Catalyst, preparation method and application thereof, and method for preparing methyl methacrylate

Abstract

The invention relates to the field of preparation of methyl methacrylate, in particular to a catalyst, a preparation method and application thereof and a method for preparing methyl methacrylate. The general chemical formula of the catalyst is shown as Au-Ya / SibNdcDdOe, and D is selected from at least one of Be, Mg, Ca, Sr, Ba, Al, Ga, In and Tl; a is the molar ratio of Y to Au and is equal to 0.1-1; b is the molar ratio of Si to Au and is equal to 10 to 200; c is the molar ratio of Nd to Au, and c is equal to 0.1-1; d is the molar ratio of D to Au, and d is equal to 1-50; and e is the mole number of oxygen atoms required by valence of each element in the active component. The catalyst is applied to preparation of methyl methacrylate, and has high raw material conversion rate and selectivity of methyl methacrylate.

Description

Technical Field

[0001] The invention relates to the field of methyl methacrylate preparation, and in particular to a catalyst, a preparation method and application thereof, and a method for preparing methyl methacrylate. Background Art

[0002] Methyl methacrylate (MMA), also known as methyl methacrylate, is an important organic chemical raw material, mainly used in the production of polymethyl methacrylate (PMMA, plexiglass), polyvinyl chloride additive ACR and as the second monomer in acrylic fiber production. It is also used in the manufacture of other resins, plastics, coatings, adhesives, lubricants, wood and cork impregnation agents, paper polishes, etc. With the enrichment and development of MMA downstream products, the demand and production capacity of MMA are increasing worldwide.

[0003] At present, the global MMA production process has gradually developed from the initial acetone cyanohydrin method to the direction of diversified raw materials and processes. The production processes are mainly ACH method, C4 method and Alpha process. Among them, the production capacity of production equipment using ACH method accounts for 59% of the world's total capacity, C4 method accounts for 31%, and Alpha method accounts for 9%. Different process routes have different technical and economic benefits. Among the current industrialized MMA production processes, the traditional ACH method has the characteristics of simple process and high maturity, but the raw material hydrocyanic acid used in this method is highly toxic, and hydrocyanic acid and sulfuric acid are highly corrosive, which places high demands on reaction equipment, and the waste acid emissions are large, which may cause great harm to the environment. Alpha technology has just begun to be industrialized, and the technical maturity and overall economic efficiency need to be further tested. The C4 route directly uses air or oxygen as an oxidant to directly oxidize methacrolein and methanol into the target product MMA in one step. It is undoubtedly a simple, green and economically competitive process route that will greatly save production costs. At the same time, the by-product of this process is water, which is green and environmentally friendly. However, the difficulty of this process lies in the preparation of high-performance catalysts, especially the preparation of catalysts with high activity, high methacrolein conversion rate and high MMA selectivity, which has become a research hotspot for the catalyst of this reaction. Summary of the invention

[0004] The purpose of the present invention is to overcome the problem of low MMA selectivity in the reaction of selective oxidation of methacrolein to prepare methyl methacrylate by existing catalysts, and to provide a catalyst and a preparation method and application thereof, as well as a method for preparing methyl methacrylate.

[0005] In order to achieve the above object, the present invention provides a catalyst in the first aspect, wherein the general chemical formula of the catalyst is Au-Y a / Si b Nd c D d O e, wherein D is selected from at least one of Be, Mg, Ca, Sr, Ba, Al, Ga, In, and Tl; a is the molar ratio of Y to Au, a=0.1-1; b is the molar ratio of Si to Au, b=10-200; c is the molar ratio of Nd to Au, c=0.1-1; d is the molar ratio of D to Au, d=1-50; e is the molar number of oxygen atoms required to satisfy the valence of each element in the active component.

[0006] The second aspect of the present invention provides a method for preparing the catalyst described in the first aspect, the method comprising the following steps:

[0007] (1) drying and first calcining a solution containing Si, Nd and D elements to obtain a carrier;

[0008] (2) The support obtained in step (1) is mixed with a solution containing Au element and Y element, and then dried and calcined for a second time to obtain the catalyst.

[0009] The third aspect of the present invention provides an application of the catalyst described in the first aspect or the catalyst prepared by the preparation method described in the second aspect in the selective oxidation of methacrolein to prepare methyl methacrylate.

[0010] A fourth aspect of the present invention provides a method for preparing methyl methacrylate, the method comprising:

[0011] (1) activating the catalyst to obtain an activated catalyst;

[0012] (2) reacting methacrolein with methanol in the presence of the activated catalyst prepared in step (1);

[0013] Wherein, the catalyst is the catalyst described in the first aspect or the catalyst prepared by the preparation method described in the second aspect.

[0014] Through the above technical scheme, the Au-based composite catalyst of the present invention is used, and the ratio between the catalyst active component and the auxiliary active component, and the ratio between the catalyst active component and the carrier are adjusted to improve the activity of the catalyst in the reaction of selective oxidation of methacrolein to produce methyl methacrylate, the conversion rate of the raw material and the selectivity of methyl methacrylate. The performance of the Au-based composite catalyst of the present invention is evaluated (the evaluation results are shown in Table 1). Compared with the comparative example, the Au-based composite catalyst prepared in the embodiment has a higher selectivity for methyl methacrylate. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The catalyst Au-Y prepared in Example 1 0.5 / Si 100 Nd 0.5 Al20 O e TEM images of

[0016] Figure 2 The catalyst Au-Y prepared in Example 6 0.5 / Si 100 Nd 0.5 Al2O e TEM image of. DETAILED DESCRIPTION

[0017] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0018] The specific embodiments of the present invention are described in detail below. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0019] The first aspect of the present invention provides a catalyst, the chemical formula of which is Au-Y a / Si b Nd c D d O e , wherein D is selected from at least one of Be, Mg, Ca, Sr, Ba, Al, Ga, In, and Tl; a is the molar ratio of Y to Au, a=0.1-1; b is the molar ratio of Si to Au, b=10-200; c is the molar ratio of Nd to Au, c=0.1-1; d is the molar ratio of D to Au, d=1-50; e is the molar number of oxygen atoms required to satisfy the valence of each element in the active component.

[0020] According to the present invention, in the chemical formula of the catalyst of the present invention, Au-Y a / Si b Nd c D d O e Preferably, a=0.2-0.5.

[0021] According to the present invention, in the chemical formula of the catalyst of the present invention, Au-Y a / Si b Nd c D d O e Preferably, b=50-100.

[0022] According to the present invention, in the chemical formula of the catalyst of the present invention, Au-Y a / Si b Nd c D d O e Preferably, c=0.2-0.5.

[0023] According to the present invention, in the chemical formula of the catalyst of the present invention, Au-Y a / Si b Nd c D d O e Preferably, d=10-30.

[0024] The catalyst composition in the above preferred embodiment has higher raw material conversion rate and MMA selectivity when catalyzing the oxidation of methacrolein to prepare methyl methylpropionate (MMA).

[0025] According to the present invention, in order to make the catalyst have a higher methyl methacrylate (MMA) yield when used in the selective oxidation of methacrolein, the ratio of d to a is (10-100):1; preferably, the ratio of d to a is (20-80):1; more preferably, the ratio of d to a is (20-60):1; further preferably, the ratio of d to a is (30-50):1.

[0026] According to the present invention, preferably, the active components of the catalyst are Au and Y, and the catalyst carrier contains Si, Nd and D.

[0027] Preferably, the average particle size of the catalyst active component is 4.5-4.7 nm.

[0028] In the present invention, the particle size of the catalyst active component refers to the maximum straight-line distance between any two different points on the particle. For example, when the particle is spherical, the particle size refers to its diameter.

[0029] The particle size of the active component of the catalyst of the present invention is obtained by transmission electron microscopy (TEM) testing. The average particle size is obtained by analyzing the particle sizes of 200 particles and calculating the average value.

[0030] Preferably, D is selected from at least one of Mg, Ca, Sr, Ba and Al, and more preferably Mg or Al.

[0031] Preferably, the mass ratio of the active component of the catalyst to the catalyst carrier is 0.51-3.96:99.49-96.04.

[0032] According to the present invention, in order to increase the contact area between the active component particles of the catalyst and the reactants during the reaction and improve the catalytic performance of the catalyst, preferably, based on the total number of particles of the active component of the catalyst, the number of active component particles of the catalyst with a particle size of 4-5nm accounts for 90-95%; further preferably, the number of active component particles of the catalyst with a particle size of 4-4.5nm accounts for r1 of 40-45%, and the number of active component particles of the catalyst with a particle size of 4.5-5nm accounts for r2 of 45-50%.

[0033] In the present invention, a particle size of 4.5 nm is included in the range of 4-4.5 nm and is no longer included in the range of 4.5-5 nm.

[0034] Preferably, the ratio of r2 to r1 is (1-1.1):1.

[0035] The particle size of the active component of the catalyst of the present invention is obtained by testing 200 particles using a transmission electron microscope (TEM).

[0036] In the present invention, the composition of the catalyst is obtained by inductively coupled plasma (ICP) testing or by calculating the amount of materials added during the preparation process.

[0037] The second aspect of the present invention provides a method for preparing the catalyst described in the first aspect, the method comprising the following steps:

[0038] (1) drying and first calcining a solution containing Si, Nd and D elements to obtain a carrier;

[0039] (2) The support obtained in step (1) is mixed with a solution containing Au element and Y element, and then dried and calcined for a second time to obtain the catalyst.

[0040] According to the preparation method of the present invention, by adjusting the ratio between the catalyst active component precursor and the co-active component precursor, and the ratio between the catalyst active component precursor and the carrier precursor, the obtained catalyst has higher catalytic activity and selectivity for methyl methacrylate in the reaction of catalyzing the selective oxidation of methacrolein to produce methyl methacrylate.

[0041] According to the preparation method of the present invention, in order to form a carrier with a specific structure and uniform distribution of elements, preferably, the solution containing Si element, Nd element and D element is obtained by mixing a solution containing Si element and Nd element with a solution containing D element.

[0042] Preferably, before the mixing, the solution containing Si element and Nd element is aged.

[0043] Preferably, the aging conditions include: stirring for 6-30 hours at a temperature of 80-150° C. The present invention has no particular limitation on the stirring speed, and those skilled in the art can select the stirring speed by conventional means.

[0044] According to the preparation method of the present invention, there is no particular limitation on the source of each element in the solution containing Si, Nd and D elements and the solution containing Au and Y elements, and each element may be derived from a compound containing the element.

[0045] Preferably, the Si element is derived from at least one of silica sol, colloidal silicon dioxide, ethyl silicate and silicon dioxide powder.

[0046] In the present invention, the Nd element may be derived from a soluble salt containing the Nd element.

[0047] Preferably, the Nd element is derived from at least one of neodymium nitrate, neodymium oxide, neodymium phosphate and neodymium trioxide.

[0048] In the present invention, the D element may be derived from a soluble salt containing the D element, wherein the soluble salt containing the D element is at least one of Be salt, Mg salt, Ca salt, Sr salt, Ba salt, Al salt, Ga salt, In salt, and Tl salt.

[0049] Preferably, the D element is derived from at least one of aluminum nitrate, aluminum phosphate, boehmite, aluminum isopropoxide, and magnesium nitrate.

[0050] According to the preparation method of the present invention, in order to make the elements on the carrier surface and the active loading points more uniform, preferably, in step (1), the drying is spray drying, and more preferably, the temperature of the spray drying is 100-180° C. and the time is 1-12 h.

[0051] According to the preparation method of the present invention, preferably, in step (1), the temperature of the first calcination is 500-700° C., and the time is 6-48 hours.

[0052] More preferably, the temperature of the first calcination is 550-650° C. and the time is 6-24 h.

[0053] Preferably, the first calcination is performed in an oxygen-free atmosphere; more preferably, an inert atmosphere, such as at least one of nitrogen, argon, neon and helium.

[0054] According to the preparation method of the present invention, there is no particular limitation on the preparation method of the solution containing Au element and Y element. In order to make the active sites more uniform, preferably, in step (2), the solution containing Au element and Y element is obtained by adding the solution containing Y element to the solution containing Au element for mixing. The present invention has a wide range of selection for the addition speed of the solution containing Y element, and those skilled in the art can make an adaptive selection according to actual production. Further preferably, the addition speed of the solution containing Y element is 1-20mL / min.

[0055] Preferably, the mixing temperature of the solution containing the Y element and the solution containing the Au element is not higher than 50°C, preferably 30-50°C.

[0056] According to the preparation method of the present invention, preferably, in step (2), the Au element is derived from at least one of chloroauric acid, gold trichloride hydrate, and potassium tetrachloroaurate hydrate.

[0057] According to the preparation method of the present invention, preferably, the Y element is derived from at least one of yttrium nitrate, yttrium acetate and yttrium phosphate.

[0058] According to the preparation method of the present invention, preferably, in step (2), the carrier obtained in step (1) is mixed with the solution containing Au element and Y element at a temperature of 30-80° C. and a time of 0.5-5 h.

[0059] Preferably, in step (2), the temperature of the second calcination is 300-500° C. and the time is 6-48 hours.

[0060] More preferably, the second calcination is carried out at a temperature of 350-450° C. and for a time of 8-15 h.

[0061] Preferably, the second calcination is performed in an oxygen-free atmosphere; more preferably, an inert atmosphere, such as at least one of nitrogen, argon, neon and helium.

[0062] In the preparation method provided by the present invention, those skilled in the art can adaptively select the amount of each substance to be added according to the amount of each component in the target catalyst.

[0063] The third aspect of the present invention provides an application of the catalyst described in the first aspect or the catalyst prepared by the preparation method described in the second aspect in the selective oxidation of methacrolein to prepare methyl methacrylate.

[0064] A fourth aspect of the present invention provides a method for preparing methyl methacrylate, the method comprising:

[0065] (1) activating the catalyst to obtain an activated catalyst;

[0066] (2) reacting methacrolein with methanol in the presence of the activated catalyst prepared in step (1);

[0067] Wherein, the catalyst is the catalyst described in the first aspect or the catalyst prepared by the preparation method described in the second aspect.

[0068] According to the present invention, in order to improve the catalytic activity of the catalyst and improve the yield of methyl methacrylate, when using the catalyst provided by the first aspect of the present invention to prepare methyl methacrylate, the catalyst is activated. Preferably, the activation conditions include: under inert atmosphere conditions, the activation temperature is 50-100° C., and the activation time is 6-48 h. Further preferably, the inert atmosphere is at least one of nitrogen, argon, neon and helium.

[0069] According to the present invention, in order to promote the mutual reaction between methacrolein and methanol and improve the conversion rate of methacrolein and the yield of methyl methacrylate, preferably, in step (2), the reaction conditions include: a molar ratio of methacrolein to methanol of 20-40:1-2, a temperature of 50-100°C, a pressure of 1-10 MPa, and a time of 1-10 h.

[0070] The present invention will be described in detail below through examples.

[0071] Example 1

[0072] (1) A silica sol (molecular formula: SiO2) containing 10 mol of Si and a neodymium nitrate (molecular formula: Nd(NO3)3) solution containing 0.05 mol of Nd were mixed, stirred and aged at 100°C for 10 hours, and then an aluminum nitrate (molecular formula: Al(NO3)3) solution containing 2 mol of Al was added, and the mixture was stirred at 80°C for 3 hours. After being stirred evenly, the mixture was spray dried at 150°C, and then first calcined at 600°C for 12 hours in a nitrogen atmosphere to obtain a carrier;

[0073] (2) 0.1 mol of chloroauric acid (molecular formula: HAuCl4) and 0.05 mol of yttrium nitrate (molecular formula: Y(NO3)3) were dissolved in deionized water at 40°C, and the yttrium nitrate solution was slowly added to the chloroauric acid solution at a rate of 10 mL / min under stirring, and then the stirring was continued for 3 hours. After mixing evenly, a mixed solution I was obtained; the mixed solution I and the carrier prepared in step (1) were added to a flask, mixed evenly, and stirred in an 80°C oil bath for 2 hours. After cooling, the mixed slurry was washed to obtain a catalyst precursor; the catalyst precursor was dried in a vacuum oven at 100°C for 3 hours, and then calcined in a muffle furnace at 400°C for 12 hours under a nitrogen atmosphere to obtain a catalyst with the following composition: Au-Y 0.5 / Si100 Nd 0.5 Al 20 O e .

[0074] Figure 1 TEM image of the catalyst prepared in Example 1. Figure 1 It can be seen that the catalyst Au-Y 0.5 / Si 100 Nd 0.5 Al 20 O e The particle size of the loaded active component is relatively small, with an average particle size of 4.6 nm; the active component particles have good dispersion on the surface of the catalyst carrier.

[0075] Example 2

[0076] According to the method of Example 1, the feed ratio was changed to prepare a catalyst with the following composition: Au-Y 0.5 / Si 100 Nd 0.5 Al5O e .

[0077] Example 3

[0078] According to the method of Example 1, the feed ratio was changed to prepare a catalyst with the following composition: Au-Y 0.5 / Si 100 Nd 0.5 Al 50 O e .

[0079] Example 4

[0080] According to the method of Example 1, the feed ratio was changed to prepare a catalyst with the following composition: Au-Y 0.5 / Si 100 Nd 0.5 Al 15 O e .

[0081] Example 5

[0082] According to the method of Example 1, 2 mol of aluminum nitrate was replaced by 2 mol of magnesium nitrate to prepare a catalyst with the following composition: Au-Y 0.5 / Si 100 Nd 0.5 Mg 20 O e .

[0083] Example 6

[0084] According to the method of Example 1, the feed ratio was changed to prepare a catalyst with the following composition: Au-Y0.5 / Si 100 Nd 0.5 Al2O e .

[0085] Figure 2 TEM image of the catalyst prepared in Example 6. Figure 2 It can be seen that the catalyst Au-Y 0.5 / Si 100 Nd 0.5 Al2O e The particle size of the loaded active component is uneven, the particle size becomes larger, and the average particle size is 4.9 nm; the dispersion of the active component particles on the surface of the catalyst carrier becomes worse.

[0086] Example 7

[0087] According to the method of Example 1, the feed ratio was changed to prepare a catalyst with the following composition: Au-Y 0.2 / Si 100 Nd 0.5 Al8O e .

[0088] Example 8

[0089] According to the method of Example 1, the feed ratio was changed to prepare a catalyst with the following composition: Au-Y 0.5 / Si 50 Nd 0.5 Al 20 O e .

[0090] Example 9

[0091] According to the method of Example 1, the feed ratio was changed to prepare a catalyst with the following composition: Au-Y 0.5 / Si 100 Nd 0.2 Al 20 O e .

[0092] Comparative Example 1

[0093] According to the method of Example 1, 0.1 mol of chloroauric acid and 0.05 mol of yttrium nitrate were replaced by 0.15 mol of chloroauric acid to prepare a catalyst with the following composition: Au 1.5 / Si 100 Nd 0.5 Al 20 O e .

[0094] Comparative Example 2

[0095] According to the method of Example 1, the feed ratio was changed to prepare a catalyst with the following composition: Au-Y 0.5 / Si 100 Nd 0.5 Al 75 O e。

[0096] Test Case

[0097] The catalysts prepared in the examples and comparative examples were subjected to TEM test to obtain the size of the particles of the active components of the catalysts. The test results are shown in Table 1.

[0098] The catalysts prepared in the examples and comparative examples were placed in a nitrogen atmosphere at 80° C. for 12 h for activation. The catalysts were evaluated, and the evaluation results are shown in Table 1. The catalyst evaluation method is as follows:

[0099] Reactor: Tank reactor, volume 250ml;

[0100] Catalyst filling amount: 2g;

[0101] Reaction temperature: 80°C;

[0102] Reaction pressure: 3MPa;

[0103] Reaction time: 3h;

[0104] Raw material molar ratio: methanol / methacrolein = 25;

[0105] Feed amount: 1.69 mol of methanol, 0.067 mol of methacrolein.

[0106] Table 1

[0107]

[0108]

[0109] As can be seen from Table 1, the catalysts prepared in Examples 1-9 and Comparative Examples 1-2 are applied to the selective catalytic oxidation of methacrolein. When other conditions are the same, compared with the catalyst whose active component is simply Au, the catalyst whose active components include Au and Y has a smaller average particle size of the active components and better dispersion on the carrier, which can significantly improve the conversion rate of the catalyst and the selectivity of methyl methacrylate (MMA).

[0110] Comparing the catalyst prepared in Example 1 with the catalysts prepared in Examples 2-4 and 6, it can be seen that the ratio of d to a in the catalyst affects the average particle size of the prepared catalyst. When other conditions are the same, when the ratio of d to a in the catalyst of the present invention is 40:1, the particle size of the catalyst is the most concentrated and the yield of MMA is also the highest.

[0111] Comparing Example 1 with Example 5, when D in the catalyst is Al, the catalyst has a higher conversion rate of the feedstock and a higher selectivity for MMA.

[0112] It can also be seen from Table 1 that, before being used to prepare methyl methacrylate, activating the catalyst prepared in Example 1 can significantly improve the catalytic activity of the catalyst and the yield of methyl acrylate.

[0113] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A catalyst, characterized in that The general chemical formula of the catalyst is Au-Y a / Si b Nd c D d O e , wherein D is selected from at least one of Be, Mg, Ca, Sr, Ba, Al, Ga, In, and Tl; a is the molar ratio of Y to Au, a=0.1-1; b is the molar ratio of Si to Au, b=10-200; c is the molar ratio of Nd to Au, c=0.1-1; d is the molar ratio of D to Au, d=1-50; e is the molar number of oxygen atoms required to satisfy the valence of each element in the active component.

2. The catalyst according to claim 1, wherein a=0.2-0.5; b=50-100; c=0.2-0.5; d=10-30.

3. The catalyst according to claim 1 or 2, wherein The ratio of d to a is (10-100): 1; Preferably, the ratio of d to a is (20-80):1; More preferably, the ratio of d to a is (20-60):1; Further preferably, the ratio of d to a is (30-50):

1.

4. The catalyst according to claim 1, wherein The active components of the catalyst are Au and Y, and the catalyst carrier contains Si, Nd and D; Preferably, D is selected from at least one of Mg, Ca, Sr, Ba and Al; Preferably, the average particle size of the catalyst active component is 4.5-4.7 nm; Preferably, the mass ratio of the active component of the catalyst to the catalyst carrier is 0.51-3.96:99.49-96.

04.

5. The catalyst according to claim 4, wherein Based on the total number of active component particles of the catalyst, the number of active component particles of the catalyst with a particle size of 4-4.5 nm accounts for r1 40-45%, the number of active component particles of the catalyst with a particle size of 4.5-5 nm accounts for r2 45-50%; the number of active component particles of the catalyst with a particle size of 4-5 nm accounts for 90-95%; Preferably, the ratio of r2 to r1 is (1-1.1):

1.

6. A method for preparing a catalyst according to any one of claims 1 to 5, comprising the following steps: (1) drying and first calcining a solution containing Si, Nd and D elements to obtain a carrier; (2) The support obtained in step (1) is mixed with a solution containing Au element and Y element, and then dried and calcined for a second time to obtain the catalyst.

7. The method according to claim 6, wherein: The solution containing Si element, Nd element and D element is obtained by mixing a solution containing Si element and Nd element with a solution containing D element; Preferably, before the mixing, the solution containing Si element and Nd element is aged; Preferably, the aging conditions include: stirring at a temperature of 80-150° C. for 6-30 hours.

8. The method according to claim 6 or 7, wherein: The Si element is derived from at least one of silica sol, colloidal silicon dioxide, ethyl silicate, and silicon dioxide; And / or, the Nd element is derived from at least one of neodymium nitrate, neodymium oxide, neodymium phosphate and neodymium trioxide; And / or, the D element is derived from at least one of aluminum nitrate, aluminum phosphate, boehmite, and aluminum isopropoxide.

9. The method according to any one of claims 6 to 8, wherein: In step (1), the drying is spray drying; Preferably, the spray drying temperature is 100-180°C and the time is 1-12h.

10. The method according to any one of claims 6 to 9, wherein: In step (1), the first calcination temperature is 500-700°C and the time is 6-48h; Preferably, the first calcination is performed in an oxygen-free atmosphere.

11. The method according to any one of claims 6 to 10, wherein: In step (2), the solution containing Au element and Y element is obtained by adding the solution containing Y element into the solution containing Au element and mixing them; Preferably, the addition rate of the solution containing element Y is 1-20 mL / min; Preferably, the mixing temperature of the solution containing the Y element and the solution containing the Au element is not higher than 50°C, preferably 30-50°C.

12. The method according to any one of claims 6 to 11, wherein: In step (2), the Au element is derived from at least one of chloroauric acid, gold trichloride hydrate, and potassium tetrachloroaurate hydrate; And / or, the Y element is derived from at least one of yttrium nitrate, yttrium acetate and yttrium phosphate.

13. The method according to any one of claims 6 to 12, wherein: The carrier obtained in step (1) is mixed with the solution containing Au element and Y element at a temperature of 30-80° C. for a time of 0.5-5 h; And / or, in step (2), the second calcination temperature is 300-500° C. and the time is 6-48 h; Preferably, the second calcination is performed in an oxygen-free atmosphere.

14. Use of the catalyst according to any one of claims 1 to 5 or the catalyst prepared by the preparation method according to any one of claims 6 to 13 in the selective oxidation of methacrolein to produce methyl methacrylate.

15. A method for preparing methyl methacrylate, characterized in that: The method comprises: (1) activating the catalyst to obtain an activated catalyst; (2) reacting methacrolein with methanol in the presence of the activated catalyst prepared in step (1); Wherein, the catalyst is the catalyst described in any one of claims 1-5 or the catalyst prepared by the preparation method described in any one of claims 6-13.

16. The method according to claim 15, wherein: In step (1), the activation conditions include: in an inert atmosphere, an activation temperature of 50-100° C., and an activation time of 6-48 h; And / or, in step (2), the reaction conditions include: a molar ratio of methacrolein to methanol of 20-40:1-2, a temperature of 50-100° C., a pressure of 1-10 MPa, and a reaction time of 1-10 h.

Images