258177 Understanding Contributions From the Aromatic and Olefin Methylation Cycles in Methanol to Hydrocarbons Conversion
The dehydrative condensation of methanol on zeolites is unique in its ability to form carbon-carbon bonds and concurrently restrict the carbon-chain length based on the shape selective characteristics of the molecular sieve. In the “hydrocarbon pool” mechanism for methanol-to-hydrocarbon (MTH) chemistry, organic species, specifically, olefins and arenes, contained inside the zeolite pore act as scaffolds for C-C bond formation. Steady state, transient, and isotopically labeled kinetic studies were done to show that the relative contribution of the olefin and arene methylation cycles prevalent in the indirect “hydrocarbon pool” mechanism for MTH conversion over zeolites can be systematically modulated at iso-conversion. These effects of seeding the 'hydrocarbon pool' in MTH catalysis persist at varying temperatures, conversion, and space velocity. Kinetic and isotopic studies that probe the identity and reactivity of specific olefin and arene components of the hydrocarbon pool, and an assessment of the relative propagation of olefin and arene methylation cycles as a function of zeolite topology will also be presented.