A gold-based catalyst and its application in the reaction for preparing dimethyl furandicarboxylate

Abstract

The present invention discloses a gold-based catalyst and its application in the reaction for preparing dimethyl furandicarboxylate, belonging to the technical field of catalyst preparation and application. First, gold is loaded onto a titanium dioxide support, and then it is modified by a modifier to obtain an Au / TiO2 catalyst with a surface covered by the modifier, thereby improving the catalytic performance of the gold-based catalyst. In the process of using the gold-based catalyst of the present invention to catalyze 5-hydroxymethylfurfural to prepare dimethyl furandicarboxylate, the conversion rate of 5-hydroxymethylfurfural is 82%, and the selectivity of dimethyl furandicarboxylate is 85%. In the reaction of catalyzing furandialdehyde to prepare dimethyl furandicarboxylate, the conversion rate of furandialdehyde can reach 100%, and the selectivity of dimethyl furandicarboxylate can reach 95%, which can be applied to actual industrial production.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalyst preparation and application, and relates to the preparation and application of a gold-based catalyst. Specifically, it relates to the preparation of a supported gold-based catalyst and its application in the catalytic oxidation esterification of 5-hydroxymethylfurfural or furandicarboxaldehyde to prepare dimethyl 2,5-furandicarboxylate. Background Art

[0002] A large number of discarded plastics are difficult to bury due to their long-term non-decay, and a large amount of harmful carcinogens are generated during the incineration of plastics, resulting in air pollution and environmental deterioration. Therefore, it is imperative to continuously develop degradable plastic alternatives. After years of research, it has been found that plastics produced from 2,5-furandicarboxylic acid (FDCA) in biomass plastics have received extensive attention and welcome. Since FDCA has a low solubility in industrial solvents, the corresponding ester (FDMC) can be used as a substitute. Dimethyl 2,5-furandicarboxylate can be used in the preparation of bio-based polyester PEF. Compared with the important petroleum-based polyester PET, the monomer structural characteristics of PEF polyester are similar, and it has biodegradability. It has passed the EU food safety certification and has great application potential. In addition, FDMC is easily soluble in common solvents, which is convenient for production.

[0003] In the reported literature, researchers used 5-hydroxymethylfurfural (HMF) as a raw material for oxidative esterification to prepare FDMC (CN110799504A, ChemSusChem, 2008, 1, 75-78). However, there are many by-products in the reaction process, and usually, a relatively high pressure and a relatively high temperature are required for a long reaction time, which is not conducive to wide application in actual industrial production. Summary of the Invention

[0004] To solve the technical problems existing in the background art, the purpose of the present invention is to provide a gold-based catalyst and its application in the reaction for preparing dimethyl 2,5-furandicarboxylate. In the process of preparing dimethyl 2,5-furandicarboxylate by catalytically oxidizing 5-hydroxymethylfurfural with the gold-based catalyst of the present invention, the conversion rate of 5-hydroxymethylfurfural is 82%, and the selectivity of dimethyl 2,5-furandicarboxylate is 85%. In the reaction of catalytically oxidizing furandicarboxaldehyde to prepare dimethyl 2,5-furandicarboxylate, the conversion rate of furandicarboxaldehyde can reach 100%, and the selectivity of dimethyl 2,5-furandicarboxylate can reach 95%.

[0005] To achieve the above purpose, the present invention provides the following technical solutions:

[0006] A preparation method of a gold-based catalyst mainly includes the following steps: mixing a gold precursor solution with a titanium dioxide support so that the loading amount of gold on the support is 0.1-5 wt%, adding an alkaline solution to adjust the pH value of the system to 8-10, adding a modifier solution to the system at 40-80 °C, aging, drying, and calcining in an air atmosphere at 300-700 °C for 1-24 h to obtain an Au / TiO2 catalyst with a modifier covering the surface.

[0007] Based on the above technical solution, further, the gold precursor includes chloroauric acid, chloroaurate, and auric chloride.

[0008] Based on the above technical solution, further, the alkaline solution is one of KOH solution, NaOH solution, K2CO3 solution, Na2CO3 solution, KHCO3 solution, NaHCO3 solution, or ammonia water.

[0009] Based on the above technical solution, further, the modifier is one of tetraethyl orthosilicate, magnesium, aluminum, nickel, lanthanum, zinc, cerium nitrate, chloride, acetate, sulfate, and the mass ratio of the added amount to the mass of titanium dioxide is 0.001-0.05.

[0010] Based on the above technical solution, further, the aging temperature is 60-80 °C and the aging time is 0.5-24 h.

[0011] Based on the above technical solution, further, the calcination temperature is 400-600 °C and the calcination time is 1-6 h.

[0012] On the other hand, the present invention provides the gold-based catalyst obtained by the above preparation method.

[0013] The present invention also provides the application of the above gold-based catalyst in the reaction for preparing dimethyl 2,5-furandicarboxylate.

[0014] Based on the above technical solution, further, the specific application is to add the above gold-based catalyst into a reaction kettle containing a mixed solution of methanol and 5-hydroxymethylfurfural, adjust the pressure of the reaction kettle to 0.5-5 MPa with a mixed gas containing 10-50% oxygen, and react at 80-120 °C for 0.5-10 hours.

[0015] Based on the above technical solution, further, the specific application is to add the above gold-based catalyst into a reaction kettle containing a mixed solution of methanol and furandialdehyde, adjust the pressure of the reaction kettle to 0.5-5 MPa with a mixed gas containing 10-50% oxygen, and react at 80-120 °C for 0.5-10 hours.

[0016] Based on the above technical solution, further, the molar ratio of methanol to 5-hydroxymethylfurfural is 5:1 - 50:1, and the addition amount of the gold-based catalyst is 1 - 50 g / L.

[0017] Based on the above technical solution, further, the molar ratio of methanol to furandicarboxaldehyde is 5:1 - 50:1; the addition amount of the gold-based catalyst is 1 - 50 g / L.

[0018] The beneficial effects of the present invention compared with the prior art are as follows:

[0019] The main active component in the catalyst of the present invention is gold, and the carrier is titanium dioxide. By modifying the titanium dioxide-supported gold particles with oxides (including coating and partial covering), the interfacial effects between the gold particles and the carrier titanium dioxide, between gold and the oxides, and between the oxides and titanium dioxide are regulated, thereby improving the catalytic performance of the gold-based catalyst. In the process of catalyzing the preparation of dimethyl furandicarboxylate from 5-hydroxymethylfurfural, the conversion rate of 5-hydroxymethylfurfural is 82%, and the selectivity of dimethyl furandicarboxylate is 85%; in the reaction of catalyzing the preparation of dimethyl furandicarboxylate from furandicarboxaldehyde, the conversion rate of furandicarboxaldehyde can reach 100%, and the selectivity of dimethyl furandicarboxylate can reach 95%. Specific embodiments

[0020] The present invention will be described in detail below in conjunction with examples, but the embodiments of the present invention are not limited thereto. Obviously, the examples described below are only partial examples of the present invention. For those skilled in the art, without creative efforts, obtaining other similar examples will fall within the protection scope of the present invention.

[0021] Comparative Example 1: Preparation of 1% Au / TiO2

[0022] Take the prepared chloroauric acid solution in a 250 mL beaker, add ultrapure water and stir, add the oxide TiO2 so that the theoretical loading amount of gold on the oxide is 1%, adjust the pH of the solution to about 8 with ammonia water, heat the solution to 70 °C and age for 3 hours, then wash and filter with deionized water, and put the sample in an 80 °C oven to dry for 3 hours. Subsequently, the catalyst is calcined in an air atmosphere at 500 °C for 4 hours, and the obtained catalyst is labeled as 1% Au / TiO2.

[0023] Example 1: Preparation of (1% Au / TiO2)@SiO2

[0024] Take the prepared chloroauric acid solution in a 250 mL beaker, add ultrapure water and stir. Add the oxide TiO2 so that the theoretical loading of gold on the oxide is 1%. Adjust the pH of the solution to 8 with ammonia water. Then heat the solution to 70 °C. Subsequently, add 1 mL of tetraethyl orthosilicate dropwise. After aging for 3 h, wash with deionized water and filter by suction. Place the sample in an oven at 80 °C and dry for 3 hours. Then calcine the catalyst in an air atmosphere at 500 °C for 4 hours, and label the obtained catalyst as (1% Au / TiO2)@SiO2.

[0025] Example 2: Preparation of (1% Au / TiO2)@NiO

[0026] Take the prepared chloroauric acid solution in a 250 mL beaker, add ultrapure water and stir. Add the oxide TiO2 so that the theoretical loading of gold on the oxide is 1%. Adjust the pH of the solution to 8.5 with ammonia water. Then heat the solution to 70 °C. Subsequently, add 0.5 mL of nickel nitrate solution with a concentration of 2 mol / L dropwise. Continue to adjust the pH to 8 with ammonia water, and after aging for 3 hours, wash with deionized water and filter by suction. Place the sample in an oven at 80 °C and dry for 3 hours. Then calcine the catalyst in an air atmosphere at 500 °C for 4 hours, and label the obtained catalyst as (1% Au / TiO2)@NiO.

[0027] Example 3: Preparation of (1% Au / TiO2)@La2O3

[0028] Take the prepared chloroauric acid solution in a 250 mL beaker, add ultrapure water and stir. Add the oxide TiO2 so that the theoretical loading of gold on the oxide is 1%. Adjust the pH of the solution to 8 with ammonia water. Then heat the solution to 70 °C. Subsequently, add 0.3 mL of lanthanum nitrate solution with a concentration of 2 mol / L dropwise. Continue to adjust the pH to 8 with ammonia water, and after aging for 3 hours, wash with deionized water and filter by suction. Place the sample in an oven at 80 °C and dry for 3 hours. Then calcine the catalyst in an air atmosphere at 500 °C for 4 hours, and label the obtained catalyst as (1% Au / TiO2)@La2O3.

[0029] Example 4: Preparation of (1% Au / TiO2)@MgO

[0030] Take the prepared chloroauric acid solution in a 250 mL beaker, add ultrapure water and stir. Add the oxide TiO2 so that the theoretical loading of gold on the oxide is 1%. Adjust the pH of the solution to 8 with ammonia water, then heat the solution to 70 °C. Subsequently, add 1 mL of magnesium nitrate solution with a concentration of 2 mol / L, continue to adjust the pH to 8 with ammonia water, age for 3 hours, wash with deionized water and filter by suction. Place the sample in an oven at 80 °C and dry for 3 hours. Then calcine the catalyst in an air atmosphere at 500 °C for 4 hours, and label the obtained catalyst as (1% Au / TiO2)@MgO.

[0031] Example 5: Preparation of (0.1% Au / TiO2)@SiO2

[0032] Take the prepared chloroauric acid solution in a 250 mL beaker, add ultrapure water and stir. Add the oxide TiO2 so that the theoretical loading of gold on the oxide is 0.1%. Adjust the pH of the solution to 8 with ammonia water, then heat the solution to 70 °C. Subsequently, add 1 mL of tetraethyl orthosilicate, age for 3 h, wash with deionized water and filter by suction. Place the sample in an oven at 80 °C and dry for 3 hours. Then calcine the catalyst in an air atmosphere at 500 °C for 4 hours, and label the obtained catalyst as (0.1% Au / TiO2)@SiO2.

[0033] Example 6: Preparation of (5% Au / TiO2)@SiO2

[0034] Take the prepared chloroauric acid solution in a 250 mL beaker, add ultrapure water and stir. Add the oxide TiO2 so that the theoretical loading of gold on the oxide is 5%. Adjust the pH of the solution to 8 with ammonia water, then heat the solution to 70 °C. Subsequently, add 1 mL of tetraethyl orthosilicate, age for 3 h, wash with deionized water and filter by suction. Place the sample in an oven at 80 °C and dry for 3 hours. Then calcine the catalyst in an air atmosphere at 500 °C for 4 hours, and label the obtained catalyst as (5% Au / TiO2)@SiO2.

[0035] Example 7: Preparation of (1% Au / TiO2)@ZnO

[0036] Take the prepared chloroauric acid solution in a 250 mL beaker, add ultrapure water and stir. Add the oxide TiO2 so that the theoretical loading of gold on the oxide is 1%. Adjust the pH of the solution to 8.5 with ammonia water, then heat the solution to 70 °C. Subsequently, add 1 mL of zinc nitrate aqueous solution with a concentration of 2 mol / L, age for 3 hours, wash with deionized water and filter by suction. Place the sample in an oven at 80 °C and dry for 3 hours. Then calcine the catalyst in an air atmosphere at 500 °C for 4 hours, and label the obtained catalyst as (1% Au / TiO2)@ZnO.

[0037] Example 8: Preparation of (1% Au / TiO2)@CeO2

[0038] Take the prepared chloroauric acid solution in a 250 mL beaker, add ultrapure water and stir, then add the oxide TiO2 so that the theoretical loading of gold on the oxide is 1%. Adjust the pH of the solution to 8.5 with ammonia water, then heat the solution to 70 °C, and then dropwise add 1 mL of cerium nitrate solution with a concentration of 1 mol / L. After aging for 3 hours, wash with deionized water and filter by suction. Place the sample in an oven at 80 °C and dry for 3 hours. Subsequently, calcine the catalyst in an air atmosphere at 500 °C for 4 hours to obtain the catalyst labeled (1% Au / TiO2)@CeO2.

[0039] Example 9

[0040] Reaction of the catalysts of Comparative Example 1 and Examples 1-4 in the preparation of dimethyl furandicarboxylate from 5-hydroxymethylfurfural:

[0041] Place a mixed solution of 12 mL of methanol and 5-hydroxymethylfurfural (molar ratio 50:1) in a reaction kettle, and add 0.5 g of the above-prepared gold-based catalyst thereto respectively; use a gas with an oxygen concentration of 50% to adjust the pressure of the reaction kettle to 3 MPa, and adjust the reaction temperature to 110 °C, then react for 0.5 hours. After the reaction is completed, the product is analyzed by gas chromatography. Calculate the conversion rate of 5-hydroxymethylfurfural and the selectivity of the product dimethyl furandicarboxylate. The results are shown in Table 1.

[0042] Reaction of the catalysts of Comparative Example 1 and Examples 1-8 in the preparation of dimethyl furandicarboxylate from furandialdehyde:

[0043] Place a mixed solution of 12 mL of methanol and furandialdehyde (molar ratio 50:1) in a reaction kettle, and add 0.5 g of the above-prepared gold-based catalyst thereto respectively; use a gas with an oxygen concentration of 50% to adjust the pressure of the reaction kettle to 3 MPa, and adjust the reaction temperature to 110 °C, then react for 0.5 hours. After the reaction is completed, the product is analyzed by gas chromatography. Calculate the conversion rate of furandialdehyde and the selectivity of the product dimethyl furandicarboxylate. The results are shown in Table 1.

[0044] Table 1. Catalytic reaction activities of different catalysts in the oxidative esterification reactions of HMF and DFF

[0045]

Claims

1. Application of a gold-based catalyst in the reaction for preparing dimethyl 2,5-furandicarboxylate, characterized in that, Add the described gold-based catalyst into a reaction kettle containing a mixed solution of methanol and 5-hydroxymethylfurfural, and use a gas mixture containing 10 - 50% oxygen to adjust the pressure of the reaction kettle to 0.5 - 5 MPa, and react at 80 - 120 °C for 0.5 - 10 hours; Alternatively, add the described gold-based catalyst into a reaction kettle containing a mixed solution of methanol and furandialdehyde, and use a gas mixture containing 10 - 50% oxygen to adjust the pressure of the reaction kettle to 0.5 - 5 MPa, and react at 80 - 120 °C for 0.5 - 10 hours; The preparation method of the described gold-based catalyst includes the following steps: Mix the precursor solution of gold with the titanium dioxide support so that the loading amount of gold on the support is 0.1 - 5 wt%, add an alkaline solution to adjust the pH value of the system to 8 - 10, and add a modifier solution to the system at 40 - 80 °C, age, dry, and calcine in an air atmosphere at 300 - 700 °C for 1 - 24 h to obtain an Au / TiO₂ catalyst with a modifier covering the surface; The described modifier is tetraethyl orthosilicate or one of the nitrates, chlorides, acetates, sulfates of magnesium, aluminum, nickel, lanthanum, zinc, and cerium, and the mass ratio of the added amount to the mass of titanium dioxide is 0.001 - 0.

05.

2. The application according to claim 1, characterized in that The described gold precursor includes chloroauric acid, chloroaurate, and gold chloride.

3. The application according to claim 1, wherein The described alkaline solution is one of KOH solution, NaOH solution, K₂CO₃ solution, Na₂CO₃ solution, KHCO₃ solution, NaHCO₃ solution, or ammonia water.

4. The application according to claim 1, wherein The aging temperature is 60 - 80 °C, and the aging time is 0.5 - 24 h; the calcination temperature is 400 - 600 °C, and the calcination time is 1 - 6 h.

5. The application according to claim 1, wherein The molar ratio of methanol to 5-hydroxymethylfurfural is 5:1 - 50:1, and the addition amount of the gold-based catalyst is 1 - 50 g / L, or the molar ratio of methanol to furandialdehyde is 5:1 - 50:1, and the addition amount of the gold-based catalyst is 1 - 50 g / L.

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