Evidence of rate-determining step variation along reactivity in acetylene hydrogenation: a systematic kinetic study on elementary steps, kinetically relevant(s) and active species

We report here that the reduction degree of the metal at the catalytic interface dominates the reactivity of acetylene hydrogenation, mainly in terms of turnover rates (TORs) and activation energies, which could certainly cause the switch of kinetically relevant steps (KRS) from "C2H3*+H*" over Ce(OH)SO4·xH2O dispersed Pd catalyst to "C2H4*+H*" elementary step over Pd/CeO2. Besides, a compact kinetic model has been established to describe the reaction process and the dissociative mechanism was confirmed by H2/D2 exchange experiment. Meanwhile, the rate-determining step (RDS) and the main adsorbed species of the reaction were confirmed by systematic kinetic studies as well as in-situ FTIR analysis. More importantly, with the aid of parity fitting and gas isothermic adsorption analysis, the energetic relationship among the steps along with the acetylene hydrogenation is quantitatively described, which provides a good support and complement for the previous research, and helps researchers build up advanced reaction systems.