Comparative Preparation of HZSM-5, SAPO-34 and SAPO-34(50%)/HZSM-5(50%) Nanostructured Catalysts with Various Si/Al Ratio Used in Methanol to Light Olefins

A series of ZSM-5 molecular sieves with different Si/Al ratios and nanostructured SAPO-34/HZSM-5composite have been synthesized by hydrothermal method. The influence of Si/Al ratio on ZSM-5 structure and itsoptimum ratio with SAPO-34 were investigated on the catalytic performance. The samples were characterized by XRD,FESEM and EDX techniques. The results of XRD patterns revealed that different Si/Al ratios play different roles in thecrystallization of crystalline phase. The catalytic performance of these catalysts showed thatthe Si/Al ratio has loweffect on methanol conversion, while it has considerable effect on stability and products selectivity.The catalyticactivity and stability of SAPO-34/HZSM-5 catalyst in MTO process was improved with theuse of ZSM-5 (Si/Al=180)due to the crystallinity, particle sizes and higher existence of Si incorporation into the framework. The selectivity ofolefins for SAPO-34/HZSM-5 sample was about 89% after 30 h time on stream.

کلیدواژه ها:

SAPO-34 ، HZSM-5 ، SAPO-34/HZSM-5 ، Catalyst ، Methanol ، Olefins