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对二甲苯是合成聚酯纤维的重要原料之一。工业上一般采用甲苯岐化或烷基化、二甲苯异构化的方法生产。因为对二甲苯只占二甲苯热力学平衡组成的20％稍多一点,且二甲苯三个异构体之性质接近,故分离精制比较困难。如何提高产物二甲苯中对位的含量,一直是人们关注的课题。T. Yashima等1970年首先报导了甲苯甲醇体系用RFY,HY分子筛催化生成对位含量为50％的二甲苯。随后,美国的Mobil公司在改性的ZSM—5分子筛上进行这一反应,对位的选择性可达90％。国内八十年代初开始这方面的研究工作,在改性的ZSM—5上择形催化生成对二甲苯。我们以不同的氧化物对H型和Zn型的ZSM—5进行改性,用脉冲气相色谱法测定了甲苯甲醇烷基化反应的初活性和选择性。
Para-xylene is one of the important raw materials for the synthesis of polyester fibers. In general, toluene is used for industrialization or alkylation, and xylene isomerization is carried out. Because paraxylene accounts for only a little more than 20% of the thermodynamic equilibrium of xylene, and the xylene isomers are close in nature, separation and purification are more difficult. How to improve the content of para-xylene in the product has always been a topic of concern. T. Yashima et al. First reported in 1970 that the toluene-methanol system was catalyzed by RFY and HY molecular sieves to produce xylene with a para-content of 50%. Subsequently, the United States Mobil company in the modified ZSM-5 molecular sieve for this reaction, the selectivity of up to 90%. In the early eighties of the country began research in this area, in the modified ZSM-5 shape selective catalytic generation of p-xylene. We modified H and Zn-type ZSM-5 with different oxides, and the initial activity and selectivity of toluene-methanol alkylation were determined by pulsed gas chromatography.