阅读说明：本技术 一种以醋酸甲酯为原料制备甲基丙烯酸甲酯的方法 (Method for preparing methyl methacrylate by taking methyl acetate as raw material ) 是由 赵国强 王光永 熊国焱 谌晓玲 王莉 于 2020-11-25 设计创作，主要内容包括：本发明提供一种以醋酸甲酯为原料制备甲基丙烯酸甲酯的方法,属于醋酸甲酯应用领域。所述方法以醋酸甲酯和浓甲醛为原料,经两步羟醛缩合,加氢和分离纯化得到甲基丙烯酸甲酯,具体包括：醋酸甲酯和浓甲醛羟醛缩合生成丙烯酸甲酯,经醋酸甲酯回收单元和丙烯酸甲酯回收单元分离后加氢得到丙酸甲酯,丙酸甲酯与浓甲醛再次进行羟醛缩合反应,产物与丙烯酸甲酯回收单元塔底物流混合后进入甲醛回收单元,甲醛回收单元塔顶有机相物流依次经脱水单元,丙酸甲酯回收单元,精制单元分离纯化得到甲基丙烯酸甲酯(MMA)产品。醋酸甲酯来源丰富且廉价,以其作为原料生产甲基丙烯酸甲酯,既拓宽了醋酸甲酯的下游应用,又提高了产品的附加值。(The invention provides a method for preparing methyl methacrylate by taking methyl acetate as a raw material, belonging to the field of methyl acetate application. The method takes methyl acetate and concentrated formaldehyde as raw materials, and methyl methacrylate is obtained by two-step aldol condensation, hydrogenation, separation and purification, and specifically comprises the following steps: methyl acetate and concentrated formaldehyde are subjected to aldol condensation to generate methyl acrylate, methyl propionate is obtained by hydrogenation after being separated by a methyl acetate recovery unit and a methyl acrylate recovery unit, the methyl propionate and the concentrated formaldehyde are subjected to aldol condensation reaction again, the product is mixed with the bottom material flow of the methyl acrylate recovery unit and then enters a formaldehyde recovery unit, and the organic phase flow at the top of the formaldehyde recovery unit sequentially passes through a dehydration unit, a methyl propionate recovery unit and a refining unit to be separated and purified to obtain a Methyl Methacrylate (MMA) product. The methyl acetate is rich in source and low in price, and is used as a raw material to produce methyl methacrylate, so that downstream application of the methyl acetate is widened, and the additional value of the product is improved.)

1. A method for preparing methyl methacrylate by taking methyl acetate as a raw material is characterized in that methyl acetate and concentrated formaldehyde are taken as raw materials, and methyl methacrylate is obtained by two-step aldol condensation, hydrogenation, separation and purification, and specifically comprises the following steps:

methyl acetate and concentrated formaldehyde are subjected to aldol condensation to generate methyl acrylate, methyl propionate is obtained by hydrogenation after being separated by a methyl acetate recovery unit and a methyl acrylate recovery unit, the methyl propionate and the concentrated formaldehyde are subjected to aldol condensation reaction again, the product is mixed with the bottom material flow of the methyl acrylate recovery unit and then enters a formaldehyde recovery unit, and the organic phase flow at the top of the formaldehyde recovery unit sequentially passes through a dehydration unit, a methyl propionate recovery unit and a refining unit to be separated and purified to obtain a Methyl Methacrylate (MMA) product.

2. The method for preparing methyl methacrylate by using methyl acetate as a raw material according to claim 1, wherein the azeotrope of methyl acetate and methanol is recycled as a raw material for aldol condensation reaction at the tower top of the methyl acetate recovery unit, and the material at the tower bottom enters the methyl acrylate recovery unit.

3. The method for preparing methyl methacrylate by using methyl acetate as a raw material according to claim 1, wherein the formaldehyde, the water, the acid and the residual methanol at the bottom of the methyl acrylate recovery unit enter the formaldehyde recovery unit, and the methyl acrylate at the top of the methyl acrylate enters a hydrogenation reactor for hydrogenation reaction to obtain the methyl propionate.

4. The process for producing methyl methacrylate as claimed in claim 1, wherein the formaldehyde recovery unit is an extraction column, brine is fed as an extractant from the upper part of the extraction column, and methyl propionate is mixed with the product of the aldol condensation reaction of concentrated formaldehyde and the bottom material of the methyl acrylate recovery unit and fed into the extraction column from the lower part of the formaldehyde recovery unit, and the two streams are operated in countercurrent to produce an organic phase stream and an aqueous phase stream, thereby reducing the concentration of formaldehyde and methanol in the organic phase stream.

5. The method for preparing methyl methacrylate by using methyl acetate as a raw material according to claim 1, wherein the aqueous phase stream at the bottom of the formaldehyde recovery unit enters an ester recovery unit, the light components at the top of the ester recovery unit return to the lower part of the formaldehyde recovery unit, and the heavy components at the bottom of the ester recovery unit enter a brine recovery unit; the materials at the top of the brine recovery unit and the dilute formaldehyde are mixed and then enter a formaldehyde concentration unit, the materials at the bottom of the brine recovery unit are discharged as wastewater, and the rest materials return to the upper part of the formaldehyde recovery unit to be used as an extracting agent.

6. The method for preparing methyl methacrylate by using methyl acetate as a raw material according to claim 1, wherein water and methyl propionate which are extracted from the top of the dehydration unit enter an oil-water separation unit, a lower water phase returns to the upper part of a formaldehyde recovery unit as an extracting agent after delamination, and an upper oil phase returns to the top of the dehydration unit; and the bottom material flow of the dehydration unit enters a methyl propionate recovery unit, methyl propionate extracted from the top of the methyl propionate recovery unit is used as a raw material to return to carry out aldol condensation reaction, and the heavy components at the bottom of the methyl propionate recovery unit enter a refining unit and are extracted from a side line to obtain a Methyl Methacrylate (MMA) product.

7. The method for preparing methyl methacrylate from methyl acetate as a raw material according to claim 1, wherein the aldol condensation reaction occurs in a condensation reactor, and the condensation reactor is one or more of a fixed bed reactor, a fluidized bed reactor and a tank reactor.

8. The method for preparing methyl methacrylate by using methyl acetate as a raw material according to claim 1, wherein the reaction temperature of the aldol condensation reaction between methyl acetate and concentrated formaldehyde is 200-500 ℃, preferably 300-400 ℃; the reaction pressure is 1.0 to 10.0bar, preferably 1.0 to 5.0 bar; the hourly space velocity of the reaction liquid is 0.5-5h^-1Preferably 1.0 to 3.0h^-1(ii) a The reaction temperature of the aldol condensation reaction of the methyl propionate and the concentrated formaldehyde is 200-500 ℃, preferably 300-400 ℃; the reaction pressure is 1.0 to 10.0bar, preferably 1.0 to 5.0 bar; the hourly space velocity of the reaction liquid is 0.5-5h^-1Preferably 1.0 to 3.0h^-1。

9. The method for preparing methyl methacrylate by using methyl acetate as a raw material according to claim 1, wherein the reaction temperature of the hydrogenation reaction is 50-150 ℃, preferably 60-100 ℃; the reaction pressure is 0.1-5.0MPa, preferably 1.0-3.0 MPa; the gas-liquid ratio is 10-100:1, preferably 30-70: 1.

10. The method for preparing methyl methacrylate from methyl acetate as a raw material according to claim 1, wherein the concentration of the concentrated formaldehyde is 80-100%, and the concentrated formaldehyde is obtained by decomposing paraformaldehyde or by concentrating 10-60% of dilute formaldehyde.

Technical Field

The invention belongs to the technical field of methyl acetate application, and particularly relates to a method for preparing methyl methacrylate by taking methyl acetate as a raw material.

Background

Methyl acetate is a byproduct of polyvinyl alcohol (PVA) production process, and about 1.5 tons of methyl acetate is generated every 1 ton of PVA. Although methyl acetate is also a chemical raw material, the demand amount is small, and the methyl acetate is not generally sold as a byproduct, most of the methyl acetate in the industry at present is hydrolyzed into acetic acid and methanol, and the acetic acid and the methanol are obtained after separation and purification, or the methyl acetate is sold as a product, or is reused in other processes or self-use, and the added value of the product is low.

Methyl Methacrylate (MMA) is used as an important organic chemical raw material, the development of the downstream terminal industry is rapid in recent years, the speed is increased by about 20 percent in the examples and the downstream of PMMA particles, the MMA market is pretty, and the price is continuously increased. At present, the industrial production process of the methyl methacrylate in China mainly adopts an acetone-cyanohydrin route (ACH) and a C4 route, and the two routes are both made in China, but the investment of the two methods is large, and the cost for producing the methyl methacrylate is high. The technology for synthesizing MMA by aldol condensation, namely the technology for alpha-MMA, does not need an acid recovery device, does not generate a highly toxic intermediate product, has mild process conditions, is safe and environment-friendly, can save investment and production cost by 40 percent compared with the traditional route, and is monopolized by British (Mitsubishi chemistry).

Disclosure of Invention

The invention aims to provide a method for preparing methyl methacrylate by taking methyl acetate as a raw material, which widens the downstream application of methyl acetate, improves the added value of products, increases the economic benefit of enterprises and provides a new way for a diversification mode of enterprise products.

The purpose of the invention is realized by the following technical scheme:

a method for preparing methyl methacrylate by taking methyl acetate as a raw material comprises the following steps of performing two-step aldol condensation, hydrogenation, separation and purification on the raw material methyl acetate and concentrated formaldehyde to obtain the methyl methacrylate, and specifically comprises the following steps:

methyl acetate and concentrated formaldehyde are subjected to aldol condensation to generate methyl acrylate, methyl propionate is obtained by hydrogenation after being separated by a methyl acetate recovery unit and a methyl acrylate recovery unit, the methyl propionate and the concentrated formaldehyde are subjected to aldol condensation reaction again, the product is mixed with the bottom material flow of the methyl acrylate recovery unit and then enters a formaldehyde recovery unit, and the organic phase flow at the top of the formaldehyde recovery unit sequentially passes through a dehydration unit, a methyl propionate recovery unit and a refining unit to be separated and purified to obtain a Methyl Methacrylate (MMA) product.

Furthermore, the top of the methyl acetate recovery unit is an azeotrope of methyl acetate and methanol which is used as a raw material for aldol condensation reaction to be recycled, and the bottom material of the methyl acetate recovery unit enters the methyl acrylate recovery unit.

Further, the formaldehyde, water, acid and residual methanol at the bottom of the methyl acrylate recovery unit enter a formaldehyde recovery unit, and the methyl acrylate at the top of the tower enters a hydrogenation reactor for hydrogenation reaction to obtain methyl propionate.

Further, the formaldehyde recovery unit is an extraction tower, brine enters from the upper part of the extraction tower as an extracting agent, methyl propionate and a product of concentrated formaldehyde aldol condensation reaction are mixed with a tower bottom material of the methyl acrylate recovery unit and then enter the tower from the lower part of the formaldehyde recovery unit, and the two material flows form countercurrent operation to generate an organic phase material flow and an aqueous phase material flow, so that the concentration of formaldehyde and methanol in the organic phase material flow is reduced.

Further, the water phase material flow at the bottom of the formaldehyde recovery unit enters an ester recovery unit, light components at the top of the ester recovery unit return to the lower part of the formaldehyde recovery unit, and heavy components at the bottom of the ester recovery unit enter a brine recovery unit; the materials at the top of the brine recovery unit and the dilute formaldehyde are mixed and then enter a formaldehyde concentration unit, the materials at the bottom of the brine recovery unit are discharged as wastewater, and the rest materials return to the upper part of the formaldehyde recovery unit to be used as an extracting agent.

Further, water and methyl propionate produced from the top of the dehydration unit enter an oil-water separation unit, a lower water phase returns to the upper part of the formaldehyde recovery unit as an extracting agent after layering, and an upper oil phase returns to the top of the dehydration unit; and the bottom material flow of the dehydration unit enters a methyl propionate recovery unit, methyl propionate extracted from the top of the methyl propionate recovery unit is used as a raw material to return to carry out aldol condensation reaction, and the heavy components at the bottom of the methyl propionate recovery unit enter a refining unit and are extracted from a side line to obtain a Methyl Methacrylate (MMA) product.

Further, the aldol condensation reaction occurs in a condensation reactor, and the condensation reactor is one or more of a fixed bed reactor, a fluidized bed reactor and a kettle type reactor.

Further, the reaction temperature of the aldol condensation reaction of the methyl acetate and the concentrated formaldehyde is 200-500 ℃, preferably 300-400 ℃; the reaction pressure is 1.0 to 10.0bar, preferably 1.0 to 5.0 bar; the hourly space velocity of the reaction liquid is 0.5-5h^-1Preferably 1.0 to 3.0h^-1。

Further, the reaction temperature of the aldol condensation reaction of the methyl propionate and the concentrated formaldehyde is 200-500 ℃, preferably 300-400 ℃; the reaction pressure is 1.0 to 10.0bar, preferably 1.0 to 5.0 bar; the hourly space velocity of the reaction liquid is 0.5-5h^-1Preferably 1.0 to 3.0h^-1。

Further, the reaction temperature of the hydrogenation reaction is 50-150 ℃, preferably 60-100 ℃; the reaction pressure is 0.1-5.0MPa, preferably 1.0-3.0 MPa; the gas-liquid ratio is 10-100:1, preferably 30-70: 1.

Further, the concentration of the concentrated formaldehyde is 80-100%, and the concentrated formaldehyde is obtained by decomposing paraformaldehyde or by concentrating 10-60% of dilute formaldehyde.

Compared with the prior art, the invention has the following beneficial effects:

the invention provides a method for preparing methyl methacrylate by taking methyl acetate as a raw material, which is particularly suitable for preparing methyl methacrylate with rich and cheap methyl acetate sources, and taking the methyl acetate as the raw material to produce the methyl methacrylate with higher added value and wider application, thereby widening the downstream application of the methyl acetate, increasing the economic benefit of enterprises and providing a new way for a diversified mode of enterprise products.

Drawings

FIG. 1 is a flow chart of the process for preparing methyl methacrylate from methyl acetate according to the present invention;

reference numerals: the system comprises a 1-formaldehyde concentration unit, a 2-condensation reactor II, a 3-formaldehyde recovery unit, a 4-dehydration unit, a 5-oil-water separator, a 6-ester recovery unit, a 7-brine recovery unit, an 8-methyl propionate recovery unit, a 9-refining unit, a 10-condensation reactor I, an 11-methyl acetate recovery unit, a 12-methyl acrylate recovery unit and a 13-hydrogenation reactor.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

Example 1

The process flow for preparing methyl methacrylate by using methyl acetate as a raw material in the embodiment is shown in the attached figure 1, and the specific method and the experimental result are as follows:

respectively loading the formed catalyst into the first condensation reactor, the second condensation reactor and the hydrogenation reactor, and using H before use₂Activating under the following conditions: the temperature is 200 ℃, the normal pressure is high, and the gas space velocity is 500h^-1And the activation time is 6 h. The conventional aldol condensation catalyst in the field is adopted as long as the technical effects of the aldol condensation of methyl acetate and formaldehyde and the aldol condensation of methyl propionate and formaldehyde in the embodiment can be achieved.

Feeding industrial-grade 37% diluted formaldehyde into a formaldehyde concentration unit 1 for concentration, mixing a part of concentrated formaldehyde with methyl acetate raw materials, and feeding the mixture into a condensation reactor I10 for aldol condensation reaction, wherein the reaction conditions are as follows: the temperature is 400 ℃, the pressure is 1.0bar, and the liquid hourly space velocity is 2.0h^-1。

And cooling the reaction product, then feeding the cooled reaction product into a methyl acetate recovery unit 11, returning an azeotrope of methyl acetate and methanol at the top of the tower to an inlet of a condensation reactor I10, and feeding the material at the bottom of the tower into a methyl acrylate recovery unit 12. The formaldehyde, water, acid and residual methanol at the tower bottom enter a formaldehyde recovery unit 3, the methyl acrylate, methyl propionate and methanol at the tower top enter a hydrogenation reactor 13 in an azeotropic mode, and the hydrogenation reaction conditions are as follows: the temperature is 80 ℃, the pressure is 2.5MPa, and the gas-liquid ratio is 50: 1.

After being hydrogenated, the obtained methyl propionate (containing methanol) is mixed with concentrated formaldehyde and then enters a condensation reactor II 2 for aldol condensation reaction, and the reaction conditions are as follows: the temperature is 350 ℃, the pressure is normal pressure, and the liquid hourly space velocity is 1.5h^-1。

The product generated in the condensation reactor II 2 is mixed with the material flow from the methyl acrylate recovery unit 12 and then enters the tower from the lower part of the formaldehyde recovery unit 3, the brine enters the tower from the upper part of the formaldehyde recovery unit 3, the two material flows form counter-current liquid-liquid extraction to generate an organic phase material flow and an aqueous phase material flow, so that the concentration of formaldehyde and methanol in the organic phase material flow is greatly reduced, the organic phase material flow at the top of the formaldehyde recovery unit 3 enters the dehydration unit 4, and the aqueous phase material flow at the bottom of the tower enters the ester recovery unit 6.

The material flow from the formaldehyde recovery unit 3 enters a dehydration unit 4, water and methyl propionate are azeotropically extracted from the tower top and enter an oil-water separator 5, after layering, a lower water phase returns to the upper part of the formaldehyde recovery unit 3 to be used as an extracting agent, an upper oil phase returns to the tower top of the dehydration unit 4, and materials at the tower bottom of the dehydration unit 4 enter a methyl propionate recovery unit 8.

The water phase material flow from the formaldehyde recovery unit 3 enters an ester recovery unit 6, the light components on the tower top return to the lower part of the formaldehyde recovery unit 3, the heavy components on the tower bottom enter a brine recovery unit 7, after being separated by the brine recovery unit, the materials on the tower top are mixed with dilute formaldehyde and then enter a formaldehyde concentration unit 1 for concentration, the materials on the tower bottom are discharged as waste water, and the rest returns to the upper part of the formaldehyde recovery unit 3 to be used as an extracting agent.

And rectifying the material flow from the dehydration unit 4 in a methyl propionate recovery unit 8, returning the material at the top of the tower to the inlet of the condensation reactor II 2, feeding the material at the bottom of the tower into a refining unit 9, separating, and performing side-draw to obtain a Methyl Methacrylate (MMA) product.

The experimental results are as follows: the conversion rate of methyl acetate is 60 percent, and the selectivity of methyl propionate is 83 percent; the conversion rate of methyl propionate is 27%, and the selectivity of methyl methacrylate is 92%.

Example 2

The test and analysis methods were the same as in example 1, except that the reaction temperature in the first condensation reactor 10 was changed to 350 ℃ and the reaction temperature in the second condensation reactor 2 was changed to 370 ℃.

The experimental results are as follows: the conversion rate of methyl acetate is 45 percent, and the selectivity of methyl propionate is 94 percent; the conversion rate of methyl propionate is 36%, and the selectivity of methyl methacrylate is 87%.

Example 3

The test and analysis methods were the same as in example 1, except that the first condensation reactor 10 was changed to 3.0bar and the second condensation reactor 2 was changed to 2.0 bar.

The experimental results are as follows: the conversion rate of methyl acetate is 62 percent, and the selectivity of methyl propionate is 82 percent; the conversion rate of methyl propionate is 28%, and the selectivity of methyl methacrylate is 91%.

Example 4

The test and analysis methods are the same as example 1, the first 10 liquid hourly space velocity of the condensation reactor is changed to 1.0h^-1The second 2 liquid hourly space velocity of the condensation reactor is changed into 1.0h^-1。

The experimental results are as follows: the conversion rate of methyl acetate is 66 percent, and the selectivity of methyl propionate is 80 percent; the conversion rate of methyl propionate is 32 percent, and the selectivity of methyl methacrylate is 89 percent.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.