JPH06329580A - Method for recovering unsaturated carboxylic acid - Google Patents

Abstract

PURPOSE:To produce a higher alcohol ester of an unsaturated carboxylic acid in high purity and economically. CONSTITUTION:An excessive amount of an unsaturated carboxylic acid is used to give a high-purity ester and a higher alcohol distilled together with a higher alcohol is extracted with a higher alcohol and reused.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recovering unsaturated carboxylic acid. More specifically, the present invention relates to a method for recovering an unsaturated carboxylic acid that is distilled together with water produced in the production of an unsaturated carboxylic acid ester in which an unsaturated carboxylic acid and a higher alcohol are reacted.

[0002]

2. Description of the Related Art Conventionally, the production of unsaturated carboxylic acid esters by reacting unsaturated carboxylic acids with higher alcohols has been
The unsaturated carboxylic acid and the higher alcohol were used in approximately equivalent amounts, and the water produced was azeotropically distilled with a solvent such as toluene and removed from the system. However, in this method, since the esterification reaction is an equilibrium reaction, it takes a long time to complete the reaction, and there are problems such as quality deterioration such as formation of oligomers of unsaturated carboxylic acid and its ester. In order to improve this, a method is used in which an unsaturated carboxylic acid or higher alcohol is used in an equivalent amount or more and is removed out of the system together with water that produces an excess unsaturated carboxylic acid or higher alcohol.

[0003]

However, in order to carry out the process industrially, it is necessary to recover the excess unsaturated carboxylic acid or higher alcohol economically, but the unsaturated carboxylic acid is used in excess. In this case, it is necessary to use a solvent such as toluene, and when the higher alcohol is used in excess, the unsaturated carboxylic acid ester itself is distilled out when the excess higher alcohol is taken out, and there is no effective recovery method.

[0004]

The present inventors have found that in an esterification reaction using an unsaturated carboxylic acid or a higher alcohol in an equivalent amount or more, which does not cause a problem such as deterioration of the quality of the unsaturated carboxylic acid ester, the unsaturated carboxylic acid is used. The present invention has been achieved as a result of intensive studies on a method of industrially effectively recovering an excess of carboxylic acid using more than 1 equivalent. That is, the present invention provides an unsaturated carboxylic acid (A) and a carbon number of 8 to 30.
In the production of an unsaturated carboxylic acid ester by reacting with the alcohol (B), the (A) distilled with the produced water is extracted with the (B). Is.

Examples of the unsaturated carboxylic acid (A) used in the method of the present invention include acrylic acid, methacrylic acid, crotonic acid and mixtures thereof. Among these, acrylic acid and methacrylic acid are preferably used, and methacrylic acid is most preferably used.

The number of carbon atoms used in the method of the present invention is from 8 to 8.
The higher alcohol (B) having 30 has 8 to 20 carbon atoms.
Alcohols (octyl alcohol, decyl alcohol, lauryl alcohol, tridecyl alcohol, tetradecyl alcohol, hexadecyl alcohol, octadecyl alcohol, etc.), alcohols having 21 to 30 carbon atoms (Naphthol 20+ and Naphthol 22+ (all manufactured by Condea Chemie), etc.) } And mixtures thereof, and the like. These alcohols may be straight chain alcohols or branched alcohols, and may have unsaturated bonds.

In the method of the present invention, the unsaturated carboxylic acid ester is prepared by reacting (A) and (B) in the presence of a catalyst (usually sulfuric acid and paratoluenesulfonic acid) and a polymerization inhibitor (hydroquinone). Manufactured.
The equivalent ratio of (A) and (B) is usually (2.0: 1) to
(1.1: 1), preferably (1.5: 1) to (1.
2: 1). If (A) exceeds 2.0, the effect of shortening the reaction time becomes small, and if it is less than 1.1, the reaction time becomes long. The reaction temperature is usually 50 to 180 ° C., preferably 80 to 180 ° C.
It is 150 ° C. If the temperature is below 50 ° C, the reaction time will be long
If it exceeds 180 ° C, the problem of quality deterioration tends to occur. Further, based on the total amount of (A) and (B), the acid catalyst is usually 0.05 to 3.0% by weight and the polymerization inhibitor is usually 0.05 to 3.0% by weight.
Use 2.0% by weight.

The unsaturated carboxylic acid ester is (A),
It is produced by mixing (B), an acid catalyst and a polymerization inhibitor and heating, but any method such as a method of dropping (A) and / or (B), a method of reacting under normal pressure, pressurization or reduced pressure may be used. It can be manufactured under the conditions.

Excess (A) is distilled off together with water produced by the reaction of (A) and (B), and the reaction is completed, but usually excess (A) still exists in the reaction system. The (A) present in this system can usually be taken out under reduced pressure and reused.

The method of the present invention is characterized in that (A) distilled with the produced water is extracted in (B).
Since (B) is an alcohol having 8 to 30 carbon atoms, the solubility in water is small and the extraction efficiency is increased. The extraction operation may be either a continuous method or a batch method. In the case of the batch method, it is usually 1
Do ~ 3 times. Although (B) is preferably liquid, it may be used in combination with a solvent (toluene or the like) which has a low solubility in water and dissolves (B) as long as it is solid. By extracting with (B), it is possible to reuse as (B) containing (A) as it is, without any special purification.

[0011]

EXAMPLES The present invention will be further described below with reference to examples, but the present invention is not limited thereto. Example,
Parts in Evaluation Examples and Comparative Examples are parts by weight. The esterification rate was measured by gas chromatography, and the methacrylic acid content in the produced water and alcohol layer was calculated by measuring the acid value.

Example 1 In a reaction tank, 400 parts of methacrylic acid and an alcohol having 14 to 15 carbon atoms (trade name, Dobanol 45, manufactured by Mitsubishi Yuka) 76
Charge 0 parts, 4 parts sulfuric acid and 2 parts hydroquinone, 1
The temperature was raised to 20 ° C. Methacrylic acid was distilled out together with the produced water, and the esterification rate reached 99% after 4 hours. The produced water containing methacrylic acid was 74.2 parts, and the methacrylic acid content was 16.5% by weight. The pressure in the reaction system was gradually reduced to remove excess methacrylic acid. To 74.2 parts of produced water containing methacrylic acid, 74.2 parts of the same alcohol used in the reaction was added and stirred for 10 minutes. 1
The alcohol layer taken out after standing for 0 minutes was 86.3 parts, the methacrylic acid content was 14% by weight, and the extraction rate was 99%.

Example 2 430 parts of methacrylic acid and alcohol having 12 to 13 carbon atoms (trade name, Dobanol 23, manufactured by Mitsubishi Yuka) 74 in a reaction tank
Charge 0 parts, 3 parts sulfuric acid and 2 parts hydroquinone, 1
The temperature was raised to 20 ° C. Methacrylic acid was distilled out together with the produced water, and the esterification rate reached 99% after 4 hours. The produced water containing methacrylic acid was 80.7 parts, and the methacrylic acid content was 16.5% by weight. The pressure in the reaction system was gradually reduced to remove excess methacrylic acid. To 80.7 parts of produced water containing methacrylic acid, 80.7 parts of the same alcohol used in the reaction was added and stirred for 10 minutes. 1
The alcohol layer taken out after standing for 0 minutes was 93.9 parts, the methacrylic acid content was 14% by weight, and the extraction rate was 99%.

Evaluation Example 1 In a reaction tank, 388 parts of methacrylic acid and alcohol having 14 to 15 carbon atoms (trade name, Dobanol 45, manufactured by Mitsubishi Yuka) 68
6 parts, 86 parts of the alcohol layer containing methacrylic acid obtained in Example 1, 4 parts of sulfuric acid and 2 parts of hydroquinone were charged, and the temperature was raised to 120 ° C. Methacrylic acid was distilled out together with the produced water, and the esterification rate reached 99% after 4 hours.
The produced water containing methacrylic acid was 74.2 parts, and the methacrylic acid content was 16.5% by weight. The pressure in the reaction system was gradually reduced to remove excess methacrylic acid. The obtained tacrylic acid ester had the same quality as that obtained in Example 1, and the extraction from the produced water containing methacrylic acid could be performed in the same manner as in Example 1.

Evaluation Example 2 417 parts of methacrylic acid and an alcohol having 12 to 13 carbon atoms (trade name: Dobanol 23, manufactured by Mitsubishi Yuka) 66 in a reaction tank
0 part, 93 parts of the alcohol layer containing methacrylic acid obtained in Example 2, 3 parts of sulfuric acid and 2 parts of hydroquinone were charged, and the temperature was raised to 120 ° C. Methacrylic acid was distilled out together with the produced water, and the esterification rate reached 99% after 4 hours.
The produced water containing methacrylic acid was 80.7 parts, and the methacrylic acid content was 16.5% by weight. The pressure in the reaction system was gradually reduced to remove excess methacrylic acid. The obtained tacrylic acid ester had the same quality as that obtained in Example 2, and the extraction from the produced water containing methacrylic acid could be performed in the same manner as in Example 2.

Comparative Example 1 In a reaction tank, 316 parts of methacrylic acid and alcohol having 14 to 15 carbon atoms (trade name, Dobanol 45, manufactured by Mitsubishi Yuka) 78
0 part, 133 parts of toluene, 4 parts of sulfuric acid and 2 parts of hydroquinone were charged, and the temperature was raised to 120 ° C. Water was separated from toluene that was distilled out together with the produced water, and the toluene was refluxed. After 4 hours, the esterification rate was 96%, and after 5 hours, the esterification rate was 97%. The pressure in the reaction system is gradually reduced,
Toluene was taken out.

From Examples 1 and 2, methacrylic acid in the produced water was efficiently extracted into a higher alcohol, and Evaluation Example 1
From 2 and 2, it is understood that the extracted alcohol solution of methacrylic acid can be reused as it is. Further, as compared with the ester of Comparative Example 1, Examples 1 and 2 and Evaluation Examples 1 and 2 were used.
It can be seen that the ester of is highly pure.

[0018]

INDUSTRIAL APPLICABILITY By the method of the present invention, unsaturated carboxylic acid used in excess can be efficiently recovered and reused without any special purification. Further, the amount of waste liquid can be reduced and the product purity can be improved, which is an extremely useful method industrially.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C07C 69/54 Z 9279-4H

Claims (2)

[Claims] 1. An unsaturated carboxylic acid (A) and 8 to 8 carbon atoms.
In the production of an unsaturated carboxylic acid ester which is reacted with 30 alcohols (B), the (A) that distills with the produced water is extracted in the (B), and the unsaturated carboxylic acid is recovered. Method. 2. The method according to claim 1, wherein the unsaturated carboxylic acid (A) is acrylic acid and / or methacrylic acid.