锌改性的分子筛催化剂上丙烷芳构化的研究

在固定床微型反应器上考察了不同分子筛锌改性后催化丙烷芳构化的反应性能。结果表明：具有8元环孔道结构的4A分子筛没有催化活性，几乎无积碳生成，具有10元环孔道结构的ZSM-5分子筛以及具有10元环和12元环的MCM-22分子筛具有较好的催化性能，积碳生成量MCM-22>ZSM-5，具有12元环孔道结构的β分子筛虽然也具有一定的催化性能，但是活性较低,且积碳的生成最多。表明分子筛催化剂的芳构化活性与其孔道结构有密切的关系。针对同一种ZSM-5分子筛改变硅铝摩尔比的研究结果表明n(SiO₂)/n(Al₂O₃)＝38的Zn/HZSM-5分子筛具有较好的芳烃选择性。

Performance of modified Zn-based zeolite catalyst in propane aromatization

The catalytic behavior of Zn-based zeolite with different pore structures and sizes, particularly with 8 membered ring (MR), 10MR, coexisted 10 and 12MR, and 12MR, was studied in propane aromatization under the conditions of WHSV=0.4h^-1, p＝0.1MPa and T=903K. It is found that the catalytic performance is correlated with the acid of the zeolite catalyst and the pore structure of the zeolite support. The zeolites that possess 10 MR or 10MR and 12MR pore structure with a pore diameter equal to or slightly larger than the dynamic diameter of benzene molecule, such as ZSM-5 and MCM-22, are fine supports. Among the tested zeolite supports, ZSM-5 exhibits the highest activity and selectivity for benzene. The Zn/HA catalyst with 8 MR did not show any activity in propane aromatization, while Zn/Hβ catalysts with 12 MR pore exhibited little activity in the reaction. It can be concluded that the zeolite with 10 MR pore, being equal to the dynamic diameter of benzene molecule, is a fine support for propane activation and aromatization. The effect of different Si/Al ratios on propane aromatization performance was also investigated. The result show that the catalyst with n(SiO₂)/n(Al₂O₃)=38 performances the highest aromatization activation.