Designing Metal-exchanged Zeolites for Non-oxidative Methane Upgrade to Chemicals

Utilization of methane to produce chemicals has become attractive due to significantly reduced prices for methane gained from recent development in natural gas recovery. However, the lack of suitable catalysts for methane conversion (other than steam reforming) hinders its advances. While intensive research has been conducted on oxidative methane upgrading over decades, the carbon selectivity and the formation of carbon dioxide have been barely improved. In contrast, oxygen-free methane conversion shows superior selectivity towards higher hydrocarbons, but it is much less explored. Here, two related non-oxidative methane upgrade reactions over metal-exchanged zeolites will be addressed. (i) Production of propylene through non-oxidative coupling (NOC) of methane and ethylene over AgZSM-5 could significantly increase feedstock flexibility in ethylene crackers, as increasingly lighter feedstock reduces the formation of propylene by-product. (ii) Methane dehydroaromatization (DHA) over Mo-ZSM-5 can form benzene, one of the most important commodity chemicals in petrochemical industry. Despite numerous studies of the two topics, improvements are still needed to enhance catalytic activity, reduce coking rate, and optimize selectivity. We will discuss how we begin to utilize advanced zeolite synthesis and characterization, in conjunction with density functional theory (DFT) calculations, to judiciously design metal-exchanged zeolites with improved reaction performance for these processes.