Production method of 3, 5-dimethylphenol and pressure-controlled production device used in production method

Abstract

The invention discloses a pressure-controlled production device which is a cracking reactor, and an outlet of a raw material container is communicated with a top inlet of a reaction tube I after sequentially passing through a sample injection pump and a preheating tube; a bottom outlet of the reaction tube I is communicated with a top inlet of a reaction tube II after passing through a pressure control valve; a bottom outlet of the reaction tube II is sequentially connected with a product collection bottle and a tail gas absorption bottle after passing through a condensation tube; and a gas bottle for containing inert gas is communicated with a top inlet of the reaction tube II after passing through a rotor flow meter. The invention further provides a method for producing 3, 5-dimethylphenol by using the device, and isophorone is used as a raw material to carry out cracking reaction under the action of a bromine-containing catalyst. According to the invention, the reaction selectivityand conversion rate can be improved.

Description

technical field [0001] The invention belongs to the field of organic synthesis, and in particular relates to a preparation method and a device used for 3,5-dimethylphenol. Background technique [0002] 3,5-Dimethylphenol, which has the molecular formula C 8 h 10 O, with a molecular weight of 122 and a structural formula as shown in Formula 1, is an important industrial intermediate and is mainly used in the production of antioxidants, antibiotics, resin binders and vitamin E. [0003] [0004] According to the domestic and foreign literatures reported at present, the main preparation method of 3,5-dimethylphenol is the catalytic cracking of isophorone, which is mainly divided into the following types according to the different catalysts selected: [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...

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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 make the raw material react completely, 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 above-mentioned technical scheme needs to be carried out under high pressure, and the inventors found that assuming that the reaction pressure is changed from 2atm to 0.5atm, the selectivity of 3,5-dimethylphenol will decrease, which is 85%-90%

[0007] The patent (CN105061155A) proposes to use a mixed catalyst of iron-nickel-chromium oxide. Under the condition of reaction temperature of 570°C and reaction pressure of 2.5MPa, the conversion rate of isophorone is 89%. The choice of 3,5-dimethylphenol The specificity is 89%. The reaction requires high temperature and high pressure, which requires high equipment, and the conversion rate and selectivity are not high.

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