DE2139622A1 - PROCESS FOR PRODUCING THYMOL - Google Patents

Description

Wesseling, August 6, 1971 VP / Dr.Sch-Β, / ΚΙ.

our reference: UK 255

Process for the production of thymol

Various processes are known for the production of thymol in which m-cresol is used as the starting product. This is reacted with propylene or a corresponding alkylating agent, for example in the presence of catalytically effective amounts of aluminum cresolate or acidic catalysts such as sulfuric acid (DKP $ 86.150, USA Patent 2. ^ 68.67O) Obtained isomers of thymol which can only be used to a limited extent. It has therefore been suggested that the isomers of thymol ζ «Β. to isomerize to thymol in the presence of concentrated sulfuric acid at temperatures of about 100 ° C. In addition to m-cresol, higher-boiling compounds are obtained as by-products (DRP 899 «197) ·

It has now been found that the synthesis of thymol can be improved by alkylating m-cresol with propylene or an alkylating agent corresponding thereto and isomerization in the presence of an acidic catalyst if the alkylation and isomerization are carried out in the presence of an aqueous catalyst solution containing zinc bromide or zinc chloride , thymol, optionally isothymol, and the resinous residue are separated from the isomer mixture freed from the catalyst and the remaining mixture is recycled to the alkylation. The process can be carried out batchwise or continuously. The alkylation is expediently carried out at about 100-1 ^ 0, the isomerization at about 150-170. The concentration of the Katalyr-atorlösung can be varied within wide limits, for instance with MolverhUütnissen of Zinkhaiogonid to water of 1: 2 to 1: 10. Activation of the solution by adding small quantities of hydrogen halide int advantageous * zinc bromide int generally more effective than zinc chloride. The work-up; of the reaction agomicG can after a wash to remove the Ka LaI yr; ator ku, [, 'egebem'tif all «with the involvement of

OFlSGINAL

309807/1

our sign ^ ^ UK ? y> './ - 2 -

Extraction stage, carried out by distillation. The procedure according to the invention, in which the remaining alkylate part is not, as was customary up to now, returned to the isomerization but to the alkylation, the thymol yield can be increased to about 50% of theory, while with the previously known processes only Yields of about 65-70 ⁰ A could be achieved.

Example:

1000 g of m-cresol and 33 ^ g of propylene were alkylated in the presence of a catalyst solution of zinc bromide, hydrogen bromide and water in a molar ratio of 1: 0.17: h at 110-120 ° and then isomerized at 150-160 °. After the reaction product had been worked up and the unreacted m-cresol (330 g) had been separated off by distillation, an alkylate was obtained from the composition

51.3 % thymol
7.7 % isothymol

17, ^ % ^ -isopropyl-m-cresol

21.8 % h. 6-diisopropyl-m-cresol 1.7 % residue

obtain. The thymol yield was 55 % based on converted m-cresol. The alkylate freed from thymol and isothymol by distillation was added to a second batch (26 g + 330 g of circular oil, m-cresol). After alkylation with 166 g of propylene and work-up of the ReEiktionsgenisches, an alkylate was obtained from

if 5.1 % thymol

10.6 % isothymol

19.5 % i-isopropyl-m-cresol

21.5 % ^ .ö-diisopropyl-m-cresol

3.3 % residue

composed.

The thymol yield was 79 %.

309SQ7 / 1294

Claims (1)

our reference: UK Claim: Process for the production of thymol by alkylation of m-cresol with propylene or an alkylating agent corresponding to this and Isomerization in the presence of a satirical catalyst, thereby marked draws that the alkylation and isomerization in the presence an aqueous catalyst solution containing zinc bromide or zinc chloride, from the isomer mixture freed from the catalyst Thymol, optionally isothymol, and the resinous residue separates and the remaining mixture in the circuit in the alkylation returns. 309807/1294