On the kinetics of the co-methanation of CO and CO2 on a co-precipitated Ni-Al catalyst

The kinetics of the gas-phase co-methanation reaction of carbon oxides over a co-precipitated 44 wt.% NiAlOx catalyst were modelled via competitive adsorption of CO and CO2 and the subsequent methanation of a common surface intermediate. Steady-state isotope experiments and model discrimination suggest the decomposition of a hydrogenated COHy surface intermediate to be the kinetically relevant step in the methanation reaction. The best fit is obtained for hydroxycarbene (y = 2). The presented kinetic model is the first to explicitly describe the full coupling of CO and CO2 transformation. It is built on the basis of CO methanation, CO2 methanation, steam reforming, and water-gas shift experiments over a wide range of conditions. All model parameters are thermodynamically consistent and statistically relevant.