Study on the synthesis of Zn/ZSM-5 by CTAB-assisted seeding method and its role in catalytic reforming cellulose volatiles

The massive consumption of petroleum and the increasingly deteriorating environment has triggered the attention and development of sustainable chemistry. The catalytic generation of aromatic hydrocarbons from biomass pyrolysis over ZSM-5 is a promising method for biomass value-added utilization. In this study, the yield of light aromatic hydrocarbons was improved and the generation of carbon deposition was inhibited by adjusting the pore structure and surface active site of ZSM-5 molecular sieve. The hierarchical Zn/ZSM-5 was synthesized by using cetyltrimethyl ammonium bromide (CTAB) as template by crystal seed method. The effect of the interaction of metal Zn and CTAB on the crystallization of ZSM-5 was described. The catalyst was used to prepare light aromatic hydrocarbons by the catalytic reforming of cellulose volatiles. The catalysts were also characterized using XRD, SEM, BET, NH₃-TPD and XPS to obtain the physical and chemical structures of the catalysts. The results showed that the addition of appropriate CTAB increased the specific surface area of the zeolite, significantly increased the mesoporous, and promoted the mass transfer of the reactants and products. Moreover, the presence of CTAB can regulate the presence of metal Zn, strengthen the interaction between metal Zn and zeolite skeleton, and form more Zn-OH⁺ active sites, so that the catalyst has a strong deoxidation ability and hydrogen transfer ability, and promote the aromatization of hydrocarbons. The ZnZ5-1 (The molar ratio of CTAB/SiO₂ in the initial material synthesized is:has suitable mesoporous (3−10 nm) and appropriate acid content, and the highest yield of light aromatic hydrocarbons is 1) 166.7 mg/g. The ZnZ5-1 has a good catalytic performance in the catalytic reforming reaction of cellulose pyrolysis volatile matter. The synthesis of this catalyst introduces both of the mesopores and the metal active sites and this synergistic action enables the regulation of catalyst characteristics. This study is expected to shed light on improving the yield of light aromatic hydrocarbons during the catalytic reforming of biomass volatile and on regulating the product selectivity.