Monte carlo and lattice-gas studies of the kinetics of hydrocarbon hydrogenation reactions

Abstract The hydrogenation of unsaturated hydrocarbons by transition metal catalysts demonstrates complex behaviour that cannot be represented by mean-field kinetic models. We illustrate these kinetic phenomena by presenting the results of an experimental study of the catalytic hydrogenation of ethene by Pt/SiO 2 Monte carlo and lattice-gas methods are then applied to the simulation of the ethene hydrogenation reaction. Both numerical approaches are shown to reproduce the kinetic discontinuities observed experimentally for the hydrogenation of ethene and ethyne. The monte carlo model is then extended to consider the hydrogenation of a number of alkenes of varying chain length. The simulations of the hydrogenation of both ethene and of the longer chain hydrocarbons suggests that the transition between the two kinetic regimes occurs at the point where the hydrocarbon surface coverage exceeds the dimer jamming limit. It is proposed that the origin of the discontinuity can be accounted for by assuming that the adsorption of the hydrocarbon approximates a random sequential adsorption process. This interpretation of the origin of the kinetic discontinuity is shown to be consistent with previous studies of hydrocarbon hydrogenation kinetics.