Structural Engineering of SAPO-34/ZSM-5 Core–Shell Zeolites for Regulating Shape Selectivity and Surface Acidity in Molybdenum-Catalyzed Methane Dehydroaromatization

In this study, novel Mo-decorated core–shell zeolite composites, namely ZSM-5@SAPO-34 and SAPO-34@ZSM-5, were synthesized and evaluated as catalysts for methane dehydroaromatization (MDA). Core–shell structures were effectively fabricated via sequential hydrothermal synthesis, utilizing SAPO-34 and ZSM-5 as cores, which were subsequently subjected to hydrothermal growth in ZSM-5 and SAPO-34 reacting solution, respectively. Catalysts with varying SAPO-34/ZSM-5 mass ratios and Mo loadings were thoroughly characterized by the XRD, BET, SEM-EDS, and NH3-TPD techniques. The catalytic performance in the MDA reaction revealed a strong correlation between composite architecture, acidity, Mo dispersion, and product selectivity. Introducing H+SAPO-34 into both core–shell composites enhanced ethylene-to-benzene conversion due to the acidic confinement provided by SAPO-34. In contrast, non-protonated SAPO-34@ZSM-5 showed limited activity as a result of its weak acidity and inadequate Mo dispersion. Among all catalysts, H+ZSM-5@SAPO-34 with a 3:1 core–shell mass ratio delivered the highest benzene yield and stability, outperforming the benchmark, H+ZSM-5. This work highlights the potential of tailored core–shell zeolite composites in optimizing acid–metal interactions and improving catalytic performance in hydrocarbon transformations.