DE1921441C - - Google Patents

Description

The invention relates to a process for the production of / f-methyladipic acid of high purity, where the starting product is a methylcyclohexanol isomer mixture from the hydrogenation of crude cresol is used, which may also contain cyclohexanol.

Auslegeschrift 1 205 516, Beidaß from an m-Methylcyclodurch Oxy

called
^ to

u ß ^{from the} & ■ ^{forth eht 'must} of m- and p-cresol and up to 20% o-cresol, or up to 20% o-cresol / phenol, or up to 20% phenol. The hydrogenated raw cresol of the composition mentioned is treated with 50 to 70% strength nitric acid with 5 or without the addition of a catalyst at the temperatures known from the literature, e.g. B. at 60 ⁰ C, oxidized. After cooling the mixture, e.g. B. to 10 to +25 ⁰ C, an almost pure /ff-Methyladipinsäi.re with a melting point of 95 ° C falls out. According to W. Marko wnik ο ff, Liebigs Annalen 336 (1904), p. 302, the connection was characterized by the dianilide. The adipoleic acid formed during the oxidation does not fail when the starting material according to the invention is used and the specified η is working conditions are observed, although it is more difficult to dissolve in the nitric acid used for the oxidation than / 3-methyladipic acid. This is due to the influence of solubility by short-chain carbide. acids, which are e ■■ '- ao as by-products.

If you cool - as stated above - to +10

a very pure ß-methyladipic acid separates out.

in about 60% yield, based on that used?

m- and p-methylcyclohexanoI mixture, from. Pic

«5 Mother liquor is - as already mentioned - either by adding anhydrous nitric acid or similar

brought back to a content of 50 Ii., 70% HNO ₃ by concentration and in the oxidation process>

returned. But since this is the one from o-meth ;. 1-

cyclohexanol and cyclohexanol formed adipic acid

pSreeredef ^ T ^ Z ^^ or a mixture of this and m-methylcyclohexanol with not more than 70% of the meta compound can be used. ^6th

It has now been found that the method for Production of ^ -Methyladipic acid from a methylcyclohexanol isomer mixture by oxidation with concentrated, aqueous nitric acid

be discharged from this. Is this also ejected Portion worked up to methyl adipic acid, the yield increases from 60 to 91%

The process of the present invention is illustrated by the following examples.

example 1 With stirring, 154.1 g of 66% nitric

^{As well as 12} ° ^{/ o}

and cyclo-

SS5Ä

^{Alcohol to} .S ^abe T ^de «™ mixture still

on the one hand ".." ww ^ no i ^ mmacn senr

is complex and expensive, it is advantageous to

._. —- .- .. »111611 of the invention

to be used directly.

In the present process, after some of the mother liquor has been discharged, it can by concentrating and / or adding highly concentrated nitric acid back to a ΗΝΟ, content of brought up to 70% and returned to the reaction process.

The oxidation of the Metfay / cyclohexanol / cyclohexanol mixture is largely continuous accomplished.

The process according to the invention is based on hydrogenated, commercially available raw cresol, consisting of

was complete. was filtered. This gave 40.3 g

based on theory

._ ___, I) received. Acid number:

703; Melting point: 95 ⁰ C.

The mother liquor obtained in the experiment was concentrated in vacuo and with 96% strength nitric acid brought back to the initial concentration of 66%. When using this mother liquor was under the conditions given above, the yield of / 9-methyladipic acid increased to 64 g ~ 91%.

Example 2

The oxidation was carried out continuously, with the acid circulation between a reactor, a Degasser as well as a cooler was accomplished by the buoyancy as a result of the gas development. at The use of a circulation pump over metering pumps is recommended for larger equipment

were per hour 750 g of methylcyclohexanol mixture and 2 kg of 67% nitric acid, 0.1% of the im Example 1 contained catalyst mixture used, introduced into the reactor through nozzles. An aliquot of the product was in front of the cooler via a separate cooler continuously withdrawn. The oxidation solution was cooled to 10% and the The precipitated / S-methyladipic acid was filtered off.

Another commercially available hydrogenated cresol mixture was used in this experiment, the consisted of 50% p- and 34% m-cyclohexanol and 16% cyclohexanol and o-methylcyclohexanol. It 505 g / S-methyladipic acid were obtained, which is a Yield, based on m- and p-methylcyclohexanoI, of 57%.

25% of the concentrated mother liquor obtained in these experiments was discharged, the The remainder was supplemented with 1.4 kg of 96% strength nitric acid and water, so that again a 67% strength acid was formed. Otherwise, as described above proceedings. The reaction of this refreshed mother liquor with 750 g / hour of the above-mentioned hydrogenated Crisp mixture gave 735 g / 9-methyladipic acid per hour (= 83% of theory).

Claims (1)

Claim: Process for the preparation of / 3-methyladipic acid from a methylcyclohexanol isomer mixture by oxidation with concentrated, aqueous nitric acid at elevated temperature, cooling of the oxidation mixture and separation the precipitated dicarboxylic acid, thereby characterized in that a methylcyclohexanol mixture from the starting material Hydrogenation of raw cresol used, which contains up to 20% o-methylcyclohexanol and / or cyclohexanol.