Preparation and application of Au supported bimetallic molecular sieve catalyst

Abstract

The invention provides preparation and application of an Au supported bimetallic molecular sieve catalyst, the catalyst is nAu / SnxMgy-Beta, the Au loading amount n is 1-3 wt%, the Si / Sn molar ratio x is 20-200, and the Si / Mg molar ratio y is 20-200. The conversion rate of the nAu / SnxMgy-Beta catalyst prepared by the invention on the raw material 5-hydroxymethylfurfural can be up to 99.0% or above, and the selectivity and the yield of the product 2, 5-furandicarboxylic acid can be up to 99% or above.

Description

Technical Field

[0001] The present invention relates to the field of molecular sieve catalysts, and particularly to the preparation and application of an Au-loaded bimetallic molecular sieve catalyst. Background Art

[0002] Modern society consumes a large amount of fossil resources, including petroleum, coal, and natural gas, to meet the main demands for energy, chemicals, and materials. However, the over-reliance on non-renewable fossil resources has led to a series of economic, social, and environmental problems. The application of biomass catalytic conversion technology provides an alternative for the production of non-fossil-based chemicals or liquid fuels, thereby reducing the dependence on fossil fuels. 5-Hydroxymethylfurfural (HMF) is an important bio-based platform molecule that can be converted into various different products. The oxidation product of 5-hydroxymethylfurfural, 2,5-furandicarboxylic acid (FDCA), is listed by the US Department of Energy as one of the important biomass-derived chemicals. It can form a series of recyclable and easily decomposable environmentally friendly polymer materials through polycondensation reactions with diols or diamines. In addition, FDCA also has broad application prospects in the fields of medicine, chemical industry, etc. Therefore, the selective oxidation of biomass-based HMF to prepare FDCA has been favored by scientific researchers and the industrial community. So far, a variety of homogeneous and heterogeneous catalysts have been applied to this process. However, homogeneous catalysts are difficult to recover from the reaction system and have poor recyclability, severely limiting their industrial applications. Chinese Patent CN118217976A discloses a method for preparing 2,5-furandicarboxylic acid by using an AuPdPt / TiO 2 -0.8CA@HNTs ternary noble metal catalyst to catalyze 5-hydroxymethylfurfural. From the reaction results disclosed in the specification, it can be seen that under normal temperature and pressure conditions, the yield of 2,5-furandicarboxylic acid reaches 91.4%. The yield is relatively low and there is certain room for improvement. Moreover, in the preparation operation process of this catalyst, there are many types of noble metals used, a large loading amount, a high preparation cost, and a large amount of homogeneous base is required to participate (the molar ratio of the homogeneous base to 5-hydroxymethylfurfural is greater than 5). Chinese Patent CN113275019A discloses a magnetic nickel cobalt oxide-supported gold catalyst, its preparation method and application, and a method for preparing 2,5-furandicarboxylic acid. Among them, the yield of 2,5-furandicarboxylic acid reaches more than 99.0%, but the required reaction temperature of this catalyst is relatively high. Chinese Patent CN118679152A discloses a method for preparing 2,5-furandicarboxylic acid by two-stage oxidation of 5-hydroxymethylfurfural. From the reaction results disclosed in the specification, it can be seen that a large amount of strong base needs to be added during the reaction process, which is not conducive to extending the service life of production equipment. Chinese Patent CN113952951A discloses a preparation method of a Rh-inserted ZnAl hydrotalcite catalyst. From the reaction results disclosed in the specification, it can be seen that the conversion rate of 5-hydroxymethylfurfural is 56.5%, and the selectivity of 2,5-furandicarboxylic acid is 60.0%. The catalytic performance is relatively low, and using DMF as a solvent is not conducive to the recovery of reaction products and is somewhat dangerous to operators. Under the condition of no homogeneous base, the selectivity of FDCA is usually low, resulting in an unsatisfactory yield. For example, for Au / Mg-MTW, the FDCA yield is 87% (Applied Catalysis A: General, 2021, 616, 118106); for MoOx-Au / TiO 2 , the FDCA yield is 71% (Green Energy Environment, 2023, 8, 785-797). Or the stability of the catalyst is poor, such as the Au / HT catalyst (Green Chemistry, 2011, 13, 824-827). The Lewis acid centers based on the metal in the zeolite framework can accept the electron pairs from organic guest molecules without forming charge imbalance in the zeolite framework during catalysis. Therefore, this behavior can contribute to the adsorption and activation of reactants with electron-rich groups such as hydroxyl and aldehyde functional groups (Advanced Science, 2024, 11, 2306533). The implantation of Sn atoms makes the molecular sieve framework contain isolated Sn 4+ ions, which have strong and abundant Lewis acid sites and promote the oxidation of aldehyde groups to carboxyl groups (Applied Surface Science, 2023, 608, 155154). Generally, in the process of HMF oxidation, an additional homogeneous base needs to be added because it not only promotes the oxidation of alcohols but also resists the deactivation of the catalyst by forming carboxylates to resist metal leaching (ACS Catal, 2018, 8, 11154-11164). When alkaline earth metal atoms are implanted into the molecular sieve framework, the electronegativity difference between the metal and the framework oxygen atoms causes the covalent electrons to bias towards the oxygen atoms, so that the framework oxygen atoms exhibit a certain Lewis basicity, which can reduce the amount of added base to a certain extent or even achieve zero addition. Based on the current existing research, it can be seen that noble metal catalysts are widely used in the process of preparing FDCA by HMF oxidation, mainly including Au, Pt, Pd, etc., all of which have excellent abilities to activate molecular oxygen. However, high temperature, high pressure, and strong base conditions are required during the reaction, and toxic organic solvents are used. Therefore, it is imperative to develop a process for the catalytic oxidation of HMF to prepare FDCA with low or even no base, mild conditions, and using water and oxygen as green solvent and oxidant respectively. Summary of the Invention

[0003] Technical problem to be solved: In view of the current situation of high pressure, high temperature, strong base conditions and the use of toxic organic solvents in the preparation process of 2,5-furandicarboxylic acid, the present invention provides a preparation method of a supported bimetallic molecular sieve catalyst, introducing Sn and Mg into the molecular sieve framework, and utilizing the advantages of the host-guest interaction between the Lewis acid-base pair molecular sieve and organic molecules, large specific surface area of the molecular sieve and high temperature resistance to play a catalytic role in the oxidation reaction of 5-hydroxymethylfurfural to prepare 2,5-furandicarboxylic acid.

[0004] Technical solution: A Au-supported bimetallic molecular sieve catalyst, characterized in that: the catalyst is nAu / SnxMgy-Beta, where the loading amount n of Au is 1-3 wt%, the Si / Sn molar ratio x is 20-200, and the Si / Mg molar ratio y is 20-200. Preferably, the preparation method includes the following steps: S1. Acid-treat and wash and dry the silicon-aluminum type Beta molecular sieve to obtain a deeply dealuminated Beta molecular sieve; S2. Mix the deeply dealuminated Beta molecular sieve obtained in S1, tin tetrachloride, magnesium-containing compound and template agent, and then carry out hydrothermal synthesis in a fluorine-containing system to obtain SnxMgy-Beta molecular sieve; S3. Add the SnxMgy-Beta molecular sieve obtained in S2, water-soluble Au precursor solution, polyvinyl alcohol solution and sodium borohydride to water in sequence, and use the sol method to prepare the nAu / SnxMgy-Beta catalyst. Preferably, the number of acid treatments in S1 is 1 to 3 times; The reagent used for acid treatment in S1 is one or more of concentrated nitric acid, concentrated hydrochloric acid or concentrated sulfuric acid; The concentration of the reagent used for acid treatment in S1 is 6-11 mol / L; The mass ratio of the silicon-aluminum type Beta molecular sieve to the reagent used for acid treatment in S1 is 1:30-50; The temperature of acid treatment in S1 is 80-140 °C, the time is 8-24 h, the drying temperature is 60-100 °C, and the time is 8-12 h. Preferably, in S2, the molar ratio of SiO 2 in the deeply dealuminated Beta molecular sieve to tin tetrachloride, magnesium nitrate hexahydrate and template agent is 1:0.005-0.05:0.005-0.05:0.2-0.7; The magnesium-containing compound in S2 is one or more of magnesium nitrate hexahydrate, magnesium sulfate or magnesium chloride; The template agent in S2 is one or two of tetraethylammonium hydroxide or tetraethylammonium fluoride; The mineralizer in the fluorine-containing system described in S2 is a fluoride, and the fluoride is one or both of hydrofluoric acid and ammonium fluoride. Preferably, the method for hydrothermally synthesizing SnxMgy-Beta zeolite in S2 is as follows: Mix deeply dealuminated Beta zeolite, tin tetrachloride, magnesium nitrate hexahydrate, and tetraethylammonium hydroxide, perform water removal treatment at 40-100 °C, perform hydrothermal treatment at 120-190 °C for 15-120 min, add ammonium fluoride after cooling, and continue to perform crystallization treatment at 120-190 °C for 1-24 h. Filter, wash, dry, and calcine the product to obtain SnxMgy-Beta zeolite. Preferably, in the deeply dealuminated Beta zeolite, the molar ratio of SiO 2 to water is 1:1-10; The molar ratio of the ammonium fluoride to SiO in the deeply dealuminated Beta zeolite 2 is 0.2-0.8:1; The drying temperature is 60-100 °C, and the time is 8-12 h; The calcination temperature is 400-600 °C, and the time is 5-10 h. Preferably, the water-soluble Au precursor in S3 is one or both of chloroauric acid and sodium chloroaurate; The mixing temperature in S3 is 25-60 °C; The amount of water used in S3 is 0.05-5 g of SnxMgy-Beta zeolite added per 2-10 mL; The mass ratio of the polyvinyl alcohol solution to SnxMgy-Beta zeolite in S3 is 1-5:1, and the concentration of the polyvinyl alcohol solution is 0.01-0.1 g / mL; The amount of the water-soluble gold precursor solution used in S3 is 10-50 mL added per 1 g of SnxMgy-Beta zeolite, and the concentration of the water-soluble gold precursor solution is 0.05-0.5 wt%; The mass ratio of sodium borohydride to the carrier SnxMgy-Beta zeolite in S3 is 0.01-0.04:1. Preferably, the application of the supported bimetallic zeolite catalyst in the efficient catalytic oxidation of 5-hydroxymethylfurfural to prepare 2,5-furandicarboxylic acid. Preferably, the specific application is as follows: Mix the nAu / SnxMgy-Beta catalyst, 5-hydroxymethylfurfural, a basic compound, and a solvent, stir in an oxygen atmosphere, and synthesize 2,5-furandicarboxylic acid through an oxidation reaction. Preferably, the dosage of the nAu / SnxMgy-Beta catalyst is 0.01-0.05 g of 5-hydroxymethylfurfural corresponding to every 20-60 mg of the catalyst; The basic compound is one or more of sodium carbonate, potassium carbonate or sodium bicarbonate, and the molar ratio of the basic substance to 2,5-furandicarboxylic acid is 0-1:1; The solvent is water, and the dosage is 0.01-0.05 g of 5-hydroxymethylfurfural corresponding to every 10-20 mL of water; The stirring speed is 700-900 rpm; The oxidation reaction temperature is 30-140 °C, the pressure is 1-3 MPa, and the time is 0.5-48 h. Beneficial effects: The present invention has the following advantages: The preparation method of the Au-loaded bimetallic molecular sieve catalyst provided by the present invention uses deeply dealuminated Beta molecular sieve as the carrier. Utilizing the structural characteristics of such molecular sieves, such as regular pore structure, good thermal stability and large specific surface area, Sn and Mg metals are implanted into the molecular sieve framework by the reconstruction method to form SnxMgy-Beta molecular sieve. Sn forms Lewis acid sites in the molecular sieve to selectively activate aldehyde groups, and the implantation of Mg can provide Lewis basic sites to promote the cleavage of the O-H bond in the hydroxyl group; Subsequently, using SnxMgy-Beta molecular sieve as the carrier, metal Au is loaded by the sol method to activate oxygen, and water is used as the solvent. Under mild conditions, 5-hydroxymethylfurfural is efficiently catalytically oxidized to prepare 2,5-furandicarboxylic acid; The conversion rate of the raw material 5-hydroxymethylfurfural by using the nAu / SnxMgy-Beta catalyst prepared by the present invention can reach up to more than 99.0%, and the selectivity and yield of the product 2,5-furandicarboxylic acid can reach more than 99%. Description of the drawings Figure 1 It is the X-ray diffraction pattern of the 2Au / Sn150Mg100-Beta molecular sieve catalyst in Example 1 of the present invention; Figure 2 It is the TEM image of the 2Au / Sn150Mg100-Beta molecular sieve catalyst in Example 1 of the present invention; Figure 3 It is the N 2 adsorption-desorption isotherm curve of the 2Au / Sn150Mg100-Beta molecular sieve catalyst in Example 1 of the present invention. Detailed implementation manners The present invention will be further described below in conjunction with the embodiments. The following embodiments are explanations of the present invention, and the present invention is not limited to the following embodiments: It should be noted that, without conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other. The raw materials, equipment, etc. used in the following examples and experimental examples are all commercially available products. Among them, the silica-alumina type Beta zeolite was purchased from Tianjin Nanhua Catalyst Co., Ltd., and the SiO 2 / Al 2 O 3 molar ratio is approximately equal to 25. Example 1 The Au-loaded bimetallic zeolite catalyst of this embodiment is 2Au / Sn150Mg100-Beta, the Au loading amount n is 2 wt%, the Si / Sn molar ratio x is 150, and the Si / Mg molar ratio y is 100. The preparation method of the supported bimetallic zeolite catalyst in this embodiment includes the following steps: S1. Weigh 5 g of the silica-alumina type Beta zeolite into a 250 mL round-bottom flask, add 150 g of commercially available 6 mol / L concentrated nitric acid for pickling treatment. Place the round-bottom flask in an oil bath, adjust the temperature to 130 °C, and treat the Beta zeolite in the concentrated nitric acid for 12 h. Repeat this process twice. After the reflux ends, cool to room temperature, filter by suction, and dry at 80 °C for 8 h to obtain the deeply dealuminated Beta zeolite, named Beta-DA. S2. Weigh 0.3000 g of the Beta-DA zeolite prepared in S1 and place it in the inner lining of a hydrothermal autoclave. Then add 1.4726 g of tetraethylammonium hydroxide (industrial grade, TEAOH≥25 wt%), 0.0117 g of SnCl 4 ·5H 2 O, 0.0128 g of Mg(NO 3 ) 2 ·6H 2 O, stir and mix for 5 min, drive off water at 80 °C until the water to silica ratio is 7, seal the hydrothermal autoclave, and perform hydrothermal static treatment at 140 °C for 1 h. Then take out the hydrothermal autoclave, cool to room temperature, open the hydrothermal autoclave, add 0.0926 g of NH 4 F, stir until it becomes a gel, seal the hydrothermal autoclave again, and perform crystallization treatment at 140 °C for 24 h. After the crystallization ends, cool to room temperature, filter by suction, wash, dry, calcine at 550 °C for 5 h, and grind to obtain the Sn150Mg100-Beta zeolite. S3. Weigh 0.12 g of a 2 wt% polyvinyl alcohol solution into a 25 mL round-bottom flask, add 3 g of deionized water, add 2 mL of a 2 wt% HAuCl 4 solution, add 0.0019 g of NaBH 4, then add 1 g of deionized water, stir at room temperature for 30 min, add 0.0980 g of Sn150Mg100-Beta, stir and mix for 5 h, centrifuge, and then use ethanol - hot water - ethanol as solvents for centrifugal washing in sequence, dry at 80 °C for 12 h, and grind to obtain the purple powder catalyst 2Au / Sn150Mg100-Beta. The X-ray diffraction pattern, TEM image, and N 2 adsorption-desorption isotherm curve of the Au-loaded bimetallic zeolite catalyst in this example are as Figure 1 , Figure 2 and Figure 3 shown, and the pore information parameters are shown in Table 1. Table 1 Pore information of 2Au / Sn150Mg100-Beta From Figure 1 , it can be seen that the zeolite has an obvious Beta topological structure and a high crystallinity. There is no diffraction peak attributed to the Au

[111] crystal plane near 38°, indicating that Au nanoparticles are highly dispersed on the zeolite support; From Figure 2 , it can be seen that the 2Au / Sn150Mg100-Beta zeolite catalyst has obvious lattice fringes, a high crystallinity, and the average particle size of Au nanoparticles is about 7.8 nm; From Figure 3 and Table 1, it can be seen that the specific surface area of 2Au / Sn150Mg100-Beta is 439 m 2 g -1 , the total pore volume is 0.36 cm 3 g -1 , the micropore volume is 0.13 cm 3 g -1 , and the mesopore volume is 0.23 cm 3 g -1 . Example 2 The preparation method of the Au-loaded bimetallic zeolite catalyst in this example is the same as that in Example 1. The application of the Au-loaded bimetallic zeolite catalyst in this example in the efficient catalytic oxidation of 5-hydroxymethylfurfural to prepare 2,5-furandicarboxylic acid is as follows: Add 15 mL of deionized water, 0.0315 g of 5-hydroxymethylfurfural, 0.0231 g of anhydrous sodium carbonate, and 40 mg of the catalyst prepared in this example into the inner lining of the reaction kettle, and mix evenly. React under the conditions of an oxygen atmosphere, a pressure of 2 MPa, a temperature of 130 °C, and a rotation speed of 800 rpm for 0.5 h. The catalytic effect is shown in Table 3. In other embodiments of the present invention, the Au-loaded bimetallic molecular sieve catalyst prepared in Example 2 was used, and the reaction rotation speed was changed to 700 rpm and 900 rpm. Other conditions were the same as those in Example 2. The catalytic performance of the molecular sieve catalyst at different rotation speeds was evaluated. The results are shown in Table 2. Table 2 Catalytic performance of molecular sieve catalyst at different rotation speeds As can be seen from Table 2, compared with 700 rpm, the yield of 2,5-furandicarboxylic acid slightly increased at 800 rpm. When the rotation speed continued to increase to 900 rpm, the catalytic activity basically remained unchanged, indicating that at 800 rpm, the external diffusion interference on the heterogeneous catalytic reaction could be excluded. The preferred reaction rotation speed was 800 rpm. Example 3 The preparation method of the Au-loaded bimetallic molecular sieve catalyst in this example was the same as that in Example 1. The application of the Au-loaded bimetallic molecular sieve catalyst in this example in the efficient catalytic oxidation of 5-hydroxymethylfurfural to prepare 2,5-furandicarboxylic acid was as follows: 15 mL of deionized water, 0.0315 g of 5-hydroxymethylfurfural, 0.0231 g of anhydrous sodium carbonate, and 40 mg of the catalyst prepared in this example were added to the inner lining of the reaction kettle and mixed evenly. The reaction was carried out for 0.25 h under the conditions of an oxygen atmosphere, a pressure of 2 MPa, a temperature of 130 °C, and a rotation speed of 800 rpm. The catalytic effect is shown in Table 3. In other embodiments of the present invention, the Au-loaded bimetallic molecular sieve catalyst prepared in Example 3 was used, and the catalyst dosage was changed to 20 mg, 30 mg, and 60 mg. Other conditions and applications were the same as those in Example 3. The catalytic performance of the molecular sieve catalyst at different reaction temperatures was evaluated. The results are shown in Table 3. Table 3 Catalytic performance of molecular sieve catalyst at different catalyst dosages As can be seen from Table 3, with the increase of the catalyst dosage, the conversion rate of 5-hydroxymethylfurfural was basically completely converted, and the selectivity of 2,5-furandicarboxylic acid first increased and then decreased. Considering the yield and economy, the preferred catalyst dosage was 40 mg. Example 4 The preparation method of the Au-loaded bimetallic molecular sieve catalyst in this example was the same as that in Example 1. The application of the Au-loaded bimetallic molecular sieve catalyst in the catalytic oxidation of 5-hydroxymethylfurfural to prepare 2,5-furandicarboxylic acid in this example is as follows: Add 15 mL of deionized water, 0.0315 g of 5-hydroxymethylfurfural, 0.0231 g of sodium carbonate, and 40 mg of the catalyst prepared in this example into the inner lining of the reaction kettle, and mix evenly. Under the conditions of O 2 atmosphere, a pressure of 2 MPa, and a rotation speed of 800 rpm, react at 130 °C for 48 h. The catalytic effect is shown in Table 4. In other examples of the present invention, the Au-loaded bimetallic molecular sieve catalyst prepared in Example 4 is used, and the reaction temperatures are changed to 30 °C, 40 °C, 50 °C, 60 °C, 70 °C, and 80 °C. Other conditions and applications are the same as those in Example 4. The catalytic performance of the molecular sieve catalyst at different reaction temperatures is evaluated. The results are shown in Table 4. Table 4 Catalytic performance of the molecular sieve catalyst at different reaction temperatures As can be seen from Table 4, with the increase of the reaction temperature, the change range of the conversion rate of 5-hydroxymethylfurfural is not large, but the selectivity of 2,5-furandicarboxylic acid increases sharply, resulting in a corresponding increase in its yield, indicating that the increase of the reaction temperature is beneficial to the progress of the catalytic reaction; when the reaction temperature is 50 °C, the conversion rate of 5-hydroxymethylfurfural reaches 100%, indicating that the 2Au / Sn150Mg100-Beta catalyst can achieve complete conversion of 5-hydroxymethylfurfural at a lower temperature. At 70 °C, the yield of 2,5-furandicarboxylic acid is as high as 95.3%; when the temperature rises to 80 °C, its yield is 100.0%; when the reaction temperature is 130 °C, its yield is also 100.0%. Considering the catalytic performance and reaction energy consumption, the preferred reaction temperature is 80 °C. Example 5 The preparation method of the Au-loaded bimetallic molecular sieve catalyst in this example is the same as that in Example 1. The application of the Au-loaded bimetallic molecular sieve catalyst in the catalytic oxidation of 5-hydroxymethylfurfural to prepare 2,5-furandicarboxylic acid in this example is as follows: Add 15 mL of deionized water, 0.0315 g of 5-hydroxymethylfurfural, 0.0231 g of anhydrous sodium carbonate, and 40 mg of the catalyst prepared in step (3) of this example into the inner lining of the reaction kettle, and mix evenly. Under the conditions of an oxygen atmosphere, a pressure of 2 MPa, a temperature of 80 °C, and a rotation speed of 800 rpm, react for 12 h. The catalytic effect is shown in Table 5. In other examples of the present invention, the pressure in Example 6 is adjusted to 1 MPa, 1.5 MPa, 2.5 MPa, and 3 MPa. Other conditions and applications are the same as those in Example 6. The catalytic performance of the molecular sieve catalyst at different reaction pressures is evaluated. The results are shown in Table 5. Table 5 Catalytic Performance of Zeolite Catalysts under Different Reaction Pressures As can be seen from Table 5, when the reaction pressure is 0.5 MPa and 1 MPa, the conversion rate, selectivity and yield of the reaction product 2,5-furandicarboxylic acid are relatively low. When the reaction pressure increases to 2 MPa, the conversion rate, selectivity and yield of the reaction product 2,5-furandicarboxylic acid reach 99.7%, 85.7% and 85.4% respectively. When the reaction pressure continues to increase to 3 MPa, the conversion rate continues to increase, but the selectivity and yield decrease to 83.3% and 83.2%. Therefore, considering the conversion rate, selectivity and yield comprehensively, the preferred reaction pressure is 2 MPa. Example 6 In this example, the preparation method of the Au-loaded bimetallic zeolite catalyst is the same as that in Example 1. The application of the Au-loaded bimetallic zeolite catalyst in this example in the catalytic oxidation of 5-hydroxymethylfurfural to prepare 2,5-furandicarboxylic acid is as follows: Add 15 mL of deionized water, 0.0315 g of 5-hydroxymethylfurfural, 0.0231 g of sodium carbonate, and 40 mg of the catalyst prepared in this example into the inner lining of the reaction kettle and mix evenly. Under the conditions of an oxygen atmosphere, a pressure of 2 MPa, a temperature of 80 °C, and a rotation speed of 800 rpm, react for 0.5 h. See Table 6 for the catalytic effect. In other examples of the present invention, the reaction times are set to 4 h, 12 h, 36 h, 48 h and 60 h respectively, and other conditions and applications are the same as those in Example 6. Evaluate the catalytic performance of the zeolite catalyst under different reaction times. See Table 6 for the results. Table 6 Catalytic Performance of Zeolite Catalysts under Different Reaction Times In the range of 0.5 - 48 h, as the reaction time prolongs, the selectivity of the reaction product 2,5-furandicarboxylic acid increases accordingly, and the prolongation of the reaction time is beneficial to the progress of the catalytic reaction. When the reaction time is 48 h, the yield of 2,5-furandicarboxylic acid can reach 100%, indicating that the 2Au / Sn150Mg100-Beta catalyst has excellent catalytic performance in the selective oxidation of 5-hydroxymethylfurfural to prepare 2,5-furandicarboxylic acid. Considering the comprehensive energy consumption and reaction efficiency, the preferred reaction time is 48 h. Example 7 In this example, the preparation method of the Au-loaded bimetallic zeolite catalyst is the same as that in Example 1. The application of the Au-loaded bimetallic molecular sieve catalyst in the catalytic oxidation of 5-hydroxymethylfurfural to prepare 2,5-furandicarboxylic acid in this example is as follows: Add 15 mL of deionized water, 0.0315 g of 5-hydroxymethylfurfural, 0.0231 g of anhydrous sodium carbonate, and 40 mg of the catalyst prepared in this example into the inner lining of the reaction kettle, and mix evenly. Under the conditions of an oxygen atmosphere, a pressure of 2 MPa, a temperature of 80 °C, and a rotation speed of 800 rpm, react for 12 h. For the catalytic effect, see Table 7. In other examples of the present invention, the solution after the reaction in Example 7 is centrifuged and dried at 80 °C for 5 h to obtain a recovered catalyst, which is reused 4 times. Other conditions and applications are the same as in Example 7. Evaluate the recycling performance of the catalyst, and the results are shown in Table 7. Table 7 Recycling performance of the catalyst As can be seen from Table 7, with the increase in the number of reaction times, the catalytic performance of the catalyst hardly changes, indicating that the 2Au / Sn150Mg100-Beta catalyst has excellent recycling performance and stability. Example 8 The preparation method of the Au-loaded bimetallic molecular sieve catalyst in this example includes the following steps: S1. The same as S1 in Example 1; S2. Weigh 0.3000 g of the Beta-DA molecular sieve prepared in S1, place it in the inner lining of the hydrothermal kettle, and then add 1.4726 g of tetraethylammonium hydroxide (industrial grade, TEAOH≥25 wt%), 0.0351 g of SnCl 4 ·5H 2 O, 0.0128 g of Mg(NO 3 ) 2 ·6H 2 O, stir and mix for 5 min, drive off water at 80 °C until the water-to-silica ratio is 7, seal the hydrothermal kettle, and perform hydrothermal static treatment at 140 °C for 1 h; then take out the hydrothermal kettle, cool it to room temperature, open the hydrothermal kettle and add 0.0926 g of NH 4 F, stir until it becomes a gel, seal the hydrothermal kettle again, and perform crystallization treatment at 140 °C for 24 h. After the crystallization is completed, cool it to room temperature, filter, wash, dry, calcine at 550 °C for 5 h, and grind to obtain Sn150Mg100-Beta molecular sieve; S3. The same as S3 in Example 1 to obtain the 2Au / Sn150Mg50-Beta catalyst. The application of the Au-loaded bimetallic zeolite catalyst in the catalytic oxidation of 5-hydroxymethylfurfural to prepare 2,5-furandicarboxylic acid in this example is as follows: Add 15 mL of deionized water, 0.0315 g of 5-hydroxymethylfurfural, 0.0231 g of anhydrous sodium carbonate, and 40 mg of the catalyst prepared in this example into the inner lining of the reaction kettle, and mix evenly. Under the conditions of an oxygen atmosphere, a pressure of 2 MPa, a temperature of 80 °C, and a rotation speed of 800 rpm, react for 12 h, take samples, and perform liquid chromatography analysis. Compared with 2Au / Sn150Mg100-Beta in Example 5 (the yield of 2,5-furandicarboxylic acid is 85.4%), 2Au / Sn50Mg100-Beta in this example shows a higher yield of 2,5-furandicarboxylic acid up to 93.2%, indicating that the increase in the Sn content in the catalyst helps the catalytic generation of the product 2,5-furandicarboxylic acid. Example 9 The preparation method of the Au-loaded bimetallic zeolite catalyst in this example includes the following steps: S1. The same as S1 in Example 1; S2. Weigh 0.3000 g of the Beta-DA zeolite prepared in S1, place it in the inner lining of the hydrothermal kettle, and then add 1.4726 g of tetraethylammonium hydroxide (industrial grade, TEAOH≥25 wt%), 0.0117 g of SnCl 4 ·5H 2 O, 0.0256 g of Mg(NO 3 ) 2 ·6H 2 O, stir and mix for 5 min, drive off water at 80 °C until the water-to-silica ratio is 7, seal the hydrothermal kettle, and perform hydrothermal static treatment at 140 °C for 1 h; then take out the hydrothermal kettle, cool it to room temperature, open the hydrothermal kettle and add 0.0926 g of NH 4 F, stir until it becomes a gel, seal the hydrothermal kettle again, and perform crystallization treatment at 140 °C for 24 h. After the crystallization is completed, cool it to room temperature, filter, wash, dry, calcine at 550 °C for 5 h, and grind to obtain Sn150Mg100-Beta zeolite; S3. The same as S3 in Example 1 to obtain the 2Au / Sn150Mg50-Beta catalyst. The application of the Au-loaded bimetallic zeolite catalyst in the catalytic oxidation of 5-hydroxymethylfurfural to prepare 2,5-furandicarboxylic acid in this example is as follows: Add 15 mL of deionized water, 0.0315 g of 5-hydroxymethylfurfural, 0.0231 g of anhydrous sodium carbonate, and 40 mg of the catalyst prepared in S3 of this example into the inner lining of the reaction kettle, and mix evenly. In O 2Under the conditions of atmosphere, pressure of 2 MPa, temperature of 80 °C, and rotation speed of 800 rpm, react for 12 h, take samples, and perform liquid chromatography analysis. Compared with 2Au / Sn150Mg100-Beta in Example 5 (the yield of 2,5-furandicarboxylic acid is 85.4%), 2Au / Sn150Mg50-Beta in this example shows a higher yield of 2,5-furandicarboxylic acid, up to 96.2%, indicating that the increase in the Mg content in the catalyst helps the catalytic formation of the product 2,5-furandicarboxylic acid. Example 10 The preparation method of the Au-loaded bimetallic molecular sieve catalyst in this example includes the following steps: S1. The same as S1 in Example 1; S2. Weigh 0.3000 g of the Beta-DA molecular sieve prepared in S1, place it in the inner lining of the hydrothermal autoclave, and then add 1.4726 g of tetraethylammonium hydroxide (industrial grade, TEAOH≥25 wt%), 0.0351 g of SnCl 4 ·5H 2 O, 0.0256 g of Mg(NO 3 ) 2 ·6H 2 O, stir and mix for 5 min, drive off water at 80 °C until the water-silica ratio is 7, seal the hydrothermal autoclave, and perform hydrothermal static treatment at 140 °C for 1 h; then take out the hydrothermal autoclave, cool it to room temperature, open the hydrothermal autoclave and add 0.0926 g of NH 4 F, stir until it becomes gel-like, seal the hydrothermal autoclave again, and perform crystallization treatment at 140 °C for 24 h. After the crystallization is completed, cool it to room temperature, filter, wash, dry, calcine at 550 °C for 5 h, and grind to obtain Sn50Mg50-Beta molecular sieve; S3. The same as S3 in Example 1 to obtain the 2Au / Sn50Mg50-Beta catalyst. The application of the Au-loaded bimetallic molecular sieve catalyst in this example in the catalytic oxidation of 5-hydroxymethylfurfural to prepare 2,5-furandicarboxylic acid is specifically as follows: Add 15 mL of deionized water, 0.0315 g of 5-hydroxymethylfurfural, and 40 mg of the catalyst prepared in this example into the inner lining of the reaction kettle, and mix evenly. Under the conditions of oxygen atmosphere, pressure of 2 MPa, temperature of 80 °C, and rotation speed of 800 rpm, react for 60 h, take samples, and perform liquid chromatography analysis. By simultaneously increasing the Sn and Mg contents in the molecular sieve catalyst framework, under alkali-free and mild conditions, using water as the solvent and molecular oxygen as the oxidant, it shows 100% conversion of 5-hydroxymethylfurfural and 97.3% selectivity and yield of 2,5-furandicarboxylic acid, showing excellent catalytic performance. Comparative Example 1 The difference between this comparative example and Example 1 is that in S3 of Example 1, SnCl 4 ·5H 2 O is not added, and the remaining steps are the same as those in Example 1, obtaining 2Au / Mg100-Beta; in S3 of Example 1, Mg(NO 3 ) 2 ·6H 2 O is not added, and the remaining steps are the same as those in Example 1, obtaining 2Au / Sn150-Beta. The application of the Au-loaded bimetallic molecular sieve catalyst in this comparative example in the efficient catalytic oxidation of 5-hydroxymethylfurfural to prepare 2,5-furandicarboxylic acid is as follows: Add 15 mL of deionized water, 0.0315 g of 5-hydroxymethylfurfural, 0.0231 g of anhydrous sodium carbonate, and 20 mg of the catalyst prepared in this example into the inner lining of the reaction kettle, and mix evenly. React under the conditions of an oxygen atmosphere, a pressure of 2 MPa, a temperature of 130 °C, and a rotation speed of 800 rpm for 0.5 h. For the catalytic effect, see Table 8. Table 8 Catalytic performance of molecular sieve catalysts implanted with different metals As can be seen from Table 8, the yield of 2,5-furandicarboxylic acid of the bimetallic molecular sieve catalyst implanted is significantly higher than that of the molecular sieve catalysts implanted with single Sn and single Mg only, reflecting the synergistic effect of Sn and Mg on this selective oxidation reaction. Comparative Example 2 In this comparative example, the Au-loaded bimetallic molecular sieve catalyst prepared in Example 3 is used, and the catalyst dosages are changed to 10 mg, 70 mg, and 80 mg respectively. Other conditions are the same as those in Example 3, and the catalytic performance of the molecular sieve catalyst under different catalyst dosages is evaluated. The results are shown in Table 9. Table 9 Catalytic performance of molecular sieve catalysts under different catalyst dosages As can be seen from Table 9 and Table 3, when the catalyst dosage is 10 mg, the catalytic performance is poor; as the catalyst dosage increases to 20 - 60 mg, the conversion of 5-hydroxymethylfurfural is basically completely converted, and the selectivity of 2,5-furandicarboxylic acid first increases and then decreases; when the catalyst dosage increases to 70 mg and 80 mg, the conversion rate, selectivity, and yield all increase compared with those when the dosage is 40 mg. Considering the cost and catalytic performance comprehensively, the preferred catalyst dosage is 40 mg. Comparative Example 3 In this comparative example, the Au-loaded bimetallic molecular sieve catalyst prepared in Example 5 was used, and the reaction pressure was changed to 0.25 MPa, 4 MPa, and 6 MPa. Other conditions and applications were the same as those in Example 5. The catalytic performance of the molecular sieve catalyst under different reaction pressures was evaluated, and the results are shown in Table 10. Table 10 Catalytic Performance of Molecular Sieve Catalyst under Different Reaction Pressures As can be seen from Table 10, too high or too low reaction pressure will have a negative impact on the catalytic performance. Comparative Example 4 In this comparative example, the Au-loaded bimetallic molecular sieve catalyst prepared in Example 6 was used, and the reaction time was changed to 0.3 h, 60 h, and 72 h. Other conditions and applications were the same as those in Example 6. The catalytic performance of the molecular sieve catalyst under different reaction times was evaluated, and the results are shown in Table 11. Table 11 Catalytic Performance of Molecular Sieve Catalyst under Different Reaction Times As can be seen from Tables 5 and 11, the catalytic performance is relatively low when the reaction time is too short. The catalytic performance is better when the reaction time is 60 h and 70 h, but the economic cost is relatively high. Therefore, the reaction time of 48 h is preferably selected. In summary, the present invention combines the reconstruction method and the sol method to prepare the Au-loaded bimetallic molecular sieve catalyst, and improves the catalytic performance by adding the bimetals Sn and Mg. The Au-loaded bimetallic molecular sieve catalyst provided by the present invention can selectively activate hydroxyl groups and aldehyde groups in the oxidation reaction of 5-hydroxymethylfurfural, with high reaction activity, high product selectivity, and good stability. Even under mild conditions without alkali, it also has excellent catalytic performance. The above experimental results show that the conversion rate of 5-hydroxymethylfurfural can reach up to 100%, and the selectivity and yield of 2,5-furandicarboxylic acid can also reach 100%. Obviously, the above examples are only for clear illustration and not for limiting the implementation mode. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all implementation modes here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. An Au-supported bimetallic molecular sieve catalyst, characterized in that: The catalyst is nAu / SnxMgy-Beta, wherein the Au loading n is 1-3wt%, the Si / Sn molar ratio x is 20-200, and the Si / Mg molar ratio y is 20-200.

2. The method for preparing the Au-supported bimetallic molecular sieve catalyst according to claim 1, characterized in that: The preparation method comprises the following steps: S1. The silicon-aluminum type Beta molecular sieve is acid-treated and washed and dried to obtain a deep dealuminated Beta molecular sieve; S2. The deeply dealuminated Beta molecular sieve obtained in S1, tin tetrachloride, a magnesium-containing compound and a template are mixed, and then hydrothermally synthesized in a fluorine-containing system to obtain SnxMgy-Beta molecular sieve; S3. The SnxMgy-Beta molecular sieve obtained in S2, a water-soluble Au precursor solution, a polyvinyl alcohol solution and sodium borohydride are sequentially added into water, and a nAu / SnxMgy-Beta catalyst is prepared by a sol method.

3. The method for preparing the Au-supported bimetallic molecular sieve catalyst according to claim 2, characterized in that: The number of acid treatments in S1 is 1 to 3 times; and / or, the reagent used for the acid treatment in S1 is one or more of concentrated nitric acid, concentrated hydrochloric acid or concentrated sulfuric acid; and / or, the concentration of the reagent used for the acid treatment in S1 is 6-11 mol / L; and / or, the mass ratio of the silica-alumina Beta molecular sieve described in S1 to the reagent used for acid treatment is 1:30-50; And / or, the acid treatment in S1 is carried out at a temperature of 80-140° C. for a time of 8-24 h, and the drying temperature is 60-100° C. for a time of 8-12 h.

4. The method for preparing the Au-supported bimetallic molecular sieve catalyst according to claim 2, characterized in that: The molar ratio of SiO2 to tin tetrachloride, magnesium nitrate hexahydrate and template in the deep dealuminated Beta molecular sieve in S2 is 1:0.005-0.05:0.005-0.05:0.2-0.7; and / or, the magnesium-containing compound in S2 is one or more of magnesium nitrate hexahydrate, magnesium sulfate or magnesium chloride; And / or, the template in S2 is one or both of tetraethylammonium hydroxide and tetraethylammonium fluoride; And / or, the mineralizer in the fluorine-containing system in S2 is a fluoride, and the fluoride is one or both of hydrofluoric acid and ammonium fluoride.

5. The method for preparing the Au-supported bimetallic molecular sieve catalyst according to claim 2, characterized in that: The method for hydrothermal synthesis of SnxMgy-Beta molecular sieve in S2 is: mixing deeply dealuminated Beta molecular sieve, tin tetrachloride, magnesium-containing compound and tetraethylammonium hydroxide, performing water removal treatment at 40-100°C, performing hydrothermal treatment at 120-190°C for 15-120min, adding ammonium fluoride after cooling, continuing crystallization treatment at 120-190°C for 1-24h, filtering, washing, drying and calcining the product to obtain SnxMgy-Beta molecular sieve.

6. The method for preparing the Au-supported bimetallic molecular sieve catalyst according to claim 5, characterized in that: The molar ratio of SiO2 to water in the deep dealuminated Beta molecular sieve is 1:1-10; And / or, the molar ratio of ammonium fluoride to SiO2 in the deep dealuminated Beta molecular sieve is 0.2-0.8:1; And / or, the drying temperature is 60-100°C and the time is 8-12h; And / or, the calcination temperature is 400-600° C. and the calcination time is 5-10 h.

7. The method for preparing the Au-supported bimetallic molecular sieve catalyst according to claim 2, characterized in that: The water-soluble Au precursor in S3 is one or both of chloroauric acid and sodium chloroaurate; And / or, the mixing temperature in S3 is 25-60°C; And / or, the amount of water used in S3 is 0.05-5 g SnxMgy-Beta molecular sieve per 2-10 mL; And / or, the mass ratio of the polyvinyl alcohol solution to the SnxMgy-Beta molecular sieve in S3 is 1-5:1, and the concentration of the polyvinyl alcohol solution is 1-10wt%; And / or, the amount of the water-soluble gold precursor solution in S3 is 10-50 mL, corresponding to the addition of 1 g of SnxMgy-Beta molecular sieve, and the concentration of the water-soluble gold precursor solution is 0.05-0.5 wt %. And / or, the mass ratio of the sodium borohydride and the carrier SnxMgy-Beta molecular sieve in S3 is 0.01-0.04:

1.

8. Use of the Au-supported bimetallic molecular sieve catalyst according to any one of claims 1 to 2 in the efficient catalytic oxidation of 5-hydroxymethylfurfural to prepare 2,5-furandicarboxylic acid.

9. The use according to claim 8, characterized in that: The application is specifically as follows: nAu / SnxMgy-Beta catalyst, 5-hydroxymethylfurfural, alkaline compound and solvent are mixed, stirred under an oxygen atmosphere, and 2,5-furandicarboxylic acid is synthesized through oxidation reaction.

10. The use according to claim 9, characterized in that: The dosage of the nAu / SnxMgy-Beta catalyst is 0.01-0.05 g of 5-hydroxymethylfurfural for every 20-60 mg of catalyst; and / or, the alkaline compound is one or more of sodium carbonate, potassium carbonate or sodium bicarbonate, and the molar ratio of the alkaline substance to 2,5-furandicarboxylic acid is 0-1:1; And / or, the solvent is water, and the amount used is 0.01-0.05 g of 5-hydroxymethylfurfural per 10-20 mL of water; And / or, the stirring speed is 700-900 rpm; And / or, the oxidation reaction temperature is 30-140° C., the pressure is 0.5-3 MPa, and the time is 0.5-48 h.

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