CN112707814A - Method for preparing methyl acrylate from methyl acetate - Google Patents

Method for preparing methyl acrylate from methyl acetate Download PDF

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Publication number
CN112707814A
CN112707814A CN201911021186.8A CN201911021186A CN112707814A CN 112707814 A CN112707814 A CN 112707814A CN 201911021186 A CN201911021186 A CN 201911021186A CN 112707814 A CN112707814 A CN 112707814A
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carrier
catalyst
methyl acetate
methyl acrylate
density
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Inventor
刘晓曦
余强
刘仲能
刘旭
施晓秋
王海之
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China Petroleum and Chemical Corp
Sinopec Shanghai Research Institute of Petrochemical Technology
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China Petroleum and Chemical Corp
Sinopec Shanghai Research Institute of Petrochemical Technology
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    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C67/00—Preparation of carboxylic acid esters
    • C07C67/30—Preparation of carboxylic acid esters by modifying the acid moiety of the ester, such modification not being an introduction of an ester group
    • C07C67/333—Preparation of carboxylic acid esters by modifying the acid moiety of the ester, such modification not being an introduction of an ester group by isomerisation; by change of size of the carbon skeleton
    • C07C67/343—Preparation of carboxylic acid esters by modifying the acid moiety of the ester, such modification not being an introduction of an ester group by isomerisation; by change of size of the carbon skeleton by increase in the number of carbon atoms
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/002—Mixed oxides other than spinels, e.g. perovskite
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
    • B01J23/02—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the alkali- or alkaline earth metals or beryllium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/40—Catalysts, in general, characterised by their form or physical properties characterised by dimensions, e.g. grain size
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J35/61—Surface area
    • B01J35/612—Surface area less than 10 m2/g
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J35/00—Catalysts, in general, characterised by their form or physical properties
    • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J35/64—Pore diameter
    • B01J35/647—2-50 nm

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Abstract

The invention provides a method for preparing methyl acrylate from methyl acetate, which comprises the step of reacting methyl acetate with an aldehyde source in the presence of a solid base catalyst to obtain the methyl acrylate, wherein the solid base catalyst comprises the following components in parts by mass: a) a catalytic amount of an alkali metal oxide; and b) 50-80 parts of a carrier; wherein the carrier is silicon hydroxyl with the density of 0.6-1.5 Si-OH/nm2Of (4) silicon dioxide. The invention also provides a solid base catalyst, and an application and a preparation method thereof. The invention obtains a catalyst which can improve the yield and the selectivity, and simultaneously can keep the catalytic activity for a longer time,Thereby realizing industrialization and solving the problem of large surplus of methyl acetate capacity.

Description

Method for preparing methyl acrylate from methyl acetate
Technical Field
The invention relates to a method for preparing methyl acrylate by using methyl acetate, a solid base catalyst and a preparation method of the solid base catalyst, and mainly relates to a catalyst for preparing methyl acrylate by condensing methyl acetate and formaldehyde and a preparation method of the catalyst.
Background
Methyl acrylate is an important fine chemical raw material with wide application, is mainly used for organic synthesis intermediates and high molecular monomers, and polymers prepared by taking methyl acrylate as monomers are widely used in the industries of coatings, textiles, leathers, adhesives and the like.
The acrylic acid and its ester are produced mainly by the propylene oxidation method, the acrylonitrile hydrolysis method, the vinyl ketone method, the propane oxidation method, the methyl formate method, and the like. However, the methods have the defects of serious pollution, high energy consumption, low product yield and the like. Therefore, the development of a green and efficient new production process has very important significance.
The well established alpha-MMA process is proposed by Lucite, Inc., which uses methyl methacrylate prepared from methyl propionate and formaldehyde. However, the process route of the Lucite company is not suitable for the national conditions of China. The national condition of China is that the production capacity of methyl acetate is greatly surplus. However, the process route of Lu Cai Te company is to synthesize the raw material of methyl methacrylate from methyl propionate, and the consumed raw material is methyl propionate, so that the problem of surplus methyl acetate production in China cannot be solved. Therefore, what is needed in the art is to realize green synthesis of methyl acrylate by using an industrial byproduct, namely methyl acetate, as a raw material, using a safe, environment-friendly and nontoxic solid base catalyst and using a clean synthesis process.
In view of this, in order to solve the problem of the large surplus of the productivity of methyl acetate in China, the synthesis of methyl acrylate by using methyl acetate and formaldehyde as raw materials and adopting a novel catalyst is proposed on the basis of the mature alpha-MMA process proposed by Lucite (Lucite) company at present. The catalyst reaction-regeneration fluidized bed coupling system is adopted, and the problems of short one-way service life, easy carbon deposition and frequent regeneration of the catalyst are solved. At present, the conversion per pass of methyl acetate is generally 15%, the selectivity of methyl acrylate can generally reach 85%, and the yield of methyl acrylate is generally 13.5%. But at present, industrialization still cannot be realized, and the key point is that the comprehensive improvement of yield, selectivity and catalyst stability cannot be achieved. In recent years, many units at home and abroad further research on the synthesis of methyl acrylate from methyl acetate and formaldehyde.
In the "catalyst science and technology" (6417-6430 at 2016) (Zhang guoliang, et Al, Catal. Sci. Techniol., 2016,6,6417-6430), Zhang Liang et Al, proceedings of the Chinese academy of sciences, reported that methyl acetate and formaldehyde were used as raw materials, and Cs-P/Al was used2O3The yield of the catalyst, namely methyl acrylate, reaches 40%, but the catalyst is quickly deactivated within 100h, and the stability needs to be further improved.
In the university of Qizihaar, proceedings of the university of Qizihaar (2007, 23(1) Vol., 24-26 pages), the Yongsheng of leaves adopts K+/SiO2Solid superbase catalyst, at 300 ℃, space velocity of 4.5h-1, aldehyde-ester ratio of 1: 3, the yield of methyl acrylate is 31%, but the stability and selectivity results of the catalyst are not given. After repeated experiments, researchers found that the conversion rate was still low.
Chinese patent No. CN104703696A reports that the LouTot International British Co., Ltd adopts Cs catalyst, regenerant and freshener for preparing methyl methacrylate and methacrylic acid from methyl propionate and formaldehyde, and the total selectivity of the two reaches 95%. The disadvantage is that the product also contains methacrylic acid and that due to the limitations of catalyst stability the cleaning process has to be increased often, thus increasing the production costs.
Chinese patent (CN 101575290A) discloses a method for synthesizing methyl acrylate by a catalyst sectional filling mode, wherein a phosphorus vanadium catalyst and a Cs catalyst are filled in a sectional mode, and the selectivity of a product is improved by changing the acidity and alkalinity of the catalyst. The disadvantage is that although the problem of low reaction conversion rate is solved, additional equipment is required; and the selectivity is not high.
Chinese patent No. CN103506107A discloses a catalyst with cesium oxide as active component, which adopts gas phase condensation reaction, the reaction temperature is above 380 deg.C, and the product contains acrylic acid product besides methyl acrylate. The disadvantage is that the selectivity is not high due to the presence of acrylic acid product.
In conclusion, the research on the synthesis of methyl acrylate by using methyl acetate and formaldehyde as raw materials is not industrialized, and is only in the research stage at present, but the cost advantage is very obvious as a new process route, and the process is mainly developed by large-scale transnational chemical companies by investing manpower and material resources.
Therefore, in view of the above, there is a need in the art for a synthetic route of methyl acrylate and a corresponding solid base catalyst, which can improve yield and selectivity, and simultaneously maintain catalytic activity for a long time, thereby realizing industrialization and solving the problem of large surplus of methyl acetate production.
Disclosure of Invention
One of the technical problems to be solved by the invention is to provide an industrialized synthesis method for obtaining methyl acrylate from ethyl acetate, which can improve the yield and selectivity and simultaneously keep the catalytic activity for a longer time.
The second technical problem to be solved by the invention is to provide a solid base catalyst for the methyl acrylate synthetic route.
The invention also provides the application of the solid base catalyst.
The fourth technical problem to be solved by the invention is to provide a preparation method of the solid base catalyst.
In order to solve one of the technical problems, the first aspect of the invention provides a method for preparing methyl acrylate from methyl acetate, which comprises the step of reacting methyl acetate with an aldehyde source in the presence of a solid base catalyst to obtain the methyl acrylate, wherein the solid base catalyst comprises the following components in parts by mass:
a) a catalytic amount of an alkali metal oxide; and
b) 50-80 parts of a carrier; the carrier is silicon hydroxyl with the density of 0.6-1.5 Si-OH/nm2Of (4) silicon dioxide.
The "aldehyde source" of the present invention includes formaldehyde but is not limited thereto. May be any source that can provide formaldehyde. Specifically, the material may be selected from formaldehyde or a material capable of generating formaldehyde in situ in a reaction system for synthesizing methyl acrylate (such as, but not limited to, trioxymethylene, paraformaldehyde, methylal, etc.).
The catalytic amount refers to the dosage of an active ingredient for synthesizing methyl acrylate from methyl acetate, and the active ingredient refers to alkali metal oxide. Specifically, the catalytic amount is more than 0 part and not more than 50 parts by weight.
In a specific embodiment of the invention, in the carrier of the component b), the carrier is a carrier with a density of silicon hydroxyl groups of 0.6-1.5 Si-OH/nm2And a carrier having a BET average pore diameter of 2 to 50nm and a BET pore volume of 0.2 to 2 ml/g.
Preferably, the BET method average pore size of the support may be 2 to 50nm, such as, but not limited to, 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, and the like.
Preferably, the BET pore volume of the support may be 0.2 to 2ml/g, such as, but not limited to, 0.4ml/g, 0.6ml/g, 0.8ml/g, 1.0ml/g, 1.2ml/g, 1.4ml/g, 1.6ml/g, 1.8ml/g, and the like.
Preferably, the carrier is 1-2.5 mm in diameter.
Most preferably, the carrier has a diameter of 1-2.5 mm, a BET average pore diameter of 21-25nm, and a BET pore volume of 0.9-1.0 ml/g.
In one embodiment of the invention, the alkali metal is selected from K, Rb and Cs or a combination thereof.
In one embodiment of the present invention, the process independently satisfies one or more of the following reaction conditions:
the reaction temperature is preferably 200-450 ℃;
the molar ratio of methyl acetate to formaldehyde in the aldehyde source is preferably 3-100;
the addition amount of the catalyst is preferably 1-10% of the weight of the methyl acetate and the aldehyde source; or is
The total mass space velocity of the methyl acetate and the aldehyde source is preferably 1-10 h-1。
In order to solve the second technical problem, the second aspect of the present invention provides a solid base catalyst, which comprises the following components in parts by mass:
a) a catalytic amount of an alkali metal oxide; and
b) 50-80 parts of a carrier; the carrier is silicon hydroxyl with the density of 0.6-1.5 Si-OH/nm2Of (4) silicon dioxide.
The solid base catalyst is used for synthesizing methyl acrylate. More preferably, the solid base catalyst of the present invention is a solid base catalyst for synthesizing methyl acrylate starting from methyl acetate.
The catalytic amount refers to the amount of active ingredient which can be used for the synthesis of methyl acrylate, and the active ingredient is alkali metal oxide. In a preferred embodiment, the catalytic amount refers to the amount of an active ingredient for synthesizing methyl acrylate from methyl acetate, and the active ingredient refers to an alkali metal oxide.
In one embodiment of the invention, the alkali metal is selected from K, Rb and Cs or a combination thereof.
In one embodiment of the present invention, the solid base catalyst is prepared by a process comprising the steps of:
(i) providing a solution containing a catalytic amount of alkali metal element precursor salt and 50-80 parts of a carrier;
the carrier is prepared by the following method:
(m1) providing silica sol and silica hydroxyl group with a density of 0.6-1.5 Si-OH/nm2The silica powder of (4);
(m2) molding the mixture to obtain a molded product;
(m3) drying the molded product to obtain a dried product;
(m4) calcining the dried substance to obtain the carrier of the step (i).
(ii) (ii) mixing the solution of step (i) with a carrier; obtaining a mixture;
(iii) (iii) calcining the mixture of step (ii) to obtain the solid catalyst.
Preferably, the alkali metal is selected from K, Rb and Cs or a combination thereof.
Preferably, the calcination temperature in step (iii) is 400 to 800 ℃.
Preferably, the roasting time of step (iii) is 4 to 15 hours.
In order to solve the third technical problem, the third aspect of the present invention provides a use of a solid catalyst for catalyzing an aldol synthesis reaction of methyl acetate and an aldehyde source to obtain the methyl acrylate.
Specifically, the solid catalyst can be used in the production of methyl acrylate or methyl propionate by the condensation of methyl acetate and formaldehyde.
In a preferred embodiment, the selectivity to methyl acrylate is greater than 90%.
In a preferred embodiment, the catalyst stability is not less than five days.
In order to solve the fourth technical problem, a fourth aspect of the present invention provides a method for preparing the solid catalyst, comprising:
(i) providing a solution containing a catalytic amount of alkali metal element precursor salt and 50-80 parts of a carrier;
(ii) (ii) mixing the solution of step (i) with a carrier; obtaining a mixture;
(iii) (iii) calcining the mixture of step (ii) to obtain the solid catalyst.
Preferably, the alkali metal comprises a metal selected from K, Rb and Cs or a combination thereof.
Preferably, the roasting temperature is 400-800 ℃.
Preferably, the roasting time is 4-15 hours.
Preferably, the carrier is prepared by a method comprising the following steps:
(m1) providing silica sol and silica hydroxyl group with a density of 0.6-1.5 Si-OH/nm2The silica powder of (4);
(m2) molding the mixture to obtain a molded product;
(m3) drying the molded product to obtain a dried product;
(m4) calcining the dried substance to obtain the carrier of the step (i).
In one embodiment of the present invention, the preparation method of the solid catalyst further comprises: after step (ii) and before step (iii) there is a drying step.
The invention has the technical effects that:
by adopting the invention, the catalyst can continuously run for 30 days, the specific surface area and the catalytic activity are not obviously reduced, the selectivity of the methyl acrylate can reach more than 90 percent, and a better technical effect is achieved.
Detailed Description
The inventor of the invention has conducted extensive and intensive research, and through improving the process, surprisingly found that the problem of poor hydrothermal stability of the catalyst in the process of preparing methyl acrylate from methyl acetate can be solved by adopting the fixed catalyst of the specific carrier; the synthesis method is more unexpectedly found to be capable of stably operating for a long time, so that the industrialization of synthesizing the methyl acrylate by taking the methyl acetate and the formaldehyde as raw materials is hopeful to be realized; the method can solve the problem of greatly surplus methyl acetate in the prior art, and can obtain good economic and social benefits.
Unless otherwise specified, various starting materials of the present invention are commercially available; or prepared according to conventional methods in the art. Unless defined or stated otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In addition, any methods and materials similar or equivalent to those described herein can be used in the methods of the present invention.
Various aspects of the invention are detailed below:
definition of
As used herein, the conversion of formaldehyde is defined as follows:
Figure BDA0002247274540000071
as used herein, the selectivity to methyl acrylate is expressed as a percentage of moles of methyl acrylate to moles of formaldehyde converted. For example, when the formaldehyde is present as trioxymethylene, the selectivity of the methyl acrylate is defined as follows:
Figure BDA0002247274540000072
as used herein, the term "alkali metal", unless otherwise specified, includes group IA alkali metal elements. More preferably, the alkali metal is selected from K, Rb and Cs or a combination thereof.
As used herein, the term "aldehyde source" includes materials selected from formaldehyde or the ability to generate formaldehyde in situ in the methyl acrylate synthesis reaction system (e.g., without limitation, trioxane, paraformaldehyde, methylal, and the like).
As used herein, the "density of silicon hydroxyl groups," unless otherwise specified, refers to the density per nm2Average number of upper hydroxyl groups. The "density of silicon hydroxyl groups" is known to those skilled in the art and can be determined by methods conventional in the art. For example, the measurement can be carried out by titration, but is not limited thereto. The specific method comprises the following steps: 2g of silica was weighed into a 200mL beaker, 25mL of absolute ethanol was added, and 75mL of a 20% by mass sodium chloride solution was added. After stirring uniformly, adding 0.1mol/L HCl to adjust the pH of the solution to 4, then slowly adding 0.1mol/L NaOH solution to raise the pH to 9, keeping the pH for 20s, keeping the pH constant, and then calculating the density of surface silanol hydroxyl according to the following formula: n ═ CVNA*10-3) Sm, C is NaOH concentration, V is NaOH solution dropping amount, NA is Avogastron constant, S is twoThe specific surface area of the silicon oxide, and m is the mass of the silicon dioxide.
Method for synthesizing methyl acrylate
The synthesis method of methyl acrylate comprises the step of reacting methyl acetate with an aldehyde source in the presence of a solid base catalyst to obtain the methyl acrylate, wherein the solid base catalyst comprises the following components in parts by mass:
a) more than 0 part and 50 parts or less of alkali metal oxide;
b) 50-80 parts of a carrier; the density of silicon hydroxyl group of the carrier is preferably 0.6-1.5 Si-OH/nm2。
Preferably, the alkali metal includes at least one selected from the group consisting of K, Rb and Cs.
The technical key of the invention is the selection of the components a) and b).
As the alkali metal oxide part is not limited to be exemplified by 0.1, 0.5, 1, 5, 10, 15, 20 and the like, but it is preferably 1 to 20 parts.
The density of the Si-OH groups on the carrier was 0.6Si-OH/nm2、0.7Si-OH/nm2、0.8Si-OH/nm2、0.9Si-OH/nm2、1.0Si-OH/nm2、1.1Si-OH/nm2、1.2Si-OH/nm2、1.3Si-OH/nm2、1.4Si-OH/nm2And so on.
The BET method average pore diameter of the carrier may be 2 to 50nm, such as, but not limited to, 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, and the like; by way of non-limiting example only, the BET pore volume of the support may be 0.2 to 2ml/g, such as, but not limited to, 0.4ml/g, 0.6ml/g, 0.8ml/g, 1.0ml/g, 1.2ml/g, 1.4ml/g, 1.6ml/g, 1.8ml/g, and the like.
The technical key of the invention is the selection of the catalyst, and the technical personnel in the field can reasonably select the specific process conditions for the reaction of the methyl acetate and the aldehyde source without creative labor.
By way of non-limiting example, the reaction temperature may be 200 to 450 ℃, such as 250 ℃, 300 ℃, 350 ℃, 400 ℃ and the like.
By way of non-limiting example, the molar ratio of methyl acetate to formaldehyde can be selected from 3 to 100, such as 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, and the like.
By way of non-limiting example, the catalyst may be added in an amount of 1 to 10% by weight, e.g., 1.5%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, etc., of the methyl acetate and aldehyde source. As long as the alkali metal content therein reaches a catalytic amount.
By way of non-limiting example, the total mass space velocity of methyl acetate and aldehyde source is preferably 1-10 h-1, such as 1.5h-1, 2h-1, 3h-1, 4h-1, 5h-1, 6h-1, 7h-1, 8h-1, 9h-1, and the like.
It is known to those skilled in the art that water is generated in the condensation reaction of formaldehyde and methyl acetate to produce methyl acrylate, and that water may cause a degree of hydrolysis side reaction of methyl acrylate or methyl acetate, and for this reason, methanol may be introduced into the reaction system to suppress the hydrolysis side reaction.
Solid base catalyst for methyl acrylate synthesis
The solid base catalyst comprises the following components in parts by mass:
a) more than 0 part and 50 parts or less of alkali metal oxide;
b) 50-80 parts of a carrier; the hydroxyl group density of the carrier silicon is preferably 0.6-1.5 Si-OH/nm2。
Preferably, the alkali metal includes at least one selected from the group consisting of K, Rb and Cs.
Preferably, the support comprises two or more silicas of different nature.
The technical key of the invention is the selection of the components a) and b). The hydroxyl group density of the carrier silicon is preferably 0.6-1.5 Si-OH/nm2Such as, but not limited to, 0.6Si-OH/nm2、0.7Si-OH/nm2、0.8Si-OH/nm2、0.9Si-OH/nm2、1.0Si-OH/nm2、1.1Si-OH/nm2、1.2Si-OH/nm2、1.3Si-OH/nm2、1.4Si-OH/nm2And so on. By way of non-limiting example only, the BET average pore size of the support can be from 2 to 50nm, such as, but not limited to, 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, and the like; by way of non-limiting example onlyBy way of example, the BET pore volume of the support may be 0.2 to 2ml/g, such as, but not limited to, 0.4ml/g, 0.6ml/g, 0.8ml/g, 1.0ml/g, 1.2ml/g, 1.4ml/g, 1.6ml/g, 1.8ml/g, and the like.
As the alkali metal oxide part is not limited to be exemplified by 0.1, 0.5, 1, 5, 10, 15, 20 and the like, but it is preferably 1 to 20 parts.
As known to those skilled in the art, the conventional silica carrier has large pore size and reduced specific surface area due to pore dissolution under a high-temperature hydrothermal environment, so that the supported active center is remarkably reduced, and the activity of the catalyst is reduced. Whereas if emphasis is placed on improving catalyst stability, selectivity and conversion will be reduced.
In order to solve the technical problems, the invention provides the solid base catalyst which is used for catalyzing the condensation of methyl acetate and formaldehyde to prepare methyl acrylate and has the advantages of good hydrothermal stability and long-term stable operation. The catalyst of the invention can be industrialized because the two contradictory problems are creatively and simultaneously solved.
Use of solid base catalyst
In order to solve the technical problems, the catalyst obtained by the invention has the advantage of high methyl acrylate selectivity when used for catalyzing the condensation of methyl acetate and formaldehyde to prepare methyl acrylate.
Surprisingly, the density of silicon hydroxyl groups is more than 0.6-1.5 Si-OH/nm2The catalyst prepared by the carrier has high catalytic activity, but low product selectivity and short catalyst life; the density of silicon hydroxyl is less than 0.6-1.5 Si-OH/nm2The catalyst prepared by the carrier has low catalytic activity and low selectivity, but the service life of the catalyst is long; the density of Si-OH is 0.6-1.5 Si-OH/nm2The catalyst prepared by the carrier has high catalytic activity, remarkably improved product selectivity and longer service life. The density of Si-OH is 0.6-1.5 Si-OH/nm2The catalyst prepared by the carrier not only can obviously improve the hydrothermal stability of the catalyst, but also has selectivity under the condition of keeping high activityAnd also improved to some extent.
In a preferred embodiment, the selectivity is between 80 and 100 percent (preferably not less than 90 percent), the formaldehyde conversion rate is between 20 and 40 percent, and the catalyst can be stable for not less than five days.
Process for preparing solid catalyst
The preparation method of the carrier comprises the following steps:
(i) the density of the silica sol and the silicon hydroxyl is 0.6-1.5 Si-OH/nm2Mixing silicon dioxide powder;
(ii) molding;
(iii) drying;
(iv) and (4) roasting.
The preparation method of the solid base catalyst comprises the following steps:
(i) obtaining a solution containing transition metal element precursor salt and alkali metal element precursor salt;
(ii) mixing the precursor salt solution with a carrier;
(iii) roasting;
the precursor salt is preferably at least one of a nitrate and an acetate.
Dispersants may be included in the solution of the precursor salt to facilitate dispersion of the active ingredient, and may be, but are not limited to, PEG, glucose, sorbitol, and the like, and PEG may have a number average molecular weight of 400 to 10000, such as, but not limited to, 500, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500.
Preferably, the alkali metal includes at least one selected from the group consisting of K, Rb and Cs.
The silica sol is not particularly limited, and for example, a commercially available low-sodium alkaline silica sol having a content of 40. + -. 20% is used.
The density of silicon hydroxyl groups is 0.6-1.5 Si-OH/nm2The "silicon hydroxyl group density" of the silica powder is known to those skilled in the art and can be determined by methods conventional in the art. The silica may be selected to have a suitable density of silicon hydroxyl groups, or commercially available hydrophobic silica may be purchased and the surface may be partially covered with silane to remove hydroxyl groupsThe resulting density of silicon hydroxyl groups or other desired parameters are within the scope of the claimed invention.
In order to obtain a stronger catalyst, the catalyst preparation preferably has a drying step after step (ii) and before step (iii). The process conditions for the specific drying can be reasonably determined by the person skilled in the art without having to resort to inventive work, as non-limiting examples:
the drying temperature is preferably 40 to 120 ℃, for example, but not limited to, 45 ℃, 50 ℃, 60 ℃, 70 ℃, 80 ℃, 90 ℃, 100 ℃, 110 ℃, and the like.
The drying time may be 4 to 72 hours. Such as, but not limited to, 5 hours, 8 hours, 10 hours, 15 hours, 20 hours, 24 hours, 30 hours, 36 hours, 42 hours, 48 hours, 54 hours, 60 hours, and the like.
The drying may be carried out under normal pressure or reduced pressure, and is not particularly limited.
The purpose of the calcination is to convert the precursor salt into an oxide, and for this purpose, the skilled person can reasonably select the calcination process conditions without creative efforts.
For example, but not limited to, the baking temperature may be selected to be 400-800 ℃. Such as but not limited to 450 deg.C, 500 deg.C, 550 deg.C, 600 deg.C, 650 deg.C, 700 deg.C, 750 deg.C, etc.
For example, but not limited to, the baking time is selected to be 4 to 15 hours. Such as, but not limited to, 4.5 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, and the like.
In the catalyst obtained by the above catalyst preparation steps (i) to (iii), the transition metal element is in a combined form, and the catalyst has activity for synthesizing methyl acrylate.
The invention is further illustrated by, but is not limited to, the following examples.
Other aspects of the invention will be apparent to those skilled in the art in view of the disclosure herein.
The invention will be further illustrated with reference to the following specific examples. It should be understood that these examples are for illustrative purposes only and are not intended to limit the scope of the present invention. The experimental procedures, in which specific conditions are not specified, in the following examples are generally carried out according to conventional conditions or according to conditions recommended by the manufacturers. Unless otherwise indicated, all parts are parts by weight, all percentages are percentages by weight, all proportions are molar ratios, and all polymer molecular weights are number average molecular weights.
In addition, unless defined or indicated otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In addition, any methods and materials similar or equivalent to those described herein can be used in the methods of the present invention.
To further illustrate the contents, essential features and significant advances of the present invention, the following comparative examples and examples are described in detail below, but not limited to the examples.
Comparative example 1
1. Catalyst preparation
Taking 100 g of cesium nitrate-PEG 2000 mixed aqueous solution (containing cesium nitrate and Cs)212 g calculated as O, containing 2g PEG 2000); with silica microspheres (silica hydroxyl density 3.0 Si-OH/nm)2Microsphere diameter of 2.5mm, BET method average pore diameter of 22nm, BET method pore volume of 1.1ml/g)60 g, standing for 24 hours, vacuum drying at 50 deg.C for 24 hours, and calcining at 500 deg.C in air atmosphere for 5 hours to obtain the final catalyst.
2. Catalyst on-line reduction activation and methyl acrylate synthesis
15 g of catalyst are charged into a fixed bed reactor (internal diameter 16mm, length 1500mm) and N is used2After three times of replacement, the reactor temperature was raised to 200 ℃ and H was introduced2And N2The flow rates are respectively 100mL/min and 1000mL/min, the pressure is 0.08MPa, the reaction is kept for 12 hours, and the activation is finished.
The temperature of the reactor is raised to 300 ℃, the pressure is adjusted to 0.5MPa, and the total mass space velocity of methyl acetate and aldehyde is 5h-1Introducing reaction raw materials (the composition of the reaction raw materials is 5:40:4 by weight, trioxymethylene, methyl acetate and methanol), sampling, adding internal standard toluene and gasThe contents of the components in the reaction mixture were measured by phase chromatography, and the conversion of formaldehyde was calculated to be 30.5% and the selectivity of methyl acrylate was calculated to be 79.3%. After 5 days of continuous operation, the formaldehyde conversion rate decreased to 9.7%.
Comparative example 2
1. Catalyst preparation
At a silicon hydroxyl group density of 2.5Si-OH/nm2Mixing 60 g of silicon dioxide powder with a proper amount of silica sol, forming, drying in vacuum at 50 ℃ for 24 hours, and roasting at 500 ℃ in air atmosphere for 5 hours to obtain a carrier finished product (the diameter is 1-2.5 mm, the average pore diameter of a BET method is 20nm, and the pore volume of the BET method is 1.0 ml/g); taking 100 g of cesium nitrate-PEG 2000 mixed aqueous solution (containing cesium nitrate and Cs)210 g of O and 2g of PEG 2000); mixing with 60 g of the prepared carrier, standing for 24 hours, then vacuum-drying for 24 hours at 50 ℃, and roasting for 5 hours at 500 ℃ in an air atmosphere to obtain a catalyst finished product.
2. Catalyst on-line reduction activation and methyl acrylate synthesis
15 g of catalyst are charged into a fixed bed reactor (internal diameter 16mm, length 1500mm) and N is used2After three times of replacement, the temperature of the reactor is raised to 300 ℃, the pressure is adjusted to 0.5MPa, and the total mass space velocity of methyl acetate and aldehyde is 5h-1Reaction raw materials (the composition of the reaction raw materials is calculated by weight, the ratio of trioxymethylene to methyl acetate to methanol is 5:40:4) are fed in, sampling is carried out, internal standard toluene is added, the content of each component in the reaction mixture is measured by gas chromatography, the conversion rate of formaldehyde is calculated to be 33.3%, and the selectivity of methyl acrylate is calculated to be 88.2%. After 5 days of continuous operation, the formaldehyde conversion dropped to 11.2%.
Comparative example 3
1. Catalyst preparation
Hydrophobicity in terms of silicon hydroxyl group density of 0.2Si-OH/nm2Mixing 60 g of silicon dioxide powder with a proper amount of silica sol, forming, then drying in vacuum at 50 ℃ for 24 hours, and roasting at 500 ℃ in air atmosphere for 5 hours to obtain a finished carrier; taking 100 g of cesium nitrate-PEG 2000 mixed aqueous solution (containing cesium nitrate and Cs)210 g of O and 2g of PEG 2000); mixing with 60 g of the prepared carrier (diameter of 1-2.5 mm, average BET pore diameter of 23nm, and BET pore volume of 1.1ml/g), standing for 24 hr, and heating at 50 deg.CVacuum drying for 24 hr, and calcining at 500 deg.c in air atmosphere for 5 hr to obtain the catalyst product.
2. Catalyst on-line reduction activation and methyl acrylate synthesis
15 g of catalyst are charged into a fixed bed reactor (internal diameter 16mm, length 1500mm) and N is used2After three times of replacement, the temperature of the reactor is raised to 300 ℃, the pressure is adjusted to 0.5MPa, and the total mass space velocity of methyl acetate and aldehyde is 5h-1Reaction raw materials (the composition of the reaction raw materials is calculated by weight, the ratio of trioxymethylene to methyl acetate to methanol is 5:40:4) are fed in, sampling is carried out, internal standard toluene is added, the content of each component in the reaction mixture is measured by gas chromatography, the conversion rate of formaldehyde is calculated to be 10.2%, and the selectivity of methyl acrylate is calculated to be 85.3%. After 5 days of continuous operation, the formaldehyde conversion rate decreased to 8.5%.
[ example 1]
1. Catalyst preparation
At a density of 0.8Si-OH/nm of Si-OH2Mixing 60 g of silicon dioxide powder with silica sol (the content of which is 40 percent), carrying out vacuum drying at 50 ℃ for 24 hours after molding, and roasting at 500 ℃ for 5 hours in air atmosphere to obtain a carrier finished product (the diameter is 1-2.5 mm, the average pore diameter of a BET method is 21nm, and the pore volume of the BET method is 1.0 ml/g); taking 100 g of cesium nitrate-PEG 2000 mixed aqueous solution (containing cesium nitrate and Cs)210 g of O and 2g of PEG 2000); mixing with 60 g of the prepared carrier, standing for 24 hours, then vacuum-drying for 24 hours at 50 ℃, and roasting for 5 hours at 500 ℃ in an air atmosphere to obtain a catalyst finished product.
2. Catalyst on-line reduction activation and methyl acrylate synthesis
15 g of catalyst are charged into a fixed bed reactor (internal diameter 16mm, length 1500mm) and N is used2After three times of replacement, the temperature of the reactor is raised to 300 ℃, the pressure is adjusted to 0.5MPa, and the total mass space velocity of methyl acetate and aldehyde is 5h-1Reaction raw materials (the composition of the reaction raw materials is calculated by weight, the ratio of trioxymethylene to methyl acetate to methanol is 5:40:4) are fed in, sampling is carried out, internal standard toluene is added, the content of each component in the reaction mixture is measured by gas chromatography, the conversion rate of formaldehyde is calculated to be 29.3%, and the selectivity of methyl acrylate is calculated to be 91.7%. After 5 days of continuous operation, the formaldehyde conversion rate decreased to 25.6%.
[ example 2]
1. Catalyst preparation
At a silicon hydroxyl group density of 1.2Si-OH/nm2Mixing 60 g of silicon dioxide powder with silica sol (the content of which is 40 percent), carrying out vacuum drying at 50 ℃ for 24 hours after molding, and roasting at 500 ℃ for 5 hours in air atmosphere to obtain a carrier finished product (the diameter is 1-2.5 mm, the average pore diameter of a BET method is 21nm, and the pore volume of the BET method is 1.0 ml/g); taking 100 g of cesium nitrate-PEG 2000 mixed aqueous solution (containing cesium nitrate and Cs)210 g of O and 2g of PEG 2000); mixing with 60 g of the prepared carrier, standing for 24 hours, then vacuum-drying for 24 hours at 50 ℃, and roasting for 5 hours at 500 ℃ in an air atmosphere to obtain a catalyst finished product.
2. Catalyst on-line reduction activation and methyl acrylate synthesis
15 g of catalyst are charged into a fixed bed reactor (internal diameter 16mm, length 1500mm) and N is used2After three times of replacement, the temperature of the reactor is raised to 300 ℃, the pressure is adjusted to 0.5MPa, and the total mass space velocity of methyl acetate and aldehyde is 5h-1Reaction raw materials (the composition of the reaction raw materials is calculated by weight, the ratio of trioxymethylene to methyl acetate to methanol is 5:40:4) are fed in, sampling is carried out, internal standard toluene is added, the content of each component in the reaction mixture is measured by gas chromatography, the conversion rate of formaldehyde is calculated to be 34.1%, and the selectivity of methyl acrylate is calculated to be 90.3%. After 5 days of continuous operation, the formaldehyde conversion rate decreased to 21.6%.
[ example 3]
1. Catalyst preparation
At a density of 0.6Si-OH/nm of Si-OH2Mixing 60 g of silicon dioxide powder with silica sol (the content of which is 40 percent), carrying out vacuum drying at 50 ℃ for 24 hours after molding, and roasting at 500 ℃ for 5 hours in air atmosphere to obtain a carrier finished product (the diameter is 1-2.5 mm, the average pore diameter of a BET method is 25nm, and the pore volume of the BET method is 0.9 ml/g); taking 100 g of cesium nitrate-PEG 2000 mixed aqueous solution (containing cesium nitrate and Cs)210 g of O and 2g of PEG 2000); mixing with 60 g of the prepared carrier, standing for 24 hours, then vacuum-drying for 24 hours at 50 ℃, and roasting for 5 hours at 500 ℃ in an air atmosphere to obtain a catalyst finished product.
2. Catalyst on-line reduction activation and methyl acrylate synthesis
15 g of catalyst are charged into a fixed bed reactor (internal diameter 16mm, length 1500mm) and N is used2After three times of replacement, the temperature of the reactor is raised to 300 ℃, the pressure is adjusted to 0.5MPa, and the total mass space velocity of methyl acetate and aldehyde is 5h-1Reaction raw materials (the composition of the reaction raw materials is calculated by weight, the ratio of trioxymethylene to methyl acetate to methanol is 5:40:4) are fed in, sampling is carried out, internal standard toluene is added, the content of each component in the reaction mixture is measured by gas chromatography, the conversion rate of formaldehyde is calculated to be 24.1%, and the selectivity of methyl acrylate is calculated to be 92.5%. After 5 days of continuous operation, the formaldehyde conversion rate decreased to 22.2%.
Discussion of results
As shown in comparative examples 1-2, the solid base catalyst prepared by the impregnation method is mainly adopted in the prior art. It can be seen that the silicon spheres for preparation thereof have a silicon hydroxyl group density of 2.5 to 3, which is hydrothermally unstable and shows pore expansion and specific surface loss.
Comparative example 3 shows that when the density of the silicon hydroxyl groups is less than 0.6, the loading of the active component is not facilitated, resulting in a lower catalyst activity.
It can be known from the background art and the comparative example that for the reaction of methyl acetate/methyl propionate and formaldehyde to directly prepare methyl acrylate/methyl methacrylate, the prior art mainly adopts a solid base catalyst loaded with Cs, and the optimal catalytic performance can be achieved only by requiring uniform distribution of base centers and high base strength, so that a strong-alkaline solid base catalyst needs to be prepared. Meanwhile, water is generated in the condensation reaction, and the catalyst is in a high-temperature hydrothermal environment, so that pore expansion of the silicon dioxide carrier is easily caused, the specific surface area is reduced, and the catalytic activity is reduced. In addition, because the high-temperature gas-phase condensation process has high requirements on the Cs catalyst, the existing reported result adopts a high-temperature gas-phase condensation form, the reaction temperature is high, the inactivation is quick, a reaction-regeneration regular switching system is generally considered, and the reaction can be continuously carried out.
The foregoing is merely a preferred embodiment of the invention and is not intended to limit the scope of the invention, which is defined by the claims appended hereto, and any other technical entity or method that is encompassed by the claims as broadly defined herein, or equivalent variations thereof, is contemplated as being encompassed by the claims.
All documents referred to herein are incorporated by reference into this application as if each were individually incorporated by reference. Furthermore, it should be understood that various changes and modifications can be made by those skilled in the art after reading the above disclosure, and equivalents also fall within the scope of the invention as defined by the appended claims.

Claims (10)

1. A method for preparing methyl acrylate by using methyl acetate comprises the step of reacting the methyl acetate with an aldehyde source in the presence of a solid base catalyst to obtain the methyl acrylate, wherein the solid base catalyst comprises the following components in parts by mass:
a) a catalytic amount of an alkali metal oxide; and
b) 50-80 parts of a carrier;
wherein the carrier is silicon hydroxyl with the density of 0.6-1.5 Si-OH/nm2Of (4) silicon dioxide.
2. The method according to claim 1, wherein the carrier of component b) has a density of Si-OH groups of 0.6 to 1.5Si-OH/nm2And a carrier having a BET average pore diameter of 2 to 50nm and a BET pore volume of 0.2 to 2 ml/g.
3. The method of claim 1 or 2, wherein the alkali metal is selected from K, Rb, Cs, or a combination thereof.
4. A process according to any one of claims 1 to 3, wherein the process independently satisfies one or more of the following reaction conditions:
the reaction temperature is preferably 200-450 ℃;
the molar ratio of methyl acetate to formaldehyde in the aldehyde source is preferably 3-100;
the addition amount of the catalyst is preferably 1-10% of the weight of the methyl acetate and the aldehyde source; and/or
The total mass space velocity of the methyl acetate and the aldehyde source is preferably 1-10 h-1。
5. A solid base catalyst for preparing methyl acrylate from methyl acetate is characterized by comprising the following components in parts by mass:
a) a catalytic amount of an alkali metal oxide; and
b) 50-80 parts of a carrier; the carrier is silicon hydroxyl with the density of 0.6-1.5 Si-OH/nm2Of (4) silicon dioxide.
6. The solid base catalyst of claim 5,
the alkali metal is selected from K, Rb, Cs or a combination thereof; and/or
The carrier is silicon hydroxyl with the density of 0.6-1.5 Si-OH/nm2And a carrier having a BET average pore diameter of 2 to 50nm and a BET pore volume of 0.2 to 2 ml/g.
7. The solid base catalyst according to claim 5 or 6, wherein the solid base catalyst is prepared by a process comprising the steps of:
(i) providing a solution containing a catalytic amount of alkali metal element precursor salt and 50-80 parts of a carrier;
the carrier is prepared by the following method:
(m1) providing silica sol and silica hydroxyl group with a density of 0.6-1.5 Si-OH/nm2The silica powder of (4);
(m2) molding the mixture to obtain a molded product;
(m3) drying the molded product to obtain a dried product;
(m4) calcining the dried substance to obtain the carrier of the step (i);
(ii) (ii) mixing the solution of step (i) with a carrier; obtaining a mixture;
(iii) (iii) calcining the mixture of step (ii) to obtain the solid catalyst.
8. Use of a solid catalyst according to claim 5 for catalysing the aldol synthesis reaction of methyl acetate with an aldehyde source to produce said methyl acrylate.
9. A method for preparing the solid catalyst of claim 5, comprising:
(i) providing a solution containing a catalytic amount of alkali metal element precursor salt and 50-80 parts of a carrier; the carrier is silicon hydroxyl with the density of 0.6-1.5 Si-OH/nm2Silicon dioxide of (a);
(ii) (ii) mixing the solution of step (i) with a carrier; obtaining a mixture;
(iii) (iii) calcining the mixture of step (ii) to obtain the solid catalyst.
10. The method for preparing a solid catalyst according to claim 9, further comprising: after step (ii) and before step (iii) there is a drying step.
CN201911021186.8A 2019-10-25 2019-10-25 Method for preparing methyl acrylate from methyl acetate Pending CN112707814A (en)

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Citations (6)

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Publication number Priority date Publication date Assignee Title
EP0265964A2 (en) * 1986-10-31 1988-05-04 Mitsubishi Gas Chemical Company, Inc. Process for preparing alpha,beta-unsaturated aliphatic monocarboxylic acids or esters thereof
US4845070A (en) * 1984-07-18 1989-07-04 Amoco Corporation Catalyst for producing alpha, beta-ethylenically unsaturated aliphatic monocarboxylic acid and method of making said catalyst
WO2006042712A1 (en) * 2004-10-20 2006-04-27 Universität Karlsruhe Method for oxidizing methane to formaldehyde
CN103801280A (en) * 2014-01-26 2014-05-21 上海华谊（集团）公司 Cs-supported silica-based catalyst and preparation method and application thereof
CN106582870A (en) * 2015-10-19 2017-04-26 中国石油化工股份有限公司 Catalyst for synthesis of allyl acetate
WO2019053438A1 (en) * 2017-09-13 2019-03-21 Lucite International Uk Limited A catalyst and a process for the production of ethylenically unsaturated carboxylic acids or esters

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4845070A (en) * 1984-07-18 1989-07-04 Amoco Corporation Catalyst for producing alpha, beta-ethylenically unsaturated aliphatic monocarboxylic acid and method of making said catalyst
EP0265964A2 (en) * 1986-10-31 1988-05-04 Mitsubishi Gas Chemical Company, Inc. Process for preparing alpha,beta-unsaturated aliphatic monocarboxylic acids or esters thereof
WO2006042712A1 (en) * 2004-10-20 2006-04-27 Universität Karlsruhe Method for oxidizing methane to formaldehyde
CN103801280A (en) * 2014-01-26 2014-05-21 上海华谊（集团）公司 Cs-supported silica-based catalyst and preparation method and application thereof
CN106582870A (en) * 2015-10-19 2017-04-26 中国石油化工股份有限公司 Catalyst for synthesis of allyl acetate
WO2019053438A1 (en) * 2017-09-13 2019-03-21 Lucite International Uk Limited A catalyst and a process for the production of ethylenically unsaturated carboxylic acids or esters

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