Catalyst for oxidative esterification and preparation method and application thereof

Abstract

The invention discloses a catalyst for oxidative esterification and a preparation method and application thereof, and belongs to the technical field of catalytic synthesis. According to the method, the composite oxide serves as a carrier, gold particles are loaded on the oxide composite carrier in combination with a plasma reduction technology and an organic matter induction mode, the dispersity and uniformity of the gold nanoparticles are improved, meanwhile, trace coating of the nanoparticles by the carrier is achieved, and a new metal oxide interface structure is constructed; adsorption and activation of oxygen are further promoted, so that the purpose of improving the oxidative esterification reaction performance is achieved, and excellent activity is shown in the oxidative esterification reaction of methylacrolein, ethylene glycol and 5-hydroxymethylfurfural.

Description

Technical Field

[0001] The invention belongs to the technical field of catalytic synthesis, and in particular relates to a catalyst for oxidative esterification and a preparation method and 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. used supported gold catalysts in the oxidative esterification of methanol and ethylene glycol (EG) to produce methyl glycolate (MGC). It was found that supported gold catalysts with a diameter of 1 to 5 nm showed better catalytic selectivity in the reaction. Asahi Kasei Co., Ltd. of Japan used AuNiO x Nanoparticles are loaded on composite oxide carriers and used in the reaction of oxidative esterification of methacrolein to methyl methacrylate. It is found that the uniformity and dispersibility of nanogold particles help to improve the activity of the catalyst. In addition, the basic sites of the carrier also play an inseparable role in the reaction activity. It is a common technical means and method to regulate and improve the oxidative esterification reaction by improving the catalyst. Although some catalysts for oxidative esterification have been developed, the existing catalysts still have relatively low catalytic activity and selectivity, which is not conducive to industrial application. Therefore, research and development of new catalysts with high catalytic activity for oxidative esterification has become a technical problem that needs to be solved urgently. Summary of the invention

[0003] In view of this, the purpose of the present invention is to provide a catalyst for oxidative esterification and 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 coat gold particles in trace amounts, construct a contact interface between the gold particles and the oxide, and 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 value of the solution to 8-11, then heating the solution to 60-80 DEG C, stirring for 2-10 hours, washing with water, filtering, and drying, then grinding and mixing the obtained powder with organic matter uniformly, putting into a plasma discharge device, evacuating, introducing hydrogen, then turning on a plasma power supply for discharge treatment for 10s-5min, then introducing inert gas to replace hydrogen, introducing oxygen for treatment for 10s-5min, and obtaining a 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 gold cyanide, gold 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 loading amount of gold 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 0.5-5 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 application 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 a catalyst are added, and then the mixed gas containing oxygen is pressurized to 1-5MPa, and the reaction is carried out at 50-130°C under stirring to obtain a 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 0.5-5h.

[0022] The beneficial effects of the present invention compared with the prior art are as follows:

[0023] The invention realizes the rapid reduction of nano-gold by plasma reduction, thereby obtaining a nano-gold catalyst with a smaller size and more uniform distribution; at the same time, organic matter is used to induce the plasma reduction process, so as to realize the micro-coating of the nano-particles by the carrier, construct a new metal oxide interface structure, further promote the adsorption and activation of oxygen, and finally 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 The high-resolution transmission electron microscopy image (A) and the local magnified image (B) of the catalyst prepared in Comparative Example 1;

[0026] Figure 2 The high-resolution transmission electron microscopy image (A) and the 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 partial embodiments of the present invention. For those skilled in the art, other similar embodiments obtained without creative labor all fall within the protection scope of the present invention.

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

[0029] Preparation of catalyst by deposition precipitation method: take the prepared chloroauric acid solution into a 250mL beaker, add 100ml ultrapure water, stir, then add 2g of composite oxide of magnesium oxide and aluminum oxide with a magnesium aluminum molar ratio of 10:1, so that the theoretical loading amount of gold on the carrier is 1wt%, and adjust the pH of the solution to about 9 by adding 1mol / L ammonia water, then heat the solution to 70°C, continue stirring for 2 hours, wash the catalyst with a large amount of deionized water, filter, and place in an oven at 80°C to dry for 3 hours, and then calcine at 500°C in an air atmosphere for 2 hours to obtain a catalyst 1% Au / MgAlO x .

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

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

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

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

[0037] The transmission electron microscopy image of the catalyst prepared in Comparative Example 1 is as follows: Figure 1 As shown in 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 The transmission electron microscope image of the catalyst prepared in Example 1 shows that the size distribution of the gold particles on the catalyst surface is significantly more uniform and smaller. At the same time, through the transmission electron microscope, it can be seen that the surface of the gold particles on the catalyst of Example 1 has an obvious oxide coating layer, indicating that a new metal oxide interface structure has been constructed. This structure can promote the adsorption and activation of oxygen. Combined with the results in Table 1, it can be seen that the activity of the catalyst prepared in Example 1 is significantly better than 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] Catalyst preparation by 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, so that the theoretical loading amount 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. After the catalyst was washed with a large amount of deionized water and filtered, it was placed in an oven at 80 ° C and dried for 5 hours, and 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] The catalyst was prepared by plasma reduction method: 0.1g chloroauric acid solution and 2g silicon dioxide and titanium oxide composite oxide carrier with a silicon-titanium molar ratio of 10:1 were dispersed in 150mL aqueous solution, and the pH of the solution was adjusted to about 9 by adding 1mol / L ammonia water, and then the solution was heated to 70°C and stirred for 8 hours. After washing and filtering, it was placed in an oven at 80°C for 5 hours. Then, the dried powder was fully ground and mixed with 0.2g PVA, and then placed in a plasma discharge device, vacuumed, hydrogen was introduced, and then the plasma power supply was turned on for discharge treatment for 30s. The above plasma treatment steps were repeated 4 times. Then, nitrogen was introduced to replace the hydrogen, and oxygen was introduced for 30s to obtain the catalyst.

[0045] 1%Au / SiTiOx-D.

[0046] The catalysts prepared in Comparative Example 2 and Example 2 catalyze the oxidative esterification reaction of ethylene glycol to produce methyl glycolate, and the specific process is 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 was increased to 3 MPa with a 50% by volume oxygen and nitrogen mixed gas. Then, the temperature was raised to 120° C. under stirring, and this temperature was maintained for 4 hours. After that, the system was cooled, the reaction products were analyzed, and the ethylene glycol conversion rate and methyl glycolate selectivity were calculated. The specific calculation formula is as follows:

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

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

[0050] Table 2 Catalytic activity of ethylene glycol oxidative esterification by catalysts of Comparative Example 2 and Example 2

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

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

[0053] Preparation of catalyst by deposition precipitation method: Take the prepared chloroauric acid solution in a 250mL beaker, add 100ml ultrapure water, stir, then add 2g of magnesium oxide and titanium oxide composite oxide with a magnesium-titanium molar ratio of 10:1, so that the theoretical loading amount of gold on the carrier is 1wt%. The pH of the solution is adjusted to about 9 by adding 1mol / L ammonia water. Then heat the solution to 70°C and continue stirring for 8 hours. After the catalyst is washed with a large amount of deionized water and filtered, it is placed 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: 0.1g chloroauric acid solution and 2g composite oxide carrier of magnesium oxide and titanium oxide with a magnesium-titanium 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, and then the solution was heated to 70°C and stirred for 8 hours. After washing and filtering, the solution was placed in an oven at 80°C for 5 hours. Then, the dried powder was fully ground and mixed with 0.2g PVA, and then placed in a plasma discharge device, vacuumed, hydrogen was introduced, and then the plasma power supply was turned on for discharge treatment for 30s. The above plasma treatment steps were repeated 4 times, and then nitrogen was introduced to replace hydrogen, and oxygen was introduced for treatment for 30s to obtain a catalyst 1% Au / MgTiO x -D.

[0056] The catalysts prepared in Comparative Example 3 and Example 3 catalyzed the oxidative esterification reaction of HMF, and 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, and then the pressure was increased to 3 MPa with a 50% by volume oxygen and nitrogen mixed gas, and then the temperature was raised to 110° C. under stirring and maintained at this temperature for 1 hour. The calculation method of HMF conversion (%) and FDME selectivity (%) is as follows:

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

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

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

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

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

[0063] Preparation of catalyst by deposition precipitation method: take the prepared chloroauric acid solution into a 250mL beaker, add 100ml ultrapure water, stir, then add 2g of magnesium oxide and zirconium oxide composite oxide with a magnesium zirconium molar ratio of 1:10, so that the theoretical loading amount of gold on the carrier is 1wt%, and adjust the pH of the solution to about 9 by adding 1mol / L ammonia water, then heat the solution to 70°C, continue stirring for 8 hours, wash the catalyst with a large amount of deionized water, filter, place in an oven at 80°C to dry for 5 hours, and then calcine at 500°C in 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 the plasma reduction method: 0.1g of chloroauric acid solution and 2g of a composite oxide carrier of magnesium oxide and zirconium oxide with a magnesium-zirconium molar ratio of 1:10 were dispersed in 150mL of aqueous solution, and the pH of the solution was adjusted to about 9 by adding 1mol / L of 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 of PVA and placed in a plasma discharge device. Vacuuming was performed, hydrogen was introduced, and the plasma power supply was turned on for discharge treatment for 30s. The above plasma treatment steps were repeated 4 times, and then nitrogen was introduced to replace the hydrogen, and oxygen was introduced for treatment for 30s. The catalyst was obtained.

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

[0067] The catalysts prepared in Comparative Example 4 and Example 4 catalyze the oxidative esterification reaction of methacrolein, and the specific process is as follows:

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

[0069] Table 4 Catalytic activity of methacrolein oxidative esterification by 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-zirconium molar ratio of 1:10 was added, so that the theoretical loading amount 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, 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, and 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: 0.1g chloroauric acid solution and 2g composite oxide carrier of titanium oxide and zirconium oxide with a titanium zirconium molar ratio of 1:10 were dispersed in 150mL aqueous solution, and the pH of the solution was adjusted to about 10 by adding 5mol / L sodium carbonate, and then the solution was heated to 70°C and stirred for 8 hours. After washing and filtering, the solution was placed in an oven at 80°C for 5 hours. Then, the dried powder was fully ground and mixed with 0.2g PVP, and then placed in a plasma discharge device, vacuumed, hydrogen was introduced, and then the plasma power supply was turned on for discharge treatment for 60s. The above plasma treatment steps were repeated 6 times, and then nitrogen was introduced to replace hydrogen, and oxygen was introduced for 60s to obtain a catalyst 1% Au / TiZrO x -D.

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

[0076] 7.3 g of methanol and 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 blade, and then the pressure was increased to 5 MPa with an oxygen-nitrogen mixed gas having an oxygen volume percentage of 10%, and then the temperature was raised to 120° C. under stirring and maintained at this temperature for 5 hours. The system was then cooled, the reaction products were analyzed, and the ethylene glycol conversion and methyl glycolate selectivity were calculated.

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

[0078] catalyst Ethylene glycol conversion rate (%) Methyl glycolate selectivity (%) <![CDATA[1%Au / TiZrO x ]]> 40 87 <![CDATA[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 amount 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. After the catalyst was filtered and washed with a large amount of deionized water, it was placed in an oven at 80 ° C and dried 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 chloroauric acid solution and 2 g titanium oxide and zirconium oxide composite oxide carrier with a titanium zirconium molar ratio of 1:10 were dispersed in 150 mL aqueous solution, and 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 continued to be stirred for 8 hours. After washing and filtering, it was placed in an oven at 80 ° C for 5 hours, and then the dried powder was fully ground and mixed with 0.2 g PVP, and then placed in a plasma discharge device, evacuated, hydrogen was introduced, and then the plasma power supply was turned on for discharge treatment for 60 seconds. The above plasma treatment steps were repeated 6 times, and then nitrogen was introduced to replace hydrogen, and oxygen was introduced for treatment for 60 seconds to obtain a 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, and 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, and then the pressure was increased to 3 MPa with a 50% by volume oxygen and nitrogen mixed gas, and then the temperature was raised to 110° C. under 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 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 aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned 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: The gold salt solution and the composite oxide carrier are dispersed in an aqueous solution, an alkaline solution is added to adjust the pH of the solution to 8-11, and then the solution is heated to 60-80°C, stirred for 2-10 hours, washed with water, filtered, and dried, and then the obtained powder is ground and mixed evenly with organic matter, placed in a plasma discharge device, evacuated, hydrogen is introduced, and then the plasma power supply is turned on for discharge treatment for 10s-5min, and then an inert gas is introduced to replace the hydrogen, and oxygen is introduced for treatment for 10s-5min to obtain a catalyst.

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 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 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.

5. The preparation method according to claim 1, characterized in that: The drying is specifically drying in an oven at 60-100° C. for 2-10 hours; the plasma treatment step is repeated 2-8 times; and 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 1-5MPa, and the reaction is carried out at 50-130°C under stirring 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 added amount of the catalyst 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°C and the reaction time is 0.5-5h.

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