A monolithic wall-flow catalyst and its preparation method and application

Abstract

The present invention provides a monolithic wall-flow catalyst and its preparation method and application. The monolithic wall-flow catalyst of the present invention is used for catalytically preparing methyl methacrylate, including a catalyst carrier and a catalytic coating coated on the catalyst carrier, wherein the catalytic coating is an Au / CeO2-MgO-Al2O3 coating, and the coating amount of the catalyst coating is 1-200 g / L, wherein the mass content of gold in the catalytic coating is 0.01%-20%. The present invention forms microchannel reactors by coating the Au / CeO2-MgO-Al2O3 coating in the sub-nanoscale pores of the inner wall of the monolithic wall-flow honeycomb carrier, and fixing the gold catalyst coating on the surface of the sub-nanoscale pores. Since the thickness of the gold catalyst coating is very thin, the diffusion problem is solved, and since each microchannel reactor reacts very fully, the side reaction is extremely low, and the reaction selectivity is high. It can solve the problem of channel flow in the fixed bed catalyst bed, the problem of wear of the slurry bed catalyst, and the problem of diffusion of the straight-through honeycomb reactor.

Description

Technical Field

[0001] The present invention belongs to the technical field of catalysts, and in particular relates to an integral wall-flow catalyst and a preparation method and application thereof. Background Art

[0002] Methyl methacrylate is an organic chemical raw material used in the production of PMMA (organic glass), the manufacturing of polyvinyl chloride additives (ACR), and acrylic fiber. It is also widely used in adhesives, coatings, resins, textiles, and papermaking.

[0003] The preparation methods of methyl methacrylate are divided into C2, C3, and C4 methods according to the number of carbon atoms in the raw materials. Among them, the current mainstream industrial methods are the C3 ACH method, the C4 two-step oxidative esterification method, and the C4 one-step oxidative esterification method. The C3 ACH method uses highly toxic hydrogen cyanide in the reaction process, and a large amount of concentrated sulfuric acid is used in the subsequent reaction process, which causes great environmental pressure and production safety issues. In the C4 two-step oxidative esterification method, methacrolein is first oxidized to methacrylic acid, and methacrylic acid is then reacted with methanol under acid catalysis to obtain methyl methacrylate. Since it uses multiple steps, the process is relatively complicated and requires oxidation, distillation, esterification, and distillation. The process has high energy consumption and high equipment investment. The C4 one-step oxidative esterification process involves the direct oxidative esterification of methacrolein and methanol to produce methyl methacrylate using a gold catalyst under oxygen conditions. This process offers low energy consumption, low equipment investment, and high product yield. Currently, the one-step oxidative esterification reaction is primarily performed using fixed-bed, slurry-bed, and straight-through honeycomb ceramic reactors. Fixed-bed reactors are composed of stacked catalyst particles. When the catalyst particles are fine, the reaction diffusion resistance is low, but the bed resistance is high. Larger catalyst particles, however, have high reaction diffusion resistance and low bed resistance. These two contradictions are irreconcilable. Due to the particle accumulation, a large amount of reaction heat accumulates and cannot be rapidly dissipated. This leads to large axial and longitudinal temperature differences, which can easily cause side reactions. In slurry-bed reactors, the catalyst is stirred in a continuous reactor at high speed. Under these conditions, the catalyst powder experiences intense friction and pulverization, resulting in catalyst loss and the need for constant replenishment of fresh catalyst, which is costly.

[0004] Asahi Kasei Corporation (CN101815579A) uses a gold catalyst supported on a SiO2-MgO-Al2O3 carrier and a fixed bed catalyst. However, the fixed bed catalyst has poor diffusion performance, so the final conversion rate is not high, only about 60%. Summary of the Invention

[0005] The present invention aims to overcome the shortcomings of the prior art and provides a monolithic wall-flow catalyst, its preparation method, and its application. The present invention forms microchannel reactors by applying an Au / CeO2-MgO-Al2O3 coating within the subnanometer-scale pores of the inner wall of a monolithic wall-flow honeycomb substrate. A gold catalyst coating is then affixed to the subnanometer-scale pore surface, thereby eliminating diffusion issues. Furthermore, each microchannel reactor exhibits a highly complete reaction, resulting in minimal side reactions and high reaction selectivity.

[0006] To achieve the above technical objectives, the technical solution adopted in the embodiment of the present invention is:

[0007] In a first aspect, an embodiment of the present invention provides an integral wall-flow catalyst, which is used to catalyze the preparation of methyl methacrylate, and includes a catalyst carrier and a catalytic coating coated on the catalyst carrier, wherein the catalytic coating is an Au / CeO2-MgO-Al2O3 coating, and the coating amount of the catalyst coating is 1-200 g / L, wherein the mass content of gold in the catalytic coating is 0.01%-20%.

[0008] Furthermore, the porosity of the catalyst carrier is 40%-80%.

[0009] Furthermore, the catalyst carrier adopts an integral wall-flow honeycomb carrier, and the material is silicon carbide or cordierite.

[0010] Furthermore, the mesh size of the catalyst carrier is 100-10000 mesh.

[0011] Furthermore, the CeO2-MgO-Al2O3 comprises, by mass fraction, 0.1%-40% cerium oxide, 0.1%-40% magnesium oxide, and 40%-80% aluminum oxide.

[0012] In a second aspect, an embodiment of the present invention provides a method for preparing a monolithic wall-flow catalyst, comprising the following steps:

[0013] Step S1, stirring and mixing 10-100g of deionized water and 1-20g of nitric acid, adding 1-30g of cerium nitrate, 10-30g of magnesium nitrate and 1-30g of aluminum nitrate to the mixture in sequence, stirring and mixing, adding 1-20% sodium hydroxide solution, adjusting the pH to 6-14, continuing stirring for 24h, and filtering and washing to obtain hydroxide colloid;

[0014] Step S2, drying the hydroxide colloid obtained by filtering and washing in step S1 at 50-150° C. for 2 h, then calcining at 400-600° C. for 2 h, naturally cooling to room temperature, and grinding to a particle size D90 ≤ 2 μm to obtain a cerium-magnesium-aluminum composite oxide;

[0015] Step S3, adding 10-20 g of the cerium magnesium aluminum composite oxide prepared in step S2 to 10-100 g of deionized water, stirring and mixing for 30 min, adding chloroauric acid solution, adjusting the pH of the solution to 6-12, filtering and washing to obtain Au(OH)3 / CeO2-MgO-Al2O3;

[0016] Step S4, adding 10-100 g of deionized water and 10-100 g of ethyl cellulose to the Au(OH)3 / CeO2-MgO-Al2O3 obtained in step S3, stirring for 1-6 hours until the viscosity reaches 1000-4000 cp, and coating the mixture into a wall-flow honeycomb substrate by negative pressure suction;

[0017] Step S5: drying the wall-flow honeycomb substrate coated with the catalytic coating in step S4 at 50-150° C. for 2 h, calcining at 300-600° C. for 2 h, and then naturally cooling to room temperature to obtain a catalyst with a coating amount of 1-200 g / L.

[0018] In a third aspect, an embodiment of the present invention provides an application of a monolithic wall-flow catalyst for preparing methyl methacrylate by one-step oxidative esterification of methacrolein.

[0019] Furthermore, when the catalyst is used for the one-step oxidative esterification of methacrolein to prepare methyl methacrylate, the process is carried out in a one-step oxidative esterification reactor, and the one-step oxidative esterification reactor includes a reactor cylinder, and the reactor cylinder includes a feed pipe section, a feed connecting pipe section, a reaction cylinder section, a discharge connecting pipe section and a discharge pipe section connected in sequence, and the outer wall of the feed pipe section is provided with a heat exchange heating module and a secondary heating module, and the outer wall of the reaction cylinder section is provided with a heat exchange cooling module and a secondary heat exchange cooling module, and an integral wall flow catalyst and high-temperature heat conductive cotton are installed in the reaction cylinder section, and the high-temperature heat conductive cotton is arranged between the inner wall of the reaction cylinder section and the outer wall of the integral wall flow catalyst, and the heat exchange cooling module and the secondary heat exchange cooling module realize heat exchange with the heat exchange heating module and the secondary heating module through heat transfer oil.

[0020] The technical solution provided by the embodiment of the present invention has the following beneficial effects:

[0021] (1) The present invention forms microchannel reactors by coating the Au / CeO2-MgO-Al2O3 coating in the sub-nanoscale pores of the inner wall of the integral wall-flow honeycomb carrier and fixing the gold catalyst coating on the surface of the sub-nanoscale pores. Since the thickness of the gold catalyst coating is very thin, the diffusion problem is solved. Moreover, since each microchannel reactor reacts very fully, the side reaction is extremely low and the reaction selectivity is high.

[0022] (2) The present invention adopts a one-step oxidative esterification reactor to effectively control the reaction temperature and solve the problem of channel flow in the fixed bed catalyst; making the catalyst into an integral wall-flow catalyst can solve the problem of slurry bed catalyst wear and the problem of diffusion in the straight-through honeycomb reactor. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 Schematic diagram of the structure of the one-step oxidative esterification reactor in an embodiment of the present invention.

[0024] Figure 2 This is the flow mode of the fluid in the one-step oxidative esterification monolithic catalyst in the embodiment of the present invention.

[0025] Figure 3 Schematic diagram of the end face structure of the monolithic catalyst in an embodiment of the present invention.

[0026] Explanation of the accompanying figures: 1-heat exchange heating module; 2-secondary heating module; 3-reactor barrel; 4-heat exchange cooling module; 5-secondary heat exchange cooling module; 6-integral wall flow catalyst; 7-high-temperature thermal conductive cotton. Figure 3 The black squares in the middle are blocked areas. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0028] Example 1

[0029] A monolithic wall-flow catalyst for preparing methyl methacrylate comprises a catalyst carrier and a catalytic coating coated on the catalyst carrier. The catalytic coating is an Au / CeO2-MgO-Al2O3 coating with a coating amount of 10 g / L. The mass content of gold in the catalytic coating is 1.5%.

[0030] The porosity of the integral wall-flow catalyst carrier is 60%, the catalyst carrier is silicon carbide, and the catalyst carrier has a mesh size of 300.

[0031] The preparation method of the above-mentioned monolithic wall-flow catalyst comprises the following steps:

[0032] Step S1, 100g of deionized water and 20g of nitric acid were stirred and mixed, 3g of cerium nitrate, 3g of magnesium nitrate and 24g of aluminum nitrate were added to the mixture in sequence, and stirred and mixed, 10% sodium hydroxide solution was added, and the pH of the solution was adjusted to 9. The mixture was stirred for 24h and filtered and washed;

[0033] Step S2, drying the solid obtained in step S1 at 150° C. for 2 h, calcining at 600° C. for 2 h, then naturally cooling to room temperature, and grinding to a particle size of D90 = 1.8 μm to obtain a cerium-magnesium-aluminum composite oxide;

[0034] Step S3, adding 9.85g of the cerium-magnesium-aluminum composite oxide obtained in step S2 to 100g of deionized water, stirring and mixing for 30min, adding 15g of 1% gold mass fraction chloroauric acid solution, adding 10% sodium hydroxide solution dropwise to pH = 10, filtering and cleaning;

[0035] Step S4: adding 100 g of deionized water and 10 g of ethyl cellulose to the solid obtained in step S3, stirring for 6 h until the viscosity reaches 4000 cp, and coating the solid into a wall-flow honeycomb substrate by negative pressure suction;

[0036] Step S5: drying the wall-flow honeycomb substrate coated with the catalytic coating at 150° C. for 2 h, calcining at 600° C. for 2 h, and then naturally cooling to room temperature to obtain a catalyst with a coating amount of 10 g / L.

[0037] Example 2

[0038] A monolithic wall-flow catalyst for preparing methyl methacrylate comprises a catalyst carrier and a catalytic coating coated on the catalyst carrier. The catalytic coating is an Au / CeO2-MgO-Al2O3 coating with a coating amount of 15 g / L. The mass content of gold in the catalytic coating is 1.5%.

[0039] The porosity of the integral wall-flow catalyst is 60%, the catalyst carrier is silicon carbide, and the mesh size of the catalyst carrier is 300.

[0040] The preparation method of the above-mentioned monolithic wall-flow catalyst comprises the following steps:

[0041] Step S1, 100g of deionized water and 20g of nitric acid were stirred and mixed, 3g of cerium nitrate, 3g of magnesium nitrate and 24g of aluminum nitrate were added to the mixture in sequence, and stirred and mixed, 10% sodium hydroxide solution was added, and the pH was adjusted to 9. The mixture was stirred for 24h and filtered and cleaned;

[0042] Step S2, drying the solid obtained in step S1 at 150° C. for 2 h, calcining at 600° C. for 2 h, then cooling naturally to room temperature, and grinding to a particle size of D90 = 1.8 μm to obtain a cerium-magnesium-aluminum composite oxide;

[0043] Step S3, adding 9.85g of cerium magnesium aluminum composite oxide to 100g of deionized water, stirring and mixing for 30min, adding 15g of chloroauric acid solution with a gold mass fraction of 1%, adding 10% sodium hydroxide solution dropwise to pH = 10, filtering and washing;

[0044] Step S4: adding 100 g of deionized water and 10 g of ethyl cellulose to the solid obtained in step S3, stirring for 6 h until the viscosity reaches 4000 cp, and coating the solid into a wall-flow honeycomb substrate by negative pressure suction;

[0045] Step S5: drying the wall-flow honeycomb substrate coated with the catalytic coating at 150° C. for 2 h, calcining at 600° C. for 2 h, and then naturally cooling to room temperature to obtain a catalyst with a coating amount of 15 g / L.

[0046] Example 3

[0047] A monolithic wall-flow catalyst for preparing methyl methacrylate comprises a catalyst carrier and a catalytic coating coated on the catalyst carrier. The catalytic coating is an Au / CeO2-MgO-Al2O3 coating with a coating amount of 10 g / L. The mass content of gold in the catalytic coating is 1.5%.

[0048] The porosity of the integral wall-flow catalyst is 80%, the catalyst carrier is silicon carbide, and the catalyst carrier has a mesh size of 300.

[0049] Calculated by mass fraction, the CeO2-MgO-Al2O3 coating comprises: 3% cerium oxide, 3% magnesium oxide, and 24% aluminum oxide.

[0050] The preparation method of the above-mentioned monolithic wall-flow catalyst comprises the following steps:

[0051] Step S1, 100g of deionized water and 20g of nitric acid were stirred and mixed, 3g of cerium nitrate, 3g of magnesium nitrate and 24g of aluminum nitrate were added to the mixture in sequence, and stirred and mixed, 10% sodium hydroxide solution was added, the pH was adjusted to 9, stirring was continued for 24h, and the mixture was filtered and cleaned;

[0052] Step S2, drying the solid obtained in step S1 at 150° C. for 2 h, calcining at 600° C. for 2 h, then cooling naturally to room temperature, and grinding to a particle size of D90 = 1.8 μm to obtain a cerium-magnesium-aluminum composite oxide;

[0053] Step S3, adding 9.85g of cerium magnesium aluminum composite oxide to 100g of deionized water, stirring and mixing for 30min, adding 15g of chloroauric acid solution with a gold mass fraction of 1%, adding 10% sodium hydroxide solution dropwise to pH = 10, filtering and washing;

[0054] Step S4: adding 100 g of deionized water and 10 g of ethyl cellulose to the solid obtained in step S3, stirring for 6 h until the viscosity reaches 4000 cp, and coating the solid into a wall-flow honeycomb substrate by negative pressure suction;

[0055] Step S5: drying the wall-flow honeycomb substrate coated with the catalytic coating at 150° C. for 2 h, calcining at 600° C. for 2 h, and then naturally cooling to room temperature to obtain a catalyst with a coating amount of 10 g / L.

[0056] Example 4

[0057] A monolithic wall-flow catalyst for preparing methyl methacrylate comprises a catalyst carrier and a catalytic coating coated on the catalyst carrier. The catalytic coating is an Au / CeO2-MgO-Al2O3 coating with a coating amount of 10 g / L. The mass content of gold in the catalytic coating is 1.5%.

[0058] The porosity of the integral wall-flow catalyst is 60%, the catalyst carrier is a type of silicon carbide, and the mesh number of the catalyst carrier is 300 meshes.

[0059] The preparation method of the above-mentioned monolithic wall-flow catalyst comprises the following steps:

[0060] Step S1, 100g of deionized water and 20g of nitric acid were stirred and mixed, 3g of cerium nitrate, 3g of magnesium nitrate and 24g of aluminum nitrate were added to the mixture in sequence, and stirred and mixed, 10% sodium hydroxide solution was added, the pH was adjusted to 10, stirring was continued for 24h, and the mixture was filtered and cleaned;

[0061] Step S2, drying the solid obtained in step S1 at 150° C. for 2 h, calcining at 600° C. for 2 h, then cooling naturally to room temperature, and grinding to a particle size of D90 = 1.8 μm to obtain a cerium-magnesium-aluminum composite oxide;

[0062] Step S3, adding 9.85g of cerium magnesium aluminum composite oxide to 100g of deionized water, stirring and mixing for 30min, adding 15g of chloroauric acid solution with a gold mass fraction of 1%, adding 10% sodium hydroxide solution dropwise to pH = 10, filtering and washing;

[0063] Step S4: adding 100 g of deionized water and 10 g of ethyl cellulose to the solid obtained in step S3, stirring for 6 h until the viscosity reaches 4000 cp, and coating the solid into a wall-flow honeycomb substrate by negative pressure suction;

[0064] Step S5: drying the wall-flow honeycomb substrate coated with the catalytic coating at 150° C. for 2 h, calcining at 600° C. for 2 h, and then naturally cooling to room temperature to obtain a catalyst with a coating amount of 10 g / L.

[0065] Comparative Example

[0066] A monolithic wall-flow catalyst for preparing methyl methacrylate comprises a catalyst carrier and a catalytic coating coated on the catalyst carrier. The catalytic coating is an Au-Ni / SiO2-MgO-Al2O3 coating with a coating amount of 10 g / L. The mass content of gold in the catalytic coating is 1.5%.

[0067] The porosity of the integral wall-flow catalyst is 60%, the catalyst carrier is silicon carbide, and the mesh number of the catalyst carrier is 300 meshes.

[0068] The preparation method of the above-mentioned monolithic wall-flow catalyst comprises the following steps:

[0069] Step S1, 100g of deionized water and 20g of nitric acid were stirred and mixed, 3g of magnesium nitrate and 24g of aluminum nitrate were added to the mixture in sequence, and stirred and mixed, and then the mixed slurry was kept at 50°C for 24h to mature, cooled to room temperature, and spray-dried with a nozzle with an outlet temperature of 130°C to obtain a solid material;

[0070] Step S2: calcining the solid obtained in step S1 by programmed temperature increase from room temperature to 300°C for 2 hours, maintaining for 3 hours, then heating to 600°C for another 2 hours, maintaining for 3 hours, and then slowly cooling to obtain a SiO2-MgO-Al2O3 carrier, which was ball-milled to a D90 of 1.8 μm.

[0071] Step S3, adding 9.7 g of cerium magnesium aluminum composite oxide to 100 g of deionized water, stirring and mixing for 30 min, adding 15 g of a mixed solution of nickel nitrate and chloroauric acid (Ni content of 1% and Au content of 1% in the mixed solution), heating to 90° C. to precipitate nickel and gold onto the support, filtering and washing to remove impurity ions, drying at 105° C. for 16 h, and calcining at 500° C. in an air atmosphere for 3 h to obtain a 1.5% Au-1.5% NiO / SiO2-MgO-Al2O3 catalyst;

[0072] Step S4: adding 100 g of deionized water and 10 g of ethyl cellulose to the solid obtained in step S3, stirring for 6 h until the viscosity reaches 4000 cp, and coating the solid into a wall-flow honeycomb substrate by negative pressure suction;

[0073] Step S5: drying the wall-flow honeycomb substrate coated with the catalytic coating at 150° C. for 2 h, calcining at 600° C. for 2 h, and naturally cooling to room temperature to obtain a catalyst with a coating amount of 10 g / L.

[0074] The monolithic catalysts prepared in Examples 1-4 and the comparative example were made into catalysts with a size of 10 mm*10 mm*10 mm. The catalysts were used for the one-step oxidative esterification of methacrolein to produce methyl methacrylate. The oxygen partial pressure was 0.4 MPa, the nitrogen partial pressure was 1.6 MPa, the temperature was 60°C, the reaction residence time was 1 h, and the reactants were methacrolein and methanol. The molar ratio of methacrolein to methanol was 1:10.

[0075] When the catalyst is used for the one-step oxidative esterification of methacrolein to prepare methyl methacrylate, it is carried out in a one-step oxidative esterification reactor, such as Figure 1 As shown, the one-step oxidative esterification reactor includes a reactor barrel 3, which includes a feed pipe section, a feed connecting pipe section, a reaction barrel section, a discharge connecting pipe section and a discharge pipe section connected in sequence. The outer wall of the feed pipe section is provided with a heat exchange heating module 1 and a secondary heating module 2, the outer wall of the reaction barrel section is provided with a heat exchange cooling module 4 and a secondary heat exchange cooling module 5, an integral wall flow catalyst 6 and a high-temperature heat conductive cotton 7 are installed in the reaction barrel section, and the high-temperature heat conductive cotton 7 is arranged between the inner wall of the reaction barrel section and the outer wall of the integral wall flow catalyst 6, the heat exchange cooling module 4 and the secondary heat exchange cooling module 5 realize heat exchange with the heat exchange heating module 1 and the secondary heating module 2 through heat transfer oil.

[0076] The reaction products were analyzed using an Agilent 7860 gas chromatograph with an HP-5 column. The temperature was programmed with an initial temperature of 50°C, an end temperature of 250°C, and a heating rate of 10°C / min. The conversion and selectivity of methyl methacrylate prepared by the catalysts in different examples were calculated. The specific results are shown in Table 1:

[0077] Table 1: Conversion rate and selectivity of one-step oxidative esterification of methacrylic acid aldehyde to MMA in Examples 1-4

[0078] Compare Projects Conversion rate / % Selectivity / % Example 1 99.2 98.3 Example 2 100 99.1 Example 3 98.2 98.8 Example 4 99.4 99.2 Comparative Example 80.6 97.5

[0079] As can be seen from Table 1, when the monolithic wall-flow catalysts prepared in Examples 1-4 of the present invention are used to prepare methyl methacrylate, the conversion rate and selectivity are higher than those of the catalyst in Comparative Example 1.

[0080] Finally, it should be noted that the above specific implementation methods are only used to illustrate the technical solutions of the present invention and are not limiting. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that the technical solutions of the present invention can be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A monolithic wall-flow catalyst, characterized in that: The catalyst is used for catalytically preparing methyl methacrylate, comprising a catalyst support and a catalytic coating coated on the catalyst support, wherein the catalytic coating is an Au / CeO2-MgO-Al2O3 coating, and the coating amount of the catalyst coating is 1-200 g / L, wherein the mass content of gold in the catalytic coating is 0.01%-20%; The porosity of the catalyst carrier is 40%-80%, and the catalyst carrier adopts a monolithic wall-flow honeycomb carrier made of silicon carbide or cordierite; Calculated by mass fraction, the CeO2-MgO-Al2O3 comprises: 0.1%-40% cerium oxide, 0.1%-40% magnesium oxide, and 40%-80% aluminum oxide.

2. The monolithic wall-flow catalyst according to claim 1, characterized in that: The mesh number of the catalyst carrier is 100-10000 mesh.

3. A method for preparing a monolithic wall-flow catalyst, characterized in that: The monolithic wall-flow catalyst according to claim 1 or 2 comprises the following steps: Step S1, 10-100g of deionized water and 1-20g of nitric acid are stirred and mixed, 1-30g of cerium nitrate, 10-30g of magnesium nitrate and 1-30g of aluminum nitrate are added to the mixture in sequence, and the mixture is stirred and mixed, 1-20% sodium hydroxide solution is added, the pH is adjusted to 6-14, stirring is continued for 24h, and filtering and washing is performed to obtain hydroxide colloid; Step S2, drying the hydroxide colloid obtained by filtering and washing in step S1 at 50-150° C. for 2 h, then calcining at 400-600° C. for 2 h, naturally cooling to room temperature, and grinding to a particle size D90 ≤ 2 μm to obtain a cerium-magnesium-aluminum composite oxide; Step S3, adding 10-20 g of the cerium magnesium aluminum composite oxide prepared in step S2 to 10-100 g of deionized water, stirring and mixing for 30 min, adding chloroauric acid solution, adjusting the pH of the solution to 6-12, filtering and washing to obtain Au(OH)3 / CeO2-MgO-Al2O3; Step S4: adding 10-100 g of deionized water and 10-100 g of ethyl cellulose to the Au(OH)3 / CeO2-MgO-Al2O3 obtained in step S3, stirring for 1-6 h until the viscosity reaches 1000-4000 cp, and coating the mixture into a wall-flow honeycomb substrate by negative pressure suction; Step S5: drying the wall-flow honeycomb substrate coated with the catalytic coating in step S4 at 50-150° C. for 2 h, calcining at 300-600° C. for 2 h, and then naturally cooling to room temperature to obtain a catalyst with a coating amount of 1-200 g / L.

4. An application of a monolithic wall-flow catalyst, characterized in that: The monolithic wall-flow catalyst according to claim 1 or 2 is used for the one-step oxidative esterification of methacrolein to prepare methyl methacrylate.

5. The use of the integral wall-flow catalyst according to claim 4, characterized in that: The catalyst is used in a one-step oxidative esterification reactor for preparing methyl methacrylate by one-step oxidative esterification of methacrolein. The one-step oxidative esterification reactor comprises a reactor barrel (3), the reactor barrel (3) comprising a feed pipe section, a feed connecting pipe section, a reaction barrel section, a discharge connecting pipe section, and a discharge pipe section connected in sequence. The outer wall of the feed pipe section is provided with a heat exchange heating module (1) and a secondary heating module (2). The outer wall of the reaction barrel section is provided with a heat exchange cooling module (4) and a secondary heat exchange cooling module (5). An integral wall flow catalyst (6) and high-temperature heat conductive cotton (7) are installed in the reaction barrel section. The high-temperature heat conductive cotton (7) is provided between the inner wall of the reaction barrel section and the outer wall of the integral wall flow catalyst (6). The heat exchange cooling module (4) and the secondary heat exchange cooling module (5) exchange heat with the heat exchange heating module (1) and the secondary heating module (2) through heat transfer oil.

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