Speaker
Description
The reaction mechanism for the formation hydrocarbons and gasoline for methanol and ethanol
was explored over zeolites FER (Ferrierite) and LTL (Perlialite) using density functional theory
calculations, so as to elucidate the specific elementary step leading to the formation of hydrocarbon
or ethylene by interaction with a hydrocarbon pool. The adsorption energies were studied with
varying Si/Al ratios. No stable protonated alcohol was observed in any of the adsorption sites but
rather only a physiosorbed alcohol. The cleaving of the C-O bond in dehydration of the alcohols
was observed when the starting geometry was of a protonated alcohol. The possible formation of
the dimethyl ether and ethanol from the adsorption of the methoxonium ion was observed with
energies -25kcal.mol and -46kcal/mol respectively. Methanol adsorption was strongest in the
zeolite FER. Adsorption of protonated ethanol in zeolite LTL led to the formation of carbonium
ion and surface ethoxy species with relative energies -9.9kcal/mol and -16kcal/mol respectively.
Both the surface ethoxy group and the carbonium ion formed is the precursors for the formation
of ethylene and long chain hydrocarbons. The results of this study offer great insight into the
optimization of zeolite catalysts to increase hydrocarbon yield in short-chain alcohol conversion.
