CN112237912B

CN112237912B - Catalyst for selective oxidative esterification of methacrolein and preparation method and application thereof

Info

Publication number: CN112237912B
Application number: CN201910656670.1A
Authority: CN
Inventors: 李杲; 郭嵩; 张佳; 张少阳
Original assignee: Dalian Institute of Chemical Physics of CAS
Current assignee: Dalian Institute of Chemical Physics of CAS
Priority date: 2019-07-19
Filing date: 2019-07-19
Publication date: 2021-12-31
Anticipated expiration: 2039-07-19
Also published as: CN112237912A

Abstract

The invention discloses a preparation method of a noble metal supported catalyst prepared by noble metal ligand protection and carrier precursor symbiosis and application thereof in selective oxidative esterification, such as the oxidative esterification of methacrolein to generate methyl methacrylate; belongs to the technical field of noble metal catalyst preparation and fine chemicals synthesis. Noble metal atoms and carrier precursor molecules are connected and symbiotically generated by taking a ligand as a bridge to form a wrapped supported catalyst, so that the stable supported catalyst with the noble metal nano size of 2-3nm is successfully obtained, and then the catalyst is used for efficiently and selectively converting the noble metal into methyl methacrylate by taking methacrolein as a reaction substrate, wherein the conversion rate is 75-92% and the selectivity is 82-93%. The catalyst is simple to prepare, the noble metal nano particles are highly dispersed, the mechanical strength is high, the catalyst is easy to regenerate and reuse, and the nano particles do not become larger obviously at the temperature of 150-500 ℃. The preparation method and the application direction of the catalyst have industrial application prospects.

Description

Catalyst for selective oxidative esterification of methacrolein and preparation method and application thereof

Technical Field

The invention belongs to the field of aldehyde group esterification, and particularly relates to a preparation method and a synthetic method of a catalyst for oxidizing and esterifying methacrolein liquid phase and methanol to obtain methyl methacrylate, and an application of the catalyst.

Background

In recent years, the petroleum industry, the organic industry and the coal chemical industry of China are rapidly developed, a large amount of carbon tetrahydrocarbon (C4) is generated in the cracking process, the ethylene production process, the coal methanol to olefin process and the separation of natural gas, and the current capacity is 5.0 Mt/a. The C4 resource mainly comprises isobutane, butane, butylene, isobutene and the like. With the increase of C4 byproducts, the effective utilization of C4 to produce chemical products has become an objective requirement for the development of low-carbon chemical industry. At present, the comprehensive utilization rate of C4 hydrocarbons in China is about 15%, and the comprehensive utilization rate of C4 hydrocarbons in developed countries can reach more than 80%. Therefore, with the development of petrochemical industry and the coal methanol-to-olefin industry in China, the high-value utilization of the by-product C4 becomes an important industry and a main competitive point.

There are many ways to comprehensively utilize the C four resources, such as isobutene polymerization hydrogenation to prepare isooctane, C four olefin catalytic cracking to prepare ethylene and propylene, etc., and further conversion of methacrolein by C four to further oxidize and esterify into ester, thus increasing the added value of chemical products.

Methyl methacrylate is mainly used for producing polymethyl methacrylate (organic glass), and is applied to many fields due to its excellent properties such as high transparency, excellent weather resistance, good processability, chemical corrosion resistance and the like. The current major processes for the production of methacrylic acid esters rely on the ACH process, Alpha process and isobutylene oxidative esterification processes. The ACH process uses hydrocyanic acid and sulfuric acid which are highly toxic and highly corrosive, and a large amount of ammonium bisulfate is generated as a byproduct, so that the method has severe requirements on production equipment, has large influence on the environment, and is not suitable for a green development route. The U.S. Air Reduction co, company, in the sixties of the last century, issued patents on the production process of MMA by Alpha process using ethylene as raw material, and later, BASF, germany, built a 36kt/a production apparatus for MMA by Alpha process in ludwigshafen, germany, to realize industrialization, but the utilization value of ethylene itself is high and the downstream industrial chains are numerous. In order to realize effective utilization of resources and reduce environmental pollution, the japanese company mitsubishi yang, sumitomo and mitsui chemistry began to develop a direct oxidation process of isobutylene in the eighties of the last century, and Asahi, industrialized an oxidative esterification process of isobutylene in the late nineties. The isobutylene line becomes an ideal process for the preparation of methacrylic acid esters.

The process for preparing methacrylic esters from isobutene or tert-butanol is generally carried out in three steps: in the first step, isobutene is catalytically oxidized into methacrolein; secondly, catalytically oxidizing methacrolein to generate methacrylic acid; in the third step, methacrylic acid is esterified with methanol to methyl methacrylate. The method is as follows: ullmann's Encyclopedia of Industrial Chemistry 2012, Wiley-VCH Verlag, Weiheim, Methacrylic Acid and Derivatives, DOI:10.1002/14356007.a 16-441. pub2 and Trends and Future of Monomer-MMA Technologies, SUMITOMO KAGAKU 2004-II.

Furthermore, patent application CN 101074192 teaches a process for preparing MMA, by first reacting propionaldehyde with formaldehyde to give methacrolein, which is then oxidized with methanol to give MMA. EP 0890569 discloses a process for obtaining methyl methacrylate by direct oxidative esterification of methanol, wherein it is explicitly stated that less than 2% by weight, preferably less than 1% by weight, of methacrolein is used as the reaction liquid. The examples only exemplify reactions in which the water content is less than 0.8%. Although other methods of synthesis of methacrolein in the liquid phase are taught by patents EP 0092097 and DE 2855504, the reaction of propionaldehyde and formaldehyde produces a large amount of water, which has an effect on the subsequent oxidative esterification of methacrolein. Therefore, if a catalyst for converting a highly selective reaction with high efficiency can be developed in the oxidative esterification of methacrolein and the tolerance to water produced by esterification would increase the applicability of the catalyst.

Disclosure of Invention

The invention adopts a one-pot synthesis method to prepare the catalyst, and synthesizes the methyl methacrylate by liquid-phase oxidative esterification of the methacrolein and the methanol, and the catalyst has the characteristics of simple preparation, high catalytic activity and high selectivity. The preparation of the catalyst utilizes silica sol as a silicon source, and has a limited domain effect and a carrier protection effect on the gold nanoclusters in the process of forming the catalyst coated by the gold noble metal. Optionally, metals such as Al, Mg and the like can be added or a composite carrier is formed by Al, Mg oxides and silicon oxide, so that the acid-base property and the active site distribution of the surface of the catalyst carrier can be regulated and controlled. The prepared noble metal oxide carrier modified catalyst is applied to the oxidative esterification reaction of methacrolein and methanol, the optimal conversion rate of raw materials reaches 92%, and the optimal selectivity of a target product MMA reaches 93%, which is a catalytic result with industrial application prospect.

The invention aims to provide a silica-coated noble metal catalyst prepared by a simple sol-gel method in one pot and a preparation method thereof, and then the catalyst is applied to the oxidative esterification reaction of methacrolein. In the preparation process, the preparation of the coated noble metal carrier modified catalyst is successfully realized by using a ligand method and a sol-gel method, and noble metal clusters are embedded in the carrier, so that the high dispersion and activity protection of noble metal active centers are facilitated, and the catalyst plays a key role in playing a role for a long time without inactivation.

The technical scheme of the invention is as follows:

the invention provides a preparation method of a noble metal nanocluster wrapped supported catalyst, which comprises the following steps:

(1) the ligand, the noble metal source, the dispersing agent and the carrier precursor form a mixed solution, and the adding sequence of the ligand, the noble metal source, the dispersing agent and the carrier precursor can be changed mutually. Stirring at 20-70 deg.C for 30min-4h to obtain sol solution,

(2) placing the sol solution in an oven at the temperature of 80-110 ℃, aging for 2-24 h, and drying to obtain a gel material, wherein the ligand can be polyvinylpyrrolidone, a sulfhydryl coupling agent, aminobenzoic acid and the like; the carrier precursor can be selected from sodium silicate, silica sol, ethyl orthosilicate, aluminum nitrate, magnesium nitrate and the like. The molar ratio of the ligand to the noble metal source to the carrier precursor is (1-20): 1: (1-1000); the molar ratio of the ligand to the noble metal source is preferably from 3:1 to 5: 1; the molar ratio of the carrier precursor to the noble metal source is 5:1-100: 1.

(2) And (3) raising the temperature of the obtained gel material to 150-500 ℃ in one or more of air, hydrogen or nitrogen, continuing for 2-8h, washing, drying at 50-120 ℃, soaking and cleaning with an alkaline solution, and finally repeatedly washing with water for 1-5 times to obtain the required noble metal carrier-coated supported catalyst.

In the preparation process, different atmospheres are used for sintering and activating the catalyst, and the heating rate can be selected from 1-5 ℃/min. Under the condition of air, hydrogen is not added, noble metal clusters with valence differences can be obtained in different noble metal valence states under different atmospheres, for example, the noble metal zero valence state under the hydrogen atmosphere is more, is a main component zero valence main body in normal distribution, and has a small positive valence.

Based on the technical scheme, preferably, the alkaline solution can be selected from NaOH, KOH, ethylenediamine and other solutions to remove surface impurities.

Based on the technical scheme, the preferable ligand can be organic ligand containing amino, carboxyl, sulfydryl and the like, can be high molecular polymer such as PVA, PVP and the like, and the decomposition temperature of the selected ligand is 150-500 ℃. The organic ligand can be selected from triethylaminosilane, glutathione, tetraethylammonium bromide and the like.

Based on the above technical scheme, the preferable noble metal source can be chloric acid, chlorate, chloride salt of corresponding metal such as chloroauric acid, palladium chloride, ruthenium chloride, palladate, platinate and the like.

Based on the technical scheme, the preferable dispersing agent is water, alcohol or ammonium salt solution; the alcohol is ethanol, ethylene glycol or isopropanol; the ammonium salt is ethylenediamine, tetrapropylammonium bromide and the like.

The invention provides a noble metal in-situ coated supported catalyst prepared by the method, which comprises an active component and a carrier; the active component is a noble metal nanoparticle; the noble metal nano particles (clusters) are wrapped by a carrier, the carrier has a pore structure, and the surface area is 100-900cm²A pore size of about 2nm to about 100nm per gram. The noble metal catalytic center is stabilized, the noble metal nano particles are embedded in the carrier, and the carrier contains holes which are responsible for mass transfer reaction of a reaction substrate.

Based on the technical scheme, the noble metal is preferably Au, Pd, Pt, Ru and the like; the carrier component is at least one of silicon oxide, aluminum oxide and magnesium oxide or a composite oxide formed by at least two of the oxides; the loading amount of the active component is 0.01-5.0%.

The loading amount of the noble metal active component of the catalyst is regulated and controlled within the range of 0.01-5.0%; the size of the noble metal catalyst nano particles is 0.5nm-4.0 nm; the size of the carrier is 0.5-100 μm. The catalyst is prepared by codeposition of a noble metal source and a carrier precursor, so that noble metal clusters are uniformly dispersed in the catalyst, the noble metal clusters are removed by sintering in the presence of a ligand, noble metal nanoparticles are left to be wrapped by the carrier, and the size of the sintered catalyst noble metal nanoparticles at the temperature of between 150 and 500 ℃ is not obviously changed.

In another aspect of the present invention, the catalyst prepared by the above method is applied to the oxidative esterification reaction of methacrolein; the catalytic reaction is carried out in a stainless steel reaction kettle by taking air, oxygen or gas components with different oxygen ratios as oxidants, wherein the molar ratio of the methacrolein substrate dosage to the noble metal catalyst active component is 10000:1-1000:1, the reaction temperature is 50-110 ℃, the reaction time is 1-4 h, and the reaction pressure is 0.3-3 MPa.

Based on the above technical scheme, the catalytic effect of the preferred components and ligands to the application is that the optimal conversion of methacrolein is 92% and the selectivity is 93%.

The regeneration method of the catalyst is simple and convenient, and the used catalyst is sintered for 2 to 4 hours in the air at the temperature of between 300 and 500 ℃ and then taken out for direct use. Supported catalysts for the oxidative esterification of methacrolein to methyl methacrylate using different ligands and support components

Advantageous effects

(1) In the catalyst, the noble metal nano particles (clusters) are wrapped by the carrier, and a pore structure is remained in the catalyst carrier due to the removal of the ligand, so that the transfer of a reaction substrate is facilitated, the domain limiting effect on the noble metal nano particles (clusters) is achieved, and the activity and the stability of the catalyst are maintained.

(2) Ligand and carrier precursor are matched for use to form sol containing noble metal source, and then the encapsulated supported catalyst is formed through a gel process. The method has the advantages of simple preparation, controllable loading capacity, uniform noble metal nanoclusters and high catalyst stability. The method has high conversion capability and selectivity in the oxidative esterification of the methacrolein, the optimal catalytic activity is that the conversion rate of the methacrolein is 92 percent, the selectivity is 93 percent, and the method is suitable for large-scale production.

Drawings

FIG. 1 is the XRD pattern of the Au @ AlMgSiOx catalyst prepared in example 1

FIG. 2 is a TEM image of the Au @ AlMgSiOx catalyst prepared in example 1

FIG. 3 is a graph showing the distribution of the nano-particle size of the Au @ AlMgSiOx catalyst prepared in example 1

Detailed Description

The present invention is further illustrated by the following examples, but is not limited thereto.

Comparative example 1

Preparation of noble metal-supported catalyst by deposition-precipitation method and selective oxidative esterification of methacrolein

(1) The preparation method comprises the steps of selecting common silicon dioxide, aluminum oxide and magnesium oxide as carriers in the literature (preparation of a high-activity high-stability palladium-silicon dioxide catalyst, Stadium shichi paper, university of great design university 2014, controllable preparation and catalytic action of nitrate radical intercalation copper-aluminum hydrotalcite, Chen Shushi paper, university of great design 2014), and mechanically mixing the common silicon dioxide, aluminum oxide and magnesium oxide as catalyst carriers.

(2) Deposition-precipitation method: dissolving chloroauric acid in water to obtain chloroauric acid with concentration of 2.0 × 10^-4mol/L, solution volume 300mL, NaBH refrigerated at 0-5 deg.C₄5mL of the solution is quickly poured into the solution, the generated gold nanoparticles are stirred for 10min in the dark, then 5g of the carrier is poured into the solution, stirred for 1h, and finally filtered, washed and dried at 80 ℃.

(3) And (3) aging and sintering the catalyst, namely putting the deposited nano-gold catalyst into a muffle furnace, sintering the nano-gold catalyst for 2 hours at 400 ℃ at the temperature rise rate of 5 ℃/min in an air environment, washing the nano-gold catalyst by using deionized water, and drying the nano-gold catalyst for later use at 80 ℃.

(4) And (3) tabletting and granulating the nano gold catalyst prepared by a deposition-precipitation method, wherein the amount of the catalyst used in the methacrolein catalytic reaction is 0.1g, the amount of the reaction substrate used is 2.0g, air is used as an oxidant, the reaction temperature is 80 ℃, the reaction pressure is 3.0MPa, and the reaction time is 2 h. The product results were analyzed by gas chromatography, and the methacrolein conversion was 60% and the selectivity was 30%.

Example 1

And (3) preparing the supported nano gold catalyst by utilizing ligand protection and carrier precursor codeposition, and carrying out methacrolein catalytic reaction evaluation.

Preparation of 1% Au @ almgsio:

(1) using a mercapto coupling agent as a ligand (30mg), an initial solution was obtained by mixing with a silicon-containing precursor such as ethyl orthosilicate (10 g).

(2) Dissolving chloroauric acid in water to obtain chloroauric acid with concentration of 2.0 × 10^-4And (3) pouring the chloroauric acid solution into the initial solution by 10mL of the solution, then quickly stirring for 30min, weighing 1g of magnesium nitrate and 1g of aluminum nitrate, dissolving in 10mL of water, then pouring the solution into the ligand and carrier precursor solution, and continuously stirring for 2 h. Finally, the gel was placed in an oven at 80 ℃ to form a solid.

(3) Putting the formed gel solid into a muffle furnace, sintering at 400 ℃ for 2h at the temperature rise rate of 5 ℃/min under the hydrogen atmosphere, taking out the sintered catalyst, repeatedly washing and filtering by using an alkali solution with the concentration of 5%, and finally washing by using water; and finally, drying the catalyst at 80 ℃ to obtain the catalyst 1% Au @ AlMgSiOx, which is named as ASMA-1 for later use. The structure and morphology of the catalyst structure are characterized by XRD and TEM, FIG. 1 is the XRD pattern of the Au @ AlMgSiOx catalyst prepared in example 1, it can be seen from the XRD pattern that the main body of the catalyst is silicon oxide containing a small amount of AlMg, and no XRD peak of Au is observed to indicate that the particle size is small, FIG. 2 is the TEM pattern of the Au @ AlMgSiOx catalyst prepared in example 1, it can be seen from the TEM pattern that the gold nanoparticles are uniformly distributed, non-agglomerated and uniform in size, FIG. 3 is the nano-particle size distribution diagram of the Au @ AlMgSiOx catalyst prepared in example 1, it can be seen from the TEM pattern that the particle size of the gold nanoparticles is mainly concentrated between 2nm and 3nm, further illustrating that the particles are small and uniform in size.

Example 2

Example 1 was repeated, replacing the ligand with an amino coupling agent, to give a 1% Au @ AlMgSiOx supported gold nanocatalyst, designated ASMA-2.

Example 3

Example 1 was repeated, replacing the ligand with glutathione, to obtain 1% Au @ AlMgSiOx supported gold nanocatalyst, denoted ASMA-3.

Example 4

Example 1 was repeated, and the carrier precursor was changed from tetraethyl orthosilicate to water glass to obtain a 1% Au @ AlMgSiOx supported gold nanocatalyst, which was designated ASMA-4.

Example 5

Example 1 was repeated, the noble metal source being replaced by palladium chloride from chloroauric acid and the support being Al₂O₃To obtain 1% Pd @ Al₂O₃The supported gold nanocatalyst is marked as PA-1.

Example 6

Example 1 was repeated, with the concentration of the chloroauric acid solution being adjusted from 2.0X 10^-4The mol/L is changed to 4.0 multiplied by 10^-4And the mol/L is 5mL, and the 1% Au @ AlMgSiOx supported gold catalyst is obtained. Designated ASMA-5.

Example 7

Example 1 was repeated, and the support precursor was changed from ethyl orthosilicate to sodium silicate to yield a 1% Au @ AlMgSiOx supported gold nanocatalyst, designated ASMA-6.

Example 8

The oxidative esterification of methacrolein is carried out in a reaction kettle with methanol as a solvent.

Tabletting and granulating the prepared ASMA-1 catalyst sample, wherein the catalyst used in the reaction is 0.2g, the reaction substrate is methacrolein, the raw material usage amount is 1.0g, the reaction temperature is 80 ℃, the air pressure is 3MPa, and the reaction time is 2 h. A sample was then taken and the product was analyzed by GC with a methacrolein conversion of 90% and a methyl methacrylate selectivity of 92%.

Example 9

Example 8 was repeated, with the catalyst being ASMA-2 and the reaction temperature being unchanged, the methacrolein conversion being 86% and the methyl methacrylate selectivity being 89%.

Example 10

Example 8 was repeated, with the catalyst being ASMA-3 and the reaction temperature being unchanged, the methacrolein conversion being 75% and the methyl methacrylate selectivity being 85%.

Example 11

Example 8 was repeated, with the catalyst being ASMA-4 and the reaction temperature being unchanged, the methacrolein conversion being 86% and the methyl methacrylate selectivity being 88%.

Example 12

Example 8 was repeated, with the catalyst being ASMA-5 and the reaction temperature being unchanged, the methacrolein conversion being 89% and the methyl methacrylate selectivity being 93%.

Example 13

Example 8 was repeated, with the catalyst being ASMA-6 and the reaction temperature being unchanged, the methacrolein conversion being 87% and the methyl methacrylate selectivity being 91%.

Example 14

Example 8 was repeated, with the catalyst being changed to PA-1 and with the reaction temperature being unchanged, the methacrolein conversion being 84% and the methyl methacrylate selectivity being 90%.

Claims

1. The application of the noble metal catalyst is characterized in that the noble metal catalyst is applied to the reaction of oxidizing and esterifying methacrolein and methanol to obtain methyl methacrylate; the noble metal catalyst is prepared by the following method:

(1) mixing a ligand, a noble metal source, a dispersing agent and a carrier precursor to form a mixed solution, and then stirring the mixed solution at the temperature of 20-70 ℃ for 30min-4h to obtain a sol solution;

(2) aging the sol solution at 80-110 ℃ for 2-24 h, and drying to obtain a gel-like material, wherein the molar ratio of noble metal in the ligand to noble metal source to carrier precursor is (1-20): 1: (1-1000);

(3) heating the gel-like material to 150-500 ℃ in the air, inert gas and/or hydrogen atmosphere, keeping for 2-8h, washing, drying at 50-120 ℃, soaking and cleaning with an alkaline solution, and then washing with water to obtain the noble metal catalyst;

the ligand is one of polyvinylpyrrolidone, a sulfhydryl coupling agent, aminobenzoic acid, triethylaminosilane, glutathione or tetraethylammonium bromide;

the carrier precursor is a mixture of at least one of sodium silicate, silica sol and ethyl orthosilicate and at least one of aluminum nitrate and magnesium nitrate;

the catalyst comprises an active component and a carrier; the active component is a noble metal nanoparticle; the noble metal nano-particles are wrapped by a carrier; the carrier has a pore structure.

2. The use according to claim 1,

the noble metal source is one of chloric acid, chlorate or chloride salt of the noble metal;

the dispersant is water, alcohol or ammonium salt solution; the alcohol is one of ethanol, ethylene glycol or isopropanol; the ammonium salt solution is an ethylenediamine or tetrapropyl ammonium bromide solution; the mass concentration of the ammonium salt solution is 1-20%.

3. Use according to claim 1, characterized in that the alkaline solution used is one of NaOH, KOH or ethylenediamine solution; the mass concentration of the alkaline solution is 5-50%.

4. Use according to claim 2, wherein the noble metal source is one of chloroauric acid, palladium chloride, ruthenium chloride, a palladate or a platinate.

5. The use according to claim 1, wherein the surface area of the support is 100-900cm²The pore diameter is 2nm-100 nm.

6. Use according to claim 1, wherein the noble metal is one of Au, Pd, Pt or Ru; the carrier component is a composite oxide formed by silicon oxide and at least one of aluminum oxide and magnesium oxide; the loading amount of the active component is 0.01-5.0%.

7. The use of claim 1, wherein the noble metal catalyst nanoparticles are 0.5nm to 4.0nm in size; the size of the carrier is 0.5-200 μm.

8. Use according to claim 1, characterized in that the reaction has a conversion of 75% to 92% and a selectivity of 82% to 93%.