Method for preparing 3,4-dimethoxytoluene by using monobromomethane-containing waste gas as raw material

Abstract

The invention provides a method for preparing 3,4-dimethoxytoluene by using monobromomethane-containing waste gas as a raw material, which comprises the following steps of: alkalifying 4-methyl guaiacol by using aqueous solution of inorganic base; and heating solution of the alkalified 4-methyl guaiacol until the temperature is between 60 and 150 DEG C, introducing the monobromomethane-containing waste gas, and after a reaction is finished, cooling reaction solution and separating directly to obtain the 3,4-dimethoxytoluene. A small amount of catalyst is added into the reaction solution, so that the reaction speed and the selectivity of a target product can be improved. The method provided by the invention can be used for recycling monobromomethane-containing industrial waste gas with high 3,4-dimethoxytoluene selectivity and yield. In addition, the method is simple and low in cost and has an excellent application prospect.

Description

【Technical field】 [0001] The invention relates to the fields of fine chemical industry and organic synthesis, and more specifically relates to a method for preparing 3,4-dimethoxytoluene by using waste gas containing bromomethane as a raw material. 【Background technique】 [0002] 3,4-Dimethoxytoluene (3,4-Dimethoxytoluene), also known as 1,2-dimethoxy-4-methylbenzene, is an important intermediate in the synthesis of perfumes and pharmaceuticals, and has a large market demand. At present, the synthesis of 3,4-dimethoxytoluene mainly has the following approaches: (1) It is obtained by decomposing complex compounds containing 3,4-dimethoxytoluene structure, wherein 3,4-dimethoxytoluene is used as a by-product product produced. Such synthesis method, the yield of 3,4-dimethoxytoluene is very low, and the product is complex, difficult to separate, and cannot efficiently produce 3,4-dimethoxytoluene. (2) The hydrogen on the 3,4-dimethoxytoluene methyl group is replaced by a halo...

AI Technical Summary

Problems solved by technology

Most of these reactions require catalysts, and the yield varies from 10% to 90%, accompanied by the generation of by-products, and the selectivity is not high. Therefore, this approach cannot effectively produce 3,4-dimethoxytoluene

(3) Using 4-methyl catechol or 4-formyl catechol as raw material and Me 2 SO 4 The reaction generates 3,4-dimethoxytoluene, and the yield of this type of reaction is higher, and the reaction steps are less, but due to Me 2 SO 4 Very easy to hydrolyze, the reaction must be carried out in an organic solvent, so it is difficult to separate the product

And the latter requires the participation of a catalyst, which increases the production cost

(4) It is also reported that 3,4-dimethoxytoluene is synthesized from p-cresol or 1,2-dimethoxybenzene as a raw material, but these reaction steps are more and the reaction time is long, which is not suitable for 3,4- Industrial production of dimethoxytoluene

If the exhaust gas is condensed to recover methyl bromide, the recovery cost is high and it is not economical