Gold-based composite oxide catalyst as well as preparation method and application thereof

Abstract

The invention discloses a gold-based composite oxide catalyst as well as a preparation method and application thereof. The catalyst comprises an active component and a carrier, the active component comprises the following general formula AuMaOx, and M is at least one of Ni, Fe and Cu; a is equal to 0.2 to 10; x is the total number of oxygen atoms required for meeting the valence of other elements; and the carrier is a composite oxide SiO2-NiO-MgO-CeO2. The catalyst provided by the invention is used for a reaction for synthesizing methyl methacrylate by oxidative esterification of methylacrolein, and has the characteristics of high catalytic activity, high monoyield of the product methyl methacrylate and the like.

Description

Technical Field

[0001] This invention relates to the field of chemical synthesis, specifically to a gold-based composite oxide catalyst and its preparation method, as well as its application in the oxidative esterification of methacrolein to synthesize methyl methacrylate. Background Technology

[0002] Methyl methacrylate (MMA) is an important organic chemical raw material, mainly used in the production of acrylic glass (PMMA), polyvinyl chloride (PVC) additive ACR, and as a second monomer in the production of acrylic fibers. It can also be used in the production of coatings, adhesives, lubricants, and textile dyes. In recent years, global demand for MMA has increased, and both its production capacity and supply have been continuously growing.

[0003] Currently, in industrialized MMA production processes, the traditional ACH process, which uses hydrogen cyanide as a raw material, is heavily influenced by the operating conditions of acrylonitrile, reducing its cost advantage. Alpha technology is still in its early stages of industrialization; Mitsubishi Chemical's planned 350,000-ton / year MMA plant in Ascension Island Parish, Louisiana, requires further testing to determine its technological maturity and overall economic viability. Compared to other processes, the direct oxidation method using C4 as a raw material offers advantages such as a wide availability of raw materials and better economics. This process can be divided into a three-step and a two-step method. The three-step method first oxidizes isobutylene to methacrolein, then further oxidizes it to methacrylic acid, and finally esterifies it with methanol to obtain methyl methacrylate. The two-step method combines the oxidation and esterification reactions into a single step to obtain methyl methacrylate. The two-step method offers numerous advantages, including a shorter reaction route, higher atom utilization, better selectivity, milder reaction conditions, and environmental friendliness, representing a significant innovation in C4 MMA production. The catalyst for the one-step oxidation-esterification of methacrolein to methacrylic acid is crucial to this technology.

[0004] Currently, oxide-supported noble metal catalysts are commonly used. For example, Suzuki et al. of Asahi Corporation in Japan supported 1.1 wt% Au nanoparticles on a composite oxide support such as SiO2-Al2O3-MgO, with catalyst costs reaching millions of yuan per ton. Au nanoparticles are highly beneficial for improving the selectivity of this reaction, but their high cost necessitates the development of better promoters and supports to enhance the activity of gold nanoparticles.

[0005] In conventional methods, such as CN117861685A, to avoid Au particle growth, the traditional catalyst is alkali metal-doped SiO2 with AuNi supported on it. The support is first calcined at high temperature, and then the catalyst is calcined at low temperature. This often leads to incomplete Ni calcination and low stability of Au-NiO on the surface active sites, thus affecting the activity of the catalyst. Summary of the Invention

[0006] The technical problem this invention aims to solve is the low catalyst conversion rate and low product yield in the prior art reaction of oxidative esterification of methacrolein to methyl methacrylate. This invention provides a gold-based composite oxide catalyst, its preparation method, and its application. The catalyst provided by this invention, used in the oxidative esterification of methacrolein to methyl methacrylate, exhibits high catalytic activity and a high yield of methyl methacrylate.

[0007] The first aspect of this invention provides a gold-based composite oxide catalyst, wherein the catalyst comprises an active component and a support, the active component comprising the following general formula AuM a O x Where M is at least one of Ni, Fe, and Cu; a = 0.2 to 10; x is the total number of oxygen atoms required to satisfy the valence of other elements;

[0008] The support is a composite oxide SiO2-NiO-MgO-CeO2.

[0009] Furthermore, the AuM a O x In this case, a = 0.2 to 10, for example, 0.5, 0.8, 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0, 10, etc., as well as any value within the range formed by any two of these values.

[0010] Furthermore, in the carrier, based on the mass of the carrier, the NiO content is 3%-20%, the MgO content is 3%-20%, the CeO2 content is 3%-22%, and the SiO2 content is 40%-91%.

[0011] Furthermore, in the carrier, based on the mass of the carrier, the NiO content is 3%-20%, for example, 3%, 5%, 9%, 10%, 15%, 17%, 20%, etc., and any value within the range formed by any two of these values.

[0012] Furthermore, in the carrier, based on the mass of the carrier, the MgO content is 3%-20%, for example, 3%, 4%, 5%, 9%, 10%, 15%, 17%, 20%, etc., and any value within the range formed by any two of these values.

[0013] Furthermore, in the carrier, based on the mass of the carrier, the CeO2 content is 3%-22%, for example, 3%, 4%, 5%, 9%, 10%, 11%, 12%, 13%, 15%, 17%, 20%, 21%, 22%, etc., and any value within the range formed by any two of these values.

[0014] Furthermore, in the carrier, based on the mass of the carrier, the SiO2 content is 40%-91%, for example, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 91%, etc., and any value within the range formed by any two of these values.

[0015] Furthermore, in the catalyst, the Au content is 0.05wt%-1.0wt% based on the mass of the catalyst.

[0016] Furthermore, the average particle size of Au particles in the catalyst is 0.5-5 nm, preferably 1-4 nm.

[0017] Furthermore, the specific surface area of ​​the catalyst is 10-300 m². 2 / g.

[0018] A second aspect of this invention provides a method for preparing a gold-based composite oxide catalyst, specifically comprising the following steps:

[0019] (1) Mix nickel source, magnesium source, cerium source and silicon source with water, and dry to obtain a carrier precursor;

[0020] (2) The carrier precursor from step (1) is first calcined in an oxygen-containing atmosphere and then calcined in an ammonia-containing atmosphere to obtain the carrier.

[0021] (3) The gold salt and the M metal salt are mixed with the support and loaded, dried, and calcined for the third time in an oxygen-containing atmosphere to obtain the catalyst.

[0022] Further, in step (1), the nickel source is selected from at least one of nickel nitrate, nickel chloride, and nickel acetate; the magnesium source is selected from at least one of magnesium nitrate, magnesium chloride, magnesium sulfate, and magnesium acetate; the cerium source is selected from cerium nitrate, cerium oxide, cerium sulfate, and cerium ammonium sulfate; and the silicon source is selected from at least one of silica sol, silica powder, and tetraethyl orthosilicate.

[0023] Further, in step (1), the nickel source is calculated as Ni, the magnesium source as Mg, the cerium source as Ce, and the silicon source as Si, and the molar ratio of the nickel source, magnesium source, cerium source and silicon source is (0.01-1):(0.01-1):(0.01-1):1.

[0024] Further, in step (1), the drying is preferably spray drying, with the drying conditions being an inlet temperature of 300-350℃, an outlet temperature of 120-180℃, and a spray disc rotation speed of 15000-25000r / min.

[0025] Further, in step (2), the temperature of the first roasting is 500-800℃, the time is 2-100h, and the oxygen atmosphere is preferably oxygen or air; the temperature of the second roasting is 450-750℃, the time is 1-72h; preferably, the temperature of the second roasting is lower than the temperature of the first roasting, and more preferably, the temperature difference between the temperature of the second roasting and the temperature of the first roasting is not less than 50℃.

[0026] Furthermore, in step (2), the volume percentage of ammonia in the ammonia-containing atmosphere is 1%-14%.

[0027] Further, in step (3), the gold salt is chloroauric acid; the M metal salt is an oxygen-containing salt and / or oxygen-containing salt hydrate selected from one or more elements selected from Ni, Fe, and Cu.

[0028] Further, in step (3), the amount of Au metal introduced into the gold salt, calculated as Au, accounts for 0.05wt%-1.0wt% of the final catalyst by mass; the molar ratio of the M metal salt to the gold salt is 0.2-10, calculated as M element and Au element.

[0029] Further, in step (3), the loading method is selected from impregnation or deposition precipitation, preferably deposition precipitation.

[0030] Further, in step (3), the temperature of the third roasting is 200-500℃, the heating rate is 0.5-5℃ / min, the roasting time is 2-200 hours, and the oxygen-containing atmosphere is preferably oxygen or air.

[0031] The third aspect of the present invention provides the application of the gold-based composite oxide catalyst described in the first aspect and / or the gold-based composite oxide catalyst prepared by the preparation method of the second aspect in the reaction of oxidative esterification of methacrolein to synthesize methyl methacrylate.

[0032] Furthermore, the application includes reacting methacrolein, methanol, and oxygen-containing gas with the above catalyst to obtain methyl methacrylate.

[0033] Furthermore, the oxygen-containing gas can be air.

[0034] Furthermore, the reaction conditions are as follows: reaction temperature 60-90℃, O2 partial pressure 0.02-3MPa, methanol to methacrolein molar ratio 10-40, methacrolein to catalyst mass ratio 1-3, and reaction time 0.5-24h.

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] The gold-based composite oxide catalyst provided by this invention has AuM as its active component. a O x The support is SiO2-NiO-MgO-CeO2, which work together to synthesize methyl methacrylate by the oxidative esterification of methacrolein. It has the characteristics of high catalytic activity and high yield of methyl methacrylate.

[0037] In the preparation method provided by this invention, the support adopts a multi-component mixture, in particular, Ni source and Mg source are added to the support, and the support is first calcined at high temperature, and then the surface of the support is treated with an ammonia atmosphere to expose Mg and Ni on the surface of the support. After loading Au and M metals, it is calcined at low temperature, so that the active components and the support have a higher synergistic effect and the catalyst has better catalytic properties. It achieves the technical effect of high single yield of methyl methacrylate in the oxidative esterification reaction of methacrolein. Detailed Implementation

[0038] The technical solution of the present invention will be further illustrated below through embodiments. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0039] In this invention, the BET method of the Tristar-3000 from Mack Company, USA, is used to test the specific surface area.

[0040] In this invention, the transmission electron microscope (TEM) used for the samples was a JEOL 2100F with a voltage of 200 kV. The size of the gold particles in the molecular sieve was determined by statistically analyzing the sizes of approximately 30 gold particles from the TEM images and then calculating the average value.

[0041] In this invention, an inductively coupled plasma atomic emission spectrometer (ICP) of model Varian 725-ES is used to detect the content of metal elements by dissolving the sample in hydrofluoric acid.

[0042] The catalyst evaluation method used in the following examples is as follows:

[0043] The reactants, methyl methacrylate and methanol, were added to a batch reactor containing the catalyst to be tested. After heating to the required temperature, a certain amount of air was introduced, and the analysis was performed using gas chromatography. During the analysis, the carbon balance was calculated, and data with a carbon balance of 95%–105% were selected as valid data. The reaction conditions were as follows:

[0044] Reactor: Stirred tank reactor, 200ml volume;

[0045] Catalyst dosage: 2 grams;

[0046] Reaction temperature: 80℃;

[0047] Reaction time: 3 hours;

[0048] Raw material molar ratio: methanol / methacrylaldehyde = 30;

[0049] Feeding amounts: 64g methanol, 4.7g methacrolein;

[0050] Air pressure: 2 MPa.

[0051] In this invention, after the reaction of methacrylaldehyde oxidative esterification to synthesize methyl methacrylate is completed, the reaction product is collected after cooling with water circulation. The reaction liquid is analyzed by gas phase to calculate the conversion rate of methacrylaldehyde, the selectivity of the product methyl methacrylate, and the single yield, wherein the formulas are as follows:

[0052] Methacrolein conversion rate = (molar amount of methacrolein consumed in the reaction) / (molar amount of methacrolein fed) × 100%.

[0053] The single-pass yield of methyl methacrylate = (molar amount of methyl methacrylate produced in the reaction) / (molar amount of methacrolein fed) × 100%.

[0054] To facilitate understanding of the present invention, the following embodiments are provided. However, these embodiments are merely for the purpose of helping to understand the present invention and should not be regarded as specific limitations of the present invention.

[0055]

Example 1

[0056] (1) Dissolve 0.1 mol magnesium nitrate, 0.1 mol cerium nitrate and 0.1 mol nickel nitrate in water to obtain solution A. Then add solution A to 1.0 mol silica sol (40 wt% SiO2, the amount of substance is SiO2), continue stirring for 1 h, and spray dry to obtain the carrier precursor.

[0057] (2) The obtained carrier precursor was calcined in air at 600°C for 4 hours. The obtained powder was transferred to a tube furnace and calcined at 500°C for 12 hours in an atmosphere of 5% ammonia and 95% nitrogen to obtain the carrier.

[0058] (3) Mix 0.006 mol (calculated as Au) gold chloride solution and 0.021 mol (calculated as Ni) nickel nitrate solution to obtain mixed salt solution B. Add it to 200 g of support and stir for a period of time. When the color of solution B becomes transparent, filter and wash, and dry in a vacuum oven at 100 °C to obtain catalyst precursor.

[0059] (4) The obtained precursor was calcined in a muffle furnace at 350°C for 2 hours to obtain a catalyst for the synthesis of methyl methacrylate.

[0060] The catalyst is AuNi 3.5 O x The catalyst consists of a 100SiO2-10NiO-10MgO-10CeO2 mixture, with each component in a molar ratio. Based on the weight of the catalyst support, the support contains 9.1 wt% NiO, 4.9 wt% MgO, 12.5 wt% CeO2, and 73.5 wt% SiO2. The catalyst contains 0.6 wt% Au. The average particle size of the Au particles in the catalyst is 2.6 nm. The specific surface area of ​​the catalyst is 163 m². 2 / g.

[0061]

Example 2

[0062] (1) Dissolve 0.1 mol magnesium nitrate, 0.1 mol cerium nitrate and 0.2 mol nickel nitrate in water to obtain solution A. Then add solution A to 1.0 mol silica sol (40 wt% SiO2, the amount of substance is SiO2), continue stirring for a period of time, and spray dry to obtain the carrier precursor.

[0063] (2) The obtained carrier precursor was calcined in air at 600°C for 4 hours. The obtained powder was transferred to a tube furnace and calcined at 500°C for 12 hours in an atmosphere of 5% ammonia and 95% nitrogen to obtain the carrier.

[0064] (3) Mix 0.006 mol (calculated as Au) gold chloride solution and 0.021 mol (calculated as Ni) nickel nitrate solution to obtain mixed salt solution B. Add it to 200 g of support and stir for a period of time. When the color of solution B becomes transparent, filter and wash, and dry in a vacuum oven at 100 °C to obtain catalyst precursor.

[0065] (4) The obtained precursor was calcined in a muffle furnace at 350°C for 2 hours to obtain a catalyst for the synthesis of methyl methacrylate.

[0066] The catalyst is AuNi 3.5 O x The catalyst consists of a 100SiO2-20NiO-10MgO-10CeO2 mixture, with each component in a molar ratio. Based on the weight of the catalyst support, the support contains 16.7 wt% NiO, 4.5 wt% MgO, 11.4 wt% CeO2, and 67.3 wt% SiO2. The catalyst contains 0.6 wt% Au. The average particle size of the Au particles in the catalyst is 2.7 nm. The specific surface area of ​​the catalyst is 153 m². 2 / g.

[0067]

Example 3

[0068] (1) Dissolve 0.1 mol magnesium nitrate, 0.2 mol cerium nitrate and 0.2 mol nickel nitrate in water to obtain solution A. Then add solution A to 1.0 mol silica sol (40 wt% SiO2, the amount of substance is SiO2), continue stirring for a period of time, and spray dry to obtain the carrier precursor.

[0069] (2) The obtained carrier precursor was calcined in air at 600°C for 4 hours. The obtained powder was transferred to a tube furnace and calcined at 500°C for 12 hours in an atmosphere of 5% ammonia and 95% nitrogen to obtain the carrier.

[0070] (3) Mix 0.006 mol (calculated as Au) gold chloride solution and 0.048 mol (calculated as Fe) ferric nitrate solution to obtain mixed salt solution B. Add it to 200 g of carrier and stir for a period of time. When the color of solution B becomes transparent, filter and wash, and dry in a vacuum oven at 100 °C to obtain catalyst precursor.

[0071] (4) The obtained precursor was calcined in a muffle furnace at 350°C for 2 hours to obtain a catalyst for the synthesis of methyl methacrylate.

[0072] The catalyst is AuFe8O x The catalyst composition is 100SiO2-20NiO-10MgO-20CeO2, with the components in a molar ratio. Based on the weight of the catalyst support, the support contains 15.0 wt% NiO, 4.1% MgO, 20.5 wt% CeO2, and 60.4% SiO2. The catalyst contains 0.6 wt% Au. The average particle size of the Au particles in the catalyst is 2.2 nm. The specific surface area of ​​the catalyst is 149 m². 2 / g.

[0073]

Example 4

[0074] (1) Dissolve 0.1 mol magnesium nitrate, 0.2 mol cerium nitrate and 0.2 mol nickel nitrate in water to obtain solution A. Then add solution A to 1.0 mol silica sol (40 wt% SiO2, the amount of substance is SiO2), continue stirring for a period of time, and spray dry to obtain the carrier precursor.

[0075] (2) The obtained carrier precursor was calcined in air at 600°C for 4 hours. The obtained powder was transferred to a tube furnace and calcined at 520°C for 12 hours in an atmosphere of 10% ammonia and 95% nitrogen to obtain the carrier.

[0076] (3) Mix 0.008 mol (calculated as Au) gold chloride solution and 0.008 mol (calculated as Bi) bismuth nitrate solution to obtain mixed salt solution B. Add it to 200 g of support and stir for a period of time. When the color of solution B becomes transparent, filter and wash, and dry in a vacuum oven at 100 °C to obtain catalyst precursor.

[0077] (4) The obtained precursor was calcined in a muffle furnace at 350°C for 2 hours to obtain a catalyst for the synthesis of methyl methacrylate.

[0078] catalyst AuBiO x The catalyst composition is 100SiO2-20NiO-10MgO-20CeO2, with each component in a molar ratio. Based on the weight of the catalyst support, the support contains 15.0 wt% NiO, 4.1% MgO, 20.5 wt% CeO2, and 60.4% SiO2. The catalyst contains 0.8 wt% Au, with an average particle size of 3.5 nm. The specific surface area of ​​the catalyst is 129 m². 2 / g.

[0079] Comparative Example 1

[0080] (1) 140.4g of silica sol (SiO2 40wt%) was spray-dried to obtain the carrier precursor.

[0081] (2) The obtained carrier precursor was calcined in air at 550°C for 4 hours to obtain the carrier.

[0082] (3) Mix 0.006 mol (calculated as Au) gold chloride solution and 0.021 mol (calculated as Ni) nickel nitrate solution to obtain mixed salt solution B. Add it to 200 g of support and stir for a period of time. When the color of solution B becomes transparent, filter and wash, and dry in a vacuum oven at 100 °C to obtain catalyst precursor.

[0083] (4) The obtained precursor was roasted in a muffle furnace at 350°C for 2 hours to obtain a catalyst for the synthesis of methyl methacrylate.

[0084] AuNi catalyst 3.5 O x / SiO2. The catalyst contains 0.6 wt% Au. The average particle size of the Au particles in the catalyst is 10.7 nm. The specific surface area of ​​the catalyst is 153 m². 2 / g.

[0085] Comparative Example 2

[0086] (1) Dissolve 0.1 mol magnesium nitrate and 0.1 mol cerium nitrate in water to obtain solution A, then add solution A to 1.0 mol silica sol (40 wt% SiO2, the amount of substance is SiO2), continue stirring for a period of time, and spray dry to obtain the carrier precursor.

[0087] (2) The obtained carrier precursor was calcined in air at 600°C for 4 hours. The obtained powder was transferred to a tube furnace and calcined at 500°C for 12 hours in an atmosphere of 5% ammonia and 95% nitrogen to obtain the carrier.

[0088] (3) Mix 0.006 mol (calculated as Au) gold chloride solution and 0.021 mol (calculated as Ni) nickel nitrate solution to obtain mixed salt solution B. Add it to 200 g of support and stir for a period of time. When the color of solution B becomes transparent, filter and wash, and dry in a vacuum oven at 100 °C to obtain catalyst precursor.

[0089] (4) The obtained precursor was calcined in a muffle furnace at 350°C for 2 hours to obtain a catalyst for the synthesis of methyl methacrylate.

[0090] The catalyst is AuNi 3.5 O x The catalyst consists of a 100SiO2-10MgO-10CeO2 mixture, with each component in a molar ratio. Based on the weight of the catalyst support, the support contains 5.4% MgO, 13.7 wt% CeO2, and 80.9% SiO2. The catalyst contains 0.6 wt% Au. The average particle size of the Au particles in the catalyst is 4.6 nm. The specific surface area of ​​the catalyst is 141 m². 2 / g.

[0091] Comparative Example 3

[0092] (1) Dissolve 0.1 mol magnesium nitrate, 0.1 mol cerium nitrate and 0.1 mol nickel nitrate in water to obtain solution A. Then add solution A to 1.0 mol silica sol (40 wt% SiO2, the amount of substance is SiO2), continue stirring for a period of time, and spray dry to obtain the carrier precursor.

[0093] (2) The obtained carrier precursor was calcined in air at 600°C for 4 hours. The obtained powder was transferred to a tube furnace and calcined in a nitrogen atmosphere at 500°C for 12 hours to obtain the carrier.

[0094] (3) Mix 0.006 mol (calculated as Au) gold chloride solution and 0.021 mol (calculated as Ni) nickel nitrate solution to obtain mixed salt solution B. Add it to 200 g of support and stir for a period of time. When the color of solution B becomes transparent, filter and wash, and dry in a vacuum oven at 100 °C to obtain catalyst precursor.

[0095] (4) The obtained precursor was calcined in a muffle furnace at 350°C for 2 hours to obtain a catalyst for the synthesis of methyl methacrylate.

[0096] The catalyst is AuNi 3.5 O x The catalyst consists of a 100SiO2-10NiO-10MgO-10CeO2 mixture, with each component in a molar ratio. Based on the weight of the catalyst support, the support contains 9.1 wt% NiO, 4.9 wt% MgO, 12.5 wt% CeO2, and 73.5 wt% SiO2. The catalyst contains 0.6 wt% Au. The average particle size of the Au particles in the catalyst is 8.3 nm. The specific surface area of ​​the catalyst is 162 m². 2 / g.

[0097] Table 1 Catalytic performance data of the examples and comparative examples

[0098]

Claims

1. A gold-based composite oxide catalyst, characterized in that, The catalyst comprises an active component and a support, the active component comprising the following general formula AuM a O x Where M is at least one of Ni, Fe, and Cu; a = 0.2 to 10; x is the total number of oxygen atoms required to satisfy the valence of other elements; The support is a composite oxide SiO2-NiO-MgO-CeO2.

2. The catalyst according to claim 1, characterized in that, In the carrier, based on the mass of the carrier, the NiO content is 3%-20%, the MgO content is 3%-20%, the CeO2 content is 3%-22%, and the SiO2 content is 40%-91%; And / or, in the catalyst, the Au content is 0.05wt%-1.0wt% based on the mass of the catalyst.

3. The catalyst according to claim 1, characterized in that, The average particle size of Au particles in the catalyst is 0.5-5 nm, preferably 1-4 nm; And / or, the specific surface area of ​​the catalyst is 10-300 m². 2 / g.

4. The preparation method of the gold-based composite oxide catalyst according to any one of claims 1-3 specifically includes the following steps: (1) Mix nickel source, magnesium source, cerium source and silicon source with water, and dry to obtain a carrier precursor; (2) The carrier precursor from step (1) is first calcined in an oxygen-containing atmosphere and then calcined in an ammonia-containing atmosphere to obtain the carrier. (3) The gold salt and the M metal salt are mixed with the support and loaded, dried, and calcined for the third time in an oxygen-containing atmosphere to obtain the catalyst.

5. The preparation method according to claim 4, characterized in that, In step (1), the nickel source is selected from at least one of nickel nitrate, nickel chloride, and nickel acetate; And / or, the magnesium source is selected from at least one of magnesium nitrate, magnesium chloride, magnesium sulfate, and magnesium acetate; And / or, the cerium source is selected from cerium nitrate, cerium oxide, cerium sulfate, and cerium ammonium sulfate; And / or, the silicon source is selected from at least one of silica sol, silica powder, and tetraethyl orthosilicate.

6. The preparation method according to claim 4, characterized in that, In step (1), the nickel source is calculated as Ni, the magnesium source as Mg, the cerium source as Ce, and the silicon source as Si. The molar ratio of the nickel source, magnesium source, cerium source and silicon source is (0.01-1):(0.01-1):(0.01-1):

1.

7. The preparation method according to claim 4, characterized in that, In step (1), the drying is spray drying, and the drying conditions are: inlet temperature 300-350℃, outlet temperature 120-180℃, and spray disc rotation speed 15000-25000r / min.

8. The preparation method according to claim 4, characterized in that, In step (2), the temperature of the first roasting is 500-800℃ and the time is 2-100h; the temperature of the second roasting is 450-750℃ and the time is 1-72h. And / or, in step (2), the temperature of the second roasting is lower than the temperature of the first roasting, preferably the temperature difference between the second roasting temperature and the first roasting temperature is not less than 50°C; And / or, in step (2), the volume percentage of ammonia in the ammonia-containing atmosphere is 1%-14%.

9. The preparation method according to claim 4, characterized in that, In step (3), the gold salt is chloroauric acid; the M metal salt is an oxygen-containing salt and / or oxygen-containing salt hydrate selected from one or more elements selected from Ni, Fe, and Cu. And / or, in step (3), the amount of Au metal introduced into the gold salt, calculated as Au, accounts for 0.05wt%-1.0wt% of the final catalyst by mass; the molar ratio of the M metal salt to the gold salt is 0.2-10, calculated as M element and Au element.

10. The preparation method according to claim 4, characterized in that, In step (3), the temperature of the third roasting is 200-500℃, the heating rate is 0.5-5℃ / min, the roasting time is 2-200 hours, and the oxygen-containing atmosphere is oxygen or air.

11. The use of the gold-based composite oxide catalyst according to any one of claims 1-3 and / or the gold-based composite oxide catalyst prepared by the preparation method according to claims 4-10 in the reaction of oxidative esterification of methacrolein to synthesize methyl methacrylate.

12. The application according to claim 11, characterized in that, The application includes reacting methacrolein, methanol, and oxygen-containing gas with the above catalyst to obtain methyl methacrylate.

13. The application according to claim 11, characterized in that, The reaction conditions are as follows: reaction temperature 60-90℃, O2 partial pressure 0.02-3MPa, methanol to methacrolein molar ratio 10-40, methacrolein to catalyst mass ratio 1-3, and reaction time 0.5-24h.

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