Enhancement of catalytic and anti-carbon deposition performance of SAPO-34/ZSM-5/quartz films in MTA reaction by Si/Al ratio regulation

Abstract

In order to further improve the catalytic performance of zeolite catalyst for methanol to aromatics (MTA) technology, the double-tier SAPO-34/ZSM-5/quartz composite zeolite films were successfully synthesized via hydrothermal crystallization. The Si/Al ratio of SAPO-34 film was used as the only variable to study this material. The composite zeolite material with 0.6 Si/Al ratio of SAPO-34 has the largest mesoporous specific surface area and the most suitable acid distribution. The catalytic performance for the MTA process showed that 0.6-SAPO-34/ZSM-5/quartz film has as high as 50.3% BTX selectivity and 670 min lifetime. The MTA reaction is carried out through the path we designed to effectively avoid the hydrocarbon pool circulation of ZSM-5 zeolite, so as to improve the aromatics selectivity and inhibit the occurrence of deep side reactions to a great extent. The coke deposition behavior was monitored by TG and GC-MS, it is found that with the increase of Si/Al ratio, the active intermediates changed from low-substituted methylbenzene to high-substituted methylbenzene, which led to the rapid deactivation of the catalyst. This work provides a possibility to employ the synergy effect of composite zeolite film synthesizing anti-carbon deposition catalyst in MTA reaction.