CN111495390A - Supported gold catalyst for synthesizing ester by oxidative esterification of alcohol/aldehyde compound and preparation and application thereof - Google Patents

Abstract

The invention discloses a supported gold catalyst for synthesizing ester by oxidizing and esterifying alcohol/aldehyde compounds, and preparation and application thereof.

Description

Supported gold catalyst for oxidative esterification of alcohol/aldehyde compound to synthesize ester and its preparation equipment and applications

technical field

The invention belongs to the technical field of chemical catalysis, and in particular relates to a supported gold catalyst used for oxidative esterification of alcohol/aldehyde compounds to synthesize ester and its preparation and application.

Background technique

The one-step oxidative esterification of alcohol/aldehyde compounds to synthesize esters is a very important chemical reaction, because ester compounds are chemicals used to synthesize various fragrances, flavors and copolymers. Take methyl methacrylate (MMA) produced by the oxidative esterification of methanol and methacrolein (MAL) as an example. It is an important organic polymer monomer and is mainly used in the synthesis of polymethyl methacrylate (PMMA, plexiglass). In recent years, with the rapid development of the domestic decoration industry, construction industry and IT industry, the market demand for PMMA is increasing.

At present, the acetone cyanohydrin (ACH) method is mainly used in the industrial production of MMA. The method uses hydrocyanic acid, sulfuric acid and caustic soda as raw materials, with the formation of a large amount of ammonium hydrogen sulfate by-products, the atom utilization rate is low, and it is a typical non-environmentally friendly process. Isobutene can be obtained from the process of petroleum cracking, and using it as a raw material to produce MMA has the advantages of simple process, high atom utilization rate, environmental protection and energy saving. This method mainly has two routes: oxidation method and direct methylation method. The former is oxidized from isobutylene to MAL, and then MAL is oxidized to methacrylic acid (MAA), which is then reacted with methanol to form MMA. The direct methylation method avoids the direct formation of MAA and reduces the problems of equipment corrosion, environmental pollution and product separation.

The oxidative esterification of MAL initially used a homogeneous reaction system catalyzed by H ₂ O ₂ or peracetic acid [R.Gopinath, BK Patel, Org. Lett., 2000, 2, 577-579.], after introducing oxygen-containing gas as an oxidant, Gradually transition to heterogeneous catalysts with noble metal Pd or Au as active components and adding different additives. Compared with homogeneous catalysts, heterogeneous catalysts have the advantages of less by-products, mild reaction conditions, easy separation and reuse, and continuous operation.

A series of palladium-based catalysts developed by Japan's Asahi Kasei Co., Ltd. have achieved good catalytic effects in laboratory research [CN 108607550 A], but when Pd is used as the active component, although the catalytic activity is high, the selection of the target product The property is not high, so it is necessary to add additives such as Pb and Bi to improve its selectivity [C.Liu, J. Wang, L. Meng, Angew. Chem. Int. Ed., 2011, 50, 5144-5148.]. However, the addition of additives such as Pb and Bi will cause environmental pollution, so it is an urgent problem to seek green heterogeneous catalysts with high efficiency and high selectivity.

Japan's Asahi Kasei Company developed a nano-gold catalyst (Au@NiO _x ) with a core-shell structure in subsequent research [K.Suzuki,T.Yamaguchi,K.Matsushita,et al.ACS Catal.,2013,3, 1845-1849.], they found that the catalyst could efficiently catalyze the oxidative esterification of methacrolein and methanol to form MMA, and its MMA selectivity was as high as 99%, and the catalyst showed excellent performance when applied to a fixed bed reactor. stability. However, the conversion rate of the catalyst in application is low, about 60%, and the cost of preparation technology and catalyst is relatively high, so it is not suitable for industrial production.

Based on the above analysis, the one-step oxidative esterification of methacrolein and methanol is the core link in the process of preparing methyl methacrylate from isobutene. The development of green and efficient supported catalysts for the oxidative esterification of alcohol/aldehyde compounds to synthesize esters has strong realistic meaning.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a supported gold catalyst for oxidative esterification of alcohol/aldehyde compound to synthesize ester, so that the catalyst can convert alcohol/aldehyde compound into ester compound in one step with high efficiency and high selectivity, and the catalyst is prepared The process is simple, the catalyst can maintain structural stability during the reaction process, and has a certain anti-sulfur effect, which is beneficial to industrial production and application in the future.

For realizing the above scheme, the technical scheme adopted in the present invention is as follows:

A supported gold catalyst for oxidative esterification of alcohol/aldehyde compound to synthesize ester, using chloroauric acid aqueous solution as raw material, using hydrotalcite as carrier, containing thiol compound as stabilizer to control the particle size of gold and keep the gold catalyst The hydrotalcite includes zinc-aluminum hydrotalcite, magnesium-aluminum hydrotalcite, nickel-aluminum hydrotalcite or cobalt-aluminum hydrotalcite, wherein the molar ratio of zinc, magnesium, nickel or cobalt to aluminum is 1:3 to 3:1 ; The mass fraction of active component gold is 0.1-20 wt %, and the mass fraction of sulfur is 0.01-10 wt %.

Preferably, the thiol-containing compound is selected from one of cysteine, homocysteine, glutathione, captopril, dodecanethiol, phenylethanethiol or hexanethiol or more.

Preferably, the average particle size of the gold catalyst is 1-5 nm.

The present invention also relates to the preparation method of the supported gold catalyst used for the oxidative esterification of alcohol/aldehyde compound to synthesize ester, and adopts the following technical scheme:

A method for preparing a supported gold catalyst for oxidative esterification of alcohol/aldehyde compounds to synthesize ester, the first method comprises: taking an appropriate amount of chloroauric acid aqueous solution, adjusting the pH value to 7-10 with NaOH solution, adding a hydrotalcite carrier, stirring After the reaction, the suspension is suction filtered and washed, then the filter cake is redispersed in an appropriate amount of ultrapure water, and a certain amount of thiol-containing compound is added under stirring conditions, and the above-mentioned liquid is subjected to suction filtration and washing after the stirring reaction to obtain The obtained filter cake is dried and calcined to obtain a supported gold catalyst, wherein the molar ratio of hydrotalcite and thiol compound to chloroauric acid is 100-500: 0.01-1.0: 1, preferably 100-200: 0.1-0.5: 1.

Or method two: adopt the sol-gel method to add the chloroauric acid solution, the solution containing the thiol compound, the NaOH solution and the NaBH solution into the container successively, and control the mol ratio of the thiol compound, NaOH, NaBH ₄ and Au to be ₁ respectively. ~4: 50 ~ 100: 1 ~ 10: 1, preferably 1.5 ~ 3: 50 ~ 65: 5 ~ 10: 1, the obtained product is centrifuged and washed with a mixture of ethanol and water, V _ethanol / V _water = 2 ~6:1, and freeze-dry the obtained black solid, the dried crystals (thiol-stabilized gold atomic clusters) are dissolved in water or acetone solution and then impregnated or adsorbed on the hydrotalcite carrier, and the load is obtained after drying and roasting. type gold catalyst.

Here, the preparation method of the hydrotalcite carrier includes adding a certain quality of zinc nitrate, magnesium nitrate, nickel nitrate, cobalt nitrate or aluminum nitrate, according to the molar ratio of zinc, magnesium, nickel or cobalt to aluminum, which is 1:3-3:1 and adding water to prepare To form solution A, take a certain amount of NaOH and Na ₂ CO ₃ solids and add deionized water to make a mixed solution and record it as solution B. Under stirring in a water bath, mix solution B and solution A in a volume ratio of 1: 1, and in At this temperature, the aged solution was subjected to suction filtration and washing with a large amount of deionized water, and the obtained filter cake was dried in an oven. The dried solid was ground into a fine powder of 100 meshes; the total amount of metal nitrates The mass accounts for 10-30wt% of solution A, the molar ratio of NaOH and nitrate is 5-7:1, and the molar ratio of Na ₂ CO ₃ solid and nitrate is 1-3: 1.

The present invention also relates to a kind of application of the supported gold catalyst for the oxidative esterification of alcohol/aldehyde compound to synthesize ester, adopting the following technical scheme:

Application of a supported gold catalyst for oxidative esterification of alcohol/aldehyde compound to synthesize ester, comprising adding a certain amount of aldehyde compound and alcohol compound into a reaction kettle, adding a certain amount of supported gold catalyst, and then using nitrogen The air in the kettle is replaced, and then a certain amount of oxygen-containing gas is filled into the kettle. The reaction kettle is placed in a heating device to heat up, and the temperature in the kettle is monitored by a thermal sensor. When the temperature rises to the specified temperature, Turn on magnetic stirring or mechanical stirring to fully mix the solution and gas in the kettle. After reacting for a period of time, put the kettle body into a cooling medium to cool down, and release the remaining gas in the kettle. The reactants and products were analyzed.

Preferably, the temperature is 50-120° C., the oxygen partial pressure is 0.1-1 MPa, the aldol molar ratio is 8-50:1, and the molar ratio of aldehyde to gold in the catalyst is 1-10 ³ :1.

An application of a supported gold catalyst for oxidative esterification of alcohol/aldehyde compounds to synthesize ester, comprising adding a certain amount of supported gold catalyst to a fixed bed reactor, then replacing the gas in the pipeline with nitrogen, and changing the gas in the pipeline with nitrogen. A certain amount of oxygen-containing gas is introduced into the reactor, the pressure and flow of the gas are controlled by a back pressure valve and a mass flow meter, and the temperature inside and outside the reactor is monitored by a thermal sensor. Compounds and alcohol compounds are formulated into a reaction solution and injected into the reaction system through a double plunger liquid pump. After a period of reaction, the reaction solution flows from the fixed bed reactor to a cold tank to cool down, and the product is taken out from the cold tank and passed through the gas phase. The chromatograph analyzes the reactants and products.

Preferably, the temperature is 50-120° C., the oxygen partial pressure is 0.1-1 MPa, the aldol molar ratio is 8-50:1, and the molar ratio of aldehyde to gold in the catalyst is 1-10 ³ :1.

Preferably, the aldehyde compounds include one or more of isobutyraldehyde, methacrolein, crotonaldehyde, cinnamaldehyde, and benzaldehyde, and the alcohol compounds include methanol, ethanol, isopropanol, isobutyraldehyde One or more of alcohol, butanol, cinnamyl alcohol and benzyl alcohol.

The gold catalyst prepared by the invention has small particle size and strong sulfur resistance, and has good activity and selectivity when applied to the oxidative esterification reaction of alcohol/aldehyde compounds, and can obtain a conversion rate of aldehydes of more than 90% and a conversion rate of more than 80%. ester selectivity. And the catalyst can maintain the stability of the structure without aggregation when applied to the reaction.

Description of drawings

Fig. 1 is the particle size distribution diagram of the supported gold catalysts prepared in Examples 1, 6, 34 and 35, (a) Au-S/Zn ₃ Al-HT; (b) Au-S/Mg ₃ Al-HT; (c) Au ₂₅ /Zn ₃ Al-HT; (d) Au ₂₅ /Mg ₃ Al-HT.

Figure 2 shows the conversion rate of MAL and the selectivity of MMA under different reaction times in Example 5.

Figure 3 shows the effect of oxygen pressure on reaction rate and target product selectivity in Example 5.

Detailed ways

The following examples further illustrate the present invention, but do not limit the scope of protection of the present invention.

Example 1:

Supported gold catalyst for oxidative esterification of alcohol/aldehyde compound to synthesize ester, with zinc-aluminum hydrotalcite as carrier, cysteine as stabilizer, the molar ratio of zinc to aluminum is 3:1; the mass of active component gold The fraction is 1.0 wt%, and the mass fraction of sulfur is 0.1 wt%.

Preparation of hydrotalcite carrier: take Zn(NO ₃ ) ₂ ·6H ₂ O (0.21mol), Al(NO ₃ ) ₃ ·9H ₂ O (0.07mol) into a beaker, add 200 mL of deionized water to make solution A, NaOH (0.438mol) and Na ₂ CO ₃ (0.113 mol) were added to the beaker, and 200 mL of deionized water was stirred and dissolved to prepare solution B. Under stirring in a water bath at 70 °C, the solution A was slowly added dropwise to the solution B with a constant flow pump, and the flow rate was controlled to be 3 mL/min. Agitation was carried out at this temperature for 24 h. After aging, washed with a large amount of deionized water and suction filtered. The filter cake was dried at 70°C, and ground into 100-mesh powder after drying.

Preparation of catalyst: take 1.02 mL of chloroauric acid solution (0.1 mol/L), dilute with 20 mL of deionized water, adjust the pH value to about 9, and add 2 g of zinc-aluminum hydrotalcite carrier (molar ratio Zn:Al=3:1) , the reaction was stirred for 12h, the solid was obtained by suction filtration and washing, then the solid was dispersed in deionized water and 9.5mg cysteine was added, and after stirring for 1h, the solid obtained by suction filtration was dried and calcined, and finally a supported gold catalyst was obtained. The average particle diameter was 1.1 nm.

Application of supported gold catalysts for oxidative esterification of alcohol/aldehyde compounds to synthesize esters

Oxidative esterification reaction: one-step oxidative esterification of alcohol/aldehyde was carried out in a 15mL stainless steel autoclave, and 5mL (123.6mmol) of methanol, 396μL (4.8mmol) of 95% methacrolein, and 121μL of o-xylene were added to the autoclave. , 0.1 g of Au-S/Zn ₃ Al-HT catalyst (the molar amount of gold is 0.005 mmol). Filled with oxygen 0.3MPa, the reaction was carried out under stirring in a water bath at 80°C for 2h. After the reaction, the product was detected with a gas chromatograph. The conversion rate of methacrolein obtained was 90%, and the selectivity of methyl methacrylate was 95%.

The cysteine in Example 1 can be replaced by homocysteine, glutathione, captopril, dodecanethiol, phenethanethiol or hexanethiol.

Example 2:

Supported gold catalyst for oxidative esterification of alcohol/aldehyde compound to synthesize ester, with zinc-aluminum hydrotalcite as carrier, cysteine as stabilizer, and the molar ratio of zinc to aluminum is 2:1; the mass of active component gold The fraction is 1.0 wt%, and the mass fraction of sulfur is 0.1 wt%.

Compared with Example 1, the difference is that Zn(NO ₃ ) ₂ ·6H ₂ O (0.14molg), Al(NO ₃ ) ₃ ·9H ₂ O (0.07mol) were used in the preparation of the hydrotalcite carrier, and the obtained The metal molar ratio of zinc-aluminum hydrotalcite is Zn/Al=2:1, the average particle size of the prepared supported gold catalyst is 1.3 nm, the obtained methacrolein conversion rate is 92%, and the methyl methacrylate has a The selectivity was 96%.

Example 3:

Supported gold catalyst for oxidative esterification of alcohol/aldehyde compound to synthesize ester, with zinc-aluminum hydrotalcite as carrier, cysteine as stabilizer, and the molar ratio of zinc to aluminum is 1:1; the mass of active component gold The fraction is 1.0 wt%, and the mass fraction of sulfur is 0.1 wt%.

Compared with Example 1, the difference is that Zn(NO ₃ ) ₂ ·6H ₂ O (0.07mol), Al(NO ₃ ) ₃ ·9H ₂ O (0.07mol) were used in the preparation of the hydrotalcite carrier, and the obtained The metal molar ratio of zinc-aluminum hydrotalcite is Zn/Al=1:1, the average particle size of the prepared supported gold catalyst is 1.5 nm, the obtained methacrolein conversion rate is 85%, and the methyl methacrylate has a The selectivity was 92%.

Example 4:

Supported gold catalyst for oxidative esterification of alcohol/aldehyde compound to synthesize ester, with zinc-aluminum hydrotalcite as carrier, cysteine as stabilizer, the molar ratio of zinc to aluminum is 1:2; the mass of active component gold The fraction is 1.0 wt%, and the mass fraction of sulfur is 0.1 wt%.

Compared with Example 1, the difference is that Zn(NO ₃ ) ₂ ·6H ₂ O (0.035mol), Al(NO ₃ ) ₃ ·9H ₂ O (0.07mol) were used in the preparation of the hydrotalcite carrier, and the obtained The metal molar ratio of zinc-aluminum hydrotalcite is Zn/Al=1:2, the average particle size of the prepared supported gold catalyst is 1.6 nm, the obtained methacrolein conversion rate is 82%, and the methyl methacrylate has a The selectivity is 90%.

Example 5:

Supported gold catalyst for the oxidative esterification of alcohol/aldehyde compounds to synthesize ester, with zinc-aluminum hydrotalcite as carrier, cysteine as stabilizer, and the molar ratio of zinc to aluminum is 1:3; the mass of active component gold The fraction is 1.0 wt%, and the mass fraction of sulfur is 0.1 wt%.

Compared with Example 1, the difference is that Zn(NO ₃ ) ₂ ·6H ₂ O (0.023mol), Al(NO ₃ ) ₃ ·9H ₂ O (0.07mol) were used in the preparation of the hydrotalcite carrier, and the obtained The metal molar ratio of zinc-aluminum hydrotalcite is Zn/Al=1:3, the average particle size of the prepared supported gold catalyst is 1.9 nm, the obtained methacrolein conversion rate is 65%, and the methyl methacrylate The selectivity was 81%.

Example 6:

Supported gold catalyst for oxidative esterification of alcohol/aldehyde compound to synthesize ester, with magnesium-aluminum hydrotalcite as carrier, cysteine as stabilizer, and the molar ratio of magnesium to aluminum is 3:1; the mass of active component gold The fraction is 1.0 wt%, and the mass fraction of sulfur is 0.1 wt%.

Compared with Example 1, the difference is that Mg(NO ₃ ) ₂ ·6H ₂ O (0.021mol), Al(NO ₃ ) ₃ ·9H ₂ O (0.07mol) were used in the preparation of the hydrotalcite carrier, and the obtained The metal molar ratio of magnesium-aluminum hydrotalcite is Mg/Al=3:1, the obtained catalyst is expressed as Au-S/Mg ₃ Al-HT, its average particle size is 1.1 nm, and the obtained methacrolein conversion rate is 88 %, the selectivity to methyl methacrylate was 77%.

Example 7:

Supported gold catalyst for oxidative esterification of alcohol/aldehyde compound to synthesize ester, with nickel-aluminum hydrotalcite as carrier, cysteine as stabilizer, the molar ratio of nickel to aluminum is 3:1; the mass of active component gold The fraction is 1.0wt%, and the mass fraction of sulfur is 0.1wt%

Compared with Example 1, the difference is that Ni(NO ₃ ) ₂ ·6H ₂ O (0.021mol), Al(NO ₃ ) ₃ ·9H ₂ O (0.07mol) were used in the preparation of the hydrotalcite carrier, and the obtained The metal molar ratio of nickel-aluminum hydrotalcite is Ni/Al=3:1, the obtained catalyst is expressed as Au-S/ _Ni3Al -HT, its average particle size is 2.1nm, and the obtained methacrolein conversion rate is 92 %, the selectivity to methyl methacrylate was 65%.

Example 8:

Supported gold catalyst for oxidative esterification of alcohol/aldehyde compound to synthesize ester, with cobalt-aluminum hydrotalcite as carrier, cysteine as stabilizer, the molar ratio of cobalt and aluminum is 3:1; the mass of active component gold The fraction is 1.0 wt%, and the mass fraction of sulfur is 0.1 wt%.

Compared with Example 1, the difference is that Co(NO ₃ ) ₂ ·6H ₂ O (0.021mol), Al(NO ₃ ) ₃ ·9H ₂ O (0.07mol) were used in the preparation of the hydrotalcite carrier, and the obtained The metal molar ratio of cobalt-aluminum hydrotalcite is Co/Al=3:1, the obtained catalyst is expressed as Au-S/Co ₃ Al-HT, its average particle size is 2.0 nm, and the obtained methacrolein conversion rate is 86 %, the selectivity to methyl methacrylate was 85%.

Example 9:

Compared with Example 1, the difference is that no thiol-containing protective agent was added in the catalyst preparation process, the particle size of the obtained supported gold catalyst was 3.5 nm, the conversion rate of methacrolein was 26%, and the methyl The selectivity to methyl acrylate was 45%.

Example 10:

Compared with Example 2, the difference is that no thiol-containing protective agent was added in the catalyst preparation process, the particle size of the obtained supported gold catalyst was 3.8 nm, the conversion rate of methacrolein was 22%, and the methyl The selectivity to methyl acrylate was 48%.

Example 11:

Compared with Example 3, the difference is that no thiol-containing protective agent was added in the catalyst preparation process, the particle size of the obtained supported gold catalyst was 4.2 nm, the conversion rate of methacrolein was 20%, and the methyl The selectivity to methyl acrylate was 39%.

Example 12:

Compared with Example 6, the difference is that no thiol-containing protective agent was added in the catalyst preparation process, the particle size of the obtained supported gold catalyst was 4.5 nm, the conversion rate of methacrolein was 21%, and the methyl The selectivity to methyl acrylate was 44%.

Example 13:

Compared with Example 7, the difference is that no thiol-containing protective agent was added in the catalyst preparation process, the particle size of the obtained supported gold catalyst was 10.5 nm, the conversion rate of methacrolein was 5%, and the methyl The selectivity to methyl acrylate was 22%.

Example 14:

Compared with Example 8, the difference is that no thiol-containing protective agent was added in the catalyst preparation process, the particle size of the obtained supported gold catalyst was 6.5 nm, the conversion rate of methacrolein was 36%, and the methyl The selectivity to methyl acrylate was 46%.

Example 15:

Compared with Example 1, the difference is that the amount of cysteine added in the catalyst preparation process is 4.5mg, the mass fraction of sulfur is 0.05wt%, and the average particle size of the prepared supported gold catalyst is 2.0nm, The resulting methacrolein conversion was 90% and the methyl methacrylate selectivity was 92%.

Example 16:

Compared with Example 1, the difference is that the amount of cysteine added in the catalyst preparation process is 19.2 mg, the mass fraction of sulfur is 0.25 wt%, and the average particle size of the prepared supported gold catalyst is 1.6 nm, The resulting methacrolein conversion was 88% and the selectivity to methyl methacrylate was 90%.

Example 17:

Compared with Example 1, the difference is that the amount of cysteine added in the catalyst preparation process is 45.1 mg, the mass fraction of sulfur is 0.5 wt%, and the average particle size of the prepared supported gold catalyst is 1.5 nm, The resulting methacrolein conversion was 42% and the selectivity to methyl methacrylate was 88%.

Example 18:

Compared with Example 1, the difference is that the thiol protective agent added in the catalyst preparation process is 5.0 mg of homocysteine, the mass fraction of sulfur is 0.1 wt%, and the average particle size of the prepared supported gold catalyst is is 1.8 nm, the conversion rate of methacrolein obtained is 91%, and the selectivity of methyl methacrylate is 92%.

Example 19:

Compared with Example 1, the difference is that the thiol protective agent added in the catalyst preparation process is 11.4 mg of glutathione, the mass fraction of sulfur is 0.1 wt%, and the average particle size of the prepared supported gold catalyst is 2.1 nm, the conversion of methacrolein obtained was 87%, and the selectivity of methyl methacrylate was 88%.

Example 20:

Compared with Example 1, the difference is that the thiol protective agent added in the catalyst preparation process is 8.1 mg of captopril, the mass fraction of sulfur is 0.1 wt%, and the average particle size of the prepared supported gold catalyst is 2.2 nm, the conversion of methacrolein obtained was 82%, and the selectivity of methyl methacrylate was 85%.

Example 21:

Compared with Example 1, the difference is that 5.1 mL of chloroauric acid solution (0.1 mol/L) and 47.5 mg of cysteine were added in the catalyst preparation process, the mass fraction of active component gold was 5.0 wt%, and the content of sulfur was 5.0 wt%. The mass fraction is 0.5 wt %, the average particle size of the prepared supported gold catalyst is 1.9 nm, and 0.05 g of the catalyst is taken during the oxidative esterification reaction, and the obtained methacrolein conversion rate is 87%, methyl methacrylate. The selectivity is 90%.

Example 22:

Compared with Example 1, the difference is that 20.4 mL of chloroauric acid solution (0.1 mol/L) and 190 mg of cysteine were added in the catalyst preparation process, the mass fraction of active component gold was 20 wt%, and the mass fraction of sulfur was The average particle size of the prepared supported gold catalyst is 2.6 nm, and 0.025 g of the catalyst is taken during the oxidative esterification reaction, and the obtained methacrolein conversion rate is 76%, and the selectivity of methyl methacrylate is 76%. is 90%.

Example 23:

Compared with Example 22, the difference is that 950 mg of cysteine was added in the catalyst preparation process, the mass fraction of active component gold was 20 wt %, and the mass fraction of sulfur was 10 wt %. The particle size is 2.5 nm, and 0.025 g of the catalyst is taken during the oxidative esterification reaction, the obtained methacrolein conversion rate is 26%, and the selectivity of methyl methacrylate is 84%.

Example 24:

Compared with Example 1, the difference is that the amount of catalyst added in the oxidative esterification reaction is 0.05 g, the conversion rate of methacrolein obtained is 62%, and the selectivity of methyl methacrylate is 91%.

Example 25:

Compared with Example 1, the difference is that the oxygen pressure charged in the oxidative esterification reaction is 0.5 MPa, the conversion rate of methacrolein obtained is 92%, and the selectivity of methyl methacrylate is 94%.

Example 26:

Compared with Example 1, the difference is that the oxygen pressure charged in the oxidative esterification reaction is 0.2 MPa, the conversion rate of methacrolein obtained is 88%, and the selectivity of methyl methacrylate is 90%.

Example 27:

Compared with Example 1, the difference is that the reaction temperature in the oxidative esterification reaction is 60° C., the conversion rate of methacrolein obtained is 80%, and the selectivity of methyl methacrylate is 93%.

Example 28:

Compared with Example 1, the difference is that the reaction temperature in the oxidative esterification reaction is 100° C., the conversion rate of methacrolein obtained is 96%, and the selectivity of methyl methacrylate is 94%.

Example 29:

Compared with Example 1, the difference is that the aldehydes added in the oxidative esterification reaction are 450 μL of isobutyraldehyde, the obtained isobutyraldehyde conversion rate is 95%, and the selectivity of methyl isobutyrate is 98.5%.

Example 30:

Compared with Example 1, the difference is that the aldehydes added in the oxidative esterification reaction are 660 μL of cinnamaldehyde, the obtained cinnamaldehyde conversion rate is 75%, and the selectivity of methyl cinnamate is 80%.

Example 31:

Compared with Example 1, the difference is that the aldehydes added in the oxidative esterification reaction are 660 μL of benzaldehyde, the obtained benzaldehyde conversion rate is 80%, and the selectivity of methyl benzoate is 65%.

Example 32:

Compared with Example 1, the difference is that the aldehydes added in the oxidative esterification reaction are crotonaldehyde 395 μL, the obtained crotonaldehyde conversion rate is 75%, and the selectivity of methyl crotonate is 65%.

Example 33:

Compared with Example 1, the difference is that the oxidative esterification reaction is carried out in a continuous fixed-bed reactor, and the reaction solution is a 10% volume fraction of methacrolein/methanol solution, Au-S/Zn ₃ Al-HT (obtained from Example 1) catalyst 0.5g, oxygen partial pressure 0.2MPa, gas flow rate 20mL/min, reaction temperature 80°C, reaction time 12h to take a sample, the product was detected with a gas chromatograph, and the obtained methacrolein was converted into The yield was 95% and the selectivity to methyl methacrylate was 95%.

Example 34:

Compared with Example 30, the difference is that the catalyst is 0.5 g of Au/Zn ₃ Al-HT catalyst without thiol protective agent, the obtained methacrolein conversion rate is 75%, and the selection of methyl methacrylate Sex is 90%.

Example 35:

Compared with Example 30, the difference is that the catalyst is Au-S/Mg ₃ Al-HT (obtained from Example 6) catalyst 0.5g, the obtained methacrolein conversion rate is 90%, methyl methacrylate The selectivity is 75%.

Example 36:

Compared with Example 30, the difference is that the catalyst is Au-S/Ni ₃ Al-HT (obtained from Example 7) catalyst 0.5g, the obtained methacrolein conversion rate is 95%, methyl methacrylate The selectivity is 77%.

Example 37:

Compared with Example 30, the difference is that the catalyst is Au-S/Co ₃ Al-HT (obtained from Example 8) catalyst 0.5g, the obtained methacrolein conversion rate is 85%, methyl methacrylate The selectivity is 86%.

Example 38:

Compared with Example 30, the difference is that the catalyst is Au ₂₅ /Zn ₃ Al-HT 0.5g, wherein the preparation of the Au ₂₅ /Zn ₃ Al-HT catalyst is to use the impregnation method to support gold atom clusters (Au ₂₅ ). It is obtained by drying and calcining on a Zn ₃ Al-HT carrier. Au ₂₅ atomic clusters are obtained by using cysteine as a stabilizer and sodium borohydride as a reducing agent. The specific preparation method is as follows: take 0.5 mL of chloroauric acid solution prepared in advance. (19.12g _Au /L), add 20mL ultrapure and 15mL cysteine solution, observe that the color of the solution changes from light yellow to dark yellow and finally becomes milky white, then take 3mL of 1M NaOH solution and quickly add it to the flask, the solution becomes clear After adding freshly prepared NaBH ₄ (0.2M NaOH) solution, it was found that the solution turned brown-red, and the reaction was stirred at room temperature for 3h, and the solution finally turned brown-black. Centrifugal washing, the obtained black solid was placed under freeze-drying for 12h to obtain Au ₂₅ atomic clusters, the average particle size of the supported gold catalyst prepared by the above method was 1.7nm, and the catalyst was used for methacrolein/methanol The conversion rate of methacrolein obtained by oxidative esterification was 95%, and the selectivity of methyl methacrylate was 96%.

Example 39:

Compared with Example 35, the difference is that the catalyst is Au ₂₅ /Mg ₃ Al-HT 0.5g, wherein the Au ₂₅ /Mg ₃ Al-HT catalyst is prepared by impregnating Au ₂₅ clusters on Mg ₃ It is obtained by drying and calcining on Al-HT carrier. In the oxidative esterification of methacrolein/methanol on a fixed bed, the average particle size of the supported gold catalyst is 2.2 nm, and the conversion rate of methacrolein obtained is 90%. , the selectivity of methyl methacrylate is 85%.

The above examples are only used to illustrate the content of the present invention, in addition, the present invention has other embodiments. However, all technical solutions formed by equivalent replacement or equivalent deformation all fall within the protection scope of the present invention.

Claims (7)

1. a supported gold catalyst for the oxidative esterification of alcohol/aldehyde compound to synthesize ester, it is characterized in that, with chloroauric acid aqueous solution as raw material, hydrotalcite is carrier, and thiol compound is stabilizer, described water Talc includes zinc-aluminum hydrotalcite, magnesium-aluminum hydrotalcite, nickel-aluminum hydrotalcite or cobalt-aluminum hydrotalcite, wherein the molar ratio of zinc, magnesium, nickel or cobalt to aluminum is 1:3 to 3:1; the mass of active component gold The fraction is 0.1-20 wt%, and the mass fraction of sulfur is 0.01-10 wt%. 2. The supported gold catalyst for oxidative esterification of alcohol/aldehyde compound to synthesize ester according to claim 1, wherein the thiol-containing compound is selected from cysteine, homocysteine, One or more of glutathione, captopril, dodecanethiol, phenethanethiol or hexanethiol. 3. A method for preparing a supported gold catalyst for oxidative esterification of alcohol/aldehyde compound to synthesize ester, wherein method 1 comprises: taking an appropriate amount of chloroauric acid aqueous solution, adjusting the pH value to 7-10 with NaOH solution, The hydrotalcite carrier is added, the suspension is suction filtered and washed after the stirring reaction, then the filter cake is redispersed in an appropriate amount of ultrapure water, and a certain amount of thiol-containing compound is added under stirring conditions, and the above-mentioned liquid is subjected to the stirring reaction. Suction filtration and washing, the obtained filter cake is dried and roasted to obtain a supported gold catalyst, wherein the molar ratio of hydrotalcite and thiol compound to chloroauric acid is 100-500:0.01-1.0:1; Or method two: adopt the sol-gel method to add the chloroauric acid solution, the solution containing the thiol compound, the NaOH solution and the NaBH solution into the container successively, and control the mol ratio of the thiol compound, NaOH, NaBH ₄ and Au to be ₁ respectively. ～4:50～100:1～10:1, the obtained product is washed by centrifugation with a mixture of ethanol and water, V _ethanol /V _water =2～6:1, and the obtained black solid is freeze-dried, dried Then, crystals of thiol-stabilized gold atom clusters are obtained, which are dissolved in water or acetone solution and then impregnated or adsorbed on a hydrotalcite carrier, and dried and calcined to obtain a supported gold catalyst. 4. an application of the supported gold catalyst for the oxidative esterification of alcohol/aldehyde compound to synthesize ester, is characterized in that, comprising adding a certain amount of aldehyde compounds and alcohol compounds in the reactor, adding a certain amount of loaded type Gold catalyst, then replace the air in the kettle with nitrogen, and then fill the kettle with a certain amount of oxygen-containing gas, place the reaction kettle in a heating device to heat up, and monitor the temperature in the kettle through a thermal sensor. After rising to the specified temperature, turn on magnetic stirring or mechanical stirring to fully mix the solution and gas in the kettle. After reacting for a period of time, put the kettle body into the cooling medium to cool down, and release the remaining gas in the kettle. The liquids were separated, and the reactants and products were analyzed by chromatography. 5. an application of the supported gold catalyst for the oxidative esterification of alcohol/aldehyde compound to synthesize ester, comprising adding a certain amount of supported gold catalyst in a fixed bed reactor, and then replacing the gas in the pipeline with nitrogen, Then a certain amount of oxygen-containing gas is introduced into the reactor. The pressure and flow of the gas are controlled by a back pressure valve and a mass flow meter. The temperature inside and outside the reactor is monitored by a thermal sensor. The aldehyde compounds and alcohol compounds are formulated into a reaction solution and injected into the reaction system through a double plunger liquid pump. After a period of reaction, the reaction solution flows from the fixed bed reactor to a cold tank to cool down, and the product is taken out from the cold tank. Reactants and products were analyzed by gas chromatography. 6. The application of the supported gold catalyst for oxidative esterification of alcohol/aldehyde compound to synthesize ester according to claim 4 or 5, wherein the temperature is 50-120°C, and the oxygen partial pressure is 0.1-1MPa , the molar ratio of aldol is 8-50:1, and the molar ratio of aldehyde to gold in the catalyst is 1-10 ³ :1. 7. The application of the supported gold catalyst for oxidative esterification of alcohol/aldehyde compound to synthesize ester according to claim 4 or 5, wherein the aldehyde compound comprises isobutyraldehyde, methacrolein, crotonaldehyde , one or more of cinnamaldehyde, benzaldehyde, and the alcohol compound includes one or more of methanol, ethanol, isopropanol, isobutanol, butanol, cinnamyl alcohol, and benzyl alcohol.

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