Study on the alkylation of thiophene and catalyst deactivation and regeneration with modified HZSM-5 zeolite

HZSM-5 zeolites were treated by different alkalis alone or different combining ways with two kind of alkalis to prepare micro-meso hierarchical pore HZSM-5 catalysts for thiophene alkylation reaction. The result show that mesopores are created in molecular sieves and the acidity of catalysts after treated is modulated by single alkali or different combining methods of double alkalis. Simultaneously, the structure of catalyst obtained by the separate treatment of Na₂CO₃ solution and TPAOH solution is most suitable for the thiophene alkylation reaction. Furthermore, the stability of the thiophene alkylation reaction over the catalyst with the best microstructure was investigated, and the reason of catalyst deactivation and the regeneration conditions were determined. The results show that the catalysts are basically inactivated after thiophene alkylation reaction for 1050 h. During the reaction, the macromolecular compounds such as olefin oligomerization formed by the cyclization, dehydrogenation and aromatics alkylation are deposited on the catalyst, blocking the pore and then covering the active site of the catalyst. From the viewpoint of the high energy consumption in regeneration at high temperature and the adverse effect of repeated high temperature regeneration on the acidity and skeleton structure of the catalyst, the catalyst should be regenerated at the temperature of 550℃.