JPS5912102B2 - Method for producing acrylic ester - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention comprises (1) producing an acrylic ester by reacting acrylic acid and a higher alcohol (having 3 to 12 carbon atoms) using an acidic cation exchange resin as a catalyst; Molar ratio of acrylic acid and higher alcohol 1:1 to 1:2.0
A method for producing an acrylic ester, characterized by carrying out the reaction at a temperature of 80 to 130°C and a reduced pressure of 30 to 500 mmHg.

and (2) When producing an acrylic acid ester by reacting acrylic acid and a higher alcohol (having 3 to 12 carbon atoms) using an acidic cation exchange resin as a catalyst, the molar ratio of acrylic acid and higher alcohol is 1. (1) Relating to a method for producing acrylic ester, which comprises reacting at a temperature of 80 to 130°C and a reduced pressure of 30 to 500 mmHg at a ratio of 1 to 1:2.0, removing water from the reaction system 10, and continuing the reaction. . Conventionally, acidic catalysts such as sulfuric acid, phosphoric acid, and benzenesulfonic 15-acid have generally been used in methods for producing higher esters of acrylic acid from acrylic acid and higher alcohols. In order to remove the water produced at this time from the reaction system and increase the reaction rate, a solvent that is azeotropic with water is used. Furthermore, in recent years, many documents and patents such as Patent No. 20 using acidic cation exchange resins have been published as acidic catalysts in esterification.

Since acidic cation exchange resin is a solid-phase acid, it is easy to separate the reaction solution from the solvent, and there are few side reactants, resulting in good reaction selectivity. Benefits are touted. 25 The reaction mode of esterification using acidic cation exchange resin is to fill and fix the acidic cation exchange resin in a reaction tower, and to carry out the reaction by continuously introducing raw materials at an elevated temperature. Common.

When producing acrylic acid higher esters, generally a solvent that is azeotropic with water (preferably as low as possible azeotropic temperature) or a solvent that is azeotropic with water is used to promote the vaporization of water in the reaction system. Use a solvent with a low boiling point even if it does not create a composition. In this case, if a solvent is not used, the conversion rate of the reaction will be low and even polymerization will occur35. This is because water generated as esterification progresses remains with the reaction solution until the end. That is, since the esterification reaction is an equilibrium reaction, if water is present in the reaction system in a liquid phase, the reaction conversion rate will inevitably be kept low. Furthermore, since acrylic acid is a substance that is extremely easy to polymerize when coexisting with water at elevated temperatures, it is extremely easy to polymerize under high temperature conditions such as pentaesterification. The present inventor continuously introduced acrylic acid and higher alcohol at elevated temperature into a reaction column filled with an acidic cation exchange resin and proceeded with esterification by using various reaction conditions and solvents. The conversion rate of ester and the state of production of by-products have been observed.

In the esterification reaction of acrylic acid, the produced water remains with the reaction solution until the end, resulting in various disadvantageous results. In general, mixtures of acrylic acid, acrylic esters and alcohols can be prepared, especially in the presence of an acidic catalyst, as acrylic acid dimers (and addition polymers of trimers or higher), hydroxypropionic acid and acrylic acid dimer esters (and esters of trimers or higher polymers). )
It is well known that , hydroxypropionate, alkoxypropionate, ether (or alkene), etc. are produced. At this time, it is well known that the production of acrylic acid dimer (ester), hydroxypropionic acid (ester), etc. rapidly increases in the presence of water. Therefore, the presence of water in the liquid phase in the reaction system not only lowers the conversion rate of the reaction but also increases the production of by-products. In particular, when producing higher esters from higher alcohols with a large number of carbon atoms, water generated in the reaction system is thought to separate and form water droplets, and in these water droplets, acrylic acid is converted into acrylic acid dimers (and trimers). It is thought that the above addition polymers) and hydroxypropionic acid become acrylic acid dimer esters (and esters of addition polymers of trimer or higher). This is due to the fact that when benzene and toluene are used as azeotropic solvents, toluene produces a much larger amount of the above-mentioned by-products, and when a solvent that dissolves water (such as acetone) is used, the above-mentioned by-products are produced. It is also estimated from the fact that the amount of products is significantly reduced. It is also known that the reaction to produce alkoxypropionic acid esters is apparently irreversible and increases at a nearly constant rate at the same reaction temperature. The present inventor has completed the present invention based on the knowledge obtained over many years as described above.

The first advantage of practicing the present invention is that high ester conversions can be achieved in one pass without the use of solvents.

In the case of the conventional method of carrying out esterification at normal pressure, in order to obtain the same conversion rate of acrylic acid, it is necessary to use at least an equal amount of solvent to the raw material. Therefore, the method of the present invention has great industrial advantages in that it is possible to obtain twice the production amount with a reactor of the same capacity, and when taking into account the cost and recovery loss of solvent recovery. The second advantage is that the reaction selectivity is better and the amount of by-products produced is smaller than in esterification under normal pressure. In the esterification reaction under reduced pressure of the present invention, the water produced has the lowest boiling point among the raw materials and the produced ester, and is thought to form an azeotrope with the raw material alcohol and the produced ester. It is thought that water is almost completely in the gaseous phase at this temperature, and this is probably the reason for the small amount of by-products.

Additionally, unexpectedly, the production of alkoxypropionate esters varies greatly depending on the degree of vacuum. Under appropriate conditions, the initial production amount is low, and the rate of increase with reaction time can be suppressed to a surprisingly low level. The third advantage is that the rate of increase in by-products is kept low. In particular, in the case of acrylic acid dimer esters and hydroxypropionate esters, it may actually decrease by lengthening the reaction time. This indicates that the rate of decomposition of these by-products is faster than that of formation in the latter half of the reaction. Therefore, it is possible to provide sufficient reaction time to increase the reaction conversion rate.

In the esterification reaction, although the initial reaction is fast, it usually takes a considerable amount of time to reach the reaction equilibrium point. In esterification at normal pressure, the rate of increase in byproducts is usually constant; if the reaction approaches the equilibrium conversion rate, more than 1% of byproducts will be produced in order to increase the reaction conversion rate by, for example, 1%. However, development may occur in which the amount of ester obtained decreases, so it is necessary to suppress the reaction conversion rate to a certain degree. The fourth advantage is that the rate of increase in by-products is extremely slow, or rather some of them are decomposed and reduced, so it is possible to carry out esterification in multiple stages. That is, by separating water from the reaction product once passed through the reaction tower and further introducing the organic layer into the reaction tower, the reaction conversion rate can be further increased.

For example, a multi-tubular cylindrical heat exchanger is advantageously used as a reaction column in the apparatus used in carrying out the present invention. An acidic cation exchange resin is filled and fixed in the inner tube of the reaction tower, and heated with a heat medium at a predetermined temperature from an external jacket.

The reaction system is maintained at a predetermined degree of reduced pressure, and the raw materials acrylic acid and higher alcohol are introduced from the lower part of the reaction tower through a back pressure valve.

The reaction product flowing out from the upper part of the reaction tower is cooled and taken out.

As the acidic cation exchange resin used in the present invention, a generally commercially available polystyrene-sulfonic acid type strongly acidic cation exchange resin or the like is used.

Since the ion exchange resin has a porous network structure, it is easily contaminated with so-called polymeric substances, and if contaminated, the surface area decreases and the catalytic activity decreases. Therefore, it is desirable that the raw material acrylic acid and higher alcohol do not contain such resin contaminants. The reaction temperature is limited to the heat resistance temperature of the cation exchange resin.

The reaction is usually carried out at a temperature of 80 to 130°C, particularly preferably 90 to 130°C.
Performed at 110°C.

The higher the temperature, the faster the rate of deterioration of the catalytic activity of the resin, and if the temperature is too low, the reaction rate will drop significantly. The ratio of acrylic acid and higher alcohol used is 1:1 to 1:2.0 (molar ratio)
It is.

If the amount of alcohol used is large, the acrylic acid conversion rate will be high, but it will be difficult to recover excess alcohol and a large amount of recovery cost will be required. Furthermore, if the amount of alcohol used is small, the conversion rate of acrylic acid will be low. The reaction is usually 30 to 500
Although the reaction is carried out under reduced pressure in the range of mmHg, suitable conditions can be selected depending on the molar ratio of acrylic acid and alcohol, the reaction temperature, and the type of alcohol.

The solution obtained by the reaction obtained from the reaction tower can be further subjected to an esterification reaction after removing water.

The esterification reaction at this time can be carried out under reduced pressure of 30 to 500 muHg and at a reaction temperature of 80 to 130°C.

As for the catalyst, an acidic cation exchange resin can be used as in the first esterification reaction. Examples of the higher alcohol used in the present invention include propanol, butanol, nonyl alcohol, and 2-ethylhexanol.

Under the reaction format and reaction conditions carried out in the present invention, polymerization hardly occurs during the reaction.

Therefore, when using commercially available acrylic acid, the polymerization inhibitor that has already been added is sufficient and there is no need to add it again. A polymerization inhibitor can be added thereto. Next, the present invention will be explained in detail with reference to examples.

Examples 1 to 5 132 CC of acidic cation exchange resin (polystyrene-sulfonic acid type) was filled and fixed in the inner tube of a glass double-tube heat exchange type reaction column with an inner diameter of 24 mm and a length of 350 mm, and the outer jacket was Circulate polyethylene glycol at a predetermined temperature.

The raw material used was a mixture of freshly distilled acrylic acid and commercially available n-butanol at a molar ratio of 1:1.2.

Hydroquinone monomethyl ether was added to the mixed raw material in an amount of 100 ppm based on acrylic acid. The mixed raw materials were introduced from the bottom of the reaction tower by a metering pump through a back pressure valve at 105.65 V/hour (contact time 1.13 hours).

At this time, the heating temperature of the reaction tower was 100°C, and the degree of pressure reduction was 250°C.
m77! It was Hg. Organic layer 96 per hour from the top of the reaction tower
, 407 and an aqueous layer of 9.257 mL. The organic layer contains 3.63% acrylic acid, 12.40% n-butanol,
Acrylic acid butyl ester (hereinafter abbreviated as BA) 80.7
5%, hydroxypropionate butyl ester (hereinafter abbreviated as HBP) 0.13%, acrylic acid dimer butyl ester (hereinafter abbreviated as DimB) 0.17%, butoxypropionate butyl ester (hereinafter abbreviate as BBP) 0.
57%, dibutyl ether (hereinafter abbreviated as BE) 0.06
% and 2.30% water.

The aqueous layer contains 1.43% acrylic acid and 2.68% butanol.
% and traces of BA. Table 1 shows the reaction results under various conditions including the above conditions.

Examples 6-8 Using the same equipment as Examples 1 to 5, acrylic The molar ratio of alcohol and butanol is 1: The disasters are shown in Table-2.

Reaction result in case 1.4 Examples 9-12 Using the same equipment as Examples 1 to 5, Molar ratio of acrylic acid and butanol: 1: The reaction results in the case of 1.6 are shown in Table 3.

Example 13 Using the same equipment as in Examples 1 to 5, raw materials prepared by mixing acrylic acid and butanol at a molar ratio of 1:1.2 were heated at a reaction temperature of 100°C and a degree of vacuum of 250 mw! Under reaction conditions, Hg was introduced at 116.767 hours per hour (contact time 1.02 hours).

Organic layer 108.13y and aqueous phase 8.63f per hour from the top of the tower
leaked out. The composition of the organic layer is 5.24% acrylic acid, 14.57% butanol, 76.2% BA, HBPO.
l2%, DimBO. 2l%, BEO. O5% and water 3
．． It was 14%. The composition in the aqueous phase is acrylic acid 1.98
%, butanol 2.61% and BA were slightly small. The acrylic acid conversion rate at this time was 88.90%, and the BA. H.B.
P., DimB. The production rate of each of BBP and BE is 88.
12%, 0.12%, 0.31%, 0.35% (based on acrylic acid) and 0.10% (based on alcohol). Further, the selectivity of acrylic acid is 99.13%, and the selectivity of butanol is 98.79%. The above-mentioned machine layer was again introduced into the reaction tower at a rate of 103,707 hours per hour (contact time 1.14 hours) under reaction conditions of a reaction temperature of 100° C. and a degree of vacuum of 200 degrees Hg. Organic layer 100.937 per hour from the top of the tower
And 2.77 tons of aqueous phase flowed out. The composition of the organic layer is acrylic acid 0.98% butanol 10.35%, BA86.38
%, HBPO. O8%, DinlBO. O7%, BBP
O. 43%, BEO. 22% and water 1.48%. The composition of the aqueous phase is 0.41% acrylic acid and 2% butanol.
．． 32% and a trace amount of BA. The acrylic acid conversion rate at this time was 97.85% and BA. HBP, DimB. BB
The production rates of P and BE are 97.37% and 0.08%, respectively.
, 0.10%, 0.31% (based on acrylic acid) and 0.41% (based on alcohol). In addition, the selectivity of acrylic acid is 99.51%, and the selectivity of butanol is 99.
．． It is 00%.

Comparative Examples 1 to 4 The same equipment as Examples 1 to 5 was used (however, the back pressure valve was not used).

) Table 4 shows the results of a similar experiment conducted at normal pressure using benzene as the solvent. Example 14, Comparative Examples 5 to 6 Using the same equipment as Examples 1 to 5 (however, the back pressure valve was not used in the case of normal pressure), acrylic acid and 2-ethylhexanol were mixed in a molar ratio of 1:1. The mixture at a ratio of .2 was used as the raw material.

In the case of normal pressure, benzene and toluene were selected as solvents, and the same operation as in the case of butyl acrylate was performed.

As in the case of acrylic acid butyl ester, a mixture consisting of an organic layer and an aqueous layer flows out from the upper part of the reaction column.

The organic layer contains acrylic acid, 2-ethylhexanol (hereinafter abbreviated as 2EH0H), acrylic acid 2-ethylhexyl ester (hereinafter abbreviated as 2EHA), hydroxypropionate 2-ethylhexyl ester (hereinafter abbreviated as HOP), and acrylic acid dimer 2. -ethylhexyl ester (
DimO), 2-ethylhexyl octoxypropionate (hereinafter abbreviated as 00P), octene, and water (and a solvent in the case of normal pressure).

Further, the water layer contained substantially only acrylic acid.

The reaction results are shown in Table-5.

Claims (1)

[Claims] 1. In producing an acrylic acid ester by reacting acrylic acid and a higher alcohol (having 3 to 12 carbon atoms) using an acidic cation exchange resin as a catalyst, at a molar ratio of 1:1 to 1:2.0 and a temperature of 8.
A method for producing an acrylic ester, characterized by carrying out the reaction under reduced pressure of 0 to 130°C and 30 to 500 mmHg. 2. When producing an acrylic ester by reacting acrylic acid and a higher alcohol (having 3 to 12 carbon atoms) using an acidic cation exchange resin as a catalyst, the molar ratio of acrylic acid and higher alcohol is 1:1 to 1. Temperature 80 at 1:2.0
A method for producing an acrylic ester, which comprises reacting at ~130°C and a reduced pressure of 30 to 500 mmHg, removing water from the reaction system, and continuing the reaction.