ZRP分子筛催化丙烷芳构化产物中二甲苯异构体的分布

Xylene Isomers Distribution in Propane Aromatization over ZRP Molecular Sieve

在小型常压固定床反应器内考察了丙烷在ZRP分子筛和硅改性ZRP分子筛上的芳构化反应,实验结果表明,在ZRP分子筛上,液体产物中的二甲苯异构体基本上呈热力学平衡分布,对位选择性差;在硅改性ZRP分子筛上,随S iO2含量的增加,ZRP分子筛外表面的活性中心被覆盖的程度增加,液体产物中二甲苯异构体对位选择性逐渐增加。用吡啶吸附红外光谱、低温N2吸附容量法对硅改性ZRP分子筛进行表征,表征结果显示,丙烷芳构化反应的中间产物在ZRP分子筛外表面的活性中心发生二次异构化反应是最终产物中二甲苯异构体对位选择性差的主要原因。

Propane aromatization over ZRP molecular sieve was studied in bench -scaled fixed bed reactor. Distribution of product xylene isomers in this reaction basically followed rule of thermodynamic equilibrium, namely low para - selectivity. After ZRP molecular sieve was modified by chemical liquid deposition （CLD） of ZRP in dimethyl silicone （ Si/ZRP）, selectivity of para - xylene in propane aromatization over Si/ZRP molecular sieve increased obviously with increase of silica deposited on ZRP molecular sieve. By means of IR and low temperature nitrogen absorption BET, it was found that external acid sites of Si/ZRP molecular sieve were mostly eliminated because of coverage of silica by CLD of dimeth.yl silicone. Secondary reaction of intermediate products over external acid sites was key factor for low para -selectivity of aromatic product in propane aromatization over ZRP molecular sieve.