阅读说明：本技术 一种蛋壳型复合金属催化剂的制备方法及其应用 (Preparation method and application of eggshell type composite metal catalyst ) 是由 张锁江 吕兆坡 闫瑞一 李春山 郭立杰 马冬菊 李增喜 于 2019-12-06 设计创作，主要内容包括：本发明涉及一种用于异丁烯/叔丁醇气相氧化合成甲基丙烯醛蛋壳型复合金属氧化物催化剂。在催化剂制备过程中加入球形载体和粘结剂,使得金属盐在球形载体表面发生反应并附着在其表面,通过焙烧将部分粘结剂除去,从而获得蛋壳型复合金属氧化物催化剂。本发明提供的催化剂制备流程简单,成本低廉,在异丁烯/叔丁醇气相氧化合成甲基丙烯醛反应中具有优异的催化性能,催化寿命长,适用于工业化。(The invention relates to an eggshell type composite metal oxide catalyst for synthesizing methacrolein by gas phase oxidation of isobutene/tertiary butanol. Adding a spherical carrier and a binder in the preparation process of the catalyst to enable metal salt to react on the surface of the spherical carrier and attach to the surface of the spherical carrier, and removing part of the binder through roasting to obtain the eggshell type composite metal oxide catalyst. The catalyst provided by the invention has the advantages of simple preparation process, low cost, excellent catalytic performance in the reaction of synthesizing methacrolein by isobutene/tert-butyl alcohol gas phase oxidation, long catalytic life and suitability for industrialization.)

1. The eggshell type composite metal oxide catalyst is characterized in that a spherical carrier and a binder are added in the preparation process of the catalyst, and metal salt directly reacts on the surface of the carrier and is attached to the surface of the carrier, so that the eggshell type composite metal oxide catalyst with high activity, good stability and low cost is obtained.

2. The eggshell composite metal oxide catalyst of claim 1 wherein said catalyst composition is:

Mo₁₂Bi_aFe_bCo_cX_dY_eO_m/Z

wherein the content of the first and second substances,

x is one or more selected from Cu, Mg, Ni, V, Ti and Zn;

y is one or more selected from K, Na, Cs, La, Ce, Nd, Zr, Nb, Yb, Er, Sb, Sr and Ag;

z is a spherical carrier selected from porous silica gel, α -Al₂O₃、β-Al₂O₃、γ-Al₂O₃One or more of silicon-aluminum molecular sieves such as MCM-41 molecular sieve, KIT-6 molecular sieve, SBA-15 and the like;

a. b, c, d, e, m represent the atomic ratio of each element in one catalyst cluster, respectively, wherein,

the range of a is selected from 0.1-6;

b is selected from 0.1-6;

c is selected from 0.5-10;

d is selected from 0.05-4;

e is selected from 0.05-3;

m is the number of oxygen atoms satisfying the oxidation state of the above elements.

3. The method for preparing the eggshell type composite metal oxide catalyst as recited in claim 1 comprises the steps of:

a) under certain conditions, a certain amount of binder and a certain proportion of metal salt aqueous solution are fully mixed and dissolved;

b) mixing the solution prepared in the step with a precipitator and a spherical carrier under a certain condition, reacting, aging and refluxing to form suspension slurry;

c) drying and roasting the suspension slurry prepared in the step under a certain condition to obtain eggshell type composite metal oxide catalyst powder;

d) and (3) molding the catalyst powder prepared in the step under a certain condition to obtain the regular or irregular catalyst to be evaluated.

4. The method according to claim 3, wherein the binder in the step a) is one or more selected from silica sol, aluminum sol, titanium sol, bentonite, ethylene glycol, polyethylene oxide, polytetrafluoroethylene, polyvinylpyrrolidone, ionic liquid binder and the like, and the mass ratio of the binder to the metal salt is 1: 100-1: 5; the dissolution temperature is 20-80 ℃.

5. The method according to claim 3, wherein the spherical carrier in the step b) is selected from one or more of silica, alumina, MCM-41 molecular sieve, KIT-6 molecular sieve, silica-alumina molecular sieve such as SBA-15, magnesia, zirconia, aluminum silicate, diatomite, pumice, vesuvianite and kaolin, and the diameter of the spherical carrier is 1-300 μm; the spherical carrier can be mixed with the precipitant or the solution prepared in the step a) in advance, or the precipitant and the metal salt solution containing the binder can be dripped into the suspension water solution of the spherical carrier together; the mass ratio of the spherical carrier to the metal salt is 20: 1-0.5: 1; the reaction temperature is 30-100 ℃, the aging reflux temperature is 50-150 ℃, and the time is 1-12 h.

6. The method according to claim 3, wherein the drying in step c) is selected from one of evaporation drying, vacuum drying, microwave drying, suction filtration drying, spray drying or reduced pressure rotary evaporation drying; the roasting temperature is 350-650 ℃, the heating rate is 1-10 ℃/min, and the roasting time is 2-24 h.

7. The method according to claim 3, wherein the molding in the step d) is one selected from the group consisting of tablet molding, extrusion molding, rotational molding, spray molding, roll coating molding and dip molding.

8. A method for synthesizing methacrolein by gas phase oxidation of isobutylene/tert-butanol, characterized in that the eggshell-type composite metal oxide catalyst according to any one of claims 1 to 7 is used.

Technical Field

The invention relates to a preparation method of an eggshell type composite metal oxide catalyst and application of the eggshell type composite metal oxide catalyst in a reaction of synthesizing methacrolein by isobutene/tertiary butanol gas phase oxidation, belonging to the field of catalyst preparation and application.

Background

As an important organic chemical raw material and an industrial intermediate, Methyl Methacrylate (MMA) is mainly used for producing organic glass (PMMA), a light guide plate, a light guide fiber and the like, and because PMMA has excellent physical and chemical properties, the PMMA has important application in national important industries such as LED, aviation, rail transit and the like. The acetone cyanohydrin method is a traditional production process of MMA, and because virulent hydrocyanic acid and strong corrosive sulfuric acid are used in the production process and the environment is seriously polluted, a new alternative process meeting the green chemical requirement is urgently needed.

At present, the new process meeting the green chemical requirements in the development stage mainly focuses on a C4 clean production process, and can be divided into a two-step method and a three-step method according to different reaction steps, wherein the two-step method mainly comprises the steps of synthesizing methacrolein through isobutene/tertiary butanol oxidation and synthesizing methyl methacrylate, namely MMA through one-step oxidation esterification; the three-step method mainly comprises the steps of synthesizing methacrolein by oxidizing isobutene/tertiary butanol, oxidizing methacrolein to generate methacrylic acid and esterifying the methacrylic acid to obtain MMA. The two processes belong to green processes, the process is simple, the operation cost is low, and as key reaction steps of the two processes, the catalyst for synthesizing methacrolein by oxidizing isobutene/tert-butanol is mainly based on Mo-Bi-Fe-Co-O composite oxide, trace elements are added into the basic components to achieve relatively high catalyst activity, but the catalysts have two more difficult problems in the industrial application process: 1. the strong heat release causes the performance reduction and the service life reduction of the catalyst; 2. the reaction of isobutene is incomplete to affect the activity of the catalyst for the subsequent reaction.

To solve the first problem, patents US5728894 and US7012039 disclose a method for achieving the purpose of prolonging the life of a catalyst by suppressing the loss of Mo as an active component by adding a component having heat resistance and reduction resistance, but this cannot fundamentally solve the problem; on the basis, the patents CN1210511A, CN145946A and CN1048540A respectively improve the thermal conductivity of the catalyst by loading and adding inert substances to dilute the catalyst, thereby inhibiting the Mo component from losing due to high temperature in the reaction process, but these methods not only reduce the activity and product yield of the catalyst more or less, but also make the preparation process and the filling process of the catalyst more complicated.

The second problem is focused on the three-step process, in which the catalyst for the preparation of methacrylic acid by oxidation of methacrolein is very sensitive to isobutylene, and excessive residual isobutylene causes poisoning deactivation of the catalyst, and therefore, in order to improve the economy of the production process and the catalyst life of the subsequent reaction, it is necessary to react isobutylene in the first step as completely as possible. Japanese patent laid-open No. Sho 55(1980) -113730 improves the activity and selectivity of the catalyst by changing the addition of K, Rb, Cs, Ti and other elements. In the methods disclosed in chinese patents CN103157486A and CN1647853A, the method of preparing the catalyst in a supported manner is adopted to improve the distribution of active components of the catalyst, thereby improving the activity of the catalyst. Despite the modest advances in conversion, the requirements for the production of methacrylic acid catalysts by the oxidation of methacrolein are still not met and a reduction in methacrolein selectivity results.

According to the requirements of the existing production process, a new preparation method of the catalyst needs to be developed, and the eggshell type composite metal oxide catalyst with high activity and strong thermal stability is prepared.

Disclosure of Invention

The invention provides a preparation method of an eggshell type composite metal oxide catalyst with excellent catalytic performance, high thermal stability, simple method and low cost. In the invention, the spherical carrier and the binder are added in the preparation process of the catalyst, so that the metal salt reacts on the surface of the spherical carrier and is attached to the surface of the spherical carrier, and then part of the binder is removed by roasting, thereby obtaining the eggshell type composite metal oxide catalyst. The catalyst is used for the reaction of synthesizing methacrolein by isobutene/tertiary butanol gas phase oxidation, and shows excellent catalytic performance and service life.

The chemical expression of the eggshell type composite metal oxide catalyst is as follows:

Mo₁₂Bi_aFe_bCo_cX_dY_eO_m/Z

wherein the content of the first and second substances,

x is one or more selected from Cu, Mg, Ni, V, Ti and Zn;

y is one or more selected from K, Na, Cs, La, Ce, Nd, Zr, Nb, Yb, Er, Sb, Sr and Ag;

z is a spherical carrier selected from porous silica gel, α -Al₂O₃、β-Al₂O₃、γ-Al₂O₃One or more of silicon-aluminum molecular sieves such as MCM-41 molecular sieve, KIT-6 molecular sieve, SBA-15 and the like;

a. b, c, d, e, m represent the atomic ratio of each element in one catalyst cluster, respectively, wherein,

the range of a is selected from 0.1-6;

b is selected from 0.1-6;

c is selected from 0.5-10;

d is selected from 0.05-4;

e is selected from 0.05-3;

m is the number of oxygen atoms satisfying the oxidation state of the above elements.

The preparation process of the catalyst comprises the following steps:

a) under certain conditions, a certain amount of binder and a certain proportion of metal salt aqueous solution are fully mixed and dissolved;

b) mixing the solution prepared in the step with a precipitator and a spherical carrier under a certain condition, reacting, aging and refluxing to form suspension slurry;

c) and (3) drying and roasting the suspension slurry prepared in the step under a certain condition to obtain the eggshell type composite metal oxide catalyst.

d) And (3) molding the catalyst powder prepared in the step under a certain condition to obtain the regular or irregular catalyst to be evaluated.

The binder in the step a) is selected from one or more of silica sol, aluminum sol, titanium sol, bentonite, ethylene glycol, polyethylene oxide, polytetrafluoroethylene, polyvinylpyrrolidone, ionic liquid binder and the like, and the titanium sol, the polyethylene glycol, the polytetrafluoroethylene, the polyvinylpyrrolidone and the ionic liquid are preferred; the mass ratio of the binder to the metal salt is 1: 100-1: 5, preferably 1: 80-1: 20; the dissolution temperature is 20-80 ℃.

The spherical carrier in the step b) is selected from one or more of silica-alumina molecular sieves such as silica, alumina, MCM-41 molecular sieve, KIT-6 molecular sieve and SBA-15, magnesia, zirconia, aluminum silicate, diatomite, pumice, vesuvianite and kaolin, preferably silica, alumina, MCM-41 molecular sieve, SBA-15, magnesia and zirconia, and the diameter of the spherical carrier is 1-300 mu m, preferably 10-100 mu m; the spherical carrier can be mixed with a precipitant or the solution prepared in the step a), or the precipitant and the metal salt solution containing the binder can be jointly dripped into the suspension water solution of the spherical carrier; the mass ratio of the spherical carrier to the metal salt is 20: 1-0.5: 1; the reaction temperature is 30-100 ℃, the aging reflux temperature is 50-150 ℃, and the time is 1-12 h.

The drying mode in the step c) can be one of evaporation drying, vacuum drying, microwave drying, suction filtration drying, spray drying or reduced pressure rotary evaporation drying; the roasting temperature is 350-650 ℃, preferably 400-500 ℃, the heating rate is 1-10 ℃/min, preferably 3-6 ℃/min, and the roasting time is 2-24 h, preferably 4-10 h.

The forming mode in the step d) is one selected from tabletting forming, extrusion molding, rotation forming, spray forming, roll coating forming and dipping forming.

The eggshell type composite metal oxide catalyst prepared by the invention is used for catalyzing isobutene gas phase oxidation in a gas phase to synthesize methacrolein in a fixed bed through molecular oxygen in air.

The isobutene conversion was calculated as follows:

x (isobutylene)%, [1- (amount of unreacted isobutylene substance/amount of supplied isobutylene substance) ] × 100%

The selectivity of methacrolein is calculated as follows:

s (methacrolein)%, [ amount of substance of formed methacrolein/(amount of substance of supplied isobutylene-amount of unreacted isobutylene) ] × 100%

According to the invention, the binder and the spherical carrier are added in the preparation process of the catalyst, so that the metal salt and the precipitator directly react on the surface of the spherical carrier, and the addition of the binder and the rich groups on the surface of the spherical carrier enable the catalyst to be attached to the surface of the carrier under the action of the physical properties of the binder and the chemical bonds on the surface of the carrier to form an eggshell type structure, so that the temperature runaway of the catalyst can be effectively inhibited, and the inactivation caused by the loss of active components can be avoided to the greatest extent. Meanwhile, in the roasting process of the catalyst, a porous structure is formed due to the removal of part of the binder, so that the performance of the catalyst is effectively improved. The catalyst is used for synthesizing methacrolein by gas phase oxidation of isobutene, and has good catalytic performance and long catalytic life. The eggshell type catalyst has simple preparation process, and the used binder and carrier raw materials have low price and are suitable for industrial application.

Detailed Description

The present invention is illustrated below by way of examples, but the scope of the present invention is not limited by the examples.