Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Patent
1994-07-25
1995-10-03
Prescott, Arthur C.
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
5625124, 562523, C07C 5500, C07C 5514, C07C 5131
Patent
active
054553750
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT JP/93/00457, Apr. 9, 1993.
FIELD OF THE INVENTION
This invention relates to a process for preparing adipic acid from cyclohexene oxide.
BACKGROUND OF THE INVENTION
Dutch Patent Application No. 6601148 discloses a process for preparing adipic acid by oxidizing 1,2-dioxycyclohexane in a nitric acid aqueous solution containing a water-soluble vanadium salt. It discloses that the advantage of the process, over the currently more common process of oxidizing cyclohexanol and/or cyclohexanone with nitric acid, is that the proportion of nitric acid consumed in the form of nitrogen and nitrous oxide is reduced. However, in Example 1 in which cyclohexene oxide is used as a starting material, and nitric acid having a concentration of 70% is used as the oxidizing agent, the yield of adipic acid attained is 92%, and 0.12 mol of nitric acid is consumed in the form of nitrous oxide and nitrogen per mol of the organic starting material. In Example 4 in which 1,2-dihydroxycyclohexane is used as a starting material, and nitric acid having a concentration of 70% is used as the oxidizing agent, the yield of adipic acid is 94%, and 0.16 mol of nitric acid is consumed in the form of nitrous oxide and nitrogen per mol of the organic starting material. Therefore, while catalysis by water-soluble vanadium salts gives some improvement, the process of the Dutch application is still unsatisfactory.
while 1,2-dihydroxycyclohexane can be obtained through various processes, hydration of cyclohexene oxide derived from cyclohexene is one of the industrially more economical processes. A method of hydration of an epoxy compound is described, e.g., in Morison Boyd Yuki Kagaku Dai-4-han (Morison Boyd Organic Chemistry 4th edition), translated by Nakanishi et al., pp. 720-728, Tokyo Kagaku Dojin. Applicants have found that the hydration of cyclohexene oxide is accompanied by the formation of by-products consisting mainly of oligomers of cyclohexene oxide represented by formula (I): ##STR2## wherein n represents a number of from 1 to 5 in number average. Applicants have observed that water for hydration must be used in large excess over a theoretical amount in order to minimize the by-production of oligomers (I).
SUMMARY OF THE INVENTION
A first object of the present invention is to eliminate the above-mentioned disadvantages associated with Dutch Patent Application No. 6601148 and to establish an industrially valuable process for preparing adipic acid in an increased yield while suppressing formation of nitrous oxide and nitrogen.
The aforesaid Dutch patent application and other existing descriptions of the preparation of adipic acid from cyclohexanol and/or cyclohexanone by oxidation with nitric acid make no specific mention of how to deal with the oligomers (I). Hence, where a conventional technique is to be followed, it seems that there is no alternative but to conduct hydration of cyclohexene oxide by using a large excess of water and then to remove the excess water by energy-intensive drying or by separating the by-product oligomers (I) by distillation or a similar means. Either removal procedure would make the steps involved complicated and require a large quantity of extra energy, resulting in disadvantages in carrying out the process on an industrial scale. Accordingly, a second object of the present invention is to provide a process in which the above problem can be solved economically.
The present invention relates to a process for preparing adipic acid from cyclohexene oxide comprising the following steps (a) and (b): oligomers represented by formula (I), and formula (I) in a nitric acid aqueous solution.
The present invention also relates to a process for preparing adipic acid from cyclohexene oxide comprising the following steps (a) and (b): oligomers represented by formula (I), and formula (I) in a nitric acid aqueous solution, the ratio of the oligomers represented by formula (I) and the 1,2-dihydroxycyclohexane being from 60/40 to 1/99 by weight.
DETAILED DESCRIPTION OF THE INVENTION
REFERENCES:
patent: 3726917 (1973-04-01), Brunie et al.
patent: 4254283 (1981-03-01), Mock
patent: 4605790 (1986-08-01), Wojtkowski
patent: 4814511 (1989-03-01), Neubauer et al.
patent: 5321157 (1994-06-01), Kollar
Ide Tohru
Yokota Masahisa
Asahi Kasei Kogyo Kabushiki Kaisha
Prescott Arthur C.
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