Facile and Rapid Synthesis of Durable SSZ-13 Catalyst Using Choline Chloride Template for Methanol-to-Olefins
Abstract In this study, a facile and rapid synthesis approach for SSZ-13 catalyst was proposed using choline chloride (CC) as template. The optimal synthesis condition was explored, and the catalytic performance for methanol-to-olefins (MTO) was examined. Results revealed that the appropriate ratio of soft template could meet the condition for rapid and ordered growth of catalyst crystals. Using environmentally friend and cheaper CC as template could greatly accelerate the formation of bi-hexagonal ring structure in SSZ-13 framework, and it could shorten the synthesis cycle to within 4 h. With a proper amount of CC addition (i.e., m(CC)/m(SiO2) = 0.14), uniform and homogeneously distributed cubic SSZ-13 crystals were obtained with relatively lower aggregation. The catalyst synthesized with m(CC)/m(SiO2)=0.14 demonstrated excellent porous features with a total specific surface area and mesopore volume of 641.706 m2.g-1 and 0.0377 cm3.g-1, respectively. The optimized strong and weak acid sites on the SSZ-13 were obtained by regulating the m(CC)/m(SiO2). As a typical acid catalytic reaction, the SSZ-13 catalyst with strong and weak acid sites exhibited bi-functional role. The lower amount of strong acid sites and larger amount of weak acid sites in the synthesized catalyst were conducive to the catalytic performance for MTO under relatively lower reaction temperature (450 oC). Consequently, the synthesized SSZ-13 showed a better conversion rate and lifetime than that of purchased one. The methanol conversion rate using synthesized catalyst was maintained over 95% within 120 min, and its lifetime was achieved to 172 min. The appropriate acidity and well-developed pore structure of synthesized SSZ-13 could slow down the carbon deposition rate and significantly increase the lifetime of the catalyst. Moreover, the initial selectivity of light olefin could maintain above 50% within 160 min. Eventually, the desirable features of synthesized SSZ-13 catalyst were thought be with good potential for industrial application.
