Reaction Kinetic Modeling of the COₓ Methanation over a Broad Range of Operation Conditions on an Impregnated Ni/Al₂O₃ Catalyst

An intrinsic kinetic model describing the COₓ methanation reaction was developed for an impregnated Ni/Al₂O₃ catalyst. The kinetic experiments were performed in a Berty-type reactor within a temperature range of 250 to 450 °C and an absolute pressure range of 3 to 10 bar. A model following the Langmuir–Hinshelwood–Hougen–Watson (LHHW) approach was selected as best fitting from 60 parameterized kinetic models based on different assumptions. For improved model prediction, the influence of interactions between strongly adsorbed carbon monoxide and active metal on the activation energy is considered in the LHHW model. To facilitate mathematic handling, in addition, a conventional LHHW model is proposed. The proposed models assume the hydrogen-assisted carbon dioxide dissociation as the rate-determining step for the reverse water–gas shift reaction and the hydrogen-assisted formyl dissociation as the rate-determining step for the CO methanation. In both models, CO, CO₂, atomic hydrogen, and H₂O form the most abundant surface intermediates.