Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Reexamination Certificate
2000-05-26
2003-01-21
Shah, Mukund J. (Department: 1623)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
C562S600000
Reexamination Certificate
active
06509498
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a process for producing sorbic acid or its salt which is useful as, for example, food additives. Specifically, the invention relates to a process for producing sorbic acid or its salt including the step of treating sorbic acid or its salt with activated carbon, which sorbic acid or its salt is produced through the decomposition of a polyester obtained from ketene and crotonaldehyde.
BACKGROUND ART
As processes for the commercial production of sorbic acid or its salt, a process of reacting ketene with crotonaldehyde to yield a polyester and hydrolyzing the polyester in the presence of an acid or an alkali, and a process of decomposing the polyester by heat are known.
A crude sorbic acid obtained by the decomposition of the polyester generally contains various colored substances, tar substances, and other impurities and is subjected to purification operations such as treatment with activated carbon, distillation and recrystallization. Particularly, the crude sorbic acid or its salt is often subjected to treatment with activated carbon to remove colored substances.
For example, Japanese Unexamined Patent Application Publication No. 54-163516 discloses a process for preparing a crystalline sorbic acid. This process includes the steps of preparing a polyester from ketene and crotonaldehyde, decomposing the polyester with hydrochloric acid in the presence of, for example, a urea compound to yield a decomposition reaction mixture, separating the decomposition reaction mixture by filtration, and washing the residue to yield a crude sorbic acid, adding a sodium hydroxide aqueous solution to the crude sorbic acid to yield a sodium sorbate aqueous solution, treating the aqueous solution with activated carbon, neutralizing and cooling the treated solution to crystallize sorbic acid. Japanese Examined Patent Application Publication No. 44-26646 discloses a process for producing a crystalline sorbic acid. The process includes the steps of preparing a polyester from ketene and crotonaldehyde, 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, cooling the reaction mixture, separating a crude sorbic acid by filtration, washing the crude sorbic acid with water, putting the washed crude sorbic acid into water, heating and dissolving the sorbic acid to yield a solution, adding activated carbon to the solution, boiling the mixture, and filtering the mixture while heating, and gradually cooling the resulting filtrate to yield a crystalline sorbic acid.
However, according to the investigations made by the present inventors, the ability for removing colored substances or the like contained in a crude sorbic acid greatly varies with the type of activated carbon for use in the treatment with activated carbon. For example, a steam-activated carbon of coconut shell origin is in wide use in the purification of organic compounds but has a low ability for removing colored substance. To obtain a high quality sorbic acid having a satisfactory hue by the use of this type of activated carbon, for example, a crystallization rate in a crystallization process subsequent to the treatment with activated carbon must be decreased or a combination of several complicated purification operations must be employed after the treatment with activated carbon.
DISCLOSURE OF INVENTION
Accordingly, an object of the invention is to provide a process for producing sorbic acid or its salt, which is capable of efficiently removing colored substances and is capable of easily producing a high quality sorbic acid having a satisfactory hue in a high yield.
The present inventors made intensive investigations to achieve the above object, and found that colored substances and other impurities can be efficiently removed by treating a solution containing sorbic acid or its salt with a specific activated carbon, which sorbic acid or its salt is prepared through the decomposition of the polyester.
Specifically, the invention provides a process for producing sorbic acid or its salt by decomposing a polyester obtained from ketene and aldehyde. The process includes the step of treating a solution containing sorbic acid or its salt with a chemically activated carbon, which sorbic acid or its salt is produced by the decomposition of the polyester.
BEST MODE FOR CARRYING OUT THE INVENTION
According to the invention, a polyester obtained from ketene and crotonaldehyde is decomposed to yield sorbic acid or its salt. 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 aldehyde in the presence of a catalyst with or without 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 incombination. 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 temperatures ranging from, for example, about 20° C. to 100° C., and preferably from about 25° C. to 80° C.
A reaction mixture containing a polyester obtained through the reaction of ketene with crotonaldehyde is usually distilled to remove unreacted crotonaldehyde and low boiling impurities, and is then subjected to a decomposition reaction.
The polyester may be decomposed by hydrolysis with an acid or an alkali or by thermal decomposition, but is preferably decomposed by hydrolysis with a mineral acid, particularly with hydrochloric acid, for a higher yield. The polyester is hydrolyzed, for example, at temperatures ranging from about 10° C. to 110° C., and preferably from about 50° C. to 100° C. An extremely low reaction temperature may invite reaction efficiency to decrease, and in contrast, an extremely high reaction temperature may increase the by-production of tar substances and other impurities. When the polyester is hydrolyzed with hydrochloric acid, the concentration of hydrochloric acid is, for example, about 15 to 40% by weight, and preferably about 23 to 36% by weight. An extremely low concentration of hydrochloric acid may invite a decreased reaction rate, and in contrast, an extremely high concentration of hydrochloric acid may invite disadvantages in handling property or ease of operation. The amount of hydrochloric acid in terms of hydrogen chloride is, for example, about 10 to 160 parts by weight, and preferably about 15 to 100 parts by weight, relative to 100 parts by weight of the polyester.
A reaction mixture obtained through the decomposition of the polyester contains colored substances, tar substances, and other impurities by-produced in the reaction, in addition to the sorbic acid or its salt and the catalyst used. The production of a high quality sorbic acid or its salt therefore requires a purification process.
The invention has a main feature of including the step of treating a solution containing the sorbic acid or its salt with a chemically activated carbon, which sorbic acid or its salt is obtained by the decomposition of the polyester.
The treatment with activated carbon can be performed at any point in the purification process of sorbic acid or its salt subsequent to the polyester decomposition proc
Kouno Mitsuhiro
Yamashita Akira
Birch & Stewart Kolasch & Birch, LLP
Daicel Chemical Industries Ltd.
Shah Mukund J.
Tucker Zachary C.
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