DE2039600A1 - Process for the production of isothymol - Google Patents

Description

Process for the production of isothymol

Wesseling, August 4th. 197O VP / Dr So-B / Ne

Our drawing: UK 245

The present invention "relates to a method of making Isothymol through catalytic ^ conversion of m-cresol with propylene *

The alkylation of phenols with alkylating agents such as olefins, Alcohols, ethers or alkyl halides, in the presence of aqueous solutions of zinc bromide or zinc chloride, optionally with additives of bromine or hydrogen chloride is "known. The alkylation takes place here primarily in o or p position. There will be mixtures of the p- and m-isomers are also obtained, but predominantly then the p-isomer content.

It has now been found that isothymol can be obtained from m-cresol and propylene in the presence of an aqueous catalyst solution which contains zinc bromide or zinc chloride and is activated by adding small amounts of bromine or hydrogen chloride by reaction with isomerization at elevated temperatures of up to about 200.degree , if appropriate at elevated pressures, can be obtained if the lower-boiling constituents of the reaction mixture are separated off by distillation before or during the isomerization. The concentration of zinc bromide or zinc chloride in the catalyst solution can be varied within wide limits; for example, 1 to 10 mol of water can be present per column of zinc halide. The addition of hydrogen halide is generally about 0.1-1.5 moles per mole of zinc halide. The catalyst solution used can be, for example, 30 fo and more, based on the cresol used, but smaller amounts, for example 15-20 %, may also be sufficient. The alkylation takes place first at a relatively low temperature and then the isomerization takes place at higher temperatures. The point in time at which the constituents boiling below the isomerization temperature are separated off by distillation can be chosen differently. For example, m-cresol can first be reacted with propylene in the presence of the catalyst solution at, for example, 100-110 °, then the mixture can be slowly heated to the isomerization temperature, for example 175 ° C.

209808/1839 originally inspected

Our reference: UK 245

20396ÖÜ

Water, remove, never work-up of the isomer mixture can in usual way. For example, it can be washed once or several times with water in order to remove the catalyst substances, and then separated e.g. by distillation. That at the Separation of accumulated water can e.g. be beneficial for the Wäsohe des Isomeric compounds are used to remove the catalyst substances will.

Another possibility for carrying out the method according to the invention consists in the mixture of m-cresol and Katalyeatorlosung first to bring to d'ie isomerization temperature, whereby the separating the abovementioned constituents of the mixture which boil below this temperature by distillation. One can do this in a simple way Bring the catalyst concentration to the desired value. It is then cooled to the selected alkylation temperature and propylene is used to, alkylated and isomerized. When working according to the invention with zinc halide solutions there is no need for a separate one Concentration of the catalyst solution, and on the other hand, highly concentrated solutions can be used without difficulty.

example 1

m-cresol was alkylated in the presence of a catalyst in the molar ratio ZnBr ₂ : HgO: HBr such as 1: 2.5: 0.2 in an amount of 30 #, based on the m-cresol used, at 110 ° C. with propylene. Subsequently, the solution was heated to I4O ⁰ C, the said temperature to the boiling products were removed by distillation ·· After three hours residence time at this temperature was cooled, washed free of acid with water and the Rohalkylat thus obtained was then untersuoht gaschromatographisoh. It was made of:

22.6 % m-cresol

39.5 % thymol
9.7 % isothymol

0.8 % 2-isopropyl-m-cresol

11.6 % 4-Ieopropyl-m-cresoI. 14.9 % 4,6-diisopropyl-m-kreeol

0.9 % other isopropyl-m-cresols

Our reference: UK 245

—3—

Example 2

The procedure was as in Example 1, if after the alkylation the Rearrangement temperature increased to 172 ° C and up to this temperature boiling components were removed. Well two hours. Dwell time the acid was washed out with water and the crude alkylate was analyzed. It was made of:

27.1 % m-cresol

12.3 Io thymol

54.2 fo isothymol

0.9 fo 2-isopropyl-m-cresol 3.0% 4-isopropyl-m-cresol 2.5 fo other isopropyl phenols

209808/1839

Claims (1)

Patent entitlement: Process for the production of isothymol from m-cresol and propylene in Presence of an aqueous catalyst solution containing zinc bromide or zinc chloride contains and by adding a small amount of bromine or hydrogen chloride is activated, by reaction with isomerization at elevated temperatures up to about 200 ° C, optionally at elevated temperatures Pressures, characterized in that the lower-boiling constituents of the reaction mixture are added before or during the isomerization separated by distillation. 209808/1839