathode electron carrier is selected from at least one of metal platinum, metal ruthenium, carbon black, iron phthalocyanine, iron-nitrogen-carbon composite, cobalt-nitrogen-carbon composite, and graphene. species; these compounds can catalyze the four-electron reduction of oxygen to water by promoting the electron transfer kinetics through the valence state change of the active center. Specifically, the reduced cathode electron carrier in the cathode discharge chamber is oxidized by the redox electrolyte or the incoming air, and the electrolyte can also be further oxidized and regenerated in the cathode liquid storage tank by contacting the incoming air. Therefore, oxygen is the final electron acceptor, and the overall reaction is that oxygen oxidizes 5-hydroxymethylfurfural to generate corresponding products. To obtain faster reaction rates and higher battery power densities, preferred cathode electron carriers and redox electrolytes can perform four-electron reduction of oxygen to water.

According to some embodiments of the present invention, the second conductive substrate is selected from one of foamed copper, foamed nickel, carbon felt, carbon paper, and carbon cloth; these compounds have good conductivity and porosity, and the above compounds are used As the second conductive substrate, it can provide abundant reaction sites for the loading and reaction of catalysts. Moreover, the choice of conductive base material also needs to take into account the acidity and alkalinity of the electrolyte. Using the above-mentioned compound as the second conductive base can also avoid the dissolution and corrosion of the second conductive base.

According to some embodiments of the present invention, the loading capacity of the cathode electron carrier is 0.001-10 mg/cm ² . As a result, a high electron transfer rate can be ensured, which is beneficial to the generation of 5-hydroxymethylfurfural oxidation products. If the load is too small, the electron transfer rate will be too slow and the current will be too low, which is not conducive to the oxidation of 5-hydroxymethylfurfural and the production of electric energy; if the load is too large, the raw materials will be wasted, and there will be obvious dropout phenomenon.

In the process of loading the cathode electron carrier on the second conductive substrate to form the cathode, the present invention does not limit the loading method, such as coating, electrodeposition, in-situ growth, etc.

According to an embodiment of the present invention, the ion exchange membrane is selected from an anion exchange membrane or a cation exchange membrane. The cation exchange membrane includes but not limited to perfluorosulfonic acid membrane, and the anion exchange membrane includes but not limited to hydroxide ion exchange membrane.

The type and ion permeability of the ion exchange membrane significantly affect the internal resistance of the battery and thus the electrode reaction rate. The selection of the ion exchange membrane is also related to the catholyte and the anolyte used, and those skilled in the art can select the appropriate type of ion exchange membrane according to the requirements of use.

According to an embodiment of the present invention, the method further includes: controlling the temperature of the anolyte in the anode storage tank and the temperature of the catholyte in the cathode storage tank to 20-100°C by means of a heating device , such as 20°C, 25°C, 30°C, 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, preferably, the temperature of the anolyte and the temperature of the catholyte The temperature is controlled at 20-60°C. The electrode reaction is significantly affected by temperature, and increasing the temperature is beneficial to increase the reaction rate on the electrode surface, the diffusion rate of the active material, and then increase the electron transfer rate. However, 5-hydroxymethylfurfural will undergo various side reactions under alkaline conditions. For example, 5-hydroxymethylfurfural will undergo polycondensation and other reactions under the catalysis of alkali to generate humus and other substances, and the formation of humus when the temperature is higher The rate increased significantly. The inventors have found that when the temperature of the anolyte and the temperature of the catholyte are controlled within the above-mentioned temperature range, there is a higher electron transfer rate, which is conducive to the generation of 5-hydroxymethylfurfural oxidation products, and has less by-product. If the temperature of the anolyte and the temperature of the catholyte are too low, the electron transfer rate will be too low, which is unfavorable for the generation of 5-hydroxymethylfurfural oxidation products; if the temperature of the anolyte and the catholyte If the temperature is too high, too many by-products will be produced.

According to an embodiment of the present invention, the concentration of the 5-hydroxymethylfurfural is 0.001-5mol/L, for example, it can be 0.001mol/L, 0.01mol/L, 0.05mol/L, 0.1mol/L, 0.15mol/L L, 0.2mol/L, 1mol/L, 2mol/L, 3mol/L, 4mol/L, 5mol/L. Preferably, the concentration of 5-hydroxymethylfurfural is 0.001-2 mol/L. Thus, when the concentration of 5-hydroxymethylfurfural is within the above range, a higher concentration of oxidation products can be obtained while reducing the generation of by-products such as humus. If the concentration of 5-hydroxymethylfurfural is too low, the concentration of 5-hydroxymethylfurfural oxidation products will be too low; if the concentration of 5-hydroxymethylfurfural is too high, the condensation or degradation of 5-hydroxymethylfurfural will generate humus The degree of also increased, resulting in excessive by-products.

According to an embodiment of the present invention, the anolyte contains the first supporting electrolyte; thus, on the one hand, the conductivity of the solution can be improved, and on the other hand, a reaction environment can be provided for the oxidation of HMF to accelerate the reaction rate.

According to some embodiments of the present invention, the first supporting electrolyte is an inorganic base, and the inorganic base includes but not limited to potassium hydroxide.

According to some embodiments of the present invention, the concentration of the first supporting electrolyte is 0.01-6 mol/L, such as 0.01 mol/L, 0.1 mol/L, 0.5 mol/L, 1 mol/L, 2 mol/L, 3 mol /L, 4mol/L, 5mol/L, 6mol/L. Preferably, the concentration of the first supporting electrolyte is 0.01-4 mol/L. Thus, it can be ensured that the charge conduction rate of the electrolyte is high and the reaction rate is fast. If the concentration of the first supporting electrolyte is too low, the charge conduction rate of the electrolyte will be too low, resulting in a large internal resistance of the battery; if the concentration of the first supporting electrolyte is too high, the side reactions will be violent, resulting in the yield of the target product. In addition, too high alkali concentration will also increase the corrosion of the electrode and the aging of the ion exchange membrane, reducing the life of the electrode and ion exchange membrane.

According to an embodiment of the present invention, the concentration of the redox electrolyte is 0.001-4mol/L, such as 0.001mol/L, 0.37mol/L, 0.8mol/L, 1mol/L, 2mol/L, 3mol/L , 4mol/L; thus, on the one hand, these electrolytes can increase the conductivity of the catholyte, on the other hand, these electrolytes can also serve as redox electron carriers to promote the further transfer of electrons to oxygen in the air.

According to some embodiments of the present invention, the catholyte also includes a second supporting electrolyte; the second supporting electrolyte includes an inorganic acid or an inorganic base, and the inorganic acid includes but not limited to sulfuric acid; the second supporting electrolyte The concentration is 0.01-6 mol/L, such as 0.01 mol/L, 0.5 mol/L, 1 mol/L, 2 mol/L, 3 mol/L, 4 mol/L, 5 mol/L, 6 mol/L. Thus, the electrical conductivity can be improved, and an acidic or alkaline environment can be provided for the electrode reaction to increase the reaction rate.

According to an embodiment of the present invention, the resistance of the external load is 0-2000 ohms, and the output voltage of the liquid flow fuel cell is 0-1V; connecting the external load constitutes a loop to realize the conversion of electrons from 5-hydroxymethylfurfural The transfer of oxygen to the air is a prerequisite, otherwise the oxidation of 5-HMF cannot proceed. The size of the external load directly determines the speed of electron transfer rate. When the external load is 0 ohms, that is, the battery is discharged in the form of a short circuit, and the electron transfer rate is the fastest at this time. When the external load resistance increases, the ohmic resistance of electron transfer increases, and the oxidation rate of 5-hydroxymethylfurfural on the anode decreases. When the external load is infinite, that is, in an open circuit state, no current is generated, electrons cannot be transferred to oxygen, and the HMF oxidation reaction cannot proceed. According to some embodiments of the present invention, the preferred external load is 0-2000 ohms, so that the output voltage of the liquid flow fuel cell is 0-1V, and at this time, good electricity generation and HMF oxidation effects can be obtained.

According to some specific embodiments of the present invention, the output voltage can be stabilized by the electrochemical workstation, and the external load will be automatically adjusted to ensure that the output voltage of the battery is stable at a set value, such as 0.7V.

In some embodiments of the present invention, the 5-hydroxymethylfurfural is fed into the anode discharge chamber in a fed-batch manner. The feeding batch type is to add 5-hydroxymethylfurfural to the anode discharge chamber, and add it several times in batches, that is, add HMF to the anode discharge chamber after a period of time, and add the first supporting electrolyte. Thus, on the one hand, the rate of HMF generating humic substances can be reduced, on the other hand, the product concentration can be increased, and the cost of product separation and purification can be reduced.

The present invention will be described below with reference to specific embodiments. It should be noted that these embodiments are only illustrative and do not limit the present invention in any way.

Example 1

Screening of anode electron carriers to compare their discharge characteristics in flow fuel cells.

Nickel sulfide, cobalt sulfide, nickel phosphide, cobalt phosphide, nickel chloride, and silver oxide prepared by electrodeposition, high-temperature firing, and co-precipitation are uniformly loaded on the foamed nickel to prepare the anode. The anolyte contained 1 mol/L potassium hydroxide as the first supporting electrolyte and 0.1 mol/L HMF. Carbon felt loaded with carbon black was used as the cathode, 0.37mol/L vanadyl sulfate (pentavalent), namely (VO ₂ ) ₂ SO ₄ was used as the redox electrolyte of the catholyte, and 2mol/L sulfuric acid was used as the second Two supporting electrolytes. Use Nafion115 membrane as ion exchange membrane. After the battery device is assembled, the anolyte and catholyte are continuously pumped into the anode discharge chamber and the cathode discharge chamber respectively by using a circulation pump, and circulated back to the anode liquid storage tank and the cathode liquid storage tank respectively.

Discharge was carried out at room temperature. The discharge characteristics, open circuit voltage, maximum output power density and product yield of different anode electron carriers are shown in Table 1. It can be seen from Table 1 that when the target is to synthesize HMFCA, the nickel foam supported by silver oxide is used as the anode, which has the highest maximum power density and product yield. For the purpose of synthesizing FDCA, the battery with nickel sulfide-supported nickel foam as the anode has the highest maximum power density and FDCA yield, which is significantly better than other electrodes. It shows that nickel foam loaded with silver oxide and nickel sulfide is an excellent anode material for the selective oxidation of HMF, and silver oxide and nickel sulfide are excellent anode electron carriers for promoting the selective oxidation of HMF. Meanwhile, the selective oxidation of HMF can be achieved by selecting a suitable anode electron carrier.

Table 1 HMF oxidation and electricity generation characteristics of different anode electron carriers

Example 2

Different cathodic redox electrolytes were screened to compare the power generation characteristics and FDCA yield in flow fuel cells when HMF was oxidized to FDCA.

The experimental process is the same as in Example 1. The nickel foam loaded with nickel sulfide is used as the anode, and the carbon felt loaded with carbon black is used as the cathode, and vanadyl sulfate (pentavalent), ferric chloride, hydrogen peroxide, potassium permanganate, and potassium dichromate are used as the cathode oxidation. Reduce the electrolyte or oxidant and compare the discharge performance. The composition of the ferric chloride electrolyte solution is 0.8 mol/L ferric chloride, and contains 0.5 mol/L sulfuric acid as the second supporting electrolyte. The composition of vanadyl sulfate (pentavalent) is 0.37mol/L vanadyl sulfate (pentavalent), and contains 2mol/L sulfuric acid as the second supporting electrolyte. The composition of the hydrogen peroxide electrolyte solution is hydrogen peroxide with a mass fraction of 10%. The electrolyte solution of potassium permanganate and potassium dichromate is composed of 50mmol/L electrolyte concentration, and 2mol/L sulfuric acid is added as the second supporting electrolyte.

Table 2 shows the discharge characteristics, open circuit voltage, maximum power density and FDCA yield of different cathode redox electrolytes. As can be seen from Table 2, the battery with vanadyl sulfate (pentavalent) as the cathode redox electrolyte, although the power density is not the largest, it can reach the highest FDCA yield of 95%; hydrogen peroxide due to the large overpotential and slow The electron transfer rate, power density and FDCA yield are almost 0, and the effective oxidation of HMF cannot be realized; when potassium permanganate is selected as the cathode redox electrolyte, the maximum power density is as high as 77.6mW/ ^cm2 , but due to the long In the process of time discharge, the manganese dioxide solid produced by the reduction of potassium permanganate will block the flow channel, resulting in the decrease of the external circuit current, the deterioration of the catalytic effect, and the reduction of the product yield; although ferric chloride and potassium dichromate Both can realize the oxidation of HMF, but the yield and power density are relatively low. It can be said that the reaction system disclosed in the present invention can conveniently realize the control of product yield and electricity generation performance by screening the redox electrolyte of the cathode.

Table 2 Discharge characteristics and FDCA yield of batteries when using different cathode redox electrolytes or oxidants

Example 3

Different cathodic redox electrolytes were screened to compare the power generation performance and product yield of flow fuel cells when HMF was oxidized to HMFCA.

The experimental process is the same as in Example 1. The nickel foam loaded with silver oxide is used as the anode, and the carbon felt loaded with carbon black is used as the cathode, and vanadyl sulfate (pentavalent), ferric chloride, hydrogen peroxide, potassium permanganate, and potassium dichromate are used as the cathode redox Electrolyte or oxidant, compare discharge performance. The composition of the ferric chloride electrolyte solution is 0.8 mol/L ferric chloride, and contains 0.5 mol/L sulfuric acid as the second supporting electrolyte. The composition of vanadyl sulfate (pentavalent) is 0.37mol/L vanadyl sulfate (pentavalent), and contains 2mol/L sulfuric acid as the second supporting electrolyte. The composition of the hydrogen peroxide electrolyte solution is hydrogen peroxide with a mass fraction of 10%. The electrolyte solution of potassium permanganate and potassium dichromate is composed of an electrolyte concentration of 50mmol/L, and 2mol/L of sulfuric acid is added as a second supporting electrolyte.

Table 3 shows the discharge characteristics, open circuit voltage, maximum power density, and HMFCA yield of different cathode redox electrolytes or oxidants. It can be seen from Table 3 that several cathode redox electrolytes or oxidants can realize the oxidation of HMF to prepare HMFCA, but limited by the electron transfer rate between hydrogen peroxide and the electrode surface, hydrogen peroxide has the lowest power density when the cathode redox electrolyte is used. and HMFCA yield. However, other cathodic redox electrolytes or oxidants can achieve a HMFCA yield of more than 90%. When using vanadyl sulfate, the maximum power density of 172.0mW/cm ² and the HMFCA yield of 97% can be obtained; in addition, when ferric chloride, potassium permanganate and potassium dichromate are used as cathode redox electrolytes, the Higher power density can be obtained while selectively oxidizing HMF to generate HMFCA. The above results also further indicate that the oxidation of HMF can be conveniently regulated by combining the screening of anodic electron carriers and the selection of cathodic redox electrolytes.

Table 3 Discharge characteristics and HMFCA yield of batteries when using different cathode redox electrolytes and oxidants

Example 4

Effects of reaction conditions on the discharge characteristics and formation of FDCA of flow fuel cells using vanadyl sulfate (pentavalent) as the cathode redox electrolyte.

The experimental process is the same as in Example 1. Using nickel foam loaded with nickel sulfide as the anode, carbon felt loaded with carbon black as the cathode, 0.37mol/L vanadyl sulfate (pentavalent) as the cathode redox electrolyte, and 2mol/L sulfuric acid as the second supporting electrolyte, change the reaction Conditions, including HMF concentration, potassium hydroxide concentration, temperature, ion exchange membrane type, explore the maximum power density of the battery and the change of product yield. The impact of related parameters is shown in Table 4.

It can be seen from Table 4 that when the target is to synthesize FDCA by oxidation of HMF, the maximum power density of the battery increases gradually with the increase of HMF concentration, but the increase range gradually decreases. When the substrate concentration increases to a certain extent, the substrate diffusion no longer It is the limiting step of the reaction, and the power density depends on the kinetics of the electrode surface; increasing the concentration of potassium hydroxide can increase the maximum power density of the battery, but the FDCA yield increases first with the increase of the alkali concentration, and then decreases, at 1mol/L hydrogen Under the concentration of potassium oxide, it has the highest FDCA yield; increasing the battery temperature can also increase the maximum power density of the battery, but the FDCA yield continues to decrease with the increase of temperature. The long-term discharge test shows that the increase of potassium hydroxide concentration and battery temperature will increase Promote HMF self-polymerization to generate a large amount of humus, thereby reducing the yield of FDCA, and the promotion effect of temperature on humus is more significant than that of alkali concentration. The above results show that the reaction system of the present invention can conveniently regulate the battery power density and product yield by changing the reaction conditions.

Table 4 Effects of different operating conditions on HMF oxidation synthesis FDCA coupled electricity generation

Example 5

Effects of Reaction Conditions on Discharge Characteristics and Formation of HMFCA in Flow Fuel Cell Using Vanadyl Sulfate (Pentavalent) as Redox Electrolyte

The experimental process is the same as in Example 1. With nickel foam loaded with silver oxide as the anode, carbon felt loaded with carbon black as the cathode, 0.37mol/L vanadyl sulfate (pentavalent) as the cathode redox electrolyte, and 2mol/L sulfuric acid as the second supporting electrolyte, change Reaction conditions, including HMF concentration, potassium hydroxide concentration, and changing the size of the external load, explore the maximum power density of the battery and the change of product yield. The influence of relevant parameters is shown in Table 5.

It can be seen from the table that when HMF is oxidized to synthesize HMFCA, as the external load increases, that is, the external output voltage increases, the yield of HMFCA increases significantly. The selective oxidation of HMFCA increases the selectivity for HMFCA, thereby improving the yield of HMFCA; the maximum power density of the battery increases gradually with the increase of the concentration of HMF; with the increase of the concentration of potassium hydroxide, the maximum power density of the battery first increases and then decreases , when the alkali concentration is 1mol/L, it has the highest power density of 172.0mW/cm ² , and the change of HMFCA yield is consistent with the change trend of power density. Under the condition of 1mol/L potassium hydroxide, the highest yield of 97% of HMFCA can be realized. The long-time discharge test shows that appropriately increasing the alkali concentration will promote the reaction, but too high alkali concentration will promote the polymerization of HMF itself to generate a large amount of humus, thereby reducing the yield of HMFCA. It can be seen that the reaction system of the present invention can conveniently regulate the battery power density and product yield by changing the reaction conditions.

Table 5 Effects of different operating conditions on HMF oxidation to HMFCA coupled electricity generation

Example 6

Effect of fed-batch operation on the oxidation of HMF to FDCA

The experimental process is the same as in Example 1. The nickel foam loaded with nickel sulfide is used as the anode, the carbon felt loaded with carbon black is used as the cathode, 0.37mol/L vanadyl sulfate (pentavalent) is used as the cathode redox electrolyte, and 2mol/L sulfuric acid is used as the second supporting electrolyte. Discharge under short circuit conditions. The anode was replenished with 0.1mol/L HMF every 60 minutes. The yield and concentration of FDCA in the anolyte measured at different times are shown in the table below. It can be seen that the concentration of FDCA increases with the increase of feeding times. After feeding 10 times, the concentration of FDCA was 925.5mmol/L, the mass concentration was 144.5g/L, and the yield of FDCA was 95.7% during the whole feeding operation. From the above results, it can be seen that a higher FDCA concentration can be obtained through fed-batch operation, and a higher FDCA selectivity can be maintained.

Table 6 Anode FDCA yield and concentration change with time in fed batch operation

Example 7

Effect of fed-batch operation on HMF oxidation to HMFCA

The experimental process is the same as in Example 1. The nickel foam loaded with silver oxide is used as the anode, the carbon felt loaded with carbon black is used as the cathode, 0.37mol/L vanadyl sulfate (pentavalent) is used as the cathode redox electrolyte, and 2mol/L sulfuric acid is used as the second supporting electrolyte. Discharging was performed under the condition that the output voltage was 0.7V. The anode was replenished with 0.15mol/L HMF every 60 minutes. The yield and concentration of HMFCA in the anolyte measured at different times are shown in Table 7 below. It can be seen that with the increase of feeding times, the concentration of HMFCA increases. After feeding 5 times, the concentration of HMFCA was 636.8mmol/L, the mass concentration was 90.5g/L, and the yield of HMFCA in the whole feeding operation was 84.9%. From the above results, it can be known that a higher HMFCA concentration can be obtained through fed-batch operation, and a higher HMFCA selectivity can be maintained.

Table 7 Anode HMFCA yield and concentration change with time in fed batch operation

time (h) HMFCA concentration (mmol/L) HMFCA yield (%) 1 142.7 94.6% 2 251.1 83.6% 3 400.5 88.9% 4 521.7 86.8% 5 636.8 84.9%

It should be noted that in this specification, the terms "first" and "second" are used for description purposes only, and cannot be understood as indicating or implying relative importance or implicitly indicating the quantity of indicated technical features.

In the description of this specification, descriptions referring to the terms "one embodiment", "some embodiments", "example", "specific examples", or "some examples" mean that specific features described in connection with the embodiment or example , structure, material or characteristic is included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the described specific features, structures, materials or characteristics may be combined in any suitable manner in any one or more embodiments or examples. In addition, those skilled in the art can combine and combine different embodiments or examples and features of different embodiments or examples described in this specification without conflicting with each other.

Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention, those skilled in the art can make the above-mentioned The embodiments are subject to changes, modifications, substitutions and variations.

Claims (10)

1. A method for selective oxidative coupling of 5-hydroxymethylfurfural to electrical energy production, comprising:

   adding an anolyte containing 5-hydroxymethylfurfural in an anode liquid storage tank into an anode discharge chamber of the flow fuel cell, and circulating the anolyte back to the anode liquid storage tank; adding the catholyte containing redox electrolyte in the cathode liquid storage tank into a cathode discharge chamber of the flow fuel cell, and circulating the catholyte back to the cathode liquid storage tank; introducing air into the cathode discharge chamber and the cathode liquid storage tank; wherein the redox electrolyte comprises at least one of vanadyl sulfate, ferric chloride, ferric nitrate, ferric citrate, phosphomolybdic acid, phosphomolybdic vanadate, cupric chloride and potassium ferricyanide;

   connecting the cathode and the anode of the liquid flow type fuel cell with an external load to form a loop, and oxidizing the 5-hydroxymethylfurfural while generating electric energy.
2. 2. The method of claim 1, further comprising the step of assembling a flow-through fuel cell comprising an anode reservoir, an anode discharge chamber, an anode graphite bipolar plate, an ion exchange membrane, a cathode graphite bipolar plate, a cathode discharge chamber, an external load, and a cathode reservoir;

   the ion exchange membrane is positioned between the anode graphite bipolar plate and the cathode graphite bipolar plate; the anode graphite bipolar plate is positioned on one side of the ion exchange membrane close to the anode discharge chamber, and the cathode graphite bipolar plate is positioned on one side of the ion exchange membrane close to the cathode discharge chamber;

   the anode graphite bipolar plate is provided with a first groove, the anode is arranged in the first groove, and the anode is positioned on one side of the anode graphite bipolar plate close to the anode discharge chamber;

   the cathode graphite bipolar plate is provided with a second groove, the cathode is arranged in the second groove, and the cathode is positioned on one side of the cathode graphite bipolar plate close to the cathode discharge chamber;

   the anode liquid storage tank is connected with the anode discharge chamber through a pipeline, and the cathode liquid storage tank is connected with the cathode discharge chamber through a pipeline;

   the external load is arranged outside the liquid flow type fuel cell, and the cathode and the anode are respectively connected with the external load.
3. 3. The method of claim 1, wherein the anode is formed from an anode electron carrier supported on a first conductive substrate;

   the anode electronic carrier is selected from at least one of silver oxide, copper oxide, nickel oxide, manganese dioxide, cobalt oxide, iron oxide, nickel phosphide, cobalt phosphide, nickel sulfide, cobalt sulfide, nickel boride, nickel chloride, nickel nitride, cobaltosic oxide, nickel hydroxide, cobalt hydroxide, nickel oxyhydroxide and cobalt oxyhydroxide;

   the first conductive substrate is selected from one of copper foam, nickel foam, carbon felt, carbon paper and carbon cloth;

   optionally, the loading amount of the anode electron carrier is 0.001-10mg/cm ² 。
4. 4. The method of claim 1, wherein the cathode is formed from a cathode electron carrier supported on a second conductive substrate;

   the cathode electronic carrier is selected from at least one of metal platinum, metal ruthenium, carbon black, iron phthalocyanine, iron-nitrogen-carbon composite, cobalt-nitrogen-carbon composite and graphene;

   the second conductive substrate is selected from one of copper foam, nickel foam, carbon felt, carbon paper and carbon cloth;

   optionally, the loading amount of the cathode electron carrier is 0.001-10mg/cm ² 。
5. 5. The method of claim 2, wherein the ion exchange membrane is selected from an anion exchange membrane or a cation exchange membrane.
6. 6. The method of claim 1, further comprising: and controlling the temperature of the anolyte in the anode liquid storage tank and the temperature of the catholyte in the cathode liquid storage tank to be 20-100 ℃ through a heating device.
7. 7. The method of claim 1, wherein the concentration of 5-hydroxymethylfurfural is 0.001 to 5mol/L.
8. 8. The method of claim 1, wherein the anolyte comprises a first supporting electrolyte;

   optionally, the first supporting electrolyte is an inorganic base;

   the concentration of the first supporting electrolyte is 0.01-6mol/L.
9. 9. The method of claim 1, wherein the redox electrolyte has a concentration of 0.001-4mol/L;

   optionally, the catholyte further comprises a second supporting electrolyte;

   the second supporting electrolyte comprises an inorganic acid or an inorganic base;

   the concentration of the second supporting electrolyte is 0.01-6mol/L.
10. 10. The method of claim 1, wherein the resistance of the external load is 0-2000 ohms, and the output voltage of the flow fuel cell is 0-1V;

    optionally, the 5-hydroxymethylfurfural is added to the anode discharge chamber in a fed-batch manner.

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