JPS58210038A - Production of trialkylhydroquinone - Google Patents

Abstract

PURPOSE:The isomerization of 4-alkoxy-2,6-dialkylphenol is effected only by bringing it into contact with a solid acid catalyst to permit high-yield production of the titled compound which is used as a synthetic intermediate of medicines such as vitamin E and additives for resins. CONSTITUTION:2-Alkoxy-2, 6-dialylphenol such as 4-methoxy-2, 6-dimethylphenol is brought into contact with a solid acid catalyst such as alumina, silica-alumina, or magnesia-titania under heating to give 2,3,6-trialkylhydroquinone. The above catalytic reaction is carried out in vapor phase, preferably in the temperature range from 300 to 400 deg.C at a space velocity of 0.01-5hr<-1> in an inert gas such as argon. The process can be effected in liquid phase as well.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing 2,3,6-trialkylhydroquinone in good yield by isomerizing 4-alkoxy-2,6-dialkylphenol.

Among 2.3.6-) realkylhydroquinones, for example, 2,3.6-)limethylhydroquinone is useful as an intermediate in the production of pharmaceuticals such as vitamin E, stabilizers for resins, etc. investigated a method for producing 2,6.6-trialkylhydroquinone from 4-alkoxy-2,6-dialkylphenol in good yield and found that 4-alkoxy-2,6-dialkylphenol was produced using a solid acid catalyst. The inventors have discovered that the above object can be achieved by contacting with the above, and have arrived at the present invention.

That is, the present invention is a method for producing 2,3.6-)realkylhydroquinone, which comprises bringing 4-alkoxy-2,6-dialkylphenol into contact with a solid acid catalyst under heating.

4-alkoxy-2 used in the method of the invention,
The alkyl group and alkoxyl group constituting 6-dialkylphenol usually have 1 to 5 carbon atoms, and specifically include methyl group, ethyl group, n-propyl group, isopropyl group, and these alkyl groups. An alkoxyl group corresponding to the group can be exemplified. 4-
Specifically, the alkoxy 2,6-dialkylphenol includes 4-methoxy-2,6-dimethylphenol, 4
Examples include -ethoxy-2,6-dinitylphenol and 4-n-propoxyl 2,6-mo2,6-diitupropylphenol.

Specific examples of the solid acid catalyst used in the method of the present invention include alumina, silica...alumina-silica, alumina/boria, magnesia/silica, magnesia, titania, and magnesia/titania. Among these solid acids, the Hammett function PKa
It is preferable that the acid strength expressed by is in the range of +6.3 or less. Among these solid acid catalysts, alumina, silica/alumina, and magnesia/titania are particularly preferred.

In the method of the present invention, 2. by contacting 4-alkoxy-2,6-dialkylphenol with the catalyst under heating; +, 6-) Realkylhydroquinone is obtained. The contact is preferably carried out by a gas phase method,
It is also possible to carry out the process using a liquid phase method.

Any conventionally known method can be employed as the contact method when the method of the present invention is carried out by a gas phase method. For example, there may be a method of contacting using a fixed bed method, a method of contacting using a moving bed method, etc. The temperature in the case of contacting by the gas phase method is usually in the range of 250 to 450°C, preferably 300 to 400°C, and the space velocity (LH3V) during the gas phase contact reaction is usually in the range of 250 to 450°C.
h r-1, preferably 0.1 to 1. Qhr""
' range. Also, 1 nitrogen, 1 argon, inorganic gas such as helium, or aliphatic carbonized leaves such as methane, ethane, 1 propane, 1 butane, hexane, or benzene,
It is also possible to carry out the reaction in an atmosphere of aromatic hydrocarbons such as toluene and xylene.

The reaction mixture obtained by the method of the present invention contains 2,3
．． 6-) In addition to IJ alkylhydroquinone, unreacted 4-alkoxy-3,4-dialkylphenol, by-product 2,6-dialkylhydroquinone 14-alkoxy-2,3,6-)realkylhydroquinone, 2. 3,
Contains 5,6-titraalkylhydroquinone, a high boiling by-product. 2.3.6-trialkylhydroquinone is obtained by treating the reaction mixture by conventional methods such as distillation, crystallization, and extraction.

Next, the method of the present invention will be specifically explained using examples.

Example 1 Commercially available alumina (
It was filled with 20mβ tablets (manufactured by JGC Chemical Co., Ltd., trade name: N611), 3 mmφ x 3 mmH. The temperature of the catalyst layer is 450
℃ and held for 5 hours, then set to 360'C.

4-methoxy-2,6-dimethylphenol was introduced in gaseous form into this reaction tube together with toluene in an amount 10 times its weight, and allowed to pass through the catalyst layer. The space velocity at this time is LHS V=
Q, 7 hr, and at the same time, 120 ml/min of nitrogen gas containing 20% hydrogen was used as a carrier gas.

The reaction solution was analyzed using gas chromatography. The results are shown in Table 1.

Example 2

Claims (1)

[Claims] (1) A method for producing 2,3.6-)realkylhydroquinone, which comprises bringing 4-alkoxy-2,6-dialkylphenol into contact with a solid acid catalyst under heating.