WO1999041226A1

WO1999041226A1 - Process for producing esters

Info

Publication number: WO1999041226A1
Application number: PCT/JP1999/000591
Authority: WO
Inventors: Tomoyuki Mori; Masaki Takai; Kazuhiko Kurita; Takeshi Ishikawa; Kazuo Murase; Nobuo Toratani
Original assignee: Mitsubishi Chemical Corporation
Priority date: 1998-02-16
Filing date: 1999-02-12
Publication date: 1999-08-19
Also published as: CN1190408C; CN1291180A; JP3799796B2; JP2002155026A; AU2300399A

Abstract

A process for producing esters from organic carboxylic acids and/or anhydrides thereof and C4-18 alcohols wherein the reaction time is shortened by elevating the reaction rate at the initial stage of the reaction and the energy cost is reduced thereby bringing about an economical advantage. The above process is characterized in that the reaction is effected under a pressure of 0.02 to 5 kg/cm2 and the feedstock alcohol is supplied within a temperature range from a temperature lower by 20 °C than the boiling p oint of the alcohol under the pressure in the reactor to the boiling point thereof.

Description

Description Ester production method Technical field

The present invention relates to a method for producing an ester such as a plasticizer used for a vinyl chloride resin. Background art

Conventionally, a method for producing an ester used as a plasticizer or the like by subjecting an acid and an alcohol to an esterification reaction has been widely industrially performed. In this ester production method, an acid catalyst such as sulfuric acid or paratoluenesulfonic acid or an organic metal catalyst such as Ti or Sn is generally used as a catalyst. When an acid catalyst such as p-toluenesulfonic acid is used, the reaction can be performed at a relatively low temperature, but there is a problem that a large amount of by-products are generated. However, there is a problem that the reaction temperature needs to be raised and the energy cost increases. This esterification reaction is a typical equilibrium reaction, and in order to increase the yield of the desired ester, the starting alcohol is generally used in excess of the stoichiometric amount (stoichiometric amount). It is common practice to produce by-produced water by continuously drawing it out of the system. As a method of removing water outside the system, the raw material alcohol and water are distilled off by azeotropic distillation, the distillate is cooled, then only water is separated by phase separation, and the alcohol is refluxed to the reactor. The method has been adopted. The azeotropic point of alcohol and by-produced water is lower than the boiling point of alcohol.If the reaction is carried out at normal pressure or reduced pressure in the initial stage of the reaction, the boiling state continues at a temperature lower than the target reaction temperature, and water is removed by azeotropy. There is a problem in that the temperature of the reaction solution does not increase until it decreases, that is, the reaction speed does not increase, and the reaction takes a long time. In addition, the latent heat of evaporation Energy is wasted in raising the reaction temperature.

Japanese Unexamined Patent Publications Nos. 55-38334 and 615-405 describe a dehydration column for removing water in refluxing alcohol in order to increase the reaction rate at the end of the reaction. The method of setting up a refuge is disclosed. However, this method does not improve the reaction rate in the initial stage of the reaction, and has a problem that special equipment such as a dehydration column is required. International Publication WO95 / 298888 discloses a method for shortening the reaction time by changing the charging ratio of alcohol and acid. That is, a method is disclosed in which the alcohol is added to a smaller amount than the theoretical amount, and then the amount of alcohol is added stepwise while monitoring the amount thereof, thereby increasing the boiling point of the reaction solution, that is, the reaction temperature to increase the reaction rate. I have. However, this method also has problems such as a slower reaction rate than the case where an excess alcohol is added. Disclosure of the invention

An object of the present invention is to provide a method for producing an ester from an organic carboxylic acid and / or an anhydride thereof and an alcohol having 4 to 18 carbon atoms, to increase the reaction rate in the initial stage of the reaction, shorten the reaction time, and reduce energy cost. It is to provide an economically advantageous method.

The present invention provides a method for producing an ester from an organic carboxylic acid and Z or an anhydride thereof with an alcohol having 4 to 18 carbon atoms, wherein the reaction is carried out at a pressure of 0.02 to 5 kg Z cm ² G. And Further, in the present invention, in addition to the reaction under the pressurized condition, the starting material alcohol having 4 to 18 carbon atoms has a boiling point under the pressure in the reactor or 20 * C lower than that. A method for producing an ester, characterized in that the reaction is performed by supplying the ester within a temperature range. BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

Examples of the organic carboxylic acid and / or anhydride thereof used in the present invention include aliphatic monocarboxylic acids such as acetic acid, propionic acid, and butyric acid, and Z or anhydride thereof, adipic acid, sebacic acid, oleic acid, and fumaric acid. Aliphatic dicarboxylic acids and aromatic dicarboxylic acids such as Z or anhydrides thereof, phthalic acid, isophthalic acid, terephthalic acid and / or aromatics such as trimellitic acid, pyromellitic acid, biphenyltetracarboxylic acid and the like Group polycarboxylic acids and z or its anhydride. Of these, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, biphenyltetracarboxylic acid and / or anhydride thereof are preferred, and phthalic acid and / or anhydride thereof are most preferred. That is, the present invention is particularly preferable as a method for obtaining a diester of an aromatic dicarboxylic acid such as phthalic acid.

Examples of the alcohol having 4 to 18 carbon atoms used in the present invention include aliphatic primary acids such as butanol, hexanol nole, heptano monole, n-octano nore, 2-ethynole hexanosle, nonyl alcohol, decyl alcohol and lauryl alcohol. Alcohols and mixtures thereof, aromatic primary alcohols such as butynolebenzyl alcohol and cresyl alcohol, glycols such as ethylene glycol, propylene glycol and butanediol, polyhydric alcohols such as pentaerythritol and And mixtures thereof. Among these, aliphatic primary alcohols having 7 to 13 carbon atoms are preferred, and 2-ethylhexyl alcohol, nonyl alcohol, and decyl alcohol are particularly preferred. The amount of the alcohol used is preferably from the stoichiometric amount to 2.0 times the amount of the organic carboxylic acid and Z or its anhydride, but industrially 2.5 times the amount is used. More preferred.

In the production method of the present invention, it is necessary to ^{carry out} the reaction at a pressure of ^{0.02 to} 5 kgZcm2G. The preferred range of pressure is from 0.03 to ² kg Z cm ^{2 G.} If the pressure is less than ^0.02 kg Zcm2G, the mixture of alcohol having 4 to 18 carbon atoms and water as a by-product tends to azeotrope, and the reaction takes a long time. In the present invention, the predetermined Since its purpose if the pressure at the reaction temperature of over vapor pressure exhibited by the mixture of water alcohol by-product of 4-1 8 carbon atoms is achieved, until the pressure exceeds a 5 kg / cm ² G There is no point in giving it.

Further, in the present invention, in order to quickly raise the temperature of the reactor に to a predetermined reaction temperature, the raw material alcohol is heated and supplied to a boiling point under the pressure in the reactor or a temperature range lower by 20 than this. Is preferred.

It is preferable that the pressure be applied from the beginning of the reaction from the outside with an inert gas such as nitrogen from the viewpoint of operability. The period during which the reaction is carried out under pressure is preferably a period from the start of the reaction until the reaction rate reaches 90%, more preferably a period from the start of the reaction until the reaction rate reaches 80%.

(Here, the reaction rate refers to the yield of ester relative to the starting organic carboxylic acid. For example, when the starting organic carboxylic acid is an aromatic dicarboxylic acid such as phthalic acid, the reaction from carboxylic acid to the monoester is performed.) The reaction from a carboxylic acid to a diester is shown here, since is often relatively quick and almost complete.)

Since the esterification reaction is an equilibrium reaction, it is necessary to increase the ester yield by removing by-produced water in the second half of the reaction. Therefore, as described above, the reaction rate is 90%, preferably 80. / ₀ becomes up period, as reaction pressure as defined in the present invention is zero. 0 2-5 range kg Z cm ^{2 G,} the initial pressurized reaction, Metsu圧from appropriate time It is desirable to gradually promote the removal of water for the first time, and to make the pressure negative at the end of the reaction when the reaction rate exceeds 90%.

Although the production method of the present invention can be carried out without a catalyst, sulfuric acid, aliphatic sulfonic acids, acid catalysts such as aromatic sulfonic acids such as para-toluenesulfonic acid, alkyl titanates such as tetrabutyl titanate and tetraisopropyl titanate, Organometallic catalysts such as Ti and Sn such as tin tetramaleate and butyltin maleate can be used. Of these, organometallic catalysts such as Ti and Sn are preferred, and alkyl titanates are most preferred. In the production method of the present invention, the reaction temperature is a temperature higher than the azeotropic point at normal pressure of the alcohol having 4 to 18 carbon atoms and water produced as a result of the reaction, which is achieved by pressurization. The range from 120 to 25 O ^ C is preferred. If the temperature is less than 120 ° C., the reaction rate tends to be low. If the temperature exceeds 250 ° C., the reaction solution may be colored or a by-product may be formed, which may impair the performance of the plasticizer. In the production method of the present invention, the preferable range of the reaction temperature depends on the catalyst to be used. In particular, when the acid catalyst is used, the preferable range of the reaction temperature is 120 to 160, with no catalyst or organic catalyst. When a metal catalyst is used, a preferred range is 160 to 250 °, and a more preferred range is 180 to 230.

Further, after the esterification reaction of the present invention is completed, purification is performed by a known method such as distillation of excess alcohol, removal of a catalyst, neutralization, washing with water, treatment with activated carbon or activated clay, and filtration to obtain an ester as a product. Can be. Example

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples. However, the present invention is not limited to the following Examples as long as the gist is not exceeded.

The following examples show examples in which phthalic acid, an aromatic dicarboxylic acid, was used as the organic carboxylic acid. In the case of this phthalic acid, the reaction to the phthalic acid monoester takes place extremely quickly and completely. The conversion in the following examples indicates the conversion to phthalic diester. That is,

Reaction rate (%) = [1-(moles of phthalic acid monoester calculated from acid value) /

(Raw material phthalic anhydride moles)] X 100

It shows.

2 liters equipped with stirrer, distillation column, condenser, oil-water separator, alcohol reflux line The four-necked flask Torr leave preheated oil path and pressurized to 100 OmmH g (0. 316 kg / cm 2 G) with nitrogen gas. 459 g (3.1 mol) of phthalic anhydride heated and melted to 140 溶融 or more was charged using a pump over 35 minutes, and at the same time, 1009 g (7.75 mol) of 170 ^ 2-ethylhexanol was pumped. The first 807 g was charged in 40 minutes and the remaining 202 g was charged in 40 minutes. As a catalyst, 0.63 ml of tetraisopropylbutanate (0.05% by weight based on the product octyl phthalate) was added after the completion of the charging of phthalic anhydride.

From the time when the charging of phthalic anhydride and 2-ethylhexanol was started (this is the reaction starting point), the 2-ethylhexanol refluxing was continued while maintaining the pressure at 1 OO mmHg (by-product). Water and 2-ethylhexanol are separated by an oil / water separator, water is removed out of the system, and 2-ethylhexanol is returned to the flask from the reflux line. The pressure was gradually reduced 40 minutes after the start of the reaction, and the pressure at about 60 minutes after the start of the reaction (about 20 minutes after the start of the depressurization) was about 90 OmmHg (about 0.184 kg gZc m ² G). The titer was 37.5 mg KOHZg. In 85 minutes after the start of the reaction, the pressure inside the reactor became negative, and the reaction rate exceeded 92%. The reaction was terminated when the acid value of the reaction solution reached 0.1 mgKOHZg (= 99.92% conversion). At this time, the pressure was 55 OmmHg (—0.276 kg / cm ² G), and the time required for the final reaction was 150 minutes.

Using the same apparatus as in Example 1, 459 g of phthalic anhydride, 1009 g of 2-ethylhexanol and 0.63 ml of tetraisopropyl titanate were charged in the same manner. As in Example 1, the temperature of the reaction solution was raised from 17 to 220 ° C. over 35 minutes while maintaining the pressure at 100 OmmHg (0.316 kg × cm ² G) from the start of the reaction. Then, while maintaining the temperature of the reaction solution at 220, the pressure was reduced with a vacuum pump. Started. From 75 minutes after the start of the reaction (40 minutes after the start of depressurization), the temperature was lowered to 185 ^ over 80 minutes while continuing the depressurization, and the reaction was terminated thereafter. (When the acid value of the reaction solution reached 0.1 mgKO HZg = reaction rate 99.92%) at this temperature. In ^{- (0. 737 kg / cm 2} G) pressure after reaction initiation 60 minutes 80 OmmH g (0. 053 kg / cm 2 G), an acid value of 40. 1 mgKOHZg, the pressure at the end of the reaction 20 OmmHg The final time required for this reaction was 180 minutes.

The preparation was carried out in the same manner as in Example 1 except that the pressure was maintained at 70 OmmHg (—0.079 kg / cm ² G). Temperature. After 70 minutes from the start of the reaction, the temperature of the reaction solution was continuously increased while further reducing the pressure from 70 OmmHg, and the temperature of the reaction solution reached 210 に after 120 minutes from the start of the reaction. Thereafter, the reaction was continued while maintaining the temperature of the reaction solution at 21, and the reaction was terminated when the acid value of the reaction solution reached 0.1 mg KOHZg (= reaction rate of 99.92%). In this case, the pressure 38 is _{OmmH g (-0. 500 kg /} cm 2 G), finally the time required for the reaction was 210 minutes.

Preparation was performed in the same manner as in Example 1 except that the pressure was maintained at 70 OmmHg (−0.079 kg / cm ² G). Then the temperature was raised. After 88 minutes from the start of the reaction, the temperature of the reaction solution was continuously increased while further reducing the pressure from 70 OmmHg, and the temperature of the reaction solution reached 21 140 minutes after the start of the reaction. Thereafter, the reaction was continued while maintaining the temperature of the reaction solution at 210 ^, and the reaction was terminated when the acid value of the reaction solution reached 0.1 mg KOHZg (= conversion of 99.92%). The pressure at this time is 38 OmmH g (-0.5 kg / cm ² G) The final time required for this reaction was 228 minutes. Evaluation of results

From the temperature and pressure conditions of Examples 1 and 2 and Comparative Examples 1 and 2, the energy required for heating was calculated using computer simulation. The software used is Γg P ROMS ”(B a r t o n a n d P a n t e l i d e s, 1 994 Im — p e r i a l C o l l e g e o f S i e n c e,

T e c h n o l o g y a n d e d i c i n e). The time required for terminating the reaction was 65% in Example 1 and 79% in Example 2, assuming that Comparative Example 2 was 100%.

From this result, it is clear that the conventional method (Comparative Example 2) requires a long time for the reaction and also requires much energy for heating. The second embodiment is an example in which optimization is performed to save necessary energy. Even in this case, the reaction time is 85% of Comparative Example 1, and the required energy is about 70%. It is 79% of Comparative Example 2, and the required energy is about 60%. Industrial applicability

According to the method for producing an ester of the present invention, the reaction time can be reduced and the energy can be reduced as compared with the conventional method.

Claims

The scope of the claims

1. A method for producing an ester from an alcohol of an organic carboxylic acid and / or anhydride and carbon number 4 to 18, the production of esters comprising reacting at a pressure of 0. 02~ 5 k gZ cm ² G Method.

2. The method for producing an ester according to claim 1, wherein the reaction is carried out at a temperature higher than the azeotropic point at normal pressure of a mixture of an alcohol having 4 to 18 carbon atoms and water as a by-product.

3. period from the start of the reaction to the ester yield is 90% ester method according to claim 1 or 2 are reacted at a pressure of 0. 02~5 k gZc m ² G.

4. The organic carboxylic acid and its anhydride are supplied in a molten or powdered state, and the alcohol is supplied at a boiling point under the pressure in the reactor or a temperature range lower than the boiling point by 20 or more. The method for producing an ester according to the above item.

5. The method for producing an ester according to any one of claims 1 to 4, wherein the reaction temperature is 120 to 250 ^.

6. The method for producing an ester according to any one of claims 1 to 5, wherein the catalyst is an organometallic catalyst.

7. The method for producing an ester according to any one of claims 1 to 6, wherein the organic carboxylic acid and Z or its anhydride are aromatic dicarboxylic acids and Z or its anhydride.

8. The method for producing an ester according to any one of claims 1 to 7, wherein the alcohol having 4 to 18 carbon atoms is an aliphatic primary alcohol.

9. The method for producing an ester according to any one of claims 1 to 8, wherein a negative pressure is applied at the end of the reaction.