A catalyst for oxidative esterification and a method for preparing and using the same

Abstract

The application discloses a catalyst for oxidative esterification and a preparation method and application thereof, and belongs to the technical field of catalytic synthesis. The application uses a composite oxide as a carrier, and gold particles are loaded on the oxide composite carrier by combining plasma reduction technology and an organic matter induction mode. The method improves the dispersity and uniformity of the gold nanoparticles, realizes trace coating of the carrier on the nanoparticles, constructs a new metal oxide interface structure, further promotes the adsorption and activation of oxygen, and thus the performance of the oxidative esterification reaction is improved. The catalyst shows excellent activity in methyl propyl aldehyde, ethylene glycol and 5-hydroxymethyl furfural oxidative esterification reactions.

Description

Technical Field

[0001] The invention belongs to the technical field of catalytic synthesis, and particularly relates to a catalyst for oxidative esterification, a preparation method and an application thereof. Background Art

[0002] Supported gold catalysts are widely used in the field of oxidative esterification. For example, methanol can be oxidatively esterified with ethylene glycol, methacrolein, and 5-hydroxymethylfurfural to produce methyl glycolate, methyl methacrylate (MMA), and dimethyl 2,5-furandicarboxylate. Japan Catalyst Co., Ltd. uses supported gold catalysts in the oxidative esterification of methanol and ethylene glycol (EG) to produce methyl glycolate (MGC). It is found that supported gold catalysts with a diameter of 1 to 5 nm exhibit better catalytic selectivity in the reaction. Asahi Kasei Corporation of Japan uses AuNiO x Nanoparticles supported on a composite oxide support were used in the oxidative esterification of methacrolein to methyl methacrylate. The uniformity and dispersion of the gold nanoparticles were found to enhance the catalyst's activity. Furthermore, the support's basic sites play a crucial role in the reaction's activity. Modifying catalysts to regulate and enhance oxidative esterification reactions is a common technique. While several catalysts for oxidative esterification have been developed, existing catalysts still suffer from relatively low catalytic activity and selectivity, hindering their industrial application. Therefore, the research and development of new, highly active catalysts for oxidative esterification has become an urgent technical challenge. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a catalyst for oxidative esterification, a preparation method and application thereof. In view of the characteristics of the oxidative esterification reaction, the present invention uses a composite oxide as a carrier, combines plasma reduction technology and organic induction to effectively control the dispersion and particle size of gold particles on the carrier. Compared with the traditional method of directly loading gold particles on the composite oxide, the method of the present invention can be used to micro-coat gold particles, construct a contact interface between the gold particles and the oxide, further regulate the adsorption and activation of oxygen, thereby regulating the reaction activity of the reactants, thereby improving the reaction activity of the oxidative esterification.

[0004] In order to achieve the above object, the present invention provides the following technical solutions:

[0005] The invention provides a preparation method of a catalyst for oxidative esterification, comprising the following steps: dispersing a gold salt solution and a composite oxide carrier into an aqueous solution, adding an alkaline solution to adjust the pH of the solution to 8-11, then heating the solution to 60-80°C, stirring for 2-10 hours, washing with water, filtering, and drying, then grinding and uniformly mixing the obtained powder with organic matter, placing the powder into a plasma discharge device, evacuating the mixture, introducing hydrogen, then turning on a plasma power supply to discharge the mixture for 10 seconds to 5 minutes, then introducing an inert gas to replace the hydrogen, and introducing oxygen for 10 seconds to 5 minutes to obtain the catalyst.

[0006] Based on the above technical solution, further, the gold salt is one or a combination of two or more of gold cyanide, potassium aurous cyanide, goldous chloride, gold chloride, chloroauric acid, chloroaurate, sodium gold sulfite or furan, and the gold loading is 0.05-10wt%.

[0007] Based on the above technical solution, further, the gold loading amount is 0.1-5wt%.

[0008] Based on the above technical solution, further, the composite oxide carrier is a mixture of any two of magnesium oxide, aluminum oxide, titanium oxide, zirconium oxide, and silicon dioxide, and the molar ratio of the metal elements between the two is 1:10-10:1.

[0009] Based on the above technical solution, further, the alkaline solution includes ammonia water, sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution, sodium bicarbonate solution, potassium carbonate solution and potassium bicarbonate solution.

[0010] Based on the above technical solution, further, the concentration of the alkaline solution is 0.5 to 5 mol / L.

[0011] Based on the above technical solution, further, the organic matter is one of polyvinyl pyrrolidone (PVP), polyvinyl alcohol (PVA), and citric acid, and the added amount is 0.1-10 times the molar amount of gold.

[0012] Based on the above technical solution, further, the drying is specifically drying in an oven at 60-100° C. for 2-10 hours.

[0013] Based on the above technical solution, further, the plasma treatment step is repeated 2-8 times.

[0014] Based on the above technical solution, further, the inert gas is at least one of nitrogen, helium, argon and neon.

[0015] Another aspect of the present invention provides a catalyst obtained by the above preparation method.

[0016] The present invention also provides use of the above catalyst in oxidative esterification reaction.

[0017] Based on the above technical solution, further, the oxidative esterification reaction is carried out in a reactor, methanol, reaction raw materials and catalyst are added, and then the mixed gas containing oxygen is pressurized to 1-5 MPa, and the reaction is carried out at 50-130° C. under stirring to obtain the product.

[0018] Based on the above technical solution, further, the reaction raw material is one of methacrolein, ethylene glycol and 5-hydroxymethylfurfural, and the molar ratio of methanol to the reaction raw material is 1-100.

[0019] Based on the above technical solution, further, the amount of the catalyst added is 1-50% of the mass of the reaction raw materials.

[0020] Based on the above technical solution, further, the oxygen-containing mixed gas is an oxygen-nitrogen mixed gas with an oxygen volume percentage of 5-50%.

[0021] Based on the above technical solution, further, the reaction temperature is 60-120° C., and the reaction time is 0.5-5 h.

[0022] The present invention has the following beneficial effects compared to the prior art:

[0023] The present invention achieves rapid reduction of nano-gold through plasma reduction, thereby obtaining a nano-gold catalyst with smaller size and more uniform distribution. At the same time, organic matter is used to induce the plasma reduction process to achieve micro-coating of the nanoparticles by the carrier, construct a new metal oxide interface structure, further promote the adsorption and activation of oxygen, and ultimately achieve the purpose of improving the performance of the oxidative esterification reaction. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the embodiments of the present invention, the drawings related to the embodiments are briefly introduced below.

[0025] Figure 1 A high-resolution transmission electron micrograph (A) and a local magnified image (B) of the catalyst prepared in Comparative Example 1;

[0026] Figure 2 A high-resolution transmission electron micrograph (A) and a local magnified image (B) of the catalyst prepared in Example 1. DETAILED DESCRIPTION

[0027] The present invention is described in detail below with reference to the embodiments, but the embodiments of the present invention are not limited thereto. Obviously, the embodiments described below are only some embodiments of the present invention. For those skilled in the art, other similar embodiments obtained without creative work all fall within the scope of protection of the present invention.

[0028] Comparative Example 1: 1% Au / MgAlO x Preparation

[0029] The catalyst was prepared by the deposition precipitation method: the prepared chloroauric acid solution was placed in a 250 mL beaker, 100 mL of ultrapure water was added, and the mixture was stirred. Subsequently, 2 g of a composite oxide of magnesium oxide and aluminum oxide with a magnesium-aluminum molar ratio of 10:1 was added to obtain a theoretical gold loading of 1 wt %. The pH of the solution was adjusted to about 9 by adding 1 mol / L ammonia water. The solution was then heated to 70°C and stirred for 2 hours. The catalyst was washed with a large amount of deionized water, filtered, and dried in an oven at 80°C for 3 hours. The catalyst was then calcined at 500°C in an air atmosphere for 2 hours to obtain a 1% Au / MgAlO catalyst. x .

[0030] Example 1: Catalyst 1% Au / MgAlO x Preparation of -D

[0031] The catalyst was prepared by plasma reduction method: 0.1 g of chloroauric acid solution and 2 g of a composite oxide support of magnesium oxide and aluminum oxide with a magnesium-aluminum molar ratio of 10:1 were dispersed in 150 mL of aqueous solution. The pH of the solution was adjusted to about 9 by adding 1 mol / L ammonia water. The solution was then heated to 70°C and stirred for 5 hours. After washing and filtering, the solution was placed in an oven at 80°C and dried for 5 hours. The dried powder was then thoroughly ground and mixed with 0.2 g of PVP and placed in a plasma discharge device. Vacuuming was carried out, hydrogen was introduced, and the plasma power supply was turned on for discharge treatment for 30 seconds. The above plasma treatment steps were repeated 4 times. Subsequently, nitrogen was introduced to replace hydrogen, and oxygen was introduced for treatment for 30 seconds to obtain the catalyst 1% Au / MgAlOx-D.

[0032] The catalysts prepared in Comparative Example 1 and Example 1 catalyzed the oxidative esterification of methacrolein to produce methyl methacrylate. The specific process was as follows:

[0033] 10 g of methanol and 1.6 g of methacrolein were placed in a 100 ml reactor, and 0.5 g of the catalyst prepared in Comparative Example 1 or Example 1 was added. The pressure was then increased to 3 MPa using a 50% by volume mixture of oxygen and nitrogen. The temperature was then raised to 80° C. with stirring and maintained at this temperature for 1 hour. The methacrolein conversion and methyl methacrylate selectivity were then analyzed.

[0034] The specific calculation formulas for methacrolein conversion and methyl methacrylate selectivity are as follows:

[0035] Methacrolein conversion rate (%) = (amount of methacrolein substance consumed) * 100% / (amount of methacrolein substance added);

[0036] Methyl methacrylate selectivity (%)=(the amount of methyl methacrylate produced)*100% / (the amount of methacrolein consumed).

[0037] The transmission electron microscope image of the catalyst prepared in Comparative Example 1 is as follows: Figure 1 As shown in Figure A, it can be found that the gold particle size of the catalyst of Comparative Example 1 is between 3-5 nm and the distribution is uneven. Figure 1 B shows that there is no oxidation coating on the surface of the gold particles.

[0038] Figure 2 This is a transmission electron micrograph of the catalyst prepared in Example 1. The results show that the gold particles on the catalyst surface have a significantly more uniform size distribution and are smaller. Furthermore, transmission electron microscopy reveals a distinct oxide coating on the gold particles in the catalyst of Example 1, indicating the formation of a novel metal oxide interface structure. This structure enhances oxygen adsorption and activation. Combined with the results in Table 1, it can be seen that the activity of the catalyst prepared in Example 1 is significantly superior to that of the catalyst prepared in Comparative Example 1.

[0039] Table 1 Methacrolein oxidative esterification activity of the catalysts of Comparative Example 1 and Example 1

[0040]

[0041] Comparative Example 2: 1% Au / SiTiO x Preparation

[0042] The catalyst was prepared by the deposition precipitation method: the prepared chloroauric acid solution was placed in a 250 mL beaker, 100 mL of ultrapure water was added, and the mixture was stirred. Subsequently, 2 g of a composite oxide of silicon dioxide and titanium oxide with a silicon-titanium molar ratio of 10:1 was added to achieve a theoretical gold loading of 1 wt %. The pH of the solution was adjusted to about 9 by adding 1 mol / L ammonia water. The solution was then heated to 70°C and stirred for 8 hours. The catalyst was washed with a large amount of deionized water, filtered, and dried in an oven at 80°C for 5 hours. It was then calcined at 500°C in an air atmosphere for 2 hours to obtain a catalyst 1% Au / SiTiO x .

[0043] Example 2: Catalyst 1% Au / SiTiO x Preparation of -D

[0044] Plasma reduction method for preparing catalyst: 0.1 g of chloroauric acid solution and 2 g of silica and titania composite oxide carrier with a molar ratio of silica to titania of 10:1 were dispersed in 150 mL of aqueous solution, the pH of the solution was adjusted to about 9 by adding 1 mol / L ammonia water, and then the solution was heated to 70°C, and stirring was continued for 8 hours. After water washing and filtration, it was dried in an oven at 80°C for 5 hours. Then the dried powder was mixed with 0.2 g of PVA by grinding and placed in a plasma discharge device. After vacuumizing and introducing hydrogen, the plasma power was turned on and discharged for 30 seconds. The above plasma treatment step was repeated 4 times. Then, after replacing the hydrogen with nitrogen, oxygen was introduced and treated for 30 seconds to obtain the catalyst

[0045] 1% Au / SiTiOx-D.

[0046] The catalyst prepared in Comparative Example 2 and Example 2 was used to catalyze the esterification of ethylene glycol by oxidation to produce methyl glycolate, and the specific process was as follows:

[0047] 7.3 g of methanol and 1.42 g of ethylene glycol and 0.5 g of the catalyst prepared in Comparative Example 2 or Example 2 were placed in a 100 mL autoclave equipped with a stirring paddle, and then the pressure of oxygen-nitrogen mixed gas with a volume percentage of 50% was increased to 3 MPa. Then the temperature was increased to 120°C under stirring, and this temperature was maintained for 4 hours. Then the system was cooled, and the reaction products were analyzed to calculate the conversion rate of ethylene glycol and the selectivity of methyl glycolate, and the specific calculation formulas were as follows:

[0048] Ethylene glycol conversion rate (%) = (consumed ethylene glycol substance amount) * 100% / (added ethylene glycol substance amount);

[0049] Methyl glycolate selectivity (%) = (generated methyl glycolate substance amount) * 100% / (consumed ethylene glycol substance amount).

[0050] Table 2 Activity of catalysts of Comparative Example 2 and Example 2 in catalyzing the esterification of ethylene glycol by oxidation

[0051] catalyst Ethylene glycol conversion rate (%) Methyl glycolate selectivity (%) <![CDATA[1%Au / SiTiO x ]]> 40 87 1% Au / SiTiO x -D]] 51 90

[0052] Comparative Example 3: Preparation of 1% Au / MgTiO x

[0053] ​The catalyst was prepared by the deposition precipitation method: the prepared chloroauric acid solution was placed in a 250 mL beaker, 100 mL of ultrapure water was added, and the mixture was stirred. Subsequently, 2 g of a composite oxide of magnesium oxide and titanium oxide with a magnesium-titanium molar ratio of 10:1 was added, so that the theoretical loading of gold on the carrier was 1 wt%. The pH of the solution was adjusted to about 9 by adding 1 mol / L ammonia water. The solution was then heated to 70°C and stirred for 8 hours. After the catalyst was washed with a large amount of deionized water and filtered, it was dried in an oven at 80°C for 5 hours, and then calcined at 500°C in an air atmosphere for 2 hours to obtain a catalyst 1% Au / MgTiO x .

[0054] Example 3: Catalyst 1% Au / MgTiO x Preparation of -D

[0055] The catalyst was prepared by plasma reduction method: 0.1 g of chloroauric acid solution and 2 g of a composite oxide support of magnesium oxide and titanium oxide with a magnesium-titanium molar ratio of 1:10 were dispersed in 150 mL of aqueous solution. The pH of the solution was adjusted to about 9 by adding 1 mol / L ammonia water. The solution was then heated to 70°C and stirred for 8 hours. After washing and filtering, it was placed in an oven at 80°C and dried for 5 hours. The dried powder was then fully ground and mixed with 0.2 g of PVA and placed in a plasma discharge device. Vacuuming, hydrogen was introduced, and the plasma power supply was turned on for discharge treatment for 30 seconds. The above plasma treatment steps were repeated 4 times. Then, nitrogen was introduced to replace hydrogen, and oxygen was introduced for treatment for 30 seconds to obtain the catalyst 1% Au / MgTiO x -D.

[0056] The catalysts prepared in Comparative Example 3 and Example 3 catalyzed the oxidative esterification reaction of HMF. The specific process was as follows:

[0057] 10 g of methanol and 1.8 g of HMF were placed in a 100 ml reactor. 0.5 g of the catalyst prepared in Comparative Example 3 or Example 3 was added. The pressure was then increased to 3 MPa using a 50% by volume mixture of oxygen and nitrogen. The temperature was then raised to 110°C with stirring and maintained at this temperature for 1 hour. The HMF conversion (%) and FDME selectivity (%) were calculated as follows:

[0058] HMF conversion (%) = (amount of HMF substance consumed) * 100% / (amount of HMF substance added);

[0059] FDME selectivity (%)=(substance amount of produced FDME)*100% / (substance amount of consumed HMF).

[0060] Table 3 Catalytic activity of HMF oxidative esterification by the catalysts of Comparative Example 3 and Example 3

[0061] catalyst HMF conversion rate (%) FDME selectivity (%) 1% Au / MgTiO x ]] 55 70 <![CDATA[1%Au / MgTiO x -D]]> 69 87

[0062] Comparative Example 4: 1% Au / MgZrO x Preparation

[0063] The catalyst was prepared by the deposition precipitation method: the prepared chloroauric acid solution was placed in a 250 mL beaker, 100 mL of ultrapure water was added, and the mixture was stirred. Subsequently, 2 g of a composite oxide of magnesium oxide and zirconium oxide with a magnesium to zirconium molar ratio of 1:10 was added, so that the theoretical loading of gold on the carrier was 1 wt%. The pH of the solution was adjusted to about 9 by adding 1 mol / L ammonia water, and then the solution was heated to 70 ° C and stirred for 8 hours. The catalyst was washed with a large amount of deionized water, filtered, and dried in an oven at 80 ° C for 5 hours. It was then calcined at 500 ° C in an air atmosphere for 2 hours to obtain a catalyst 1% Au / MgZrO x .

[0064] Example 4: Catalyst 1% Au / MgZrO x Preparation of -D

[0065] The catalyst was prepared by plasma reduction method: 0.1g chloroauric acid solution and 2g composite oxide carrier of magnesium oxide and zirconium oxide with a magnesium-zirconium molar ratio of 1:10 were dispersed in 150mL aqueous solution, and the pH of the solution was adjusted to about 9 by adding 1mol / L ammonia water. The solution was then heated to 70°C and stirred for 8 hours. After washing and filtering, the solution was placed in an oven at 80°C and dried for 5 hours. The dried powder was then fully ground and mixed with 0.2g PVA and placed in a plasma discharge device. Vacuuming was carried out, hydrogen was introduced, and the plasma power supply was turned on for 30s. The above plasma treatment steps were repeated 4 times. Then nitrogen was introduced to replace hydrogen, and oxygen was introduced for 30s. The catalyst was obtained.

[0066] 1%Au / MgZrO x -D.

[0067] The catalysts prepared in Comparative Example 4 and Example 4 catalyzed the oxidative esterification reaction of methacrolein. The specific process was as follows:

[0068] 10g of methanol and 1.6g of methacrolein were placed in a 100ml reactor. 0.5g of the catalyst prepared in Comparative Example 4 or Example 4 was added. The pressure was then increased to 2 MPa using a 30% by volume oxygen-nitrogen mixture. The temperature was then raised to 70°C with stirring and maintained at this temperature for 2 hours. The methacrolein conversion and methyl methacrylate selectivity were calculated.

[0069] Table 4 Catalytic activity of methacrolein oxidative esterification by the catalysts of Comparative Example 4 and Example 4

[0070]

[0071] Comparative Example 5: 1% Au / TiZrO x Preparation

[0072] The catalyst was prepared by the deposition precipitation method: the prepared chloroauric acid solution was placed in a 250 mL beaker, 100 mL of ultrapure water was added, and the mixture was stirred. Subsequently, 2 g of a composite oxide of titanium oxide and zirconium oxide with a titanium to zirconium molar ratio of 1:10 was added, so that the theoretical loading of gold on the carrier was 1 wt%. The pH of the solution was adjusted to about 10 by adding 5 mol / L sodium carbonate. The solution was then heated to 70°C and stirred for 8 hours. The catalyst was washed with a large amount of deionized water, filtered, and dried in an oven at 80°C for 5 hours. It was then calcined at 500°C in an air atmosphere for 2 hours to obtain a catalyst 1% Au / TiZrO x .

[0073] Example 5: Catalyst 1% Au / TiZrO x Preparation of -D

[0074] The catalyst was prepared by plasma reduction method: 0.1 g of chloroauric acid solution and 2 g of a composite oxide support of titanium oxide and zirconium oxide with a titanium-zirconium molar ratio of 1:10 were dispersed in 150 mL of aqueous solution. The pH of the solution was adjusted to about 10 by adding 5 mol / L sodium carbonate. The solution was then heated to 70 ° C and stirred for 8 hours. After washing and filtering, it was placed in an oven at 80 ° C and dried for 5 hours. The dried powder was then fully ground and mixed with 0.2 g of PVP and placed in a plasma discharge device. Vacuuming, hydrogen was introduced, and the plasma power supply was turned on for 60 seconds. The above plasma treatment steps were repeated 6 times. Then, nitrogen was introduced to replace hydrogen, and oxygen was introduced for 60 seconds to obtain the catalyst 1% Au / TiZrO x -D.

[0075] The catalysts prepared in Comparative Example 5 and Example 5 catalyzed the oxidative esterification reaction of ethylene glycol. The specific process is as follows:

[0076] 7.3 g of methanol, 1.42 g of ethylene glycol, and 0.5 g of the catalyst prepared in Comparative Example 5 or Example 5 were placed in a 100 mL autoclave equipped with a stirring paddle. The pressure was then increased to 5 MPa using a 10% by volume oxygen-nitrogen mixture. The temperature was then raised to 120°C with stirring and maintained at this temperature for 5 hours. The system was then cooled, and the reaction products were analyzed to calculate the ethylene glycol conversion and methyl glycolate selectivity.

[0077] Table 5 Catalytic activity of ethylene glycol oxidative esterification by the catalysts of Comparative Example 5 and Example 5

[0078] catalyst Ethylene glycol conversion rate (%) Methyl glycolate selectivity (%) <![CDATA[1%Au / TiZrO x ]]> 40 87 1% Au / TiZrO x -D]] 51 90

[0079] Comparative Example 6: 0.5% Au / TiZrO x Preparation

[0080] The catalyst was prepared by a deposition precipitation method: the prepared chloroauric acid solution was placed in a 250 mL beaker, 100 mL of ultrapure water was added, and the mixture was stirred. Subsequently, 2 g of titanium-zirconium composite oxide (titanium oxide and zirconium oxide) with a titanium-zirconium molar ratio of 1:10 was added, and the theoretical loading of gold on the carrier was 0.5 wt%. The pH of the solution was adjusted to about 9 by adding 3 mol / L ammonia water, and then the solution was heated to 70 ° C and stirred for 8 hours. The catalyst was filtered and washed with a large amount of deionized water, and then dried in an oven at 80 ° C for 5 hours, and then calcined at 500 ° C in an air atmosphere for 2 hours to obtain a catalyst 0.5% Au / TiZrO x .

[0081] Example 6: Catalyst 0.5% Au / TiZrO x Preparation of -D

[0082] The catalyst was prepared by plasma reduction method: 0.05 g of chloroauric acid solution and 2 g of titanium oxide and zirconium oxide composite oxide support with a titanium-zirconium molar ratio of 1:10 were dispersed in 150 mL of aqueous solution. The pH of the solution was adjusted to about 9 by adding 3 mol / L ammonia water. The solution was then heated to 70 ° C and stirred for 8 hours. After washing and filtering, it was placed in an oven at 80 ° C and dried for 5 hours. The dried powder was then fully ground and mixed with 0.2 g of PVP and placed in a plasma discharge device. Vacuuming, hydrogen was introduced, and the plasma power supply was turned on for 60 seconds. The above plasma treatment steps were repeated 6 times. Then, nitrogen was introduced to replace hydrogen, and oxygen was introduced for 60 seconds to obtain the catalyst 0.5% Au / TiZrO x -D.

[0083] The catalysts prepared in Comparative Example 6 and Example 6 catalyzed the oxidative esterification reaction of HMF. The specific process was as follows:

[0084] 10 g of methanol and 1.8 g of HMF were placed in a 100 ml reactor. 0.5 g of the catalyst prepared in Comparative Example 6 or Example 6 was added. The pressure was then increased to 3 MPa using a 50% by volume mixture of oxygen and nitrogen. The temperature was then raised to 110°C with stirring and maintained at this temperature for 1 hour. The HMF conversion (%) and FDME selectivity (%) were calculated.

[0085] Table 6 Catalytic activity of HMF oxidative esterification by the catalysts of Comparative Example 6 and Example 6

[0086]

[0087] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the above embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a catalyst for oxidative esterification, characterized in that: The following steps are involved: Disperse the gold salt solution and the composite oxide support into the aqueous solution, add alkaline solution to adjust the pH of the solution to 8-11, and then heat the solution to 60-80 o C, stirring for 2-10 hours, washing with water, filtering, and drying, then grinding and mixing the obtained powder with an organic matter to uniformly mix, placing it in a plasma discharge device, evacuating, introducing hydrogen, then turning on the plasma power supply for discharge treatment for 10 seconds to 5 minutes, then introducing inert gas to replace the hydrogen, and introducing oxygen for treatment for 10 seconds to 5 minutes to obtain a catalyst; the organic matter is one of polyvinyl pyrrolidone (PVP), polyvinyl alcohol (PVA), and citric acid.

2. The preparation method according to claim 1, characterized in that The gold salt is one or a combination of two or more of gold cyanide, potassium aurous cyanide, goldous chloride, gold chloride, chloroauric acid, chloroaurate, sodium gold sulfite or furan, and the gold loading amount is 0.05-10wt%.

3. The preparation method according to claim 1, characterized in that The composite oxide carrier is a mixture of any two of magnesium oxide, aluminum oxide, titanium oxide, zirconium oxide and silicon dioxide, and the molar ratio of the metal elements between the two is 1:10-10:

1.

4. The preparation method according to claim 1, characterized in that The alkaline solution includes ammonia water, sodium hydroxide solution, potassium hydroxide solution, sodium carbonate solution, sodium bicarbonate solution, potassium carbonate solution and potassium bicarbonate solution; the concentration of the alkaline solution is 0.5-5 mol / L; the amount of the organic matter added is 0.1-10 times the molar amount of gold.

5. The preparation method according to claim 1, characterized in that The drying step is specifically to dry the o C oven for 2-10 hours; the plasma treatment step is repeated 2-8 times; the inert gas is at least one of nitrogen, helium, argon and neon.

6. The catalyst obtained by the preparation method according to any one of claims 1 to 5.

7. Use of the catalyst according to claim 6 in oxidative esterification reaction.

8. The use according to claim 7, characterized in that The oxidative esterification reaction is carried out in a reactor, methanol, reaction raw materials and catalyst are added, and then the mixed gas containing oxygen is pressurized to 1-5 MPa and stirred at 50-130 o C to obtain the product.

9. The use according to claim 8, characterized in that The reaction raw material is one of methacrolein, ethylene glycol and 5-hydroxymethylfurfural, and the molar ratio of methanol to the reaction raw material is 1-100; the amount of catalyst added is 1-50% of the mass of the reaction raw material; and the oxygen-containing mixed gas is an oxygen-nitrogen mixed gas with an oxygen volume percentage of 5-50%.

10. The use according to claim 8, characterized in that The reaction temperature is 60-120 o C, reaction time is 0.5-5h.

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