Low-cost organosilane-assisted synthesis of hierarchical SAPO-34 with improved stability in methanol-to-olefins reaction

A series of hierarchical SAPO-34 molecular sieves were successfully synthesized through the organosilane-assisted method, employing low-cost 3-aminopropyltriethoxysilane (APTES) as a mesoporous template and partial silica source. The influence of APTES content on the crystallinity, pore structures, acidity, and catalytic performance of the products in the methanol-to-olefins (MTO) reaction was systematically investigated by XRD, XRF, SEM, N 2 adsorption-desorption, NH 3 -TPD measurements and a fixed-bed reactor. It revealed that the introduction of APTES created mesopores and simultaneously modulated the acidic properties, notably reducing both the strength and density of strong acid sites. Compared to the conventional microporous SAPO-34-C, the hierarchical SAPO-34 catalysts, particularly SAPO-34-0.1, demonstrated a superior catalytic lifetime and enhanced selectivity to light olefins in the MTO reaction. This performance enhancement could be attributed to their hierarchical pore systems and the moderated acidities. However, excessive APTES addition (SAPO-34-0.2) led to a decline in crystallinity and a consequent reduction in catalytic stability.