Selective regulation of products for oleic acid pyrolysis by adjusting acid strength and the acidic environment of the catalysts

In recent years, the catalytic pyrolysis of biomass to produce benzene, toluene and xylene (BTX) by ZSM-5 zeolite with hierarchical pore structure has received significant research interest. The dendritic ZSM-5 (DZ) zeolite with high specific surface area and hierarchical pore structure was synthesized in present work. The acid strength and acid type of the catalyst were systematically tailored by precisely adjusting the Si/Al molar ratio and incorporating zinc and iron modifications. The crystal structure, morphology, pore characteristics, and acidic properties of the catalyst were systematically characterized by XRD, TEM, FTIR, 27 Al MAS NMR, NH 3 -TPD, and Py-IR. The results show that adjusting the acid strength and acid type effectively promoted the catalytic pyrolysis of oleic acid into BTX. The metal Zn modification could significantly reduce the Brønsted-to-Lewis (B/L) acidity ratio of DZ, which not only optimized the balance of acid site types but also enhanced its catalytic performance. The appropriate modification with Fe not only further optimized the acid site distribution but also enhanced the dispersion of Zn species, leading to the formation of additional ZnOH + activation centers and thereby promoting the aromatization of low-carbon olefins. The 2Fe5Zn/DZ 30-0.05 catalyst achieved a high BTX yield of 14.8% while maintaining stable catalytic performance for up to 40 h.