WO2020107539A1 - Preparation method for catalyst for producing methyl methacrylate, and application thereof - Google Patents

Abstract

A catalyst for producing methyl methacrylate (MMA), and preparation method therefor and application thereof. The catalyst comprises a carrier and an active center supported on the carrier. The active center comprises gold, a transition metal, and a lanthanide metal. The carrier comprises SiO₂, Al₂O₃, and one of an alkali metal or an alkali earth metal. The loading of the gold is 0.05-0.98 wt%, the loading of the lanthanide metal is 1-2.5 wt%, and the loading of the transition metal is 1-2.5 wt%. A polymer protection method is used as the preparation method and comprises: fully mixing a precursor of gold with a reductant and deionized water to obtain gold sol; sequentially adding the gold sol to a lanthanide metal and a transition metal; then adding a carrier; continuing to stir for 2-20 h and slowly rising the temperature to 65-85°C; after the stirring ends, lowering the temperature to the room temperature; and carrying out still standing, filtering, washing, drying, and roasting to obtain a catalyst. The catalyst is applied to a reaction for producing MMA, has excellent activity and stability, features low costs, high methacrolein conversion rate and MMA selectively, and is suitable for industrial production.

Description

Preparation method and application of catalyst for producing methyl methacrylate Technical field

The invention belongs to the technical field of catalyst preparation, and particularly relates to a preparation method and application of a catalyst for producing methyl methacrylate.

Background technique

Methyl methacrylate (MMA) is an important organic chemical raw material. It is a colorless and transparent liquid with ether flavor at room temperature. In the past, MMA was mainly produced by the acetone cyanohydrin method in industry. In recent years The one-step preparation of MMA by methacrolein is a green process route with great development potential, because there is no methacrylic acid formation in the middle, and there is no subsequent esterification process of methacrylic acid and methanol, which will greatly save production costs. At the same time, the by-product of the process is water, which is green and environmentally friendly. However, the difficulty of this process lies in the preparation of the catalyst. Therefore, many efforts have been made to solve this problem. For example, Asahi Kasei of Japan developed the oxidation of isobutylene to methacrolein, and methacrolein was oxidized with methanol under the action of Pd-Pb catalyst to prepare MMA. This process does not involve highly corrosive methacrylic acid and does not require high requirements for reaction equipment. In addition, the process is very simple, requiring only two steps of reaction. The by-product is only water, which is green and environmentally friendly. Compared with the original MMA preparation process, this process requires lower raw material costs, high product purity, compact equipment, and significantly reduced construction costs, but it requires high catalyst design and preparation requirements. The first-generation Pd-Pb catalyst has a low selectivity for MMA, about 84%, which will increase the subsequent separation cost and affect the quality of the product.

Subsequently, in a follow-up study, Asahi Kasei of Japan found that the core-shell nanogold catalyst (Au@NiOx) can efficiently catalyze the co-oxidation of methacrolein and methanol to produce MMA. The process is simple and the catalyst shows excellent stability. However, the catalyst preparation technology requires high, and when the conversion rate of methacrolein is 65%, the selectivity of MMA is about 95%, and in actual application process, it is often necessary to ensure high activity (usually based on high conversion rate) At the same time, it can maintain a high selectivity of the target product; in addition, the cost of the catalyst is also high, the cost is about 6 million/ton, which will also limit its industrial application to a certain extent.

Chinese Patent Publication No. CN107107034A discloses a gold-based catalyst for the oxidative esterification of aldehydes to obtain carboxylic acid esters, with gold as the active component, and silicon, aluminum and other elements in the oxidized state as carriers, and other elements are selected from Alkali metal, alkaline earth metal, rare earth metal, Ti, Zr, Cu, Mn, Pb, Sn or Bi, form a particle form of the catalyst, the catalyst can be used for a long time to oxidize aldehyde to carboxylic acid ester, especially in the water And mixtures containing carboxylic acid. However, this catalyst catalyzes the conversion of methacrolein to MMA, the catalytic conditions are harsh, and the conversion rate of methacrolein and the selectivity of MMA are not ideal, especially in the industrial expansion test, the selectivity to MMA is not high, affecting product quality.

Summary of the invention

In order to make up for the shortcomings of the prior art, the present invention provides a preparation method and application of a catalyst for producing methyl methacrylate. The catalyst preparation process is simple, the operation is convenient, has excellent activity and good stability, and the choice of MMA High performance, suitable for industrial production.

The present invention is achieved through the following technical solutions:

One aspect of the present invention provides a catalyst for producing methyl methacrylate. The catalyst includes a carrier and an active center supported on the carrier; the active center includes gold, transition metal, and lanthanide metal; and the carrier includes SiO ₂ , Al ₂ O ₃ and alkali metals or alkaline earth metals; in the catalyst, the loading of gold is 0.05wt%-0.98wt%, the loading of lanthanide metal is 1wt%-2.5wt%, the transition metal The loading is 1wt%-2.5wt%.

Based on the above technical solution, preferably, the alkali metal or alkaline earth metal is Na, K, Rb, Cs, Be, Mg, Ca, Sr; the lanthanide metal is one of La, Ce, Pr, Nd, The transition metal is one of Cu, Co, Fe, Mn, and Cr.

Based on the above technical solution, preferably, based on the carrier mass of 100%, the mass fraction of alkali metal and alkaline earth metal ranges from 1 to 25%; the molar ratio of alkali metal or alkaline earth metal to SiO ₂ in the carrier is 1 to 6: 0.5～4.

Another aspect of the present invention provides a method for preparing the above-mentioned catalyst for producing methyl methacrylate, which is special in that: the catalyst is prepared by a polymer protection method, and the precursor of gold and the reducing agent are removed under stirring conditions. Ion water is fully mixed to obtain a stable, uniform and high-dispersed gold sol. In the presence of a polymer protective agent, the lanthanide metal precursor and the transition metal precursor are added to the gold sol in sequence, and then the carrier is added , Slowly raise the temperature to 65-85°C and continue to stir for 2-20h. After stirring, return to room temperature, let stand and filter, wash with deionized water until no chloride ion can be detected, dry it and roast in air to obtain the catalyst

Based on the above technical solution, preferably, the preparation process of the carrier is: adding an alumina precursor, an alkali metal or an alkaline earth metal precursor to the silica precursor solution under stirring conditions, and after fully stirring and mixing, adding an acid Adjust the PH value to 0.5-5.5, and continue to stir for 1-24h to obtain a mixture. The mixture is spray-dried to form spherical particles with a particle size of 50-100μm, and the carrier is obtained by calcination under an air atmosphere.

Based on the above technical solution, preferably, the precursor of Au is gold cyanide (Au(CN) ₃ ), potassium gold cyanide, gold chloride (AuC1), gold chloride (AuC1 ₃ ), gold chloride One or more of acid, chloroaurate, sodium gold sulfite or thunder gold.

Based on the above technical solution, preferably, the polymer protective agent is polyvinyl alcohol, polyvinylpyrrolidone, tetramethylolphosphonium chloride, polydimethyldipropylene ammonium chloride, sodium citrate, and thiol.

Based on the above technical solution, preferably, the reducing agent is sodium citrate, tetramethylolphosphonium chloride, oxalic acid, and sodium borohydride.

Based on the above technical solution, preferably, the lanthanide metal precursor and the transition metal precursor are sulfates, nitrates, phosphates, carbonates, and acetates of corresponding metals.

Based on the above technical solution, preferably, in the method, the amount of lanthanide metal precursor, transition metal precursor, gold precursor, reducing agent, polymer protective agent and carrier added is: lanthanide metal element: transition metal element : Gold element: reducing agent: polymer protective agent: carrier: water mass ratio is 1: (0.4-2.5): (0.02-0.98): (0.2-0.5): (0.2-0.5): (50-200) : (200-400).

Based on the above technical solution, preferably, before adding the alkali metal or alkaline earth metal to the silica precursor solution, the alumina precursor is added to the silica precursor solution and dissolved.

Based on the above technical solution, preferably, the precursor of the alkali metal or alkaline earth metal is a simple substance, oxide, hydroxide, other compound or composite of the corresponding metal; the precursor of the silica is a silica sol, solid state One of silica gel and white carbon black; the precursor of alumina is one of aluminum nitrate, aluminum sulfate, aluminum phosphate, aluminum carbonate, or alumina powder.

Based on the above technical solution, preferably, the acid is one of nitric acid, sulfuric acid, hydrochloric acid, and phosphoric acid.

In yet another aspect, the present invention provides a method for producing methyl methacrylate, which uses the above-mentioned catalyst to synthesize methyl methacrylate by a one-step oxidation method using methacrolein and methanol as reaction raw materials.

Based on the above technical solution, preferably, the synthesis method of methyl methacrylate is as follows: the reaction raw material A is added to the reactor to be fully mixed, and then the catalyst is added to the reactor; the reactor is sealed, stirring is started, and the bottom of the reactor is Air and inert gas are fed at the rate of 0.8-1.3L/min and 2.5-3.2L/min, and the reaction raw materials are added to the reaction kettle at a rate of 8-12ml/min using a liquid constant flow sampling pump. The same rate as the reaction material feed rate is stored in the storage tank; the mass concentration of methanol in the reaction mixture is 50-70%, the reaction raw material and the catalyst constitute a reaction system; the mass concentration of the catalyst in the reaction system 15-20%; the reaction index obtained after the reaction is carried out for 150-200h is: the conversion rate of methacrolein ≥97%, and the selectivity of methyl methacrylate ≥98%.

Beneficial effect

The beneficial effects of the present invention are: the present invention adopts the polymer protection method, and the active center Au obtained has a small and uniform particle size, high activity, and excellent stability. The method for preparing the supported catalyst does not have high requirements on the carrier, and can be used in a range wide. In the present invention, a supported catalyst having a trimetallic active center is composed of a lanthanide metal, a transition metal, and gold. The lanthanide and transition metal in the catalyst exist in elemental form and cooperate with Au to catalyze, so that the selectivity and conversion rate of the catalyst high. The load of Au is low, which greatly reduces the cost of the catalyst. The preparation process is easy to operate. The catalyst is applied to the preparation of methyl methacrylate. The conversion rate of methacrolein is greater than 97% when running on a small evaluation device for 4000h. A The selectivity of methyl acrylate is greater than 97%. At this time, the active sites Au, lanthanides and transition metals on the catalyst are still stable without loss.

BRIEF DESCRIPTION

Figure 1 is an electron micrograph of the catalyst prepared in Example 2.

detailed description

The present invention will be further described in detail below in conjunction with specific embodiments to help those skilled in the art have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention. The scope of protection of the present invention includes but is not limited to the following examples Any modifications to the details and forms of the technical solutions of the present invention fall within the protection scope of the present invention without departing from the spirit and scope of the present application.

Comparative Example 1

Weigh 50kg of silica sol (30wt%), add 9kg of aluminum nitrate during stirring, add 7kg of magnesium nitrate after dissolution, add 250ml of concentrated nitric acid to adjust the PH value, continue stirring at 50°C for 24h, cool to room temperature, spray dry, spray The conditions are: 10ml/min feed rate, inlet temperature 200-220°C, outlet temperature 80-100°C, spherical SiO ₂ -Al ₂ O ₃ -MgO powder with a particle size of about 70 μm is obtained, and then the powder is air at 700° C. Roast for 6h in an atmosphere, and use it after it has cooled to room temperature.

Under stirring conditions, 250g of chloroauric acid and 250g of sodium citrate are fully mixed with 60L of deionized water to obtain a stable, uniform, and highly dispersed gold sol. Under stirring, 260g of polyvinylpyrrolidone (PVP, (Molecular weight 8000-10000), after complete dissolution, add 30kg of the SiO ₂ -Al ₂ O ₃ -MgO powder prepared above, continue to stir and slowly warm up to 75 ℃, continue to stir at this temperature for 14h and then drop to room temperature, pour out after standing The upper layer liquid was washed with deionized water until no chloride ion was detected in the solution. After drying at 100°C for 24 hours, it was baked at 300°C for 24 hours to obtain catalyst Au/SiO ₂ -Al ₂ O ₃ -MgO. The mass percentage of Au in the catalyst is 0.48%.

Example 1

The preparation and molding conditions of the carrier are the same as Comparative Example 1.

Under stirring conditions, 250g of chloroauric acid and 250g of sodium citrate are fully mixed with 60L of deionized water to obtain a stable, uniform, and highly dispersed gold sol. Under stirring, 260g of polyvinylpyrrolidone (PVP, Molecular weight 8000-10000), then add 935g of lanthanum nitrate and 1170g of copper nitrate in sequence, after complete dissolution add 30kg of the SiO ₂ -Al ₂ O ₃ -MgO powder prepared above, continue to stir and slowly raise the temperature to 75 ℃, continue to stir at this temperature After 14h, the temperature was lowered to room temperature, and the upper liquid was poured out after standing. The lower precipitate was washed with deionized water until no chloride ion was detected in the solution. After drying at 100℃ for 24h, it was calcined in air at 300℃ for 24h to obtain the catalyst Cu-La- Au/SiO ₂ -Al ₂ O ₃ -MgO. The mass percentages of La, Ce, and Au in the catalyst are 1%, 1%, and 0.48%, respectively.

Example 2

The carrier molding conditions are the same as Comparative Example 1, in which magnesium nitrate is replaced with rubidium nitrate to obtain a spherical SiO ₂ -Al ₂ O ₃ -RbO powder with a particle size of about 70 μm, which is then calcined at 700°C in an air atmosphere for 6 hours and cooled to room temperature Later to spare.

The catalyst preparation conditions are the same as in Example 1, and the catalyst Cu-La-Au/SiO ₂ -Al ₂ O ₃ -RbO is obtained, in which the mass percentages of La, Ce, and Au in the catalyst are 1%, 1%, and 0.48%, respectively .

As shown in Figure 1, the electron micrograph of the catalyst prepared in this example, it can be seen that the particles of Au are uniform and highly dispersed on the surface of the carrier, and the particle size is 2nm; the particles of La and Ce are slightly larger than Au, but uniformly distributed, The particle size is around 4 nm.

Example 3

The carrier molding conditions are the same as Comparative Example 1, in which magnesium nitrate is replaced with cesium nitrate to obtain spherical SiO ₂ -Al ₂ O ₃ -CsO powder with a particle size of about 70 μm, and then the powder is calcined in an air atmosphere at 700° C. for 6 hours and cooled to room temperature. Later to spare.

The catalyst preparation conditions were the same as in Example 1, and the catalyst Cu-La-Au/SiO ₂ -Al ₂ O ₃ -CsO was obtained, in which the mass percentages of Cu, La, and Au in the catalyst were 1%, 1%, and 0.48%, respectively. .

Example 4

The carrier molding conditions are the same as in Comparative Example 1, in which magnesium nitrate is replaced with strontium nitrate to obtain spherical SiO ₂ -Al ₂ O ₃ -SrO powder with a particle size of about 70 μm, and then the powder is calcined in an air atmosphere at 700° C. for 6 h and cooled to room temperature Later to spare.

The catalyst preparation conditions were the same as in Example 1, and the catalyst Cu-La-Au/SiO ₂ -Al ₂ O ₃ -SrO was obtained, in which the mass percentages of La, Ce, and Au in the catalyst were 1%, 1%, and 0.48%, respectively. .

Example 5

The carrier molding conditions were the same as in Example 2. A spherical SiO ₂ -Al ₂ O ₃ -RbO powder with a particle size of about 70 μm was obtained, and then the powder was fired at 700° C. in an air atmosphere for 6 hours, and then lowered to room temperature for use.

The catalyst preparation conditions are the same as in Example 2, in which copper nitrate is replaced with cobalt nitrate to obtain the catalyst Co-La-Au/SiO ₂ -Al ₂ O ₃ -RbO, wherein the mass percentages of Co, La and Au in the catalyst are: 1%, 1%, 0.48%.

Example 6

The carrier molding conditions were the same as in Example 2. A spherical SiO ₂ -Al ₂ O ₃ -RbO powder with a particle size of about 70 μm was obtained, and then the powder was fired at 700° C. in an air atmosphere for 6 hours, and then lowered to room temperature for use.

The catalyst preparation conditions are the same as in Example 2, in which copper nitrate is replaced with chromium nitrate to obtain the catalyst Cr-La-Au/SiO ₂ -Al ₂ O ₃ -RbO, in which the mass percentages of Cr, La and Au in the catalyst are: 1%, 1%, 0.48%.

Example 7

The carrier molding conditions were the same as in Example 2. A spherical SiO ₂ -Al ₂ O ₃ -RbO powder with a particle size of about 70 μm was obtained, and then the powder was fired at 700° C. in an air atmosphere for 6 hours, and then lowered to room temperature for use.

The catalyst preparation conditions are the same as in Example 2, in which copper nitrate is replaced with manganese nitrate to obtain the catalyst Mn-La-Au/SiO ₂ -Al ₂ O ₃ -RbO, in which the mass percentages of Mn, La and Au in the catalyst are: 1%, 1%, 0.48%.

Example 8

The carrier molding conditions were the same as in Example 2. A spherical SiO ₂ -Al ₂ O ₃ -RbO powder with a particle size of about 70 μm was obtained, and then the powder was fired at 700° C. in an air atmosphere for 6 hours, and then lowered to room temperature for use.

The catalyst preparation conditions are the same as in Example 2, in which lanthanum nitrate is replaced with praseodymium nitrate to obtain the catalyst Cu-Ce-Au/SiO ₂ -Al ₂ O ₃ -RbO, in which the mass percentages of Cu, Ce and Au in the catalyst are: 1%, 1%, 0.48%.

Example 9

The carrier molding conditions were the same as in Example 2. A spherical SiO ₂ -Al ₂ O ₃ -RbO powder with a particle size of about 70 μm was obtained, and then the powder was fired at 700° C. in an air atmosphere for 6 hours, and then lowered to room temperature for use.

The catalyst preparation conditions were the same as in Example 2, in which lanthanum nitrate was replaced with neodymium nitrate to obtain the catalyst Cu-Nd-Au/SiO ₂ -Al ₂ O ₃ -RbO, in which the mass percentages of Cu, Nd and Au in the catalyst were: 1%, 1%, 0.48%.

Example 10

The carrier molding conditions were the same as in Example 2. A spherical SiO ₂ -Al ₂ O ₃ -RbO powder with a particle size of about 70 μm was obtained, and then the powder was fired at 700° C. in an air atmosphere for 6 hours, and then lowered to room temperature for use.

The catalyst preparation conditions are the same as in Example 2, in which lanthanum nitrate is replaced with praseodymium nitrate to obtain the catalyst Cu-Pr-Au/SiO ₂ -Al ₂ O ₃ -RbO, in which the mass percentages of Cu, Pr and Au in the catalyst are: 1%, 1%, 0.48%.

Comparative Example 2

Under stirring conditions, 750g of chloroauric acid and 750g of sodium citrate and 60L of deionized water were mixed thoroughly to obtain a stable, uniform and single gold sol with high dispersion. Under stirring conditions, 760g of polyvinylpyrrolidone (PVP, Molecular weight 8000-10000), then add 935g of lanthanum nitrate and 1170g of copper nitrate in sequence, after complete dissolution add 30kg of the SiO ₂ -Al ₂ O ₃ -MgO powder prepared above, continue to stir and slowly raise the temperature to 75 ℃, continue to stir at this temperature After 14h, the temperature was lowered to room temperature, and the upper liquid was poured out after standing. The lower precipitate was washed with deionized water until no chloride ion was detected in the solution. After drying at 100℃ for 24h, it was calcined in air at 300℃ for 24h to obtain the catalyst Cu-La- Au/SiO ₂ -Al ₂ O ₃ -MgO. The mass percentages of La, Ce, and Au in the catalyst are 1%, 1%, and 1.4%, respectively.

Example 11

The catalysts of Comparative Examples and Examples 1-10 were applied to the synthesis of methyl methacrylate under the same conditions. The reaction conditions were:

Fully mix 2000mL of methacrolein with methanol in a 3L stainless steel autoclave, add 500g of catalyst, and mix thoroughly. The concentration of methacrolein is 30wt%. Seal the kettle, start stirring, and start the reaction at a bath temperature of 80℃. The bottom of the reaction kettle was fed with air and nitrogen at a rate of 1L/min and 3L/min, respectively, and the reaction raw materials were added to the reaction kettle at a rate of 10ml/min into the system using a liquid constant flow sample pump. The resulting product was continuously taken out to storage In the feed tank, the feed liquid is taken out at regular intervals, and the feed liquid is analyzed by gas chromatography. Using n-decane as an internal standard, the conversion rate of methacrolein and the selectivity of methyl methacrylate are calculated, and the reaction 200h.

Example 12

Fully mix 2000mL of methacrolein with methanol in a 3L stainless steel autoclave, add 500g of the catalyst in Example 1, and mix thoroughly, where the concentration of methacrolein is 30wt%, seal the kettle, start stirring, and bath temperature is 80 Start the reaction at ℃, pass air and nitrogen at the bottom of the reactor at a rate of 1L/min and 3L/min respectively, and use a liquid constant flow injection pump to the system to add reaction raw materials to the reactor at a rate of 10ml/min to generate The product is continuously taken out to the storage tank, the feed liquid is taken out at regular intervals, and the feed liquid is analyzed using gas chromatography, using n-decane as an internal standard, and calculating the conversion rate of methacrolein and methyl methacrylate Selectivity, reaction 4000h.

The results of Examples 11 and 12 are as follows: From the table, it can be seen that the addition of transition metals and lanthanide metals improves the activity of the catalyst, and the conversion and selectivity of the reaction are both improved; after increasing the loading of Au, the catalysis of the catalyst Performance is reduced.

Claims (17)

1. A catalyst for producing methyl methacrylate, characterized in that the catalyst includes a carrier and an active center supported on the carrier; the active center includes gold, transition metal and lanthanide metal; the carrier includes SiO ₂ , One of Al ₂ O ₃ and alkali metal or alkaline earth metal; in the catalyst, the loading of gold is 0.05wt%-0.98wt%, the loading of lanthanide metal is 1wt%-2.5wt%, the loading of transition metal The amount is from 1 wt% to 2.5 wt%.
2. The catalyst for producing methyl methacrylate according to claim 1, wherein the alkali metal or alkaline earth metal is Na, K, Rb, Cs, Be, Mg, Ca, Sr; the lanthanide metal is La , Ce, Pr, Nd, the transition metal is one of Cu, Co, Fe, Mn, Cr.
3. The catalyst for producing methyl methacrylate according to claim 1, characterized in that, based on the carrier mass of 100%, the mass fraction of alkali metal and alkaline earth metal ranges from 1 to 25%; the alkali metal or alkaline earth metal in the carrier The molar ratio to SiO ₂ is 1 to 6: 0.5 to 4.
4. A method for preparing a methyl methacrylate catalyst according to any one of claims 1 to 4, characterized in that: under stirring conditions, the gold precursor and the reducing agent are thoroughly mixed with deionized water to obtain a gold sol In the presence of a polymer protective agent, add lanthanide metal precursor and transition metal precursor to the gold sol in sequence, then add the carrier, heat to 65-85℃, continue stirring for 2-20h, and drop to room temperature after the stirring , Standing and filtering, washing with deionized water, drying and roasting in the air to obtain the catalyst.
5. The preparation method of a catalyst for producing methyl methacrylate according to claim 4, characterized in that: the preparation process of the carrier is: adding an alumina precursor and an alkali to the silica precursor solution under stirring conditions Precursor of metal or alkaline earth metal, after fully stirring and mixing, add acid to adjust PH value to 0.5-5.5, continue stirring for 1-24h to obtain a mixture, and spray-dry the mixture to form a spherical shape with a particle size of 50-100μm The particulate matter is calcined in an air atmosphere to obtain the carrier.
6. The method for preparing a methyl methacrylate catalyst according to claim 4, characterized in that the precursor of Au is gold cyanide (Au(CN) ₃ ), potassium gold cyanide, gold gold chloride One or more of (AuC1), gold chloride (AuC1 ₃ ), chloroauric acid, chloroaurate, gold sodium sulfite, or thallium.
7. The preparation method of a catalyst for producing methyl methacrylate according to claim 4, wherein the polymer protective agent is polyvinyl alcohol, polyvinylpyrrolidone, tetramethylolphosphonium chloride, polydimethyl bis Propylene ammonium chloride, sodium citrate, thiols.
8. The preparation method of a catalyst for producing methyl methacrylate according to claim 4, wherein the reducing agent is sodium citrate, tetramethylolphosphonium chloride, oxalic acid, and sodium borohydride.
9. The method for preparing a methyl methacrylate catalyst according to claim 4, wherein the lanthanide metal precursor and the transition metal precursor are sulfate, nitrate, phosphate, carbonic acid of the corresponding metal Salt, acetate.
10. The method for preparing a methyl methacrylate catalyst according to claim 4, wherein in the method, a lanthanide metal precursor, a transition metal precursor, a gold precursor, a reducing agent, a polymer protective agent and The amount of carrier added is: lanthanide metal element: transition metal element: gold element: reducing agent: polymer protective agent: carrier: water mass ratio is 1:0.4～2.5:0.02～0.98:0.2～0.5:0.2～0.5 :50～200:200～400.
11. The method for preparing a methyl methacrylate catalyst according to claim 4, characterized in that: before the alkali metal or alkaline earth metal precursor is added to the silica precursor solution, the alumina precursor is added and dissolved.
12. The method for preparing a methyl methacrylate catalyst according to claim 5, wherein the precursor of the alkali metal or alkaline earth metal is a simple substance, oxide, hydroxide, compound or composite of the corresponding metal.
13. The method for preparing a methyl methacrylate catalyst according to claim 5, wherein the acid is one of nitric acid, sulfuric acid, hydrochloric acid, and phosphoric acid.
14. The method for preparing a methyl methacrylate catalyst according to claim 5, wherein the precursor of silica is one of silica sol, solid silica gel, and white carbon black.
15. The method for preparing a methyl methacrylate catalyst according to claim 5, characterized in that the precursor of alumina is aluminum nitrate, aluminum sulfate, aluminum phosphate, aluminum acetate, aluminum acetate or alumina powder One kind.
16. A method for synthesizing methyl methacrylate, characterized in that the catalyst described in any one of claims 1-3 is used, methacrylic acid and methanol are used as reaction raw materials, and methacrylic acid is catalyzed by one-step oxidation Methyl ester.
17. The method for synthesizing methyl methacrylate according to claim 16, characterized in that: the reaction raw materials are added to the reactor and mixed thoroughly, and then the catalyst is added to the reactor; the reactor is sealed, the stirring is started, and the reactor The bottom is fed with air and inert gas at a rate of 0.8-1.3L/min and 2.5-3.2L/min, and the reaction raw materials are added at a rate of 8-12ml/min using a liquid constant flow pump. The storage rate is the same as the addition rate; the mass concentration of methanol in the reaction mixture is 50-70%, and the reaction raw materials and the catalyst constitute a reaction system; the mass concentration of the catalyst in the reaction system is 15-20%.

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