Kinetics, Model Discrimination, and Parameters Estimation of CO₂ Methanation on Highly Active Ni/CeO₂ Catalyst

The reaction kinetics of CO2 methanation over a highly active 8.5% Ni/CeO2 catalyst was determined in fixed-bed reactor, the absence heat- and mass-transfer limitations. Once activity stabilized, more than 120 kinetic experiments (with varying values temperature, total pressure, space velocity (GHSV), partial pressure products reactants) were performed. From initial rates, an apparent activation energy 103.9 kJ mol–1 determined, as well effect reactants (positive) water pressures (negative) on rate. Three mechanistic models reported literature, which is adsorbed dissociatively (carbon formyl routes) or directly (formate route), explored for modeling entire kinetics. For that, corresponding rate equations developed through Langmuir–Hinshelwood–Hougen–Watson (LHHW) approach. In agreement with DRIFTS experiments, formate route, hydrogenation bicarbonate to considered be rate-determining step, reflects data accurately, operating from differential conversion thermodynamic equilibrium. fact, this mechanism results mean deviation (D) 10.38%. Based previous own studies, participation two different sites has been also considered. Formate route maintains high fitting quality experimental data, providing parameters higher physical significance. Thus, LHHW mechanism, Ni0 oxygen vacant near Ni-CeO2 interface participate methanation, able predict accurately wide range operational conditions.