DFT studies of the adsorption of propane and propene on metallic surfaces in Ag/ZrO₂ catalysts as a model for catalytic combustion reactions of light hydrocarbons

Abstract

Molecular modelling studies were carried out at the DFT level of the adsorption of propane and propene on Ag surfaces as a model of the interaction of light hydrocarbons with Ag/ZrO₂ catalysts for catalytic combustion reactions. It was found that the most stable mode of adsorption of propene through its π system on Ag atom has energies consistent with chemisorption and generates an elongation of the C1=C2 bond, which would explain the increase in the activity of the catalysts as a function of its metallic charge. The results obtained from the DFT calculations explain the different types of interactions between propene and propane with the metallic surface. The propene is chemisorbed on the Ag surface, distorting its bonds and generating its activation. This would imply that a higher metallic charge in the catalyst would increase the number of active sites in which this activation occurs, generating a higher activity. In addition, with the addition of O, the binding energy between the propene and the metal surface increased. On the other hand, the presence of a metallic surface is not enough for the activation of the propane molecule. This would explain why, by increasing the amount of metal in the catalyst, the activity for the combustion of propane is practically not affected.