C2H2 selective hydrogenation over transition metal carbide (MxCy): Probing into the influences of crystal facet, M type and M: C ratio on C2H4 activity, selectivity and catalyst stability

Abstract

Aiming at probing into the structure and composition sensitivity of transition metal carbides (MxCy) to catalytic performance of C2H2 selective hydrogenation, twenty-three kinds of MxCy (M = Ti, Zr, Hf, Mo, W and Co) catalysts with different M types, crystal facets and M: C ratios are investigated using DFT calculations and microkinetic modeling. The results show that C2H4 activity and selectivity depend on surface composition and structure due to the ensemble and/or ligand effects. Charge transfer number from M to C atoms and d-band center can be used as the descriptors to efficiently evaluate C2H4 selectivity and activity over MxCy catalysts, respectively. α-MoC(101) is screened out to exhibit Pt-like electronic properties with better C2H4 activity, selectivity, and catalyst stability to resist green oil formation compared to Pt and other MxCy catalysts when the temperature is ≤425 K and H2: C2H2 ratio is ≥1: 1, which is superior to the industrial PdAg/Al2O3 catalyst.