Designing Metal-Exchanged Zeolites for Non-Oxidative Methane Upgrade to Chemicals

Recent advances in natural gas recovery have significantly reduced prices for methane, but the lack of suitable catalysts for methane conversion, other than steam reforming, limits its potential. Decades of intensive research on oxidative methane upgrade processes have not been able to improve the carbon selectivity and avoid the formation of carbon dioxide by-product. In contrast, methane upgrade in the absence of oxygen is selective to higher hydrocarbons, but requires energy input and is much less explored. In this talk, we will discuss two related non-oxidative methane upgrade processes over metal-exchanged zeolites: (i) non-oxidative coupling (NOC) of methane and ethylene to propylene could significantly increase feedstock flexibility in ethylene crackers, as increasingly lighter feedstock reduces the formation of propylene by-product, and (ii) methane dehydroaromatization (DHA) to form benzene, a major component of gasoline and an important commodity chemical. The prototype NOC and DHA catalysts are the metal-exchanged zeolites Ag-ZSM-5 and Mo-ZSM-5, respectively, but further improvements are needed to increase their activity, optimize selectivity, and reduce the rate of coking. We will discuss how we are beginning to combine advanced zeolite synthesis and characterization with kinetics measurements and detailed density functional theory calculations to rationally design metal-exchanged zeolites with improved product yield and lifetime for non-oxidative methane upgrade processes.