KR100380017B1 - Manufacturing method of unsaturated carboxylic ester by continuous process - Google Patents

Abstract

The present invention is a method for continuously producing unsaturated carboxylic acid esters, and when the esterification reaction of an aliphatic alcohol having 1 to 10 carbon atoms with an unsaturated carboxylic acid in the presence of a cation exchange resin catalyst, the reaction product is changed by changing the composition ratio of the reactants. By having this suitable composition, the present invention relates to a process for producing esters of unsaturated carboxylic acids in high yield by optimizing the reaction and separation processes of esters.

Description

Method for producing unsaturated carboxylic acid esters by a continuous process

The present invention relates to a process for preparing unsaturated carboxylic acid esters, and more particularly, by optimizing the composition of the reaction product, maximizing the yield of ester production in the reactor and smooth acid separation in the separation process to achieve the unsaturated carboxylic acid It relates to a process which can continuously produce esters in high yield.

Japanese Patent Laid-Open No. 63-17844 discloses the commercialization of an ester production process due to the low mechanical strength and heat resistance of the resin catalyst when the esterification reaction is carried out using a heterogeneous resin catalyst instead of a homogeneous liquid catalyst. Not only discloses the problems associated with the reaction, but also the unreacted unsaturated carboxylic acid, water and the corresponding aliphatic alcohol in the resulting reaction product, when the alcohol and the ester are separated through azeotropic distillation, It is pointed out that there are many problems such as the acid is discharged to the top of the tower of the acid separation azeotropic column due to the strong affinity. In order to solve the above problems, Japanese Laid-Open Patent Publication No. 49-41413 proposes a method of adding an organic solvent having a greater affinity with water in order to reduce the affinity between water and unsaturated carboxylic acid. A separate process for the recovery and separation of the solvent is added, which is disadvantageous in terms of economics. In addition, in order to reduce the proportion of acid in the lower part of the acid separation column, there is also a method of increasing the amount of the corresponding aliphatic alcohol to induce the esterification reaction in the forward direction, but this method purifies the aliphatic alcohol used in excess after the reaction. And there is a problem in that the recovery process is expensive, the reactor capacity and the use of utility (economic) is also increased and economically disadvantageous. U.S. Patent No. 4,464,229 discloses a method for increasing the stage and reflux ratio of a separation column in order to increase the separation efficiency of the reaction product in the separation column, but the relationship between the stage and reflux ratio when the acid and water are distilled together under the column composition conditions The acid moves to the top of the tower, reducing the separation efficiency.

U.S. Patent No. 4,464,229 discloses that commercially prepared unsaturated carboxylic acid esters are introduced into a separation column by controlling the reaction and separation conditions of the reactor in consideration of economics, ease of operation and process simplification. It is disclosed that controlling the composition of the reaction product is the most effective way to obtain unsaturated carboxylic esters in high yield. U.S. Patent 5,645,696 uses a fixed bed catalytic reactor and the composition of the reaction product is about 0 to 1% by weight of water, about 10 to 15% by weight of unsaturated carboxylic acid, about 20 to 26% by weight of aliphatic alcohol and unsaturated carboxylic ester Although the case of about 60 to 65% by weight is disclosed, the composition of the aliphatic alcohol is 10% or more, so that the efficiency of ester separation in the acid separation column when operating in a continuous process is greatly reduced, Since the ratio is increased, there is a problem in that the effect of improving the efficiency of the reactor cannot be obtained.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and when the esterification reaction of an aliphatic alcohol having 1 to 10 carbon atoms with an unsaturated carboxylic acid in the presence of a cation exchange resin catalyst, the reaction product has a suitable composition so that the reaction product is separated. It is an optimization to provide a process for producing unsaturated carboxylic esters in high yield.

1 is a process diagram of the present invention.

* Description of the symbols for the main parts of the drawings *

1: catalytic reactor 2: catalyst bed in reactor

3: in-reactor filter 4: water separation column

5: heat exchanger 6: acid separation tower

7: Decanter 8: Mountain Separator

9: circulation pump 10: first condenser

11: second condenser

In order to achieve the above object, the present invention, when the esterification reaction of an aliphatic alcohol having 1 to 10 carbon atoms with an unsaturated carboxylic acid, the reaction product is about 2% by weight or less of water, about 10 to 13% by weight of unsaturated carboxylic acid , Having a composition of about 7 to 10% by weight of aliphatic alcohol and about 70 to 80% by weight of unsaturated carboxylic acid ester, thereby increasing the separation efficiency of the reaction product in an acid separation column to continuously produce unsaturated carboxylic acid ester in high yield. Provide a way to.

Hereinafter, the present invention will be described in detail.

In the present invention, in order to prepare unsaturated carboxylic acid ester in high yield, a fixed bed catalytic reactor in which the circulation direction of the reactant is directed from top to bottom is used, and a part of the reaction product is forced to a heat exchanger located outside the reactor, thereby requiring the reactor. Indirectly supply calories. This method eliminates the problems associated with the use of conventional catalysts, such as physical damage due to the agitation of the reactants and degradation of the catalyst activity by direct heating. And when the reaction and separation of the unsaturated carboxylic acid ester is carried out continuously, the reaction and separation conditions for effectively separating the unreacted acid and the produced ester in the acid separation column while maximizing the yield of the ester in the reactor use.

The main apparatus and process diagram of the present invention are shown in FIG. 1, and the present invention will be described in detail with reference to FIG. In the reactor (1) filled with a conventional strongly acidic cation exchange resin, unsaturated carboxylic acid and aliphatic alcohol having 1 to 10 carbon atoms are mixed outside the reactor and introduced through the pipe (12), and an esterification reaction occurs under an acid atmosphere to produce a corresponding reaction. To produce carboxylic ester and water.

Acrylic acid, methacrylic acid, and the like may be used as the unsaturated carboxylic acid, and butanol, 2-ethyl-hexanol, and the like may be used as the aliphatic alcohol.

The esterification reaction is a reversible reaction, so that the equilibrium of the reaction must be maintained towards the forward reaction to increase the yield of the ester, so that the water produced in the reaction is continuously removed in a water separation column connected to the top of the reactor. In carrying out the above-mentioned esterification reaction and separation process continuously, the reaction efficiency in the reactor is optimized, and in the acid separation column, unreacted unsaturated carboxylic acid is introduced into the bottom of the reaction product and unsaturated carboxylic acid ester is as much as possible. Establishing the conditions for the separation by moving to the top of the column is one of the most important factors in obtaining unsaturated carboxylic acid esters in high yield. Of these, the reaction efficiency in the reactor is determined by the amount of catalyst used in the reaction, the reaction temperature and the molar ratio of the unsaturated carboxylic acid and the corresponding aliphatic alcohol. The amount of catalyst charged is 1100 to 1900 g by weight of catalyst in the 3.5 liter reactor. The amount of catalyst charge is related to the residence time of the reactants, where the residence time in the catalyst is expressed as the amount of catalyst per unit reactant flow rate. Generally, in fixed bed catalytic reactors, the residence time in the catalyst of the reactant has a great influence on the yield of the product. The residence time of the reactants of the present invention is 1.0 to 2.0 hours.

If the amount of catalyst used exceeds a suitable range based on the amount of reactants added, the residence time in the catalyst layer of the reactants becomes longer, which increases the reaction chance between the reactants and / or products, thereby improving the conversion rate of the reactants, but the longer residence time. In addition, the reaction yield of the reactants as well as the production of by-products increases, resulting in lower yields of esters, and less economical per unit volume of catalyst for the production of esters. When the catalyst is filled in an amount below the suitable range, the residence time in the catalyst layer of the reactants is shortened, so that the reaction equilibrium is not reached, and the conversion rate of the reactants is reduced, thereby lowering the yield of ester production.

The reaction temperature is 60 to 90 ℃, preferably 70 to 80 ℃. When the reaction temperature is operated above 90 ℃ the activity of the reactants increases to increase the by-products production, below 60 ℃ the reaction rate decreases to slow the time to reach the reaction equilibrium to decrease the conversion rate.

The reaction pressure is 100 to 150 torr, preferably 100 to 120 torr.

Some of the reaction products are sent to an acid separation column, which is a continuous step according to the reaction, where the unreacted acid and aliphatic alcohol, water and the resulting ester are separated, wherein the unreacted aliphatic alcohol, water and ester are each binary or Distillation by ternary azeotropy separates the column top of the acid separation tower. The separation efficiency of such an acid separation tower depends largely on the composition of the reaction product flowing into the acid separation column, and the composition of the reaction product is greatly influenced by the molar ratios of the reactants in the reactors listed above. The molar ratio of the fresh corresponding aliphatic alcohol and acid in the reaction solution introduced into the reactor is maintained at 1.0 to 1.8, preferably 1.1 to 1.4, and reacted. When an excess amount of aliphatic alcohol is introduced into the reactor, the opportunity for the formation of by-products in the reactor also increases, and the following reaction formula 1

Scheme 1

As can be seen, the yield is affected. In the separation process, an increase in the ratio of aliphatic alcohol to the steam composition at the top of the column lowers the selectivity of the produced esters, thereby reducing the separation efficiency, and requires a lot of energy for aliphatic alcohol recovery and purification. Too much acid entering the reactor is analogous to aliphatic alcohols

Scheme 2

As can be seen by reacting with the produced esters to produce by-products to reduce the yield of the esters, the polymer production is increased, the catalytic activity is lowered, there is a problem that it is difficult to purify the reaction product in the subsequent process.

Under the above reaction conditions, the optimum reaction product composition for efficiently carrying out the separation process in the acid separation column is about 0 to 2% by weight of water, about 7 to 10% by weight of aliphatic alcohol, about 10 to 13% by weight of unsaturated carboxylic acid. % And about 75 to 83 weight percent unsaturated carboxylic ester. When a reaction product having a composition of more than 10% by weight of unreacted aliphatic alcohol is introduced into the acid separation column, separation of the unreacted unsaturated carboxylic acid and the reaction product in the acid separation column is performed smoothly, but the unsaturated carboxylic acid at the top of the column is The proportion of esters is significantly reduced and the proportion of aliphatic alcohols is increased. Thus, the amount of unsaturated carboxylic acid ester finally obtained decreases, and the productivity of the ester decreases even if the reactor efficiency increases. In addition, the presence of more than 13% by weight of unsaturated carboxylic acid in the reaction product composition reduces the separation efficiency of the unreacted acid and the reaction product in the separation column increases the possibility of discharge of the unreacted acid on the top of the column. The esters that do not separate the unreacted acid from the acid separation column deteriorate the economics of the process, such as having to undergo a separate separation process by accompanying the acid to the last step to obtain the product to reduce the purity of the ester. Therefore, in the process of producing unsaturated carboxylic acid esters by a continuous process using a fixed bed catalytic reactor, it can be seen that the composition of the reaction product obtained in the present invention shows the optimum efficiency when linking the reactor and the separation column. .

Referring to the process of the present invention with reference to Figure 1 as follows.

The reactor 1 is filled with a conventional cation exchange resin 2 in the form of a fixed bed, and a filter 3 is built into the catalyst holder at the bottom of the reactor. The outer wall of the reactor (1) is indirect heating method in which a part of the reaction product is supplied with the amount of heat required for the reaction through the heat exchanger (5) located outside the reactor. Unsaturated carboxylic acids and aliphatic alcohols having 1 to 10 carbon atoms used as reactants enter the reactor (1) via a pipe (12). The reactant introduced into the reactor 1 is brought into contact with the catalyst bed 2 to cause an esterification reaction, producing a corresponding unsaturated carboxylic acid ester and water. The esterification reaction is a reversible reaction and in order to increase the reactivity to the forward reaction, the generated water must be efficiently removed in the reactor 1. Accordingly, the water generated in the reaction is removed in the water separation tower 4 attached to the reactor, and the water generated is azeotropic with the aliphatic alcohol and ester and is transferred to the water separation tower 4 through the pipe 16. . The conveyed gas is liquefied via the first condenser 10 and then separated into an organic layer and a water layer in a decanter 7. Of these, the organic layer is refluxed with the aliphatic alcohol supplied to the upper portion of the water separation tower 4 through the pipe 19 to the upper portion of the water separation tower 4, and is transferred to the reactor through the pipe 17 to be separated from the reactor. Discharge of acid to (4) is prevented. The gas sent to the water separation tower 4 does not contain unreacted unsaturated carboxylic acid. The water layer is transferred to the receiver 8 via a pipe 20. The reactor bottoms (reaction products and unreacted materials) are passed through pipes 13 and 14 to a heat exchanger 5, in part via a circulation pump 9, to supply the heat required for the reaction in the heat exchanger 5. After receiving, the pipe 15 is supplied to the upper portion of the reactor 1. The heat medium of the heat exchanger enters through pipe 26 and then supplies heat to the reactor circulating fluid and exits through pipe 27. A portion of the bottoms of the reactor 1 enter the bottom of the acid separation tower 6 via a pipe 18 via a circulation pump 9. The acid separation column 6 uses a porous tray of 30 or more stages in theory. The material flowing into the acid separation column 6 is composed of water, aliphatic alcohol, unsaturated carboxylic acid and unsaturated carboxylic acid ester. Among them, water, ester and aliphatic alcohols are moved to the top of the acid separation tower 6 by the respective azeotropic composition. In the introduced reaction product, material not separated to the top including unsaturated carboxylic acid remains at the bottom of the acid separation column 6, and in this way, separation of the reaction product and unreacted carboxylic acid is performed. The reflux of the distillate was performed in order to suppress the discharge of acid to the top of the acid separation tower 6, and the composition ratio of the reaction product flowing in from the reactor 1 was kept constant. The gas moved to the top of the acid separation tower 6 is liquefied through the second condenser 11 and then transferred to the receiver 8 through the pipe 28, where it is separated into an organic layer and a water layer. Some of the organic layer and the water layer are again refluxed through the pipes 21 and 22 to the top of the acid separation tower 6 to prevent discharge of acid from the bottom of the acid separation tower 6 to the top. The organic layer and the water layer remaining after reflux are transferred to the post purification system through pipes 23 and 24, respectively. The solution containing the unreacted unsaturated carboxylic acid under the acid separation tower 6 is circulated through the pipe 25 to the reactor 1 for reuse.

In the reactor 1 and the acid separation column 6, PT (phenothiazine), which is a polymerization inhibitor, is introduced together with air in a small amount in order to prevent polymerization during the reaction of the unsaturated carboxylic acid ester and the separation of the unreacted carboxylic acid.

The following presents preferred examples and comparative examples to aid in understanding the invention. However, the following examples are merely provided to more easily understand the present invention, and the present invention is not limited to the following examples. Examples 1, 2 and 3 below are results within experimental conditions that may have optimization of ester production reactions and separation processes when linking the reaction and separation processes.

Example 1

This experiment involved the butyl acrylate manufacturing process. The reaction used a 3.5 liter capacity vitreous reactor. The heat exchanger is made of shell-and-tube type porcelain. The 3.5 liter vitreous reactor was charged with a wet volume of 2.0 liters of strongly acidic cation exchange resin catalyst (Amberlyst 39 from Rohm & Hass). As a catalyst, pretreatment was performed by a washing process for removing excess acid and a water removal process using a mixture of 60% butyl acrylate, 30% acrylic acid, and 10% butanol. The reactor was operated under reduced pressure such that the top pressure of the water separation tower was 110 Torr and the top pressure of the acid separation tower was 190 Torr. After mixing so that the molar ratio of butanol and acrylic acid is 1.32 (butanol / acrylic acid = 1.32), 1.3 to 1.5 liters of the reactant is introduced into the reactor, the reaction product is circulated for about 2 hours, and the reaction temperature is raised to about 75 ° C. The reaction was then introduced into the reactor at 400 g / hour continuously. The composition of the circulating fluid circulated from the bottom of the acid separation column into the reactor was about 2% water, about 8% butanol, about 63% butyl acrylate and about 27% acrylic acid, and the flow rate was about 580 g / hour. Water generated during the circulation of the reaction solution was continuously removed by a water separation column, and the reaction solution was continuously circulated through a catalyst bed to a heat exchanger. Some of the reaction liquid is transferred to the lower part of the acid separation tower, and after a certain time, it began to flow into the acid separation tower. The temperature in the reactor was raised to 75 ° C. and operated at this temperature. After the continuous operation for 5 hours or more under the above conditions, the reaction product was introduced into the acid separation column at a flow rate of about 960 g / hour, and the acid separation column was maintained at a lower temperature of about 85 ° C and an upper temperature of about 58 ° C. Drive. In addition, the reflux ratio of the organic layer and the water layer of the receiver to the separation column was operated to be 0.5 to 1 (reflux liquid / tower top gas) based on the weight of the gas at the top of the tower. Unreacted unsaturated carboxylic acid under the acid separation column separated from the reaction product was circulated to the reactor. The presence of unreacted unsaturated carboxylic acid in the solution liquefied in the receiver via an acid separation column is confirmed by titration using a NaOH solution, and the separation is stable when the content of the unsaturated carboxylic acid in the solution is 20 to 50 ppm or less. It was judged that. PT was dissolved in a mixture of 70% butyl acrylate and 30% butanol, and then charged into a reactor and an acid separation tower. The reactor was charged with 2000 to 2500 ppm or more based on the weight of the reaction solution, and a small amount of air was exchanged. It was introduced simultaneously at the bottom. A small amount of air was also introduced into the acid separation tower so as to be 1000 ppm or more based on the weight of the tower upper gas.

Under the reaction conditions, the composition of the reaction product was about 0.5% water, about 9% butanol, about 77% butyl acrylate, about 12% acrylic acid, about 175 ppm dibutyl ether, about 0.8% dimer acid, and about 0.70% dimer acid ester. The gas composition at the top of the acid separation tower was about 40% water, about 9% butanol and about 51% butyl acrylate, and the conversion of acrylic acid was about 60%.

Example 2

The reactant butanol and acrylic acid has a molar ratio of 1.24 (butanol / acrylic acid = 1.24), and the composition of the circulating fluid recycled at the bottom of the acid separation column is about 2% water, about 7% butanol, about 66% butyl acrylate and about 25% acrylic acid. % And the ester reaction was carried out in the same manner under the same conditions as in Example 1 except that the flow rate was about 530 g / hour. In addition, the reaction product is introduced into the acid separation column at a flow rate of about 940 g / hour, and the acid separation column is operated while maintaining the lower temperature of about 87 ℃ and the upper temperature of about 57 ℃. It was carried out in the same manner as in Example 1.

In this case, when the reactor reached equilibrium, the composition of the reaction product was about 0.7% water, about 9% butanol, about 75.9% butyl acrylate, about 13% acrylic acid, about 117 ppm dibutyl ether, about 0.9% dimer acid, and dimer The acid ester was 0.45%, the gas composition at the top of the acid separation column was about 41% water, about 8% butanol and about 51% butyl acrylate, and the conversion of acrylic acid was about 57%.

Example 3

The reactant butanol and acrylic acid has a molar ratio of 1.37 (butanol / acrylic acid = 1.37), and the composition of the circulating fluid recycled at the bottom of the acid separation column is about 2% water, about 7% butanol, about 71% butyl acrylate and about 20 acrylic acid. %, And the ester reaction was carried out in the same manner under the same conditions as in Example 1 except that the flow rate was about 560 g / hour. In addition, the reaction product is introduced into the acid separation column at a flow rate of about 980 g / hour, and the acid separation tower is operated while maintaining the lower temperature of about 84 ℃ and the upper temperature of about 50 ℃. It was carried out in the same manner as in Example 1.

In this case, when the reactor reaches equilibrium, the composition of the reaction product is about 0.4% water, about 10% butanol, about 75.7% butyl acrylate, about 12% acrylic acid, about 200 ppm dibutyl ether, about 1.0% dimer acid and dimer The acid ester was 0.85%, the gas composition at the top of the acid separation column was 38% water, about 12% butanol and about 50% butyl acrylate, and the conversion of acrylic acid was about 63%.

Comparative Example 1

The reactant butanol and acrylic acid has a molar ratio of 1.5 (butanol / acrylic acid = 1.5), and the composition of the circulating fluid recycled at the bottom of the acid separation column is about 1% water, about 12% butanol, about 65% butyl acrylate and about 21 acrylic acid. %, And the ester reaction was carried out in the same manner under the same conditions as in Example 1 except that the flow rate was about 540 g / hour. In addition, the reaction product is introduced into the acid separation column at a flow rate of about 940 g / hour, and the acid separation column is operated except that the operation is performed while maintaining the lower temperature of about 87 ℃, the upper temperature of about 57 ℃. It carried out in the same manner as in Example 1.

In this case, when the reactor reached equilibrium, the composition of the reaction product was about 0.8% water, about 13% butanol, about 73% butyl acrylate, about 11% acrylic acid, about 308 ppm dibutyl ether, about 0.6% dimer acid, and dimer. The acid ester was 1.0%, the gas composition at the top of the acid separation column was about 39% water, about 22% butanol and about 39% butyl acrylate, and the conversion of acrylic acid was about 67%.

Comparative Example 2

The molar ratio of butanol and acrylic acid as reactants is 1.0 (butanol / acrylic acid = 1,0), and the composition of the circulating fluid recycled at the bottom of the acid separation column is about 2% water, about 5% butanol, about 64% butyl acrylate and acrylic acid The ester reaction was carried out in the same manner as in Example 1 except that the flow rate was about 30% and the flow rate was about 550 g / hour. In addition, the reaction product is introduced into the acid separation column at a flow rate of about 970 g / hour, and the acid separation column is operated while maintaining the lower temperature of about 89 ℃ and the upper temperature of about 56 ℃. It was carried out in the same manner as in Example 1.

In this case, when the reactor reached equilibrium, the composition of the reaction product was about 0.8% water, about 8% butanol, about 73% butyl acrylate, about 16% acrylic acid, about 100 ppm dibutyl ether, about 1.75% dimer acid, and dimer. The acid ester was 0.37%, the gas composition on the top of the acid separation column was about 42% water, about 7% butanol, about 50.9% butyl acrylate and about 0.1% acrylic acid, and the conversion rate of acrylic acid was about 54%.

As described in Examples 1 to 3 and Comparative Examples 1 to 2, when the ester production reaction and the separation process are performed in combination, when the composition of the reaction product of the present invention is optimized, the composition of the reaction product is not optimized. It can be seen that the efficiency of the separation column is greatly improved such that the proportion of aliphatic alcohol in the vapor composition at the top of the separation column is reduced, and the discharge of unreacted acid is reduced.

The method for continuously producing unsaturated carboxylic acid esters of the present invention, when esterifying a C1-10 aliphatic alcohol and an unsaturated carboxylic acid in the presence of a cation exchange resin catalyst, changes the composition ratio of the reactants to produce a reaction product. By having a suitable composition, the reaction and separation process of esters can be optimized, and unsaturated carboxylic acid can be manufactured in high yield.

Claims (4)

In the method of continuously producing an unsaturated carboxylic ester by reacting an aliphatic alcohol having 1 to 10 carbon atoms and an unsaturated carboxylic acid in the presence of a cation exchange resin catalyst, Reaction temperature 70 to 80 ° C, Reaction pressure 100 to 150 torr; Molar ratio of aliphatic alcohol to unsaturated carboxylic acid in the reactor: 1.1: 1 to 1.4: 1; Residence time of the reactants 1.0 to 2.0 hours; 110 Torr top pressure of water separation tower; And Reflux ratio 0.5 to 1 at the lower temperature of the acid separation tower of 80 to 90 ℃, the upper temperature of the acid separation tower of 50 to 60 ℃ Method for producing an unsaturated carboxylic acid ester, characterized in that the operation. The method of claim 1, wherein the C1-10 fatty acid alcohol is butanol or 2-ethyl-hexanol. The method of claim 1, wherein the unsaturated carboxylic acid is acrylic acid or methacrylic acid. The method of claim 1, The composition of the reaction product is 0 to 2% by weight of water, 10 to 13% by weight of unsaturated carboxylic acid, 7 to 10% by weight of aliphatic alcohol and 75 to 83% by weight of unsaturated carboxylic ester; The vapor composition at the top of the acid separation column is 38-41 wt% water, 7-13 wt% aliphatic alcohol and 46-53 wt% unsaturated carboxylic ester It is operated to be a method for producing an unsaturated carboxylic ester.