Solid base catalyst, method for preparing the same, and method for synthesizing methyl methacrylate

Abstract

The application discloses a methyl methacrylate synthesis method, which is synthesized by using methyl propionate and an aldehyde source as raw materials under the action of a solid alkali catalyst. The solid alkali catalyst comprises a silicon dioxide carrier which is surface-modified by a modifier, and a metal active component loaded on the silicon dioxide carrier. The modifier is at least one of 3-aminopropyltrimethoxysilane, diethylenetriamine propyl trimethoxysilane and gamma-glycidyl propyl trimethoxysilane.

Description

TECHNICAL FIELD

[0001] The present application relates to a preparation of solid base catalyst and a synthesis method of methyl methacrylate. BACKGROUND

[0002] Methyl acrylate is an important fine chemical raw material with wide application, mainly used in organic synthesis intermediates and polymer monomers. The polymers prepared by using methyl acrylate as monomer are widely used in coating, textile, leather making, adhesive and other industries. The preparation methods of acrylic acid and its esters mainly include propylene oxidation method, propylene nitrile hydrolysis method, ethylene ketone method, propylene These methods have the disadvantages of serious pollution, high energy consumption, low product yield, etc. Therefore, it is of great significance to develop a new green and efficient production process.

[0003] In view of this, on the basis of the mature α-MMA process proposed by Lucite company, a new catalyst is used to synthesize methyl acrylate by using methyl acetate and formaldehyde as raw materials. The catalyst reaction-regeneration fluidized bed coupling system is adopted to solve the problems of short single-pass life of catalyst, easy carbon deposition and frequent regeneration. At present, the single-pass conversion rate of methyl acetate is generally 15%, the selectivity of methyl acrylate is generally 85%, and the yield of methyl acrylate is generally 13.5%. However, industrialization has not been realized at present, the main key is that the comprehensive improvement of yield, selectivity and catalyst stability cannot be achieved. In recent years, many units at home and abroad have further studied the synthesis of methyl acrylate from methyl acetate and formaldehyde.

[0004] Chinese patent

CN104703696A

[0005] Chinese patent

CN101575290A

[0006] Chinese patent

CN103752305A

[0007] The technical problem to be solved by the present application is to improve the yield of methyl methacrylate, while avoiding the reduction of methyl methacrylate generated in the first reactor into methyl isobutyrate in the second reactor, thereby causing waste of formaldehyde and reducing the yield of methyl methacrylate.

[0008] The purpose of the present application is achieved by the following technical solutions.

[0009] In a first aspect, the present application provides a method for synthesizing methyl methacrylate, which is catalytically synthesized from methyl propionate and an aldehyde source under the action of a solid base catalyst, the solid base catalyst includes a silica carrier that is surface-modified with a modifier, and a metal active component supported thereon, the modifier is at least one of 3-aminopropyltrimethoxysilane, diethylenetriaminepropyltrimethoxysilane, and γ-glycidylpropyltrimethoxysilane, and the percentage of the modifier in the mass of the carrier is 1-20%.

[0010] In some embodiments, the metal active component includes a cesium active component.

[0011] In some embodiments, the precursor of the cesium active component is cesium carbonate, cesium nitrate, and cesium acetate.

[0012] In some embodiments, the mass percentage of elemental cesium in the catalyst, i.e., the loading of cesium in the catalyst, is 0.5%-20%.

[0013] According to the method for synthesizing methyl methacrylate of the present application, a first reactor and a second reactor are used in series for the catalytic synthesis of methyl methacrylate, and a solid base catalyst is used in both the first reactor and the second reactor to catalyze the synthesis of methyl methacrylate.

[0014] In some embodiments, nitrogen gas is introduced into both the first reactor and the second reactor, and the flow rate of nitrogen gas in the second reactor is greater than that in the first reactor.

[0015] In some embodiments, the reaction temperature of the first reactor is 300-400℃.

[0016] In some embodiments, the reaction temperature of the first reactor is 300-400℃.

[0017] In some embodiments, the liquid phase volume flow rate in the first reactor is 0.01-0.2 ml / min.

[0018] In some embodiments, the flow rate of nitrogen introduced into the first reactor is 0-150 ml / min.

[0019] In some embodiments, the reaction temperature of the second reactor is 300-400℃.

[0020] In some embodiments, the reaction pressure of the second reactor is 0.1-0.5 MPa.

[0021] In some embodiments, the liquid phase volume flow rate in the second reactor is 0.01-0.2 ml / min.

[0022] In some embodiments, the flow rate of nitrogen introduced into the second reactor is 0-150 ml / min.

[0023] According to the method for synthesizing methyl methacrylate of the present application, the specific surface area of the silica carrier by BET method is 50-500 m 2 / g.

[0024] In some embodiments, the pore size of the silica carrier by BET method is 6-30 nm.

[0025] In some embodiments, the porosity of the silica carrier by BET method is 0.6-1 ml / g.

[0026] According to the method for synthesizing methyl methacrylate of the present application, the solid base catalyst is pretreated by high-temperature calcination, and the temperature is reduced to the reaction temperature of 250-400℃.

[0027] According to the method for synthesizing methyl methacrylate of the present application, the surface modifier of the solid base catalyst is 3-aminopropyltrimethoxysilane, diethylenetriamine propyl trimethoxysilane and γ-glycidyl propyl trimethoxysilane, preferably 3-aminopropyltrimethoxysilane.

[0028] In some embodiments, methyl acetate is first introduced through the catalyst for 0-2 h, and then trioxane and methyl acetate are introduced simultaneously.

[0029] In a second aspect, the present application provides a solid base catalyst for synthesizing methyl methacrylate, the solid base catalyst comprising a silica carrier surface-modified with a modifier, and a metal active component supported thereon, the modifier being at least one of 3-aminopropyltrimethoxysilane, diethylenetriaminepropyltrimethoxysilane and γ-glycidoxypropyltrimethoxysilane, the modifier accounting for 1-20% of the mass of the carrier, and the metal active component comprising a cesium active component, the mass percentage of elemental cesium in the catalyst being 0.5-20%.

[0030] In some embodiments, the silica carrier has a specific surface area of 50-500 m 2 / g.

[0031] In some embodiments, the silica carrier has a pore size of 6-30 nm.

[0032] In some embodiments, the silica carrier has a porosity of 0.6-1 ml / g.

[0033] In a third aspect, the present application provides a synthesis method of a solid base catalyst, comprising dispersing 0.5-10 g of a silica carrier into a toluene solution, introducing 0-15 g of 3-aminopropyltrimethoxysilane, and treating at a certain temperature.

[0034] In some embodiments, the carrier treatment temperature is 0-300℃.

[0035] In some embodiments, the treatment is a reflux treatment.

[0036] In some embodiments, the treatment time is 0-12 h.

[0037] In some embodiments, after the carrier is treated in the reflux liquid of 3-aminopropyltrimethoxysilane, the carrier is cleaned with ethanol multiple times to remove residues on the surface of the carrier.

[0038] Compared with the prior art, the present application has the following advantages:

[0039] (1) The basic active center of the cesium-based solid base catalyst used in the prior art can destroy the Si-O-Si structure in the silica carrier, and the synthesis method of methyl methacrylate provided by the present application can effectively avoid the destruction of the basic active center to the Si-O-Si structure by grafting 3-aminopropyltrimethoxysilane on the surface of the silicon hydroxyl, thereby improving the stability of the catalyst.

[0040] (2) The application adopts a specific carrier fixed catalyst to overcome the poor stability of the catalyst in the preparation process of methyl methacrylate; the synthesis method can be operated stably for a long time, so that the synthesis of methyl acrylate from methyl acetate and formaldehyde as raw materials can be realized industrialization. DETAILED DESCRIPTION

[0041] In order to make the application more easily understood, the application will be described in detail below with reference to the embodiments, which are only illustrative and do not limit the scope of application of the application.

[0042] Unless otherwise specified, the various raw materials of the application can be obtained by market or prepared according to the conventional method in the art. Unless otherwise defined or specified, all professional and scientific terms used herein have the same meaning as familiar to those skilled in the art. In addition, any method and material similar or equivalent to the described content can be applied to the method of the application.

[0043] As used herein, when the formaldehyde exists in the form of trioxane, the conversion rate and selectivity of the methyl propionate are defined as follows:

[0044] The average pore size of the silica carrier is 2-20 nm.

[0045]

[0046]

[0047] Comparative Example 1

[0048] 1. Catalyst preparation

[0049] 10 g of silica carrier was weighed, 10 wt% cesium carbonate was used as the impregnation liquid, the catalyst was impregnated by the equal volume method, the drying temperature was 110°C, and the calcination was carried out at 500°C for 6 h. The cesium loading of the obtained catalyst was 10 wt%.

[0050] 2. On-line reduction activation of the catalyst and synthesis of methyl acrylate

[0051] The solid base catalyst Cs / SiO2 catalyst was added in the first reactor and the second reactor, the nitrogen flow rate in the first reactor was 60 ml / min, the nitrogen flow rate in the second reactor was 110 ml / min, the reactor temperature was 370°C, the pressure was 0.2 MPa, and the composition of the reaction raw material was trioxane:methyl propionate:methanol = 5:40:4 by weight. Sampling was carried out, the monomer formaldehyde was supplemented at the inlet of the second reactor, the internal standard toluene was added, the content of each component in the reaction mixture was measured by gas chromatography, and the conversion rate of methyl propionate was calculated to be 19.5%, and the yield of MMA was 14%. After continuous operation for 10 days, the conversion rate of methyl propionate decreased to 11%, and the yield was 8.5%.

[0052] Example 1

[0053] 1. Catalyst preparation

[0054] Take 20 grams of silica microspheres (microsphere diameter 2.5 mm, average pore size by BET method 15 nm) and disperse them in 70 g of toluene solution, then add 2 g of 3- aminopropyltrimethoxysilane, and set the temperature to 110 degrees Celsius for reflux treatment. The treated carrier is washed with ethanol several times to remove the surface residual liquid, and the carrier is dried at 110 degrees Celsius for standby, marked as M-SiO2. Take 10 g of M-SiO2 carrier, use 10 wt% cesium carbonate as the impregnating liquid, and impregnate the catalyst by the equal volume method, dry at 110 degrees Celsius, and calcine at 500 degrees Celsius for 6 hours to obtain a solid base catalyst Cs / SiO2. The cesium loading of the obtained catalyst is 10 wt%.

[0055] 2. Catalyst online reduction activation and methyl acrylate synthesis

[0056] Add solid base catalyst Cs / SiO2 catalyst to both the first reactor and the second reactor, and the catalyst loading is 10 mL in each reactor. The nitrogen flow rate in the first reactor is 60 ml / min, and the nitrogen flow rate in the second reactor is 110 ml / min. The reactor temperature is 370 degrees Celsius, and the pressure is 0.2 MPa. The composition of the reaction raw material is 5:40:4 by weight of trioxane: methyl propionate: methanol. Take samples, supplement monomer formaldehyde at the inlet of the second reactor, add internal standard toluene, and measure the content of each component in the reaction mixture by gas chromatography to calculate the conversion rate of methyl propionate as 23% and the yield as 18.5%. After continuous operation for 10 days, the conversion rate of methyl propionate is 21.5%, and the yield is 17.5%.

[0057] Example 2

[0058] 1. Catalyst preparation

[0059] Take 20 grams of silica microspheres (microsphere diameter 2.5 mm, average pore size by BET method 15 nm) and disperse them in 70 g of toluene solution, then add 2 g of 3- aminopropyltrimethoxysilane, and set the temperature to 70 degrees Celsius for reflux treatment. The treated carrier is washed with ethanol several times to remove the surface residual liquid, and the carrier is dried at 110 degrees Celsius for standby, marked as M-SiO2. Take 10 g of M-SiO2 carrier, use 10 wt% cesium carbonate as the impregnating liquid, and impregnate the catalyst by the equal volume method, dry at 110 degrees Celsius, and calcine at 500 degrees Celsius for 6 hours to obtain a solid base catalyst Cs / SiO2. The cesium loading of the obtained catalyst is 10 wt%.

[0060] 2. Catalyst online reduction activation and methyl acrylate synthesis

[0061] The solid base catalyst Cs / SiO2 catalyst was added to both the first reactor and the second reactor, and the catalyst loading was 10 mL. The nitrogen flow rate was 60 ml / min in the first reactor and 110 ml / min in the second reactor. The reactor temperature was 370°C, and the pressure was 0.2 MPa. The composition of the reaction raw material was 5:40:4 by weight of trioxane: methyl propionate: methanol. Sampling was performed, monomer formaldehyde was supplemented at the inlet of the second reactor, internal standard toluene was added, and gas chromatography was used to measure the content of each component in the reaction mixture. The conversion rate of methyl propionate was calculated to be 22.6%, and the yield was 17.9%. After continuous operation for 10 days, the conversion rate of methyl propionate was 16%, and the yield was 12.5%.

[0062] Example 3

[0063] 1. Catalyst preparation

[0064] 20 grams of silica microspheres (microsphere diameter 2.5 mm, BET method average pore size 15 nm) were dispersed in 70 g of toluene solution, then 2 g of 3-aminopropyltrimethoxysilane was added, and the temperature was set to 150 degrees Celsius for reflux treatment. The treated carrier was washed with ethanol several times to remove the surface residual liquid, and the carrier was dried at 110 degrees Celsius for standby, marked as M-SiO2. 10 g of M-SiO2 carrier was weighed, and cesium carbonate was used as the impregnating liquid, and the catalyst was impregnated by the equal volume method. The drying temperature was 110°C, and the catalyst was calcined at 500°C for 6h to obtain a solid base catalyst Cs / SiO2 with a cesium loading of 10wt%.

[0065] 2. Online reduction activation of the catalyst and synthesis of methyl acrylate

[0066] The solid base catalyst Cs / SiO2 catalyst was added to both the first reactor and the second reactor, and the catalyst loading was 10 mL. The nitrogen flow rate was 60 ml / min in the first reactor and 110 ml / min in the second reactor. The reactor temperature was 370°C, and the pressure was 0.2 MPa. The composition of the reaction raw material was 5:40:4 by weight of trioxane: methyl propionate: methanol. Sampling was performed, monomer formaldehyde was supplemented at the inlet of the second reactor, internal standard toluene was added, and gas chromatography was used to measure the content of each component in the reaction mixture. The conversion rate of methyl propionate was calculated to be 22.6%, and the yield was 17.9%. After continuous operation for 10 days, the conversion rate of methyl propionate was 16%, and the yield was 12.5%.

[0067] Example 4

[0068] 1. Catalyst preparation

[0069] Take 52 grams of silica microspheres (microspheres diameter 2.5 mm, average pore size 15 nm by BET method) dispersed in 70 g of toluene solution, then add 2 g of diethylenetriamine propyl trimethoxysilane, set the temperature to 60 degrees Celsius for reflux treatment. The treated carrier is washed with ethanol several times to remove the surface residual liquid, and the carrier is dried at 110 for standby, marked as M-SiO2. Take 10 g of M-SiO2 carrier, use cesium carbonate as the impregnating liquid, and impregnate the catalyst by equal volume method, dry at 110°C, and calcine at 500°C for 6h to obtain a solid base catalyst Cs / SiO2 with a cesium loading of 10wt%.

[0070] 2. Catalyst online reduction activation and methyl acrylate synthesis

[0071] Solid base catalyst Cs / SiO2 catalyst is added to both the first reactor and the second reactor, and the catalyst loading is 10 mL. The nitrogen flow rate in the first reactor is 60 ml / min, and the nitrogen flow rate in the second reactor is 110 ml / min. The reactor temperature is 370°C, and the pressure is 0.2 MPa. The composition of the reaction raw material is 5:40:4 by weight of trioxane: methyl propionate: methanol. Sampling, adding internal standard toluene to the inlet of the second reactor, and measuring the content of each component in the reaction mixture by gas chromatography, the conversion rate of methyl propionate is 18.5%, and the yield is 13.2%. After continuous operation for 10 days, the conversion rate of methyl propionate is 15.8%, and the yield is 11.6%.

[0072] Example 5

[0073] 1. Catalyst preparation

[0074] Take 20 grams of silica microspheres (microspheres diameter 2.5 mm, average pore size 15 nm by BET method) dispersed in 70 g of toluene solution, then add 2 g of γ-glycidyl propyl trimethoxysilane, set the temperature to 60 degrees Celsius for reflux treatment. The treated carrier is washed with ethanol several times to remove the surface residual liquid, and the carrier is dried at 110 for standby, marked as M-SiO2. Take 10 g of M-SiO2 carrier, use cesium carbonate as the impregnating liquid, and impregnate the catalyst by equal volume method, dry at 110°C, and calcine at 500°C for 6h to obtain a solid base catalyst Cs / SiO2 with a cesium loading of 10wt%.

[0075] 2. Catalyst online reduction activation and methyl acrylate synthesis

[0076] The solid base catalyst Cs / SiO2 catalyst was added in the first reactor and the second reactor, the catalyst loading was 10 mL, the nitrogen flow rate of the first reactor was 60 ml / min, the nitrogen flow rate of the second reactor was 110 ml / min, the reactor temperature was 370℃, the pressure was 0.2 MPa, the composition of the reaction raw material was 5:40:4 of trioxane:methyl propionate:methanol by weight, sampling, the monomer formaldehyde was supplemented at the inlet of the second reactor, the internal standard toluene was added, the content of each component in the reaction mixture was measured by gas chromatography, and it was calculated that the conversion rate of methyl propionate was 16.5% and the yield was 12.9%. After continuous operation for 10 days, the conversion rate of methyl propionate was 12.8% and the yield was 9.7%.

[0077] The above only describes the preferred examples of the present application. It should be noted that for those skilled in the art, under the technical inspiration provided by the present application, other equivalent modifications and improvements can also be made as the common knowledge in the art, and should also be considered as the protection scope of the present application.

Claims

1. A solid base catalyst for synthesizing methyl methacrylate, characterized by, The solid base catalyst comprises a silica carrier which is surface-modified by a modifier, and a metal active component supported thereon, the modifier being at least one of 3-aminopropyltrimethoxysilane and diethylenetriaminepropyltrimethoxysilane, the mass percentage of the modifier in the carrier being 1-20%, and the metal active component comprising a cesium active component, the mass percentage of elemental cesium in the catalyst being 0.5-20%. In the synthesis method of the solid base catalyst, the carrier treatment temperature is 70-150°C.

2. The solid base catalyst according to claim 1, characterized in that, the specific surface area of the silica support by the BET method is 50-500 m 2 / g; and / or the pore size of the silica support by the BET method is 6-30 nm; and / or the porosity of the silica support by the BET method is 0.6-1 ml / g.

3. A method for synthesizing the solid base catalyst according to any one of claims 1 to 2, characterized in that, The method comprises dispersing 0.5-10 g of a silica carrier in a toluene solution, introducing 2-15 g of at least one of 3-aminopropyltrimethoxysilane and diethylenetriaminepropyltrimethoxysilane, and heating treatment, the carrier treatment temperature being 70-150°C.

4. The method of synthesis of solid base catalyst according to claim 3, characterized in that, 3-aminopropyltrimethoxysilane is introduced.

5. The method of synthesis of solid base catalyst according to claim 3, wherein, The carrier is treated by reflux.

6. The method of synthesis of solid base catalyst according to any one of claims 3-5, characterized in that, The metal active component of the solid base catalyst comprises a cesium active component, the precursor of the cesium active component being at least one of cesium carbonate, cesium nitrate and cesium acetate, and the mass percentage of elemental cesium being 0.5-20%.

7. A method for the synthesis of methyl methacrylate, characterized in that, The solid base catalyst is used in the catalytic synthesis of methyl propionate and an aldehyde source.

8. The method of claim 7, wherein the methyl methacrylate is synthesized by the reaction of methyl acrylate and formaldehyde in the presence of a catalyst. The catalytic synthesis of methyl methacrylate is carried out by using a first reactor and a second reactor in series, and the synthesis of methyl methacrylate is catalyzed by using the solid base catalyst in the first reactor and the second reactor.

9. The method of claim 8, wherein the methyl methacrylate is synthesized by the reaction of methyl acrylate and formaldehyde in the presence of a catalyst. Nitrogen gas is introduced into the first reactor and the second reactor, and the flow rate of the nitrogen gas in the second reactor is greater than that in the first reactor.

10. The method of synthesis of methyl methacrylate according to claim 9, characterized in that, The reaction temperature of the first reactor is 300-400°C, and / or the reaction pressure of the first reactor is 0.1-0.5 MPa, and / or the liquid phase volume flow rate in the first reactor is 0.01-0.2 ml / min, and / or the flow rate of the nitrogen gas introduced into the first reactor is 0-150 ml / min.

11. The process for the synthesis of methyl methacrylate according to any one of claims 7 to 10, characterized in that, The reaction temperature of the second reactor is 300-400°C, and / or the reaction pressure of the second reactor is 0.1-0.5 MPa, and / or the liquid phase volume flow rate in the second reactor is 0.01-0.2 ml / min, and / or the flow rate of the nitrogen gas introduced into the second reactor is 0-150 ml / min.

12. The process for the synthesis of methyl methacrylate according to any one of claims 7 to 10, characterized in that, Before the catalytic synthesis, the solid base catalyst is pretreated by high-temperature calcination, and the temperature is reduced to the reaction temperature of 250-400°C; and / or the catalyst is pretreated by methyl propionate for 0-2 h, and then the catalytic synthesis is carried out by simultaneously introducing trioxane and methyl propionate.

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