Preparation of TiO2@Au / TS-1 catalyst and application thereof in preparation of methyl methacrylate

Abstract

The application discloses a kind of TiO2@Au / TS-1 catalyst preparation and its application in preparation methyl methacrylate, belong to catalytic synthesis technical field.The application is titanium-silicon molecular sieve as carrier and gold are loaded, and TiO2 is modified on catalyst, the intervention of titanium oxide, gold particle is more stable, and it plays a protective role to gold particle, and the carrier TS-1 and gold particle are modified, the interaction between gold and TiO2 is regulated, the gold-based catalyst prepared is placed into reactor, and the mixed solution of methanol and methyl methacrylaldehyde with mass concentration of 45-80% is added, oxygen is introduced into the bottom of reactor, oxidation esterification reaction occurs at 70-160 DEG C, 0.5-2MPa, and methyl methacrylate is prepared.The efficient gold-based catalyst prepared by the application significantly improves the conversion rate of methyl methacrylaldehyde and the selectivity of methyl methacrylate.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of catalyst synthesis, and particularly relates to preparation of a TiO2@Au / TS-1 catalyst and application of the TiO2@Au / TS-1 catalyst in oxidation esterification of methanol and methyl propenyl aldehyde to prepare methyl methacrylate. BACKGROUND

[0002] As an important organic chemical raw material, methyl methacrylate (MMA) is a colorless transparent, ether-like liquid, and is mainly used in the production of organic glass and resin materials. So far, the main processes for producing MMA include the acetone nitrile alcohol method (ACH method), the isobutene oxidation method (i.e. C4 method), the ethylene carbonylation method and the Alpha method. The ACH method needs to use a toxic raw material, consumes a large amount of sulfuric acid in the reaction process, has a high requirement on equipment, has a large amount of ammonium bisulfate as a byproduct, has a long process flow and a large environmental protection pressure. The C4 method includes a three-step method and a two-step method. In the three-step method, isobutene is oxidized to methyl propenyl aldehyde (MAL), then oxidized to methyl methacrylate (MAA), and finally esterified with methanol to generate MMA. In the two-step method, isobutene is oxidized to MAL, and then oxidized and esterified to obtain MMA. The ethylene carbonylation method first generates propyl aldehyde by catalyzing the carbonyl reaction of ethylene, H2 and CO under the action of a rhodium complex, then generates MAL by condensation reaction with formaldehyde, then generates methyl methacrylate by gas phase under the action of a heteropoly acid catalyst, and finally generates MMA by esterification with methanol. The Alpha method mainly generates methyl propionate by using ethylene, CO and methanol as raw materials under the action of a palladium catalyst, then generates MMA by hydroxy aldehyde condensation reaction with formaldehyde. Chinese Invention Patent CN110981728B discloses a preparation method of methyl methacrylate, the catalyst used is a molecular sieve with a silicon-aluminum ratio of 80-120 loaded with gold, the molecular sieve includes one of sodium type ZSM-5, beta, 4A and 5A molecular sieve spherical particles, and the size of the molecular sieve is 50-100 μm. From the aspects of economy, green environmental protection and the like, it is still necessary to develop a new process route and a novel and efficient catalyst to improve the yield of MMA. SUMMARY

[0003] In view of this, the purpose of the present application is to provide a kind of TiO2@Au / TS-1 catalyst preparation and its application in methanol and methyl methacrolein oxidation esterification preparation methyl methacrylate.The gold-based catalyst is prepared with TS-1 molecular sieve as carrier, titanium-silicon molecular sieve has better hydrophobicity, weaker acidity, Ti-O-Au bond can be formed between the framework titanium species in TS-1 molecular sieve and nano gold particles, the strong interaction between carrier and metal is conducive to the formation of smaller nano gold particles, further provides nano gold dispersion, at the same time, modify TiO2 on the catalyst, the intervention of titanium oxide makes gold particles more stable, plays a protective role for gold particles, and at the same time, the carrier TS-1 and gold particles are modified, the interaction between gold and TiO2 is regulated, thereby improving the activity and stability of the catalyst.

[0004] The purpose of the present application is realized by the following technical solutions:

[0005] A kind of TiO2@Au / TS-1 catalyst preparation for methanol and methyl methacrolein oxidation esterification preparation methyl methacrylate, comprising the following steps:

[0006] (1) the silicon source, template agent and water are uniformly mixed, and hydrolyzed at 25-85 DEG C for 30-120 min to obtain silicon ester hydrolysate;Add alcohol solution to titanium source, hydrolyze at 25-85 DEG C for 10-60 min to obtain titanium ester hydrolysate;The obtained silicon ester hydrolysate and titanium ester hydrolysate are uniformly mixed, and alcohol is removed by heating to 50-90 DEG C, and the obtained titanium-silicon sol is loaded into crystallization kettle, and crystallized at 150-200 DEG C for 10-48 h;

[0007] (2) the mother liquor obtained in step (1) is added with aluminum sol or silicon sol or silicon-aluminum sol and amaranth powder, and is aged at 50-90 DEG C for 10-72 h under stirring condition, is formed by spraying, is dried, and is calcined at 300-600 DEG C for 2-24 h to obtain molecular sieve;

[0008] (3) add alcohol solution to titanium source, add template agent aqueous solution, and prepare solution A;The molecular sieve obtained in step (2) is added to the gold salt-containing aqueous solution, then solution A is added dropwise, stirred at room temperature for 1-10 h, filtered, dried, and calcined at 400-500 DEG C for 1-5 h.

[0009] Further, the silicon source in step (1) is one or a mixture of two or more of tetraethyl orthosilicate, tetramethyl orthosilicate, tetrapropyl orthosilicate and tetrabutyl orthosilicate;The template agent is one or a mixture of two or more of tetrapropylammonium hydroxide, tetramethylammonium hydroxide and tetraethylammonium hydroxide;The mass ratio of silicon source, template agent and water is 1:0.1-0.5:0.5-2.

[0010] Further, the titanium source in step (1) is one of tetraethyl orthotitanate, tetra-n-butyl orthotitanate, tetraisopropyl titanate, titanium trichloride, titanium tetrachloride or a mixture of two or more thereof; the alcohol solution is isopropyl alcohol or ethanol; and the mass ratio of the titanium source to the alcohol solution is 1:10-20.

[0011] Further, the mass ratio of the titanium source to the silicon source in step (1) is 1:10-50.

[0012] Further, the alcohol treatment time in step (1) is 4-12 h.

[0013] Further, the mass ratio of the mother liquor to the aluminum sol or the silicon sol or the silicon-aluminum sol and the sesbania powder in step (2) is 1:0.1-1:0.02-0.08.

[0014] Further, the drying temperature in step (2) is 100-180℃, and the drying time is 12-72 h.

[0015] Further, the titanium source in step (3) is one of tetraethyl orthotitanate, tetra-n-butyl orthotitanate, tetraisopropyl titanate, titanium trichloride, titanium tetrachloride or a mixture of two or more thereof, and the alcohol solution is isopropyl alcohol or ethanol; the molar concentration of the titanium source is 0.1-1 mol / L; and the template agent is one of tetrapropylammonium hydroxide, tetramethylammonium hydroxide and tetraethylammonium hydroxide or a mixture of two or more thereof, and the molar concentration of the template agent is 0.01-0.1 mol / L.

[0016] Further, the gold salt in step (3) is one of gold cyanide, potassium gold cyanide, gold chloride, gold chloride, chloroauric acid, chloroaurate, sodium gold sulfite or auric sodium or a mixture of two or more thereof; the mass ratio of the gold salt to the molecular sieve is 0.05-5:100, the loading amount of gold is 0.1-2 wt%, and the loading amount of TiO2 is 0.01-1 wt%.

[0017] In another aspect, the present application provides a TiO2@Au / TS-1 catalyst prepared by the above preparation method.

[0018] The present application also provides an application of the above TiO2@Au / TS-1 catalyst in a reaction of oxidizing esterification of methanol and methyl propyl aldehyde to prepare methyl methacrylate.

[0019] Further, the reaction is specifically mixing the TiO2@Au / TS-1 catalyst, methyl propyl aldehyde and methanol in a reactor, introducing a gas containing oxygen into the bottom of the reactor, the reaction temperature is 70-160℃, the reaction pressure is 0.5-2 MPa, the reaction time is 1-12 h, and methyl methacrylate is obtained by separation.

[0020] Further, the mass concentration of the methacrolein is 10-55%, and the oxygen input rate is 12 L / min.

[0021] The beneficial effects of the present application are:

[0022] The present application uses TS-1 as a carrier, which can not only stabilize gold salt, but also form Ti-O-Au bonds between the titanium species in the TS-1 molecular sieve and the nano gold particles, thereby improving the interaction between the metal and the carrier, effectively limiting the size of the gold particles, increasing the specific surface area of the catalyst, and significantly improving the contact area between the reactants and the active sites. At the same time, the catalyst is modified with TiO2, which further stabilizes the gold particles and protects them, and the carrier TS-1 and the gold particles are modified, thereby improving the catalytic activity by regulating the interaction between gold and TiO2, which is suitable for industrial production. BRIEF DESCRIPTION OF DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present application, the drawings involved in the embodiments will be briefly introduced below.

[0024] Figure 1 The transmission electron microscope image of TiO2@Au / TS-1 of Example 1. DETAILED DESCRIPTION

[0025] The present application will be described in detail below in combination with the embodiments, but the embodiments of the present application are not limited thereto. Obviously, the embodiments described below are only some of the embodiments of the present application, and for those skilled in the art, other similar embodiments can be obtained without creative labor, which fall within the protection scope of the present application.

[0026] Comparative Example 1:

[0027] The preparation of Au / TS-1(1) gold-based catalyst includes the following steps:

[0028] (a) Preparation of molecular sieve mother liquor

[0029] Into a jacketed three-necked reactor, 100 g of tetraethyl orthosilicate was added, and 90 g of 20 wt% aqueous TPAOH and 80 g of deionized water were added under magnetic stirring at 25°C, and the tetraethyl orthosilicate was hydrolyzed for 90 min, and the temperature was continuously increased to 85°C, to obtain a silicon ester hydrolysate; 30 g of anhydrous isopropyl alcohol was added to 4 g of tetrabutyl titanate, and the mixture was hydrolyzed at room temperature for 30 min to obtain a titanium ester hydrolysate; the titanium ester hydrolysate and the silicon ester hydrolysate were mixed, and the mixture was continuously reacted at 85°C for 6 h to remove alcohol, and the obtained clear titanium-silicon sol was placed into a stainless steel sealed autoclave with a polytetrafluoroethylene liner, and crystallization was performed at 170°C under autogenous pressure for 24 h to obtain a titanium-silicon molecular sieve mother liquor 300 g, wherein the mass of titanium-silicon molecular sieve was about 30 g.

[0030] (b) 200 g of the above titanium-silicon molecular sieve mother liquor was taken, 30 g of an aluminum sol with a mass concentration of 30% and 1 g of sesbania powder were added, and the mixture was aged at 70°C for 24 h under stirring, and was spray-formed using a small spray forming machine, and the spray-formed catalyst was dried at 100°C for 12 h and calcined at 540°C for 12 h to obtain a spray-formed TS-1 molecular sieve catalyst, and the particle size of the catalyst was about 50-200 μm.

[0031] (c) 0.5 g of chloroauric acid was dissolved in pure water, and TS-1 molecular sieve was added at room temperature, and then an aqueous solution of tetrapropylammonium hydroxide (20 wt%) with a molar concentration of 0.1 mol / L was added, and the above materials were added to a crystallization kettle, and rotation treatment was performed at 170°C for 24 h, and the mixture was filtered, dried and calcined at 500°C for 2 h.

[0032] Example 1:

[0033] Preparation of TiO2@Au / TS-1(1) gold-based catalyst, including the following steps:

[0034] (1) Preparation of molecular sieve mother liquor

[0035] Into a jacketed three-necked reactor, 100 g of tetraethyl orthosilicate was added, and 90 g of 20 wt% aqueous TPAOH and 80 g of deionized water were added under magnetic stirring at 25°C, and the tetraethyl orthosilicate was hydrolyzed for 90 min, and the temperature was continuously increased to 85°C, to obtain a silicon ester hydrolysate; 30 g of anhydrous isopropyl alcohol was added to 4 g of tetrabutyl titanate, and the mixture was hydrolyzed at room temperature for 30 min to obtain a titanium ester hydrolysate; the titanium ester hydrolysate and the silicon ester hydrolysate were mixed, and the mixture was continuously reacted at 85°C for 6 h to remove alcohol, and the obtained clear titanium-silicon sol was placed into a stainless steel sealed autoclave with a polytetrafluoroethylene liner, and crystallization was performed at 170°C under autogenous pressure for 24 h to obtain a titanium-silicon molecular sieve mother liquor 300 g, wherein the mass of titanium-silicon molecular sieve was about 30 g.

[0036] (2) Take 200 g of the above-mentioned titanium silicalite mother liquor, add 30 g of 30% by mass alumina sol and 1 g of sesbania powder, and age at 70°C for 24 hours under stirring. Spray forming is performed using a small spray forming machine. The spray-formed catalyst is dried at 100°C for 12 hours and calcined at 540°C for 12 hours to obtain a spray-formed TS-1 molecular sieve catalyst, with a particle size of about 50-200 μm.

[0037] (3) Tetrabutyl titanate is added to isopropyl alcohol (0.1 mol / L), and 0.1 mol / L of a tetrapropylammonium hydroxide aqueous solution (20 wt%) is added to prepare solution A. 0.5 g of chloroauric acid is dissolved in pure water, and the above-mentioned TS-1 molecular sieve is added at room temperature. 20 mL of solution A is added dropwise to the TS-1 molecular sieve, which is stirred at room temperature for 5 h, filtered, dried, and calcined at 500°C for 2 hours.

[0038] Example 2:

[0039] Preparation of TiO2@Au / TS-1(2) gold-based catalyst, including the following steps:

[0040] (1) Preparation of molecular sieve mother liquor

[0041] The preparation process of the molecular sieve mother liquor is the same as in Example 1.

[0042] (2) Take 200 g of the above-mentioned titanium silicalite mother liquor, add 30 g of 30% by mass silica sol and 1 g of sesbania powder, and age at 70°C for 36 hours under stirring. Spray forming is performed using a small spray forming machine. The spray-formed catalyst is dried at 150°C for 12 hours and calcined at 500°C for 2 hours to obtain a spray-formed TS-1 molecular sieve catalyst, with a particle size of about 50-200 μm.

[0043] (3) Tetrabutyl titanate is added to isopropyl alcohol (0.1 mol / L), and 0.1 mol / L of a tetrapropylammonium hydroxide aqueous solution (20 wt%) is added to prepare solution A. 0.5 g of chloroauric acid is dissolved in pure water, and the above-mentioned TS-1 molecular sieve is added at room temperature. 20 mL of solution A is added dropwise to the TS-1 molecular sieve. Stirring is performed at room temperature for 8 h, the mixture is filtered, dried, and calcined at 500°C for 2 hours.

[0044] Example 3:

[0045] Preparation of TiO2@Au / TS-1(3) gold-based catalyst, including the following steps:

[0046] (1) Preparation of molecular sieve mother liquor

[0047] The preparation process of the molecular sieve mother liquor is the same as in Example 1.

[0048] (2) Take 200 g of the above-mentioned titanium silicalite mother liquor, add 30 g of a 30% mass concentration silica sol and 1 g of sesbania powder. Age at 70°C for 72 hours under stirring conditions. Spray form using a small spray forming machine. Dry the spray formed catalyst at 150°C for 12 hours and calcine at 500°C for 2 hours to obtain a spray formed TS-1 molecular sieve catalyst, with a catalyst particle size of about 50-200 μm.

[0049] (3) Add tetrabutyl titanate to isopropyl alcohol (0.1 mol / L), add 0.1 mol / L of a tetraethylammonium hydroxide aqueous solution (20 wt%), and prepare solution A; dissolve 0.5 g of chloroauric acid in pure water, and add the above-mentioned TS-1 molecular sieve at room temperature. Add 15 mL of solution A dropwise to the TS-1 molecular sieve, stir at room temperature for 5 h, filter, dry, and calcine at 400°C for 12 hours.

[0050] Example 4:

[0051] Preparation of a TiO2@Au / TS-1(4) gold-based catalyst, including the following steps:

[0052] (1) Preparation of a molecular sieve mother liquor

[0053] The preparation process of the molecular sieve mother liquor is the same as in Example 1.

[0054] (2) Take 200 g of the above-mentioned titanium silicalite mother liquor, add 30 g of a 30% mass concentration silica sol and 1 g of sesbania powder, age at 70°C for 72 hours under stirring conditions, and spray form using a small spray forming machine. Dry the spray formed catalyst at 150°C for 12 hours and calcine at 500°C for 2 hours to obtain a spray formed TS-1 molecular sieve catalyst, with a catalyst particle size of about 50-200 μm.

[0055] (3) Add tetrabutyl titanate to isopropyl alcohol (0.1 mol / L), add 0.1 mol / L of a tetraethylammonium hydroxide aqueous solution (20 wt%), and prepare solution A; dissolve 0.5 g of chloroauric acid in pure water, and add the above-mentioned TS-1 molecular sieve at room temperature. Add 18 mL of solution A dropwise to the TS-1 molecular sieve, stir at room temperature for 6 h, filter, dry, and calcine at 400°C for 12 hours.

[0056] Example 5:

[0057] Preparation of a TiO2@Au / TS-1(5) gold-based catalyst, including the following steps:

[0058] (1) Preparation of a molecular sieve mother liquor

[0059] The preparation process of the molecular sieve mother liquor is the same as in Example 1.

[0060] (2) Take 200 g of the above-mentioned titanium silicalite mother liquor, add 30 g of silicon-aluminum sol with a mass concentration of 30% and 1 g of sesbania powder. Age at 70°C for 72 hours under stirring conditions. Spray form using a small spray forming machine. Dry the spray-formed catalyst at 150°C for 12 hours and calcine at 500°C for 2 hours to obtain a spray-formed TS-1 molecular sieve catalyst, with a catalyst particle size of about 50-200 μm.

[0061] (3) Tetra-n-butyl titanate is added to isopropyl alcohol (0.1 mol / L), and 0.1 mol / L of a tetraethylammonium hydroxide aqueous solution (20 wt%) is added to prepare solution A; 1.5 g of chloroauric acid is dissolved in pure water, and the above-mentioned TS-1 molecular sieve is added at room temperature. 15 mL of solution A is added dropwise to the TS-1 molecular sieve, stirred at room temperature for 5 h, filtered, dried, and calcined at 400°C for 12 hours.

[0062] Example 6:

[0063] Preparation of TiO2@Au / TS-1 (6) gold-based catalyst, including the following steps:

[0064] (1) Preparation of molecular sieve mother liquor

[0065] The preparation process of the molecular sieve mother liquor is the same as that of Example 1.

[0066] (2) Take 200 g of the above-mentioned titanium silicalite mother liquor, add 30 g of silicon-aluminum sol with a mass concentration of 30% and 1 g of sesbania powder. Age at 70°C for 72 hours under stirring conditions. Spray form using a small spray forming machine. Dry the spray-formed catalyst at 150°C for 12 hours and calcine at 500°C for 2 hours to obtain a spray-formed TS-1 molecular sieve catalyst, with a catalyst particle size of about 50-200 μm.

[0067] (3) Tetra-n-butyl titanate is added to isopropyl alcohol (0.1 mol / L), and 0.1 mol / L of a tetraethylammonium hydroxide aqueous solution (20 wt%) is added to prepare solution A; 1.5 g of chloroauric acid is dissolved in pure water, and the above-mentioned TS-1 molecular sieve is added at room temperature. 15 mL of solution A is added dropwise to the TS-1 molecular sieve, stirred at room temperature for 5 h, filtered, dried, and calcined at 400°C for 12 hours.

[0068] Example 7:

[0069] Take 200 g of the catalyst prepared in Comparative Example 1 and Examples 1-6, respectively, and add into a 1.2 L stainless steel autoclave, add 800 mL of a mixture of methanol and methylacrolein, wherein the concentration of methylacrolein is 30 wt%, start the stirring and air inlet, and start the reaction at a bath temperature of 80°C. After the reaction, continuously pump the raw material into the reactor at a rate of 10 ml / min, control the reaction temperature at 80°C, and the reaction time is 1.5 hours. After continuously taking out the generated product, analyze the discharge liquid using gas chromatography, use n-decane as an internal standard, calculate the conversion rate of methylacrolein and the selectivity of methyl methacrylate, and the results are shown in Table 1.

[0070] Table 1. Catalytic performance of the catalyst prepared in Comparative Example 1 and Examples 1-6

[0071] Examples Catalyst MAL conversion % MMA selectivity % Comparative Example 1 Au / TS-1 (1) 92.0 99.0 Example 1 TiO2@Au / TS-1(1) 94.5 99.2 Example 2 TiO2@Au / TS-1(2) 93.6 99.6 Example 3 TiO2@Au / TS-1(3) 93.3 99.3 Example 4 TiO2@Au / TS-1(4) 92.4 99.2 Example 5 TiO2@Au / TS-1(5) 90.4 96.6 Example 6 TiO2@Au / TS-1(6) 89.4 97.9

[0072] From the results of the above table, it can be seen that if the gold catalyst loading is too high or too low, the conversion rate of MAL and the selectivity of MMA will be affected, and both will decrease. Therefore, the appropriate gold loading and the good interaction between gold particles and the carrier are the key to improving the conversion rate of MAL and the selectivity of MMA. It can be seen that TS-1 as a carrier indeed provides significant advantages for the catalytic oxidation esterification of methanol and methylacrolein to prepare methyl methacrylate.

[0073] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing examples, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing examples, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A method for preparing a TiO2@Au / TS-1 catalyst for the oxidative esterification of methanol and methacrolein to methyl methacrylate, characterized in that, Includes the following steps: (1) Mix the silicon source, template agent and water evenly, and hydrolyze at 25~85℃ for 30~120min to obtain silicon ester hydrolysate; add alcohol solution to titanium source, and hydrolyze at 25~85℃ for 10~60min to obtain titanium ester hydrolysate; mix the obtained silicon ester hydrolysate and titanium ester hydrolysate evenly, heat to 50~90℃ to remove alcohol, and load the obtained titanium silica sol into crystallization kettle, and heat at 150℃. Crystallization at 200℃ for 10 48h; (2) Add aluminum sol or silica sol or silica-alumina sol and guar gum powder to the mother liquor obtained in step (1), age it at 50~90℃ for 10~72h under stirring, spray mold, dry it, and calcine it at 300~600℃ for 2~24h to obtain molecular sieve. (3) Add alcohol solution to titanium source, add template agent aqueous solution to prepare solution A; add molecular sieve obtained in step (2) to aqueous solution containing gold salt, then add solution A dropwise, stir at room temperature for 1-10h, filter, dry, calcine at 400-500℃ for 1-5h to obtain; The silicon source mentioned in step (1) is one or a mixture of two or more of tetraethyl orthosilicate, tetramethyl orthosilicate, tetrapropyl orthosilicate and tetrabutyl orthosilicate; the template agent is one or a mixture of two or more of tetrapropylammonium hydroxide, tetramethylammonium hydroxide and tetraethylammonium hydroxide; the mass ratio of silicon source, template agent and water is 1:0.1-0.5:0.5-2; The titanium source mentioned in step (1) is one or a mixture of two or more of tetraethyl orthotitanate, tetrabutyl orthotitanate, tetraisopropyl orthotitanate, titanium trichloride, and titanium tetrachloride; the alcohol solution is isopropanol or ethanol; the mass ratio of the titanium source to the alcohol solution is 1:10-20. The mass ratio of the titanium source to the silicon source in step (1) is 1:10-50; The titanium source mentioned in step (3) is one or a mixture of two or more of tetraethyl orthotitanate, tetrabutyl orthotitanate, tetraisopropyl orthotitanate, titanium trichloride, and titanium tetrachloride; the template agent is one or a mixture of two or more of tetrapropylammonium hydroxide, tetramethylammonium hydroxide, and tetraethylammonium hydroxide. The loading of gold is 0.1-2 wt%, and the loading of TiO2 is 0.01-1 wt%.

2. The preparation method according to claim 1, characterized in that, The alcohol removal process in step (1) takes 4 to 12 hours.

3. The preparation method according to claim 1, characterized in that, The mass ratio of the mother liquor to aluminum sol or silica sol or silica-alumina sol and guar gum powder in step (2) is 1:0.1~1:0.02~0.

08.

4. The preparation method according to claim 1, characterized in that, The gold salt mentioned in step (3) is one or a mixture of two or more of gold cyanide, potassium gold cyanide, gold chloride, gold chloride, chloroauric acid, chloroaurate, sodium gold sulfite or regrin; the mass ratio of gold salt to molecular sieve is 0.05~5:

100.

5. The TiO2@Au / TS-1 catalyst prepared by the method according to any one of claims 1-4.

6. The application of the TiO2@Au / TS-1 catalyst according to claim 5 in the reaction of methanol and methacrolein oxidative esterification to produce methyl methacrylate.

7. The application according to claim 6, characterized in that, The reaction specifically involves mixing TiO2@Au / TS-1 catalyst, methacrolein, and methanol in a reactor, introducing oxygen-containing gas at the bottom of the reactor, maintaining a reaction temperature of 70-160℃, a reaction pressure of 0.5-2MPa, and a reaction time of 1-12h, and then separating methyl methacrylate.

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