Adsorption and dehydrogenation of methanol on alkali-cation-exchanged zeolite: A first-principles density functional study

The adsorption and dehydrogenation of methanol on an alkali-cation-exchanged zeolite model, M-zeolite (M = Na(+), K(+), Rb(+), and Cs(+)), were studied using first-principles calculations based on density functional theory (DFT). The adsorption energies, geometric structures, and vibrational frequencies of the transition states were computed by full-geometry optimization with a 6MR (membered-ring) cluster model. We have calculated the transition states and adsorption complexes of the reactants, transition states, and products, as well as the corresponding activation barriers and adsorption energies of the numerous reactions involved in these processes. The interaction first leads to the formation of a methanol complex, where the methanol via the oxygen atom and the alkali metal cation of the 6MR. Then, a transition state involves the coordination of two hydrogen bonds. Finally, the adsorbed formaldehyde and hydrogen complex is formed. The calculated results are compared with the data obtained from previous experimental studies. (C) 2009 Elsevier Inc. All rights reserved