화학공학소재연구정보센터
Applied Catalysis A: General, Vol.551, 34-48, 2018
Facile synthesis of a superior MTP catalyst: Hierarchical micro-meso-macroporous ZSM-5 zeolites
With the growing demand for propylene and the rapid depletion of petroleum resources, the methanol-to-propylene (MTP) reaction has aroused much interest in the industrial and academic research fields as an alternative route to produce propylene. Developing a highly efficient MTP catalyst by adopting a facile, efficient route is currently an important research goal. It is clear that the synthesis of a hierarchical micro-meso-macroporous ZSM-5 zeolite is regarded as the ideal strategy owing to its ability to minimize coke formation and to produce maximal catalytic efficiency in the MTP reaction. In this study, a superior MTP catalyst with a hierarchical micro-meso-macroporous structure (denoted as M-ZSM-5) has been successfully developed based on the passivation effect and the strong self-condensation of the short-chain organosilane 3-aminopropyltrimethoxy-silane (APTES) on the surfaces of nanocrystals in a quasi solid-state system. This environmentally friendly synthetic strategy is operationally simple, with a high yield (above 80%) and low cost and thus has considerable potential for industrial applications. In the quasi-solid-state system, APTES not only induced the formation of ultrafine nanocrystals but also ensured that these ultrafine nanocrystals were assembled in situ into hierarchical micro-meso-macroporous ZSM-5 zeolites. When applied to the methanol-to-propylene (MTP) reaction, the synthesized MZ-x (x = 1-5) zeolites exhibited a longer catalytic lifetime (31 h-89 h) (at a high weight hourly space velocity of 8 h-1) than that of a commercial ZSM-5 catalyst (denoted as C1Z-1)(11 h), which are nearly three times and eight times longer than that of the C1Z-1 sample. In addition, the MZ-x (x = 1-5) catalysts also present a slightly higher propylene selectivity (39.92%-41.89%), butylene selectivity (22.29%-23.65%) and light olefins (C2 = - C4 =) selectivity (69.19%-71.43%) than that of the C1Z-1 (39.86%, 21.70%, 68.46%). These results were attributed to the abundant mesopores and macropores of M-ZSM-5 built by the ultrafine nanocrystals, offering a shorter diffusion path and more-accessible active sites for reaction.