Synthesis, characterization, and catalytic performance in 1-butene cracking of ZSM-5 zeolites prepared with different cross-linked silicon species

Abstract

ZSM-5 zeolites were prepared via a hydrothermal synthesis approach, wherein the alkalinity of the synthesis system was precisely regulated to achieve directional control over the cross-linked configuration of silicon species. XRD, XPS, and ²⁷Al MAS NMR techniques were employed to conduct comprehensive characterization of the synthesized ZSM-5 zeolite, followed by a systematic evaluation of its catalytic performance in the conversion of 1-butene to propylene via catalytic cracking. The results demonstrated that low alkalinity conditions favored the formation of silicon species with low cross-linking, whereas high alkalinity conditions facilitated the generation of highly cross-linked silicon species. Leveraging this insight, C-series and T-series ZSM-5 zeolites were successfully synthesized using highly cross-linked and low cross-linked silicon species as silicon sources, respectively. Compared to T-series ZSM-5 zeolites, C-series zeolites exhibited lower acid strength, reduced Brønsted acid site density, fewer structural defects, and a more uniform distribution of framework aluminum. These inherent properties conferred superior catalytic selectivity. Notably, when employed in the catalytic cracking of 1-butene to propylene, C-series zeolites achieved an impressive 55% propylene selectivity, demonstrating significant potential for industrial applications.