Density functional theory study on catalytic dehydrogenation of methylcyclohexane on Pt(111)

Density Functional Theory (DFT) method was used to study the step-by-step dehydrogenation of methylcyclohexane (MCH) to toluene on a Pt(111) surface to understand adsorption properties of the reactants, intermediates and the products involved. The results indicate that dehydrogenation occurs preferentially in the para position. Methylcyclohexane is a saturated molecule and its adsorption on the surface of Pt(111) falls into the category of physical adsorption. 4-methyl-cyclohexene and methyl-cyclohexadiene are the most likely dehydrogenation intermediates. The C–C bond on the six-membered ring has a significant shrinkage after the dehydrogenation reaction. The highest energy barrier of 32.46 kcal/mol is calculated for the first dehydrogenation step, which may potentially be the rate-determining step for the entire reaction network. These are consistent with the experimental results.