Si, P, S and Se surface additives as catalytic activity boosters for dehydrogenation of methylcyclohexane to toluene - A liquid organic hydrogen carrier system: Density functional theory insights

Abstract

The controlled or optimized loading of sulfur (S) on a catalyst surface has been credited with boosting the catalytic activity of the catalyst. This is because the S binds strongly to the surface of the catalyst hence blocking other catalyst poisons such as CO and unwanted reaction intermediates from docking at the active sites. Using density functional theory calculations with van der Waals corrections, we investigated Si, P and Se surface additives as catalytic activity boosters, in addition to S. Different surface additive concentrations were considered (n = 0, 1, 2, 3, 4 — equivalent to 0, 0.2, 0.4, 0.6, 0.8 wt%). The calculated reaction energies for the full dehydrogenation of methylcyclohexane (MCH) to toluene revealed that at lower concentrations of Si, P, S and Se as surface additives, n = 1 (∼0.2 wt%) and n = 2 (∼0.4 wt%), all these surface additives reduced the overall MCH dehydrogenation reaction energy by about 40% on the Pt (111) surface. Increasing the additive concentration to n = 4 (∼0.8 wt%) yielded reaction energies of the same order of magnitude as obtained with a pristine Pt (111) surface. Our results revealed that Si, P and Se surface additives can also boost the catalytic activity of catalysts, in the same manner as S does.