JPH05125028A - Production of carbonic acid ester - Google Patents

Abstract

PURPOSE:To obtain the subject compound in improved workability while suppressing the foaming by reacting a lower aliphatic carboxylic acid with a specific aromatic-substituted alcohol in the presence of an acid catalyst, adding a specific alcohol to the reactional mixture and neutralizing the reactional liquid with an alkali metal carbonate, etc. CONSTITUTION:A carboxylic acid ester can be produced in high workability while suppressing the foaming caused by the carbon dioxide gas generated in neutralization reaction by esterifying a lower aliphatic carboxylic acid (e.g. propionic acid) or its acid anhydride with an aromatic-substituted alcohol of formula (X is carbamoyl, cyano or nitro) [e.g. 4-(2-hydroxyethoxy)benzamide] in the presence of an acid catalyst (e.g. p-toluenesulfonic acid) in a toluene solvent under refluxing the toluene for 5hr, adding a 6-12C aliphatic alcohol (e.g. 1-hexanol) to the reactional liquid containing the produced ester compound and neutralizing the mixture with an alkali metal carbonate or alkali metal bicarbonate (e.g. sodium carbonate).

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 a carboxylic acid ester, which is obtained by an esterification reaction of a lower aliphatic carboxylic acid or an acid anhydride thereof with an aromatic substituted alcohol in the presence of an acid catalyst. The present invention relates to a method for producing a carboxylic acid ester having an improved method for neutralizing an acidic substance present in a reaction solution.

The product ester obtained in the present invention has physical properties of high boiling point and high melting point and can be used as a special solvent.

[0003]

2. Description of the Related Art In a reaction solution obtained by an esterification reaction of an aliphatic carboxylic acid or an aliphatic carboxylic acid anhydride with an aromatic substituted alcohol in the presence of an acid catalyst, an unreacted carboxylic acid and an acid are added as acidic substances. Coexist with a catalyst. In order to remove this acidic substance, neutralization treatment is usually performed using an aqueous solution of an alkali metal carbonate or bicarbonate in which the pH of the wastewater is easily adjusted, and then liquid separation into an ester layer and a water layer is performed. The ester layer is washed again with water. In this case, since carbon dioxide generated by the neutralization reaction causes vigorous bubbling, the neutralization operation becomes extremely complicated and becomes a serious problem particularly in the case of large-scale industrial production.

As a method for solving this foaming problem, for example, in JP-A-59-127692, metal carbonates or bicarbonates such as sodium carbonate, sodium bicarbonate, etc.
A method has been proposed in which a low-foaming neutralizing agent is prepared by adding an antifoaming agent such as 01% by weight or more of a silicon-based or mineral oil-based anti-foaming agent and used for neutralizing an acidic waste liquid.

However, when this method is applied to the method for neutralizing and removing the acidic substance in the production of the carboxylic acid ester of the present invention, since these antifoaming agents are hardly dissolved in water, the organic layer containing the ester is depleted. Defoamer mixed in,
As a result, it remains in the product ester, resulting in a decrease in the purity of the carboxylic acid ester and a decrease in the function of the product.

[0006]

Under such circumstances, the acidic substance present in the reaction solution obtained by the esterification reaction is neutralized by an industrially easy method, and the desired carvone is obtained. There has been a problem to prevent the purity of the acid ester from decreasing.

[0007]

In order to solve the above problems, the inventors of the present invention have diligently studied a method of neutralizing a reaction solution containing a carboxylic acid ester when producing the carboxylic acid ester. The present invention has been completed by discovering that the amount of foaming is significantly reduced by neutralizing with an aqueous solution of an alkali metal carbonate or an alkali metal bicarbonate after adding an aliphatic alcohol compound.

That is, the present invention relates to a reaction solution containing an ester compound produced in an esterification reaction of a lower aliphatic carboxylic acid or its acid anhydride with an aromatic substituted alcohol represented by the following general formula in the presence of an acid catalyst. A method for producing a carboxylic acid ester, which comprises adding an aliphatic alcohol compound having a carbon number of 6 to 12 before neutralization with an aqueous solution of an alkali metal carbonate or an alkali metal bicarbonate. Is.

[0009]

[Chemical 1]

(In the formula, X represents one of a carbamoyl group, a cyano group and a nitro group.)

The lower aliphatic carboxylic acids used in the present invention are acetic acid, propionic acid and butyric acid, and any of acetic anhydride, propionic anhydride and butyric anhydride can be used as the acid anhydride.

The aromatic substituted alcohol represented by the above general formula is, for example, 4- (2-hydroxyethoxy) benzamide, 2- (2-hydroxyethoxy) benzonitrile, 2- (2-
3-nitrophenyloxy) ethanol and the like.

The acid catalyst is an organic sulfonic acid such as p-toluenesulfonic acid, ethanesulfonic acid and benzenesulfonic acid, but p-toluenesulfonic acid is generally used.

The reaction method may be a conventional method, in which a carboxylic acid and / or a carboxylic acid anhydride and an aromatic substituted alcohol are reacted in the presence of a solvent. Here, as the reaction solvent,
Benzene, toluene, etc. used in general esterification reaction are used.

In the reaction solution obtained by the esterification reaction,
In addition to the target ester compound, when an acid catalyst and a carboxylic acid or a carboxylic acid anhydride are used in excess equivalent numbers (here, equivalents refer to acid-base equivalents. The same applies hereinafter) with respect to the aromatic substituted alcohol. It also contains unreacted carboxylic acid.

The removal of these acidic substances present in the reaction solution is carried out by adding an aliphatic alcohol to the reaction solution and then neutralizing the solution with an aqueous solution containing a basic neutralizing agent. It is dissolved in the layer and separated from the organic layer containing the desired ester.

The aliphatic alcohol compound has 6 to 6 carbon atoms.
Examples of the 12 alcohols include 1-hexanol, 1-heptanol, 2-ethylhexanol, 2-methyl-1-heptanol, 3-ethyl-2-nonanol and the like. Alcohols having 5 or less carbon atoms have high solubility in water and a small defoaming effect, and alcohols having a number of carbon atoms greater than 12 have a high melting point and a high viscosity even at the neutralization temperature, and are not expected to have a foam suppressing effect.

The amount of the aliphatic alcohol compound added to the reaction solution is preferably 0.1 to 5.0% by weight based on the reaction solvent. If the addition amount is too small, a large amount of foaming due to carbon dioxide generated in the neutralization reaction cannot be avoided, and if the addition amount is excessive, it becomes difficult to separate the aqueous layer and the organic layer containing the ester after the neutralization treatment. ..

The basic neutralizing agents are alkali metal carbonates and alkali metal bicarbonates. The alkali metal carbonates include sodium carbonate and potassium carbonate, and the alkali metal bicarbonates include sodium hydrogen carbonate and carbonate. Examples include potassium hydrogen.

The amount of the basic neutralizing agent added is preferably in the range of 1 to 3 times the equivalent of the acid in the reaction solution. If the amount of the neutralizing agent is too small, the acidic substance in the reaction solution is not sufficiently neutralized and is mixed in the product ester as an impurity. If the amount of the neutralizing agent exceeds the above range, the alkali metal remains in the organic layer after neutralization, and it becomes necessary to increase the number of times of washing with water after neutralization, which extends the process time.

The concentration of the aqueous solution of the basic neutralizing agent is not particularly limited, but is preferably 5 to 20% by weight. If the concentration is too high, neutralized salts and the like will precipitate in the system, while if the concentration is too low, the amount of wastewater will increase significantly.

The neutralization temperature is not particularly limited, but is preferably 80 ° C. or lower, and boiling of the solvent begins to occur at 80 ° C. or higher.

[0023]

[Function] It is known that lower alcohols having a carbon number of 5 or less have a foam-breaking action of eliminating bubbles, but do not suppress the generation of bubbles themselves. The mechanism of the antifoaming action or the foam suppressing action of the aliphatic alcohol having 6 to 12 carbon atoms in the present invention is not necessarily clear, but the presence of alcohol at the interface between the aqueous phase and the organic phase lowers the interfacial tension. It is considered that the generation of bubbles is suppressed.

[0024]

EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 4- (2-hydroxyethoxy) benzamide 45 g (0.25 equivalent), p-toluenesulfonic acid 9.5 g (0.05 equivalent), propionic acid 22.2 g (0.3 equivalent) and toluene 250 g were charged at the same time under toluene reflux. The reaction was carried out for 5 hours (reaction temperature 110 ° C).

The reaction solution was transferred to a 500 ml measuring cylinder,
Add the additives shown in Table 1 and maintain at 70 ° C with stirring,
Neutralization treatment was carried out with an aqueous solution prepared by dissolving 10.6 g (0.2 equivalent) of sodium carbonate in 90 g of water, and the amount of foaming at that time was measured.
The results are shown in Table 1.

[0027]

As described above in detail, the present invention provides a method for producing a carboxylic acid ester by an esterification reaction from an aliphatic carboxylic acid or its acid anhydride and an aromatic substituted alcohol in the presence of an acid catalyst. Before neutralizing the reaction solution containing it with an alkali metal carbonate or an alkali metal bicarbonate, by adding a small amount of an aliphatic alcohol compound to the reaction solution, foaming due to the generation of carbon dioxide in the neutralization reaction is suppressed, It is possible to improve the workability.

[Table 1]

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location C07C 255/54 6917-4H // C07B 61/00 300

Claims (1)

[Claims] 1. A lower aliphatic carboxylic acid or an acid anhydride thereof in the presence of an acid catalyst and a general formula: (In the formula, X represents one of a carbamoyl group, a cyano group and a nitro group.) In an esterification reaction with an aromatic substituted alcohol represented by the formula, the reaction solution containing the produced ester compound is treated with an alkali metal carbonate or an alkali. When neutralizing with an aqueous solution of metal bicarbonate,
A method for producing a carboxylic acid ester, which comprises adding 6 to 12 aliphatic alcohol compounds.