JPS60239438A - Production of adipic acid - Google Patents

Abstract

PURPOSE:Readily available dicyclohexyl ether is used as a starting material to effect oxidation with nitric acid whereby high-quality adipic acid, a feedstock of polyamides, is obtained in high yield. CONSTITUTION:Dicyclohexyl ether, which is readily obtained by hydrogenation of diphenyl ether, is oxidized with nitric acid of preferably 10-80wt%, most particularly 30-75wt% concentration at 40-150 deg.C, preferably 40-100 deg.C and 0.1-7atms., preferably 0.1-2atms. to form adipic acid. Even when the dicyclohexyl ether as the feedstock contains cyclohexanol or cyclohexanone, the merit of the present invention is not damaged at all.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing adipic acid. More specifically, the present invention relates to a completely new method for producing adipic acid, which uses dicyclohexyl ether as a raw material and converts it into nitric acid.

Conventionally, adigic acid is an industrially important substance as a raw material for polyamide, and various production methods have been proposed. In particular, cyclohexene,
Methods of oxidizing cyclohexanol, cyclohexanone, etc. singly or as a mixture are well known.

The present inventors have repeatedly studied the method for producing adipic acid, and as a result, they have found that adipic acid can be easily obtained by using dicyclohexyl ether as a raw material and converting it into nitric acid, thereby achieving the present invention.

Dicyclohexyl ether in the present invention can be easily obtained, for example, by hydrogenation of diphenyl ether (eg, lngθ1hard engineering.

Tich, Bull, vol, 9, p 14-19
(1968)).

For the nitrification of dicyclohexyl ether, the conditions normally used for the oxidation of cyclohexanol and/or cyclohexanone can be applied as they are. For example, a method (Japanese Unexamined Patent Publication No. 46-111) in which raw materials are added dropwise to 50% nitric acid containing copper and vanadium catalysts and reacted at the boiling point.
It can be carried out under a wide range of conditions, including the following. Specifically, the concentration of nitric acid used is preferably 10 to 80% by weight, more preferably 30 to 80% by weight.
75% by weight, reaction temperature is preferably 40-150°C,
The reaction is more preferably carried out at 40 to 100°C, and the reaction pressure is preferably 0.1 to 7 atm, more preferably 0.1 to 2 atm. Although it is not necessary to add a catalyst, etc., in order to accelerate the reaction, NoXNo2, NaNO
3. The reaction mother liquor containing these, metals such as copper and vanadium, or vanadium nitrates, oxides, hydroxides, or panadate compounds, and other known materials used for the oxidation of cyclohexanol and/or cyclohexanone. A catalyst may also be added.

Moreover, even if the raw material dicyclohexyl ether contains cyclohexanol or cyclohexanone, the effects of the present invention will not be impaired in any way.

The present invention will be explained in more detail with reference to the following examples, but the present invention is not limited to these examples in any way.Example-1 A 60-kg flask with an internal volume of 500 d equipped with a cooling tube and a dropping funnel was used. Add 250g of basic acid, 90~1
While keeping the temperature at 00°C, 50 g of dicyclohexyl ether was slowly added dropwise without stirring. After the generation of nitrogen oxide was observed, the reaction vessel was cooled and kept at 60 to 65°C, and the remaining dicyclohexyl ether was added to about 60-65°C. It was added dropwise over a period of 6 hours. After the completion of the dropwise addition, the above temperature was maintained for another 2 hours to complete the reaction. The reaction solution was cooled with ice, and the precipitated white solid was filtered, washed with 100 ml of cold water, and dried. .7 g (yield: 47) of white adipic acid was obtained.

Example 2 In a 2-ton Mitsuro flask equipped with a cooling tube and a dropping funnel, 1,500 g of a 60% by weight nitric acid aqueous solution and 1.5 g of ammonium metavanadate were added. o, 9, 3.0 g of copper nitrate was added and maintained at 80°C while stirring. 200 g of dicyclohexyl ether was added dropwise to this over about 2 hours, and the reaction was continued for another 2 hours. The reaction solution was ice-cooled, and the precipitated solid was filtered off, washed six times with IQQm/ of water, and dried.
2.9 (yield 91.0%) of white adipic acid was obtained.

Example-6 A 30% by weight nitric acid aqueous solution (100.9%) was placed in a Mitsuro flask with an internal volume of 500 d and equipped with a cooling tube and a dropping funnel. 0.20 g of ammonium metavanadate and 1.0 g of sodium nitrite were added, and the temperature was maintained at 40 to 45° C. with stirring. 22.7 g of dicyclohexyl ether and 110 g of a 65% by weight aqueous nitric acid solution were separately added dropwise over a period of about 13 hours to prevent the temperature from rising. Furthermore, after this, the reaction solution was heated to 50%
After reacting at 60°C for 1 hour each, the mixture was heated at 8°C for 2 hours to complete the reaction. This reaction solution was ice-cooled, and the precipitated white solid was filtered, washed with 501 water, and dried. ! ii (yield: 82 g) of extremely pure adipic acid was obtained.

Furthermore, in order to examine the coloring properties of the obtained adipic acid, 1 g of adipic acid was treated with 4 g of ethylene glycol at 140°C for 30 minutes, and the color of the solution was compared. 10 Q d
The results were as follows, and almost no coloring was observed.

As described above, it is clear that adipic acid of extremely high quality can be obtained in high yield by oxidizing dicyclohexyl ether with nitric acid.

Patent applicant: Asahi Kasei Industries, Ltd.

Claims (1)

[Claims] A method for producing adipic acid characterized by converting dicyclohexyl ether into nitric acid