Process for catalytically synthesizing p-xylene

Abstract

The invention relates to a method for the catalytic synthesis of para-dimethyl benzol. The method takes green chemicals, methyl carbonate (DMC) and toluene as raw materials, and ZSM-5 molecular sieve or beta-molecular sieve as catalyst; when the catalyst provided by the invention is adopted, better raw material transformation efficiency and object product selectivity can be obtained under the experiment conditions of a temperature of between 300 and 400 DEG C and raw material molar ratio toluene: methyl carbonate of between 2:1 and 6:1; moreover, the transformation efficiency of toluene can reach to 41.3 percent and the selectivity of para-dimethyl benzol can reach to 75.8 percent. The method takes DMC as methylated reagent and has the advantages of low-toxicity raw materials, wide sources and high catalytic efficiency, etc.

Description

technical field [0001] The invention relates to the field of organic chemical industry, in particular to a method for catalytically synthesizing p-dimethylbenzene. Background technique [0002] p-Xylene is an important raw material for the synthesis of polyester fibers, pesticides, medicines and dyes. Terephthalic acid can be obtained from the oxidation of p-xylene, and then polyester, an important raw material for synthetic fibers and plastics, can be obtained. Therefore, the demand for p-xylene will increase year by year. [0003] At present, p-xylene is mainly produced in industry by isomerization of mixed dimethylbenzene, disproportionation of toluene and C9 aromatics, and selective disproportionation of toluene. The equilibrium concentration of p-xylene obtained by the first two methods in all dimethylbenzene isomers only accounts for about 24%. In the disproportionation reaction, two moles of toluene are needed to generate p-xylbenzene with a purity of more than 85%,...

AI Technical Summary

Problems solved by technology

The equilibrium concentration of p-xylene obtained by the first two methods in all dimethylbenzene isomers only accounts for about 24%. In the disproportionation reaction, two moles of toluene are needed to generate p-xylbenzene with a purity of more than 85%, and the utilization rate of toluene is low, and the production cost is high (Zou Wei et al., metal oxide modified HZSM-5 upper toluene Alkylation with methanol, Acta Catalytica Sinica, 2005, 26 (5): 470-474); Alkylation of toluene and methanol to directly synthesize high-concentration p-xylylene technology is a synthetic process that is currently studied more. In this technique, the toluene utilization rate is high, and the product is easy to separate, but the reaction temperature is higher (mostly in the range of 400-600 ° C), which easily leads to catalyst deactivation (Zou Wei, Selective toluene toluene on the modified ZSM-5 molecular sieve Basicization, Fudan University Master Thesis, 2004, 11)