Process for the preparation of sorbic acid

Details Process for the preparation of sorbic acid Process for the preparation of sorbic acid

2000-05-24

2003-04-08

Gitomer, Ralph (Department: 1651)

Organic compounds -- part of the class 532-570 series

Organic compounds

Carboxylic acids and salts thereof

Reexamination Certificate

active

06545180

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a process for producing sorbic acid which is useful as, for example, food additives. Particularly, the invention relates to a process for producing sorbic acid by decomposing a polyester by action of hydrochloric acid, which polyester is obtained from ketene and crotonaldehyde.
BACKGROUND ART
As processes for the commercial production of sorbic acid, processes are known which include the step of decomposing a polyester with hydrochloric acid, which polyester is obtained by a reaction of ketene with crotonaldehyde. For example, Japanese Examined Patent Application Publication No. 44-26646 discloses a process for producing sorbic acid. The process includes the steps of reacting ketene with crotonaldehyde in the presence of a catalyst to yield a reaction mixture, heating the reaction mixture under reduced pressure to remove unreacted crotonaldehyde and by-products of the reaction by distillation to yield a polyester containing the catalyst, decomposing the polyester with hydrochloric acid to yield a reaction mixture, and cooling the reaction mixture to yield sorbic acid.
In the step of decomposing the polyester with hydrochloric acid to yield sorbic acid, the polyester should be preferably decomposed at somewhat high temperatures in a short time, from the viewpoint of a production efficiency. Separately, in the decomposition of the polyester with hydrochloric acid, the mixture must be heated in an initial stage but the heat may invite by-production of tar substances. Particularly, the by-production is enhanced at high temperatures. When the polyester is decomposed in a batch system, a large amount of heat is evolved after the initiation of the decomposition reaction. Such heat includes precipitation heat evolved through precipitation of formed sorbic acid. The reaction mixture must be aged at somewhat high temperatures even after the heat generation calms down. If the aging temperature is excessively high, side reactions increase, and if the aging temperature is excessively low, the decomposition rate or isomerization rate of the polyester decreases. In both cases, the yield of sorbic acid decreases. Accordingly, in the polyester decomposition step, the reaction temperatures, particularly the maximum temperature upon heat generation (hereinafter referred to as “peak temperature”) and the reaction temperature in an aging stage after attaining the peak temperature must be delicately and precisely controlled.
Generally, the polyester decomposition reaction is performed using a reactor with a jacket. The reaction temperature is controlled by allowing steam to pass through the jacket in an early stage of the reaction, or by allowing a cooling water to pass through the jacket in a later stage after the reaction proceeds to some extent. However, if the reaction is performed at relatively high temperatures to complete the reaction in a short time, heat such as the precipitation heat of sorbic acid is convergently evolved just before attaining the peak temperature. The heat cannot be immediately removed according to the above techniques for heat removal, and the reaction temperatures (peak temperature and aging temperature) cannot be significantly precisely controlled.
The Japanese Examined Patent Application Publication No. 44-26646 discloses a process for producing sorbic acid. The process includes the steps of preparing a polyester from ketene and crotonaldehyde, and decomposing the polyester with hydrochloric acid having a concentration of 35% by weight or more at temperatures ranging from room temperature to around the boiling point of the hydrochloric acid used. Japanese Examined Patent Application Publication No.45-16445 discloses a process for producing sorbic acid. This process includes the steps of putting the polyester into relatively large amounts of hydrochloric acid, treating the polyester at temperatures ranging from room temperature to 80° C., removing hydrochloric acid from a reaction mixture containing precipitated sorbic acid and unreacted polyester, heating the mixture to high temperatures ranging from 110° C. to 250° C. to thereby recover the formed sorbic acid by distillation. Japanese Unexamined Patent Application Publication No. 9-227447 discloses a process for producing sorbic acid. The process includes the step of performing isomerization after the completion of heat generation in the hydrolysis of the polyester. The isomerization is performed at a temperature of 25° C. or higher, which temperature is 4° C. or more lower than the temperature at the time when heat generation completes. Japanese Unexamined Patent Application Publication No. 10-95745 discloses a process for producing sorbic acid, including the step of hydrolyzing the polyester with a mineral acid in the presence of a saturated fatty acid. However, these publications fail to describe how the reaction temperatures in decomposition of the polyester with hydrochloric acid should be controlled.
DISCLOSURE OF INVENTION
Accordingly, an object of the invention is to provide a process which is capable of yielding sorbic acid in a short time in a high yield and capable of producing sorbic acid with a high production efficiency.
Another object of the invention is to provide a process which is capable of easily and precisely controlling reaction temperatures in a polyester decomposition step and of stably providing a high-quality sorbic acid.
To achieve the above objects, the present inventors made intensive investigations on processes for controlling reaction temperatures in decomposition of a polyester with hydrochloric acid, which polyester is obtained by a reaction of ketene with crotonaldehyde. Consequently, the inventors found that the reaction temperatures can be easily controlled even at relatively high temperatures by adding a specific hydrochloric acid to a reaction mixture in a heat generation stage after the initiation of a reaction. The present invention has been accomplished based on these findings.
Specifically, the invention provides a process for producing sorbic acid. The process includes the step of decomposing a polyester at temperatures of 100° C. or less by action of hydrochloric acid, which polyester is obtained from ketene and crotonaldehyde. In the process, the reaction temperature after the initiation of a polyester decomposition reaction is controlled by adding a hydrochloric acid to a reaction mixture, which hydrochloric acid has a temperature lower than that of the reaction mixture.
BEST MODE FOR CARRYING OUT THE INVENTION
According to the invention, a polyester obtained from ketene and crotonaldehyde is decomposed with hydrochloric acid to yield sorbic acid. The polyester is generally shown by the following formula (1):
In the above formula, R is an acetoxy group or a hydroxyl group, and n denotes an integer of 2 or more (e.g., about 3 to 40).
The polyester can be obtained by conventional or known processes. For example, the polyester is obtained by reacting ketene with crotonaldehyde in the presence of a catalyst and in the absence of or in the presence of an inert solvent. Such catalysts include, but are not limited to, simple substances or compounds of manganese, cobalt, nickel, zinc, cadmium, and other transition metals; and pyridine, picoline, and other nitrogen-containing basic compounds. Examples of the compounds of the transition metals are oxides; salts of acetic acid, salts of isobutyric acid, salts of isovaleric acid, and salts of other organic acids; salts of sulfuric acid, salts of nitric acid, and salts of other inorganic acids; chlorides and other halides; acetylacetone complex salts, and other complex salts and complexes. Each of these catalysts can be used alone or in combination. The amount of the catalyst differs according to the type of the catalyst, but is generally about 0.1 to 10% by weight relative to the weight of ketene.
The reaction of ketene with crotonaldehyde is performed at a temperature of, for example, about 20° C. to 100° C., and preferably about 25° C. to 80° C.
A reaction mixture containing a pol

Affiliated with

Also associated with

Rating

Process for the preparation of sorbic acid does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Process for the preparation of sorbic acid, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Process for the preparation of sorbic acid will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3017311