Chloromethane-to-olefin using metal oxide-impregnated small-pore SSZ-13 zeolites with controlled acidity, reactant affinity, and reaction pathway

The conversion of chloromethane (CH3Cl) to olefin (CMTO) is an energy-efficient C1-molecular reaction that utilizes CH3Cl as a reactive C1 resource to produce C2–C4 light olefins. Despite its potential, enhancing the activity, olefin selectivity, and catalyst lifetime remain critical challenges in attaining the industrial standard established by the methanol-to-olefin (MTO) reaction. To address these challenges, we synthesized a range of metal oxide-impregnated small-pore H-SSZ-13 zeolites, controlling the type and loading of metal oxide, to investigate their effects on CH3Cl conversion, light olefin selectivity, and catalyst lifetime. Our findings revealed that impregnation of SnO2 at a given metal oxide loading resulted in the highest olefin selectivity (>85%). The variation in SnO2 loading controlled the surface acidity, which influenced the affinity of CH3Cl and led to a systematic change in reaction pathways, governing CH3Cl conversion, olefin selectivity, and catalyst lifetime. Through our analysis of the structure–performance relationships, we elucidated the underlying catalyst promotion by SnO2 impregnation and proposed a reaction process based on the hydrocarbon pool mechanism that systematically controlled selectivity in C2–C4 olefins. These insights provide a robust framework for the design of novel catalysts that offer superior performance in the CMTO reaction.