Selective synthesis of the SAPO-5 and SAPO-34 mixed phases by controlling Si/AI ratio and their excellent catalytic methanol to olefins performance

摘要

The selective synthesis of SAPO-5, SAPO-5/SAPO-34 mixture and SAPO-34 was performed by increasing Si/Al ratio and pH through hydrothermal synthesis route, in which the product was successively switched from AFI to AFI/CHA and to CHA. The samples were characterized by XRD, XRF, SEM, and NH3-TPD techniques. It indicates that the SAPO-5/SAPO-34 mixture exhibits higher acidity than the pure SAPO-5 and SAPO-34 phases. During methanol-to-olefins reaction, the catalytic lifetime of the SAPO-5/SAPO-34 mixture was significantly longer than that of SAPO-34, which may be attributed to the moderate acidity of the SAPO-5/SAPO-34 mixture.