Mechanistic insights into the dominant reaction route and catalyst deactivation in biogas reforming using ab initio microkinetic modeling

Abstract

An ab initio microkinetic model (MKM) is developed to understand the reactivity trends of the terrace (111) and step (211) sites of transition metal catalysts for biogas reforming (BGR) to produce syngas. Over the (111) sites, Ni, Rh and Pd show high turnovers for CH₄ consumption (>1 s⁻¹), however, with enhanced coke formation (>0.1 s⁻¹). In comparison, Co and Ru exhibit reduced coke formation rates (<10⁻³ s⁻¹) with appreciable methane turnovers (0.1 s⁻¹). Specifically, on these two metals, the H₂/CO ratio (3 to 4) is found to be the closest to the desired ratio (2 to 3) for syngas valorisation. As compared to dry reforming, steam reforming rates are more pronounced on both the surfaces. In general, (211) facets show significantly high turnovers for coke formation (>1 s⁻¹) via methane dissociation. Here also on the (211) surface, Ru shows significantly reduced coke formation rates (0.1 s⁻¹).