Preparation and Evaluation of Nanostructured Composite SAPO-34(90%)/HZSM-5(10%) Catalyst Used in Conversion of Methanol to Ethylene and Propylene

Nanostructured SAPO-34 and ZSM-5 catalysts are well-known catalysts for the conversion of methanol to light olefins. SAPO-34 catalyst demonstrated higher light olefins selectivity while ZSM-5 catalyst has shown long lifetime. Therefore, combination of these catalysts can lead to the formation of a composite catalyst with optimum light olefins selectivity and longer lifetime. In this study, SAPO-34/ZSM-5 composite catalyst was synthesized with 10 wt.% ZSM-5 loading in initial gel of SAPO-34 via hydrothermal method. Also, pure SAPO-34 sample was synthesized in order to compare with composite catalyst. The synthesized catalysts were characterized by various methods such as XRD, FESEM, EDX, BET and FTIR techniques. According to XRD analysis, it is observed that by ZSM-5 loading to initial gel of SAPO-34, crystallinity reduced. Also, the presence of ZSM-5 in composite catalyst confirmed by small peaks related to ZSM-5. For the composite catalyst, spherical particles were produced with aggregation of small cubic particles. Prepared catalysts were applied in methanol to olefins process to investigate catalytic performance of the samples. Olefins selectivity for both catalysts was rarely similar with time on stream. However, composite catalyst showed longer lifetime and after 1000 min, olefins selectivity reduced with slow rate. Well catalytic performance of composite catalyst could be attributed to the modifying of its properties in the presence of ZSM-5.