Kinetic studies of CO2 methanation over a Ni/γ-Al2O3 catalyst using a batch reactor

• CO2 methanation investigated in a spinning-basket reactor operated in batch.
• Rate and selectivity determined for 12 wt% Ni/γAl2O3 catalyst, 453–483 K to 20 bar.
• Convenient method of determining the effect of H2O on the rate was developed.
• Kinetics were consistent with adsorbed CO2 dissociating to adsorbed CO and O.
• The RDS is the subsequent dissociation of adsorbed CO.

The methanation of CO2 was investigated over a wide range of partial pressures of products and reactants using a gradientless, spinning-basket reactor operated in batch mode. The rate and selectivity of CO2 methanation, using a 12 wt% Ni/γ–Al2O3 catalyst, were explored at temperatures 453–483 K and pressures up to 20 bar. The rate was found to increase with increasing partial pressures of H2 and CO2 when the partial pressures of these reactants were low; however, the rate of reaction was found to be insensitive to changes in the partial pressures of H2 and CO2 when their partial pressures were high. A convenient method of determining the effect of H2O on the rate of reaction was also developed using the batch reactor and the inhibitory effect of H2O on CO2 methanation was quantified. The kinetic measurements were compared with a mathematical model of the reactor, in which different kinetic expressions were explored. The kinetics of the reaction were found to be consistent with a mechanism in which adsorbed CO2 dissociated to adsorbed CO and O on the surface of the catalyst with the rate-limiting step being the subsequent dissociation of adsorbed CO.