The preparation method of 3,5-dimethylphenol

Abstract

The invention discloses a preparation method of 3,5-dimethylphenol, which uses isophorone as a raw material and carries out a cracking reaction under the action of a catalyst, which specifically includes the following steps: using a water-absorbing agent to remove isophorone Water treatment until the water content of isophorone is ≤0.2%, add catalyst to isophorone after water removal, after uniform mixing, to obtain raw material mixture; under the protection of inert gas, raw material mixture from the top Pumped into the tubular reactor, the residence time of the raw material mixture in the tubular reactor is 40s-48s; the reaction temperature is 480-520°C; the reaction pressure is normal pressure; the product is discharged from the bottom of the tubular reactor. The preparation of 3,5-dimethylphenol by the method has the characteristics of high reaction conversion rate, high selectivity, low catalyst price and the like.

Description

Technical field [0001] The present invention belongs to the field of organic synthesis, specifically relates to the preparation method of 3,5-dimethylphenol. Background [0002] 3,5-Dimethylphenol with the formula C 8 H 10 O, molecular weight of 122, structural formula as shown in Equation 1, it is an important industrial intermediate, mainly used for the preparation of antioxidants, antibiotics, resin adhesives and vitamin E and the like production. [0003] [0004] Judging from the domestic and foreign literature currently reported, the main preparation method of 3,5-dimethylphenol is isophorone catalytic cracking, which is mainly divided into the following types according to the different catalysts selected: [0005] Patent (CN101348421A) proposes the use of n- bromobutane as a catalyst, under the condition of reaction temperature of 550 °C, reaction pressure of 2 atm, catalyst dosage of 0.8%, the conversion of isophorone is 96%, the selectivity of 3,5-dimethylphenol is 89%...

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Problems solved by technology

[0005] The patent (CN101348421A) proposes to use n-bromobutane as a catalyst, and under the condition that the reaction temperature is 550°C, the reaction pressure is 2atm, and the catalyst dosage is 0.8%, the conversion rate of isophorone is 96%, and 3,5- The selectivity of dimethylphenol is 89%; the catalyst cannot completely react the raw materials, and the selectivity is low

Using methyl iodide as a catalyst, under the conditions of a reaction temperature of 550°C, a reaction pressure of 2 atm, and a catalyst dosage of 0.5%, the conversion rate of isophorone is 100%, and the selectivity of 3,5-dimethylphenol is 95%. %, the catalytic effect of methyl iodide is good, but its price is expensive, and it is a highly toxic drug, so there are certain safety problems

[0006] The patent (CN105061155A) proposes to use iron-nickel-chromium oxide mixture as a catalyst. Under the conditions of reaction temperature of 570°C and reaction pressure of 2.5MPa, the conversion rate of isophorone is 89%, and that of 3,5-dimethylphenol The selectivity is 89%. The reaction requires high temperature and high pressure, which requires high equipment, and the conversion rate and selectivity are not high

[0007] In the above-mentioned prior art, if the reaction is changed to normal pressure, the conversion rate of isophorone will be reduced to a large extent, and the selectivity of 3,5-dimethylphenol will be reduced to a large extent.

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