JPH06157405A - Production of ester - Google Patents

Abstract

PURPOSE:To produce an ester, capable of reducing energy required for reflux without lowering a reaction rate. CONSTITUTION:An acid compound is reacted with an alcohol component in a reactor 1, a reaction solution is sent from the reactor to a dehydrating unit 3 which is arranged independently from the reactor 1 and has a larger gas-liquid interface than the reactor and water is removed in an unheated state in the dehydrating unit 3 to produce an ester.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an ester from an acid component and an alcohol component, and more particularly to a method for producing an ester capable of reducing the energy required for reflux without reducing the reaction rate.

[0002]

2. Description of the Related Art Conventionally, when producing an ester from an acid component and an alcohol component, various catalysts are used,
Alternatively, it has been attempted to increase the production rate and yield of the ester by devising various reaction conditions such as temperature and pressure. For example, a metal-based catalyst such as tetrabutyl titanate has been conventionally used as the above catalyst. However, when such a catalyst is used, the yield can be increased by suppressing the production of by-products, but the above-mentioned catalyst is activated at a high temperature, so that the energy cost is high. There was a problem. Further, Japanese Patent Publication No. 2-11577 proposes a method of accelerating the reaction by causing the reaction solution to flow down in a thin film form and heating the thin film reaction solution to react.

On the other hand, since the esterification reaction is a typical equilibrium reaction, the reaction equilibrium may be moved to the product side by removing the reaction product. Therefore, a reactive distillation method has been conventionally used as a method for removing water generated by the reaction.

However, in the reactive distillation method, other components are distilled out of the reactor together with the water produced by the reaction. Therefore, a reflux operation of cooling and condensing the distillate and returning it to the reactor again is required. However, among the energy costs required for ester production, the energy cost required for the above reflux is not small, and therefore, it is desired to reduce the energy cost required for the reflux.

In order to reduce the energy cost required for the above reflux, a method of reducing the reflux amount, a method of reducing the temperature difference between the reflux liquid temperature and the reaction liquid temperature, or the like can be considered. In order to simultaneously achieve the above and, the reaction temperature may be lowered. That is, due to the vapor-liquid equilibrium relationship between water and other components, the reflux amount decreases at a lower temperature and the temperature difference between the reflux temperature and the reaction temperature decreases at a lower reaction temperature. However, when the reaction temperature is lowered, the evaporation rate of water decreases and the dehydration rate decreases. As a result, the rate of ester formation is reduced.

Therefore, if the reaction temperature is simply lowered,
Energy costs cannot be reduced without slowing the rate of ester formation.

[0007]

SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks of the prior art, the present invention, when producing an ester from an acid component and an alcohol component, does not reduce the rate of ester formation and requires the energy required for reflux. It is an object of the present invention to provide a method by which the production cost of ester can be effectively reduced.

[0008]

In the method for producing an ester of the present invention, an acid component and an alcohol component are reacted in a reactor, and the ester is provided independently of the reactor and larger than the reactor. The reaction liquid is sent from the reactor to a dehydration unit capable of forming a liquid interface, and water is removed in the dehydration unit in a non-heated state.

The dewatering unit used in the present invention is provided independently of the reactor and is used for removing water in a non-heated state.
Those having no heating function are preferably used. Also,
The dehydration unit needs to have a gas-liquid interface larger than that of the reactor, and a filling type, particularly an ordered packing filling type device is preferably used, but other devices such as a plate type and a falling film are used. Type or a forced stirring type thin film type device may be used.

The acid component used in the method for producing an ester of the present invention includes monobasic acids such as acetic acid, propionic acid or butyric acid, phthalic acid, adipic acid, sebacic acid,
Examples thereof include dibasic acids such as oleic acid and fumaric acid, polybasic acids such as trimellitic acid and pyromellitic acid, and acid anhydrides such as phthalic anhydride.

As the alcohol component, butanol, heptanol, octanol, aliphatic alcohols such as 2-ethylhexanol or decanol, methanediol, ethanediol, pentanediol, heptanediol, ethylene glycol, propylene glycol or neopentyl glycol, etc. And polyhydric alcohols such as pentaerythritol.

The lower the reaction temperature in the reactor is, the more the amount of reflux of components other than water is reduced, which is preferable. However, if the reaction temperature is too low, the reaction rate will decrease. Further, if the reaction temperature is too high, the amount of reflux of components other than water increases. Therefore, from such a point, in order to reduce the reflux amount of components other than water without decreasing the reaction rate,
The reaction temperature is preferably in the range of 80 to 120 ° C.

When the reaction liquid is sent from the reactor to the dehydration unit, it is preferable to send the reaction liquid without heating for the same reason as above. In the present invention, first, an acid component, an alcohol component slightly in excess of the theoretical amount, and an appropriate catalyst are charged into a reactor, and the reaction is started by heating the mixture to a predetermined temperature while stirring under reduced pressure. As the catalyst, for example, p-toluenesulfonic acid, methanesulfonic acid, benzenesulfonic acid, etc. can be used.

Next, after the stage where a predetermined reaction temperature is reached by heating, the reaction solution is circulated between the reactor and the dehydration unit, and the reaction product water is removed in the dehydration unit while the esterification reaction proceeds. Let After completion of the reaction, the above-mentioned catalyst is recovered from the reaction solution, then neutralized with an alkali, washed with water, and excess alcohol is removed by distillation, followed by treatment with activated carbon or activated clay to obtain an ester as a product. Can be obtained.

In the method for producing an ester of the present invention, it is not always necessary to circulate the reaction solution immediately after the reaction is started, and the circulation may be started during the reaction. Further, the present invention is not limited to the method by the batch type operation, but can be applied to the continuous operation.

[0016]

In the method for producing an ester of the present invention, the reaction liquid is sent to a dehydrating unit which is provided independently of the reactor and has a larger gas-liquid interface than the reactor, and water is removed in the dehydrating unit. It Therefore, the amount of reflux of components other than water can be reduced without decreasing the reaction rate, and the temperature difference between the reflux liquid temperature and the reaction liquid temperature can be reduced. Therefore, the energy required for reflux can be reduced.

[0017]

EXAMPLE An outline of an ester production apparatus used in Example 1 described later will be described with reference to FIG. A stirrer 1a is provided in the reactor 1 to stir the acid component, the alcohol component and the catalyst charged in the reactor 1. The reactor 1 is configured so that the inside thereof can be depressurized by a vacuum pump 7 described later.

The reactor 1 is connected to a dehydration unit 3 via a reaction solution circulation pump 2. The dehydration unit 3
It is composed of a packed column having a gas-liquid interface larger than that of the reactor 1. Further, the dehydration unit 3 does not have a heating function. Therefore, from the reactor 1 to the reaction solution circulation pump 2
The reaction liquid sent by is not heated in the dehydration unit 3. Further, since the dehydration unit 3 has a larger gas-liquid interface than the reactor 1, dehydration is efficiently performed. Reference numeral 4 denotes a rectification column, which is connected to the dehydration unit 3 and the reactor 1. Also, 5 is a capacitor,
6 is a decanter and 7 is a vacuum pump.

Example 1 An ester was produced in the following manner using the apparatus outlined in FIG. As the reactor 1, a glass reactor equipped with a stirrer having a capacity of 2 liters was used, which was connected to the reaction solution circulation pump 2 by a glass tube, and further, the reaction solution circulation pump and the dehydration unit 3
1 was constructed by connecting the above-mentioned packed column (packing; Sumitomo Heavy Industries Ltd., Sumitomo / Sulzer Lab packing, diameter 50 mm, 7 pieces) with a glass tube.

Phthalic anhydride 492.8 g (3.33 mol), 2-ethylhexanol 997.4 g (7.66)
Mol) was charged to the above reactor 1 and 100
The temperature was raised to ℃, and then p-toluenesulfonic acid monohydrate 5
6.1 g (0.295 mol) was added, and the point at which this p-toluenesulfonic acid monohydrate was added was used as the reaction starting point, and the temperature was kept at 100 ° C to carry out the esterification reaction.

After the start of the reaction, a fixed amount of the reaction solution is sampled from the reactor 1 every hour, water is added to the sampled reaction solution and mixed well, and 15,000 rpm × 5.
Centrifugation was carried out under the condition of minutes to separate a crude ester layer and an aqueous layer. To the separated crude ester in the upper layer, metacresol purple and thymol blue were used as indicators in a weight ratio of 1: 1.
The mixed solution containing the above was added and titrated with potassium hydroxide to measure the acid value of the unreacted monoester. From the measured acid value,
The reaction rate based on phthalic anhydride was determined.

After the reaction rate reached 90%, the reaction solution circulation pump 2 was driven to circulate the reaction solution at a flow rate of 4.6 kg / hour to continue the esterification reaction. Reaction rate 9
The time required for the reaction to proceed to 9.8% was 3.8 hours. The reflux amount of 2-ethylhexanol at this time was 78 g.

Comparative Example 1 A glass reactor equipped with a stirrer having a capacity of 2 liters was charged with 492.8 g (3.33 mol) of phthalic anhydride and 997.4 g (7.66 mol) of 2-ethylhexanol, and the mixture was heated to 190 ° C. under reduced pressure. The temperature was raised to 0.74 g (0.0022 mol) of tetrabutyl titanate (this point was used as the reaction starting point), and the temperature was maintained at 190 ° C. to carry out the esterification reaction.

A certain amount of the reaction solution was sampled from the reaction solution every 1 hour after the start of the reaction, titrated with potassium hydroxide using phenolphthalein as an indicator, and the acid value of the unreacted monoester was measured. The reaction rate based on phthalic acid was calculated. The time required for the reaction to proceed to the above reaction rate of 99.8% was 3.8 hours. The reflux amount of 2-ethylhexanol at this time was 585 g.

COMPARATIVE EXAMPLE 2 56.1 g (0.2%) of p-toluenesulfonic acid monohydrate was used as the catalyst in place of 0.74 g of tetrabutyl titanate.
The esterification reaction was carried out in the same manner as in Comparative Example 1 except that the reaction temperature was 100 ° C.

A constant amount of the reaction solution was sampled from the reactor every hour after the reaction was started, and the reaction rate was determined in the same manner as in Example 1. The time required for the reaction to proceed to the reaction rate of 99.8% was 7 hours. The reflux amount of 2-ethylhexanol at this time was 73 g.

Comparative Example 3 In the ester production apparatus shown in FIG. 1, a heater was installed between the packed column as the dehydration unit 3 and the reaction circulation pump 2, and the temperature of the reaction solution supplied to the dehydration unit 3 was set to 130.
The esterification reaction was performed in the same manner as in Example 1 except that the temperature was changed to 0 ° C. The time required for the reaction to proceed to the reaction rate of 99.8% was 3.6 hours. The reflux amount of 2-ethylhexanol at this time was 117 g.

[0028]

According to the method for producing an ester of the present invention,
Since water is removed in a non-heated state in a dehydration unit that is provided independently of the reactor and has a larger gas-liquid interface than the reactor, the amount of reflux is reduced without lowering the reaction rate. Therefore, the energy required for reflux can be effectively reduced, and the production cost of the ester can be reduced.

[Brief description of drawings]

FIG. 1 is a flow diagram showing an outline of an ester production apparatus used in Example 1.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Reactor 2 ... Reactant circulation pump 3 ... Dehydration unit 4 ... Fractionation tower 5 ... Condenser 6 ... Decanter 7 ... Vacuum pump

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location // B01J 31/02 103 7821-4G C07B 61/00 300

Claims (2)

[Claims] 1. A dehydration unit which reacts an acid component and an alcohol component in a reactor and is provided independently of the reactor and which is capable of forming a gas-liquid interface larger than that of the reactor. The reaction liquid is sent from the vessel, and water is removed in the dehydration unit in a non-heated state,
Method for producing ester. 2. The acid component and the alcohol component are reacted in the reactor at a reaction temperature of 80 to 120 ° C.
The method for producing an ester according to 1.