Hydrogen transfer in hydrocarbon conversions over transition metal surfaces

Hydrogen-transfer steps are a poorly studied and rarely proposed class of elementary reactions in heterogeneous catalysis over metal surfaces. In these steps, a hydrogen atom that is attached to the carbon in one surface species transfers to a carbon atom of another species. Unity bond index–quadratic exponential potential (UBI–QEP) calculations of the activation energies for three model surfaces representing substrates with strong, weak, and intermediate chemisorption abilities, combined with UBI–QEP/DFT data for the Pt(1 1 1) surface, suggest that there is no great energetic impediment to these steps. Therefore, they should not be arbitrarily ignored when building mechanisms of hydrocarbon conversions over metal surfaces. Moreover, kinetics simulations show that conditions are possible under which one-step hydrogen transfer is faster than the two-step process with the formation of adsorbed hydrogen.