CN111185169B

CN111185169B - Preparation method of nanogold catalyst for producing (methyl) acrylic ester

Info

Publication number: CN111185169B
Application number: CN202010038316.5A
Authority: CN
Inventors: 高爽; 宁春利; 王连月; 娄报华; 李国松; 马建学; 庄岩
Original assignee: Dalian Institute of Chemical Physics of CAS; Shanghai Huayi Group Corp
Current assignee: Dalian Institute of Chemical Physics of CAS; Shanghai Huayi Group Corp
Priority date: 2020-01-14
Filing date: 2020-01-14
Publication date: 2023-02-03
Anticipated expiration: 2040-01-14
Also published as: CN111185169A

Abstract

The invention provides a preparation method of a nanogold catalyst for producing (methyl) acrylic ester. The preparation method of the nano-gold catalyst comprises the steps of reacting a mixture of a carrier, a hyperbranched polymer and an active center or an active center precursor, and calcining the obtained solid to obtain the catalyst.

Description

Preparation method of nanogold catalyst for producing (methyl) acrylic ester

Technical Field

The invention belongs to the technical field of catalysis, and particularly relates to a nanogold catalyst, preparation and application thereof, and an intermediate for preparing the catalyst.

Background

Methyl Methacrylate (MMA) is an important bridging monomer for coupling and synthesizing chemical and polymer materials, has very wide application, and can be used for preparing organic glass, water-based paint, synthetic resin, functional polymer materials and the like.

At present, the main processes for industrially producing methyl methacrylate include the conventional acetone cyanohydrin method, isobutylene oxidation method and the like. Compared with the acetone cyanohydrin method, the isobutene oxidation method takes refinery carbon four resources as raw materials, the byproduct is water, and the degree of greening of the reaction raw materials and the production process is remarkably improved.

The processes developed for the oxidation of isobutene mainly include a direct oxidation process and a direct methyl ester process.

The direct oxidation method oxidizes isobutene or tert-butanol to obtain methacrolein, and then the methacrolein reacts with oxygen to obtain methacrylic acid. Finally, the methyl methacrylate is generated by esterifying the methacrylic acid and the methanol. The method has complex process route, can not avoid the problem of acid corrosion of equipment, and has lower total yield.

The three-step method is a traditional process and is firstly industrialized by Mitsubishi rayon company, namely isobutene is firstly oxidized into methacrolein under a molybdenum-based catalyst, the methacrolein is then oxidized into methacrylic acid, and the methacrylic acid is then esterified with methanol to obtain MMA. Compared with the method, the two-step method is developed by Asahi formation and is industrialized earliest in 1996, methacrolein and methanol are directly subjected to one-step oxidative esterification to obtain MMA, the process flow is shortened, and the energy consumption is reduced, so that the investment cost and the operation cost are greatly reduced, and the method has great economic significance.

The core of the direct methyl ester process (two-step process) lies in the preparation of a novel catalyst, the development of the catalyst goes through the process of improving heteropoly acid type catalysts, platinum-series catalysts, ruthenium-series catalysts, palladium-series catalysts, gold-series precious metal catalysts and the like, wherein the palladium-series (Pd-Pb) developed by Asahi chemical company in Japan successfully realizes the two-step conversion, compared with the three-step process, the process has high product purity, simple process equipment and low construction cost, but the Pd-Pb catalyst has the problems of low MMA selectivity (about 84 percent) and increased subsequent separation cost. On the basis, the Asahi chemical company develops a nanogold catalyst (Au @ NiOx) with a core-shell structure, the catalyst has excellent activity, selectivity and stability, and when the conversion rate of methacrolein is 65%, the selectivity of MMA is about 95%. However, the nanogold catalyst has high requirements on preparation technology, and the effective utilization rate (loading rate) of Au is only about 70%, so that the cost is high, and the industrial application of the nanogold catalyst is limited to a certain extent.

Chinese patent CN107107034a reports a catalyst comprising gold, silicon oxide, aluminum oxide and one or more oxides of elements selected from the group consisting of: li, na, K, rb, cs, be, mg, ca, sr, ba, sc, Y, ti, zr, cu, mn, pb, sn, bi or lanthanides having atomic numbers from 57 to 71, which solves the problem of the water resistance of the catalyst. The patent synthesizes a catalyst with a shell structure, which has high activity, selectivity, hydrolytic stability and long service life by controlling conditions. However, since gold is still supported by the immersion method in this patent, the effective Au supporting rate is only about 70%, which is expensive.

Chinese patents CN109331839A, CN109395732 and CN109569600A respectively prepare catalysts for producing methyl methacrylate by selecting different active centers (gold and a lanthanide metal and a transition metal, gold and a rare earth metal, gold and two lanthanide metals) and applying a polymer protection method. The method comprises the steps of fully mixing a gold precursor, a reducing agent and deionized water under the stirring condition to obtain stable and high-dispersion gold sol, sequentially adding a promoter precursor and a carrier in the presence of a high-molecular protective agent, standing, filtering, drying and calcining after the reaction is finished to obtain the catalyst, wherein the selected high-molecular protective agent is polyvinyl alcohol, polyvinylpyrrolidone, tetrakis (hydroxymethyl) phosphonium chloride, polydimethyl-dipropenyl ammonium chloride, sodium citrate and thiol substances. Although the catalyst is simple to prepare, has excellent activity and stability, and the loading rate of Au can reach up to 100%, the production cost is effectively reduced, the selected macromolecular protective agent is a straight-chain polymer or a micromolecular substance, the coating property of the macromolecular protective agent on gold particles in gold sol is poor, and the aggregation of gold cannot be effectively prevented. Therefore, in order to improve the encapsulation of gold particles in the gold sol, the usage amount of the polymeric protective agent (the mass ratio of the polymeric protective agent to the chloroauric acid is more than 1) must be increased, and the industrial application is limited. Meanwhile, the macromolecule protection method is to prepare the catalyst by generating gold sol and then loading the gold sol on a carrier, so that the concentration of a gold source in an aqueous solution is limited, and only a gold-based catalyst with low loading capacity can be prepared.

Compared with the traditional linear macromolecular polymer, the hyperbranched polymer is always a research hotspot in the field of macromolecules in the last 90 years, on one hand, the type and the number of functional groups in the molecule are accurately controllable, the molecular weight has polydispersity, the molecular configuration is an irregular ellipsoidal three-dimensional space structure, the polymer is highly branched like a tree, the interior of the polymer has unique nano micropores, the surface of the polymer contains a large number of functional groups, the number of amino (amine) functional groups (primary amine, tertiary amine, amide and the like) in the molecule is increased by geometric progression along with the increase of molecular algebra, and the molar number of the amino and hydroxyl groups in unit mass is far greater than that of a dispersion stabilizer (such as polyvinylpyrrolidone) on the market, so the polymer can be used as a high-capacity complexing agent for metal ions, and has better dispersion stability effect. On the other hand, the hyperbranched polymer can realize the synthesis of one-pot method (one-step), generally does not need to be separated and purified step by step, and has simple process and lower cost. The characteristics make the compound has potential application value in a plurality of fields, and become a research hotspot in related fields.

In summary, the preparation of the catalyst for direct methyl ester process by obtaining MMA from methacrolein and methanol through one-step oxidative esterification still has the following problems:

1) The reported impregnation method has the problems of high technical requirement, low Au effective loading rate (about 70-90%), high cost and the like, and the obtained catalyst has low selectivity and activity.

2) In the reported polymer protection method, the polymer protective agent is a straight-chain polymer or a small molecular substance, and the method has poor gold particle wrapping property in gold sol and large using amount (polymer protective agent: the mass ratio of the chloroauric acid is more than 1), the concentration of the gold source in the loaded mother liquor is low, and the like.

Therefore, there is still a need in the art for a highly active and stable nanogold catalyst and a preparation method thereof, which can improve the effective loading rate of gold, reduce the cost of the catalyst and/or improve the activity of the catalyst.

The invention content is as follows:

based on the defects of the prior art, the invention provides the nano-gold catalyst and the preparation method and the application thereof, and the obtained catalyst has the advantages of good dispersion degree of active components, high activity, good stability and the like. The preparation process of the catalyst is simple, a reducing agent is not required to be added, the effective loading rate of the active component Au and the auxiliary active component is high, the waste of noble metals in the mother liquor is reduced, the cost is low, and the catalyst is suitable for industrial production.

In a first aspect of the present invention, there is provided a method for preparing a nanogold catalyst, comprising:

and (3) reacting the carrier, the hyperbranched polymer and the active center or the mixture of the active center precursors, and calcining the obtained solid to obtain the catalyst.

In a second aspect of the present invention, there is provided a nanogold catalyst, which is prepared by a method comprising the steps of: and (3) reacting the carrier, the hyperbranched polymer and the active center or the mixture of the active center precursors, and calcining the obtained solid to obtain the catalyst.

In a third aspect of the present invention, there is provided a method for producing a (meth) acrylate, comprising:

adding the nano gold catalyst into the mixture of (methyl) acrolein compound and alcohol, and introducing oxygen to carry out one-step oxidation esterification reaction to obtain (methyl) acrylic ester.

In a fourth aspect of the present invention, there is provided an intermediate for preparing a nanogold catalyst, comprising a hyperbranched polymer, a support, and an active center or an active center precursor supported on the support, wherein the hyperbranched polymer molecule is hydrogen-bonded to the support.

In a fifth aspect of the invention, there is provided a use of a nanogold catalyst in the preparation of a (meth) acrylate.

Detailed Description

The present invention will be described in further detail with reference to specific embodiments, and the scope of the present invention includes, but is not limited to, the following examples, and any modifications in detail and form of the technical solution of the present invention may fall within the scope of the present invention without departing from the meaning and scope of the present application.

Herein, "(meth) acrylate" refers to acrylate, methacrylate, or a mixture thereof; "(meth) acrolein" means acrolein, methacrolein, or a mixture thereof.

The preparation method of the nano gold catalyst comprises the following steps:

Preferably, in this method, the support is an oxide support; preferably, the oxide support is a metal oxide composite support, more preferably, the metal oxide composite support is a silicon-aluminum-containing metal oxide composite support, and further preferably, the silicon-aluminum-containing metal oxide composite support is a composition formed by silica, alumina and other metal oxides selected from alkali metal oxides, alkaline earth metal oxides, tiO ₂ 、CeO、ZrO ₂ Spinel, hydrotalcite and CoO _x (x＝0.5-2.5)、NiO _y (y = 0.5-2.5). Preferably, the silicon-aluminum containing metal oxide composite carrier contains 65-98 wt% of SiO based on the total weight of the silicon-aluminum containing metal oxide composite carrier ₂ 1-35% by weight of Al ₂ O ₃ (ii) a 1-20 wt.% of other metal oxides.

Preferably, the silicon-aluminum-containing metal oxide composite support can be prepared by the following process: under the condition of stirring, fully mixing a silicon dioxide precursor, an aluminum oxide precursor and other metal precursors, adding acid to adjust the pH value of the mixed solution to 0.5-1.4, keeping the temperature at 30-80 ℃, continuously stirring and curing for 1-24h to obtain a mixture, spray-drying and molding the mixture to obtain spherical particles of 10-200 mu m, and calcining in air or inert atmosphere to obtain the metal oxide composite carrier.

Preferably, the acid used to adjust the pH is selected from one or more of an inorganic or organic acid, such as nitric acid, hydrochloric acid, formic acid, acetic acid.

Preferably, the precursor of the silicon dioxide is selected from silica sol, solid silica gel and white carbon black; the precursor of the aluminum oxide is selected from aluminum nitrate, aluminum chloride, aluminum hydroxide, aluminum phosphate, aluminum sulfate and aluminum oxide powder; the other metal precursor is one or more of nitrate, oxide, hydroxide, compound or other compounds of corresponding metal, and the other compounds refer to special metal salt precursors of some metals, such as zirconium oxychloride as a precursor of zirconium dioxide, titanyl sulfate as a precursor of titanium dioxide, cerium oxalate as a precursor of cerium dioxide, and the like.

The active center comprises an active component gold and a co-active component comprising a rare earth metal, a transition metal or a combination thereof, preferably the rare earth metal is selected from Sc, Y, la, ce, pr, nd, pm, sm or a combination of one or more thereof; the transition metal is selected from Cr, mn, fe, co, ni, cu, zn, cd or one or more combination thereof.

Preferably, the gold loading (by weight of the element) in the catalyst is 0.03 to 3%, preferably 0.1 to 1.0%, further preferably 0.1 to 0.8%, more preferably 0.3 to 0.7%, most preferably 0.4 to 0.6%, most preferably 0.45 to 0.5% by weight based on the total weight of the catalyst. The loading amount (by weight of the element) of the rare earth metal is 0 to 2.8wt%, preferably 0.005wt% to 2.0wt%, further preferably 0.008 to 1wt%, more preferably 0.01 to 0.7wt%, further preferably 0.015 to 0.5wt%, most preferably 0.03 to 0.5wt%. The loading amount (by weight of the element) of the transition metal is 0 to 3.0%, preferably 0.005wt% to 2.0wt%, further preferably 0.008 to 1wt%, more preferably 0.01 to 0.7wt%, more preferably 0.015 to 0.5wt%, most preferably 0.2 to 0.4wt%.

According to the method, the loading rate of the active component gold is 95% -100%.

Preferably, the gold precursor is selected from the group consisting of aurous chloride, gold chloride, chloroauric acid salts, chloroauric acid (HAuCl) ₂ ) One or more of tetrabromoauric acid, tetrabromoaurate, potassium aurous cyanide or sodium gold sulfite; the precursor of the rare earth metal is one or two of nitrate and acetate of corresponding metal; the precursor of the transition metal is one or two of nitrate and acetate of corresponding metal.

Preferably, the hyperbranched polymer is a mixture of one or more of a series of hyperbranched polymers containing hydroxyl, amino, amide or sulfur groups; the hyperbranched polymer can be one or more of a first-generation hyperbranched polymer, a second-generation hyperbranched polymer, a third-generation hyperbranched polymer and a fourth-generation hyperbranched polymer; more preferably one or more of polyesters, polyethers, polyamides, polyimides, polysiloxanes containing hydroxyl, amino, amido or thio groups and hyperbranched polymers containing large pi conjugated structures (polyphenyls, polyfluorene-benzenes, polythiophenes, etc.).

Preferably, the molecular weight of the hyperbranched polymer is from 100 to 50000g/mol, preferably from 200 to 20000 g/mol, more preferably from 300 to 8000g/mol.

The hyperbranched polymer can be, for example, hyperbranched polyamide HyPer HPN202, hyperbranched polyamide HyPer N101, hyperbranched polyamide HyPer N102, hyperbranched polyamide HyPer N103, hyperbranched polyester HyPer H102, hyperbranched polyester HyPer H103, hyperbranched polyester HyPer H302, hyperbranched polyester HyPer H303, and the like.

Preferably, the reaction between the support, the hyperbranched polymer and the active centre or the mixture of active centre precursors is carried out under heating conditions of 40 to 150 ℃, preferably 60 to 120 ℃, more preferably 80 to 100 ℃. Preferably, the reaction time is 10min-12h,0.5-10h, preferably 1-8 h.

Preferably, the calcination temperature is from 300 to 650 ℃, preferably from 400 to 600 ℃, more preferably from 450 to 550 ℃.

Preferably, the reaction of the support, the hyperbranched polymer and the active center or the mixture of active center precursors is carried out in the presence of water, and the co-active component comprises a rare earth metal, a transition metal or a combination thereof, wherein the mass ratio of the components is as follows, the rare earth metal: transition metal: gold: hyperbranched polymer: the mass ratio of water is 1:0-1:0-1.43: 10-250:100-800, preferably (1, 0.02-1.43.

The addition sequence of the hyperbranched polymer, the carrier, the active center or the active center precursor has diversity. The carrier and the hyperbranched polymer can be added in sequence, and the active center or the active center precursor mixed solution is added after the uniform dispersion; or sequentially adding active center or active center precursor mixed solution and hyperbranched high molecular polymer to form hyperbranched high molecular flocculate, adding the carrier, and loading the carrier.

In one embodiment, the catalyst of the present invention is prepared as follows: adding a hyperbranched polymer, an active center or an active center precursor into a carrier, reacting at 40-150 ℃, then cooling to room temperature, standing, filtering, washing, drying, and calcining at 300-650 ℃ to obtain the catalyst.

The nanogold catalyst of the invention is prepared by the method described above.

The active center of the nano-gold catalyst comprises an active component gold and an auxiliary active component, wherein the auxiliary active component comprises rare earth metal, transition metal or combination thereof, and the rare earth metal is selected from Sc, Y, la, ce, pr, nd, pm, sm or combination of one or more of Sc, Y, la, ce, pr, nd, pm and Sm; the transition metal is selected from Cr, mn, fe, co, ni, cu, zn, cd or one or more combination thereof.

Preferably, the gold loading (by weight of the element) in the catalyst is 0.03 to 3%, preferably 0.1 to 1.0%, further preferably 0.1 to 0.8%, more preferably 0.3 to 0.7%, most preferably 0.4 to 0.6%, most preferably 0.45 to 0.5% by weight based on the total weight of the catalyst. The loading amount (by weight of the element) of the rare earth metal is 0 to 2.8wt%, preferably 0.005wt% to 2.0wt%, further preferably 0.008 wt% to 1wt%, more preferably 0.01 wt% to 0.7wt%, further preferably 0.015 wt% to 0.5wt%, most preferably 0.03 wt% to 0.5wt%. The loading amount (by weight of the element) of the transition metal is 0 to 3.0%, preferably 0.005 to 2.0%, further preferably 0.008 to 1%, more preferably 0.01 to 0.7%, more preferably 0.015 to 0.5%, most preferably 0.2 to 0.4%.

The active components gold, rare earth metal, transition metal and carrier component contained in the catalyst exist in the form of metal and/or oxide, multi-metal compound in the catalyst.

The nanogold catalyst of the invention can be used for preparing (meth) acrylic ester, and the method for preparing the methyl (meth) acrylate comprises the following steps:

adding the nano gold catalyst into a mixture of (methyl) acrolein and alcohol, and introducing oxygen to perform one-step oxidation esterification reaction to obtain methyl methacrylate.

Preferably, the mixture of (meth) acrolein and alcohol further contains a polymerization inhibitor. The polymerization inhibitor is selected from one or more of hydroquinone, methyl hydroquinone, p-hydroxyanisole, tert-butyl catechol, phenothiazine, N-oxyl-4-hydroxy-2,2,6,6-tetramethylpiperidine and tris (N-oxyl-2,2,6,6-tetramethylpiperidine) phosphite.

Preferably, the molar ratio of the alcohol hydroxyl groups of the alcohol to the aldehyde groups of the (meth) acrolein is 1:1 to 100, preferably 1:1 to 20, more preferably 1:1 to 8:1, and further preferably 1:1 to 4:1.

The alcohol may be a monohydric alcohol, such as methanol, ethanol, and the like.

Preferably, the conditions of the oxidative esterification reaction are: the reaction temperature is 40-100 ℃, preferably 65-85 ℃, the reaction pressure is 0.1-4MPa, and the reaction time is 0.5-8 h, preferably 2-4h.

Preferably, the catalyst of the invention is added into a reaction kettle, after (methyl) acrolein and alcohol are uniformly mixed according to the molar ratio of the aldehyde group to the alcohol hydroxyl group of 1:1-1:4, a constant flow pump is used for feeding the reaction kettle at the speed of 10ml/min, and air and inert gas are simultaneously introduced, so that the oxygen concentration in the reactor is lower than the explosion limit of 8%. Discharging the product after reaction at the rate same as the feeding rate of the reaction raw material, and analyzing the reaction result by GC; in the catalyst system, the molar ratio of gold/propylene aldehyde compounds is 1.

The intermediate for preparing the nanogold catalyst comprises a hyperbranched polymer, a carrier and an active center loaded on the carrier, wherein the hyperbranched polymer molecule is linked to the carrier through hydrogen bonds.

The carrier is an oxide carrier; preferably, the oxide support is a metal oxide composite support, more preferably, the metal oxide composite support is a silicon-aluminum-containing metal oxide composite support, and further preferably, the silicon-aluminum-containing metal oxide composite support is a composition formed by silica, alumina and other metal oxides selected from alkali metal oxides, alkaline earth metal oxides, tiO ₂ 、CeO、ZrO ₂ Spinel, hydrotalcite and CoO _x (x＝0.5-2.5)、NiO _y (y = 0.5-2.5). Preferably, the silicon-aluminum-containing metal oxide composite support contains 65-98 wt% of SiO based on the total weight of the silicon-aluminum-containing metal oxide composite support ₂ 1-35% by weight of Al ₂ O ₃ (ii) a 1-20 wt.% of other metal oxides.

Preferably, the silicon-aluminum-containing metal oxide composite support can be prepared by the following process: under the condition of stirring, fully mixing a silicon dioxide precursor, an aluminum oxide precursor and other metal precursors, adding acid to adjust the pH value of the mixed solution to 0.5-1.4, keeping the temperature at 30-80 ℃, continuously stirring and curing for 1-24h to obtain a mixture, spray drying and molding the mixture to obtain spherical particles of 10-200 mu m, and calcining in air or inert atmosphere to obtain the metal oxide composite carrier.

Preferably, the acid used to adjust the pH is selected from inorganic or organic acids, such as one or more of nitric acid, hydrochloric acid, formic acid, acetic acid.

Preferably, the active center comprises an active component gold and a co-active component comprising a rare earth metal, a transition metal, or a combination thereof. Preferably, the rare earth metal is selected from Sc, Y, la, ce, pr, nd, pm, sm or a combination of one or more thereof; the transition metal is selected from Cr, mn, fe, co, ni, cu, zn, cd or one or more combination thereof.

The gold precursor is selected from aurous chloride, gold chloride, chloroauric acid salt, and chloroauric acid (HAuCl) ₂ ) One or more of tetrabromoauric acid, tetrabromoaurate, potassium aurous cyanide or sodium gold sulfite; the precursor of the rare earth metal is one or two of nitrate and acetate of corresponding metal; the precursor of the transition metal is one or two of nitrate and acetate of corresponding metal.

And washing, drying and calcining the intermediate to obtain the catalyst.

The beneficial effects of the invention are:

1) The preparation method of the catalyst does not need to add a reducing agent, but adopts the characteristic of hyperbranched polymer coordination flocculation, and the hyperbranched polymer coordination flocculation is coordinated with active center particles, and the complex is uniformly precipitated on a carrier through the bonding of hydrogen bonds. Meanwhile, the three-dimensional space structure of the hyperbranched polymer can effectively prevent the aggregation of gold and the auxiliary active component, so that the nano particles are more dispersed, and the gold nano particles in the obtained catalyst have the granularity of 1-5nm, narrow distribution, good dispersibility and high stability.

Compared with the dipping method, the dispersion chelation characteristic of the high molecular polymer overcomes the problems of agglomeration, blackening and inactivation of precursors of rare earth metals or transition metals and gold nanoparticles and low effective loading rate of active components in the dipping method, improves the loading capacity of the active components, reduces the loss of the active components in mother liquor, and has the advantages of low cost, simple process, convenient operation and great industrial application prospect.

Compared with a gold sol macromolecule protection method, the method avoids the problems of low loading capacity and the like caused by excessive protective agents such as polyvinyl alcohol and the like, poor wrapping property and low concentration of a gold source of the loaded mother solution.

2) The rare earth metal and/or the transition metal are/is cooperated with Au for catalysis, so that the activity is improved, and the loading capacity of Au is reduced. When the catalyst is applied to the production of acrylate derivatives, such as the production of methyl methacrylate, the reaction is continuously operated for 2000 hours, the conversion rate of methacrolein is still more than 98%, the selectivity of methyl methacrylate is more than 98%, and the active components of gold, rare earth elements and transition elements on the catalyst are hardly lost through ICP-OES determination.

Example (b):

the source of the starting materials is seen in the following table:

example 1

Preparation of the carrier:

10g of 30% silica sol (pH = 4.5), 7.5026g of aluminum nitrate nonahydrate, 0.8748g of magnesium hydroxide, 2g of 75% concentrated nitric acid and 50mL of deionized water are mixed uniformly at 50 ℃, the temperature is kept for stirring for 24 hours to obtain a uniform solid solution suspension, and the suspension is stirred and cooled to room temperature and then spray-dried. Spraying conditions are as follows: 8ml/min, a drying tower temperature of 260-280 ℃ and an outlet temperature of 110-130 ℃ to obtain spherical powder with a particle size of 58 mu m. Placing the solid powder in a tube furnace, carrying out temperature programming roasting under nitrogen or air, heating to 30-300 ℃ for 3h (heating rate 1.5 ℃/min), keeping the temperature at 300 ℃ for 4h, heating to 300-600 ℃ for 3h (heating rate 1.7 ℃/min), and keeping the temperature at 600 ℃ for 4h. Naturally cooling to obtain the Si-Mg-Al metal composite oxide carrier.

Preparation of the catalyst:

adding 96g of carrier and 100mL of deionized water into a reactor in sequence, uniformly mixing, after uniformly stirring at 90 ℃, adding 0.5g of hyperbranched polyamide HyPer HPN202 and 60mL of active component mixed solution containing 1g of chloroauric acid and 1.525g of scandium nitrate in sequence, keeping the temperature, continuously stirring for 2 hours, after the reaction is finished, cooling and filtering, washing with deionized water and ethanol in sequence, drying at 80 ℃ for 1 hour, placing in a muffle furnace, and calcining at 500 ℃ to obtain the catalyst a (Au-Sc/Si-Mg-Al). Wherein the mass percentage of Au and Sc in the catalyst is 0.4844% and 0.2071% respectively. The Au loading rate was 97.98%.

The calculation method of the Au load rate is as follows:

m total mass/g of catalyst obtained

w ₁ The mass percentage of Au in the catalyst is%

m ₀ The mass/g of chloroauric acid added in the supported catalyst

w ₀ The mass percentage of Au in the chloroauric acid reagent is%

Comparative example 1

Preparation of the support is as in example 1

The preparation method of the catalyst comprises the following steps of changing the adding sequence of materials:

adding 60mL of active component mixed solution containing 1g of chloroauric acid and 1.525g of scandium nitrate, 100mL of deionized water and 0.5g of hyperbranched polyamide HyPer HPN202 into a reactor in sequence, stirring uniformly at 90 ℃ for 0.5h, then adding 96g of carrier, keeping the temperature, continuously stirring for 2h, cooling and filtering after the reaction is finished, washing with deionized water and ethanol in sequence, drying at 80 ℃ for 1h, then placing in a muffle furnace, and calcining at 500 ℃ to obtain the catalyst a (Au-Sc/Si-Mg-Al). Wherein the mass percentage of Au and Sc in the catalyst is 0.4907% and 0.2044% respectively. The Au loading rate was 99.25%.

Comparative example 2

Preparation of the support is as in example 1

Preparation of nano gold catalyst (impregnation method)

And sequentially adding 96g of the Si-Mg-Al-Ce metal composite oxide carrier and 100mL of deionized water into a reactor, uniformly mixing, stirring uniformly at 90 ℃, adding 60mL of active component mixed solution containing 1g of chloroauric acid and 1.525g of scandium nitrate, keeping the temperature, continuously stirring for 2h, cooling and filtering after the reaction is finished, sequentially washing with deionized water and ethanol, drying for 1h at 80 ℃, placing in a muffle furnace, and calcining at 500 ℃ to obtain the catalyst b (Au-Sc/Si-Mg-Al). Wherein the mass percentage of Au and Sc in the catalyst is 0.4347% and 0.1931% respectively. The Au loading was 87.92%.

Comparative example 3

Preparation of the support is as in example 1

Preparation of nano gold catalyst (impregnation method)

And sequentially adding 96g of the Si-Mg-Al-Ce metal composite oxide carrier and 100mL of deionized water into a reactor, uniformly mixing, stirring uniformly at 90 ℃, adding 60mL of active component mixed solution containing 1g of chloroauric acid and 1.50g of lanthanum nitrate, keeping the temperature, continuously stirring for 2 hours, cooling and filtering after the reaction is finished, sequentially washing with deionized water and ethanol, drying for 1 hour at 80 ℃, placing in a muffle furnace, and calcining at 500 ℃ to obtain the catalyst c (Au-La/Si-Mg-Al). Wherein the mass percentage of Au and La in the catalyst is 0.4247% and 0.4422% respectively. The Au loading rate was 86.15%.

Example 2

The support was prepared as in example 1.

The preparation conditions of the catalyst were the same as in example 1, and the hyperbranched polymer used was replaced with hyperbranched polyamide HyPer N101 to obtain catalyst d (Au-Sc/Si-Mg-Al). Wherein the mass percentage of Au and Sc in the catalyst is 0.4866%,0.2010% and the Au loading rate is 98.42%.

Example 3

The support was prepared as in example 1.

When the catalyst is prepared, hyperbranched polyamide HyPer N103 is used for replacing hyperbranched polyamide HyPer HPN202 to obtain a catalyst e (Au-Sc/Si-Mg-Al). Wherein the mass percentage contents of Au and Sc in the catalyst are 0.4928%,0.2034% respectively, and the Au loading rate is 99.68%.

Example 4

The support was prepared as in example 1.

When the catalyst is prepared, hyperbranched polyamide HyPer N103 is used for replacing hyperbranched polyamide HyPer HPN202, and 0.10g of lanthanum nitrate is used for replacing scandium nitrate, so that the catalyst f (Au-La/Si-Mg-Al) is obtained. Wherein the mass percentage of Au and La in the catalyst is 0.4927 percent and 0.0320 percent respectively, and the Au loading rate is 99.48 percent.

Example 5

The support was prepared as in example 1.

When the catalyst is prepared, hyperbranched polyamide HyPerH103 is used for replacing hyperbranched polyamide HyPer HPN202, and 1.5g of cobalt nitrate is used for replacing scandium nitrate, so that a catalyst g (Au-Co/Si-Mg-Al) is obtained. Wherein the mass percentage of Au and Co in the catalyst is 0.4930%,0.3135% and the Au loading rate is 99.82%.

Example 6

In the preparation step of the carrier, 4.4g of zirconium nitrate was added.

When the catalyst is prepared, hyperbranched polyamide HyPer H303 is used for replacing hyperbranched polyamide HyPer HPN202, and 1.5g of cobalt nitrate is used for replacing scandium nitrate, so that the catalyst H (Au-Co/Si-Mg-Al-Zr) is obtained. Wherein the mass percentage of Au and Co in the catalyst is 0.4915%,0.3098% and the Au loading rate is 99.51%.

Comparative example 4

In the preparation step of the carrier, 4.4g of zirconium nitrate was added.

Preparation of the catalyst As in comparative example 1, scandium nitrate was replaced with 1.5g of cobalt nitrate to obtain catalyst i (Au-Co/Si-Mg-Al-Zr). Wherein the mass percentage of Au and Co in the catalyst is 0.4173% and 0.2683% respectively. The catalyst is black, and the Au loading rate is 84.49%. The method is used for one-step oxidation esterification of methacrolein to generate methyl methacrylate, and no activity and no product are generated.

Example 7

In the preparation step of the carrier, 4.4g of zirconium nitrate was added.

When the catalyst is prepared, hyperbranched polyamide HyPer H303 is used for replacing hyperbranched polyamide HyPer HPN202, and 0.8g of cobalt nitrate and 0.8g of nickel nitrate are used for replacing scandium nitrate, so that the catalyst j (Au-Co-Ni/Si-Mg-Al-Zr) is obtained. Wherein the mass percentage of Au, co and Ni in the catalyst is 0.4928%,0.1658%,0.1634% and the Au loading rate is 99.80%.

Comparative example 5

In the preparation step of the carrier, 4.4g of zirconium nitrate was added.

Catalyst preparation procedure similar to comparative example 1, replacing scandium nitrate with 0.8g of cobalt nitrate and 0.8g of nickel nitrate, resulted in catalyst k (Au-Co-Ni/Si-Mg-Al-Zr). Wherein the mass percentage of Au, co and Ni in the catalyst is 0.4182%,0.1398% and 0.1407%, respectively. The Au loading rate was 84.69%. The catalyst appeared to be grey black.

Example 8

The catalysts obtained in examples 1 to 7 and comparative examples 1 to 5 were used for the preparation of methyl methacrylate by one-step oxidative esterification under the same conditions as follows:

the catalyst of the invention is added into a reaction kettle, so that the molar ratio of gold/methacrolein in the catalyst system is 1. Uniformly mixing methacrolein and methanol according to the molar ratio of 1:4, feeding the mixture into a reaction kettle at the speed of 10ml/min by using a constant flow pump, and simultaneously introducing air and inert gas to ensure that the oxygen concentration in the reactor is lower than the explosion limit of 8 percent. The reaction temperature was 80 ℃. Discharging the product after reaction at the same rate as the feeding rate of the reaction raw materials, taking out the feed liquid at regular intervals, adding tert-amyl alcohol as an internal standard substance, and analyzing the reaction result by using Gas Chromatography (GC). The conversion of methacrolein and the selectivity of methyl methacrylate were calculated at 1000h and 2000h of reaction, respectively.

Comparing examples 1-7 with comparative examples 1-5 in the table, the hyperbranched polymer-based nanogold catalyst maintains higher activity and selectivity for a long time reaction on the premise of improving the effective loading rate of the active component. The hyperbranched polymer is introduced into the carrier, and the three-dimensional space structure of the hyperbranched polymer can effectively prevent the aggregation of gold and the auxiliary active component, so that the nano particles are more dispersed, and the activity of the catalyst is improved.

Claims

1. A method of preparing a nanogold catalyst, comprising:

reacting a mixture of a carrier, a hyperbranched polymer and an active center or an active center precursor, and calcining the obtained solid to obtain the catalyst, wherein the carrier is a silicon-aluminum-containing metal oxide composite carrier, the silicon-aluminum-containing metal oxide composite carrier is a composition formed by silicon dioxide, aluminum oxide and other metal oxides, and the other metal oxides are selected from alkali metal oxides, alkaline earth metal oxides and TiO ₂ 、CeO、ZrO ₂ Spinel, hydrotalcite, coO _x 、NiO _y One or more of (a) or (b),x =0.5-2.5, y =0.5-2.5; the active center comprises an active component gold and an auxiliary active component, and the auxiliary active component comprises rare earth metal, transition metal or combination thereof; the rare earth metal is selected from one or more of Sc, Y, la, ce, pr, nd, pm and Sm; the transition metal is selected from one or more of Cr, mn, fe, co, ni, cu, zn and Cd;

the hyperbranched polymer is one or a mixture of hyperbranched polymers containing hydroxyl, amino, amido or sulfur groups.

2. The method of claim 1, wherein the silicon aluminum-containing metal oxide composite support comprises from 65 to 98 weight percent SiO based on the total weight of the silicon aluminum-containing metal oxide composite support ₂ 1-35% by weight of Al ₂ O ₃ (ii) a 1-20 wt.% of other metal oxides.

3. The method of claim 1, wherein the reaction between the support, the hyperbranched polymer, and the active site or the mixture of active site precursors is carried out under heating conditions of 40 ℃ to 150 ℃.

4. The method of claim 1, wherein the calcination temperature is from 300 ℃ to 650 ℃.

5. The method of claim 1, wherein the calcination temperature is 400-600 ℃.

6. The method of claim 1, wherein the calcination temperature is from 450 ℃ to 550 ℃.

7. A nanogold catalyst produced by the method of any one of claims 1 to 6.

8. The nanogold catalyst according to claim 7, wherein the gold element loading in the catalyst is 0.03 to 3 wt%, based on the total weight of the catalyst; the loading amount of the rare earth metal element is 0-2.8 wt%; the loading amount of the transition metal element is 0-3.0 wt%.

9. A method of making a (meth) acrylate comprising:

adding the nanogold catalyst according to claim 8 to a mixture of a (meth) acrolein compound and an alcohol, and introducing oxygen to perform a one-step oxidative esterification reaction to obtain a (meth) acrylate.

10. The method of claim 9, wherein the mixture further comprises a polymerization inhibitor.

11. The method of claim 10, wherein the polymerization inhibitor is selected from one or more of hydroquinone, methyl hydroquinone, p-hydroxyanisole, t-butyl catechol, phenothiazine, N-oxyl-4-hydroxy-2,2,6,6-tetramethyl piperidine and tris (N-oxyl-2,2,6,6-tetramethyl piperidine) phosphite.

12. An intermediate for preparing a nanogold catalyst, comprising a hyperbranched polymer, a support and an active center or an active center precursor loaded on the support, wherein the hyperbranched polymer molecules are linked to the support through hydrogen bonds, the active center comprises an active component gold, and a co-active component selected from 1) rare earth metals; 2) A transition metal; or 1) in combination with 2);

the carrier is a metal oxide composite carrier, the metal oxide composite carrier is a silicon-aluminum-containing metal oxide composite carrier, the silicon-aluminum-containing metal oxide composite carrier is a composition formed by silicon dioxide, aluminum oxide and other metal oxides, and the other metal oxides are selected from alkali metal oxides, alkaline earth metal oxides and TiO ₂ 、CeO、ZrO ₂ Spinel, hydrotalcite and CoO _x 、NiO _y One or more of (a) or (b),wherein x =0.5-2.5, y =0.5-2.5;

the active center comprises an active component gold and an auxiliary active component, the auxiliary active component comprises rare earth metal, transition metal or combination thereof, and the rare earth metal is selected from one or more of Sc, Y, la, ce, pr, nd, pm and Sm; the transition metal is selected from one or more of Cr, mn, fe, co, ni, cu, zn and Cd;

13. The intermediate of claim 12, wherein the silicon-aluminum containing metal oxide composite support comprises from 65 to 98 weight percent SiO based on the total weight of the silicon-aluminum containing metal oxide composite support ₂ 1-35% by weight of Al ₂ O ₃ (ii) a 1-20 wt.% of other metal oxides.

14. The intermediate of claim 12, wherein the gold precursor is selected from one or more of aurous chloride, gold chloride, chloroauric acid, chloroaurate, aurous acid chlorohydrate, tetrabromoauric acid, tetrabromoaurate, potassium aurous cyanide, or sodium aurous sulfite; the precursor of the rare earth metal is one or two of nitrate and acetate of corresponding metal; the precursor of the transition metal is one or two of nitrate and acetate of corresponding metal.