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

• Published in: Faraday discussions 2016-10, Vol.192, p.529-544
• Main Authors: Hubble, R. A, Lim, J. Y, Dennis, J. S
• Format: Article
• Language: English
• Subjects: Carbon dioxide; Carbon monoxide; Catalysts; Methanation; Natural gas; Partial pressure; Reaction kinetics; Reactors
• ISSN: 1359-6640; 1364-5498
• DOI: 10.1039/c6fd00043f

The production of methane by reacting CO 2 with H 2 (CO 2 methanation) has the potential for producing synthetic natural gas, which could be exported using the existing infrastructure for the distribution of natural gas. The methanation of CO 2 was investigated over a wide range of partial pressures of products and reactants using (i) a gradientless, spinning-basket reactor operated in batch mode and (ii) a laboratory-scale packed bed reactor operated continuously. The rate and selectivity of CO 2 methanation, using a 12 wt% Ni/γ-Al 2 O 3 catalyst, were explored at temperatures 445-497 K and pressures up to 20 bar. Research with the batch reactor showed that the rate increased with increasing partial pressures of H 2 and CO 2 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 H 2 and CO 2 when their partial pressures were high. A convenient method of determining the effect of H 2 O on the rate of reaction was also developed using the batch reactor and the inhibitory effect of H 2 O on CO 2 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 CO 2 dissociated to adsorbed CO and O on the surface of the catalyst with the rate-limiting step being the subsequent dissociation of adsorbed CO. The ability of the kinetic expressions to predict the results from the continuous, packed-bed reactor was explored, with some discrepancies discussed.