(544ex) CO2 Hydrogenation with Ni/MgO Catalysts

Loder, A., Graz University of Technology
Lux, S., Graz University of Technology
Baldauf-Sommerbauer, G., Graz University of Technology
Siebenhofer, M., Graz University of Technology
CO2 hydrogenation makes use of CO2 to produce either hydrocarbons or CO. The product selectivity depends on the catalyst and the process parameters. The hydrogenation activity of bifunctual Ni/MgO catalysts was investigated. Nickel provides the adsorbent capacity for H2, and it is highly selective to CH4. MgO provides CO2-adsorption, and it contributes to suppression of catalyst deactivation. The Ni/MgO catalyst is a cheap, highly active, easy to synthesize, easy to recycle and robust catalyst, offering access to CO2 hydrogenation of high CO2-load off-gas in metallurgy and in the refractory industry.

The influence of the nickel load on the performance of Ni/MgO catalysts in terms of rate controlling steps and the reaction kinetics were investigated. The MgO backbone was compared to Ni/MgO catalysts with different Ni load between 11-27%wt.

The MgO backbone without Ni-load is selective to CO formation, admixture of nickel shifts the selectivity to methane with high nickel load leading to higher methane selectivity and higher CO2 conversion. The reaction kinetics of the CO2 methanation can be modelled with a Langmuir-Hinshelwood based approach, as proposed by Koschany et. al. [1]. Different rate models can be applied, depending on what is assumed to be the rate determining step. Temperature dependency was modelled with an Arrhenius approach. The activation energy depends on the Ni-load, suggesting that with increasing Ni-load mass transfer becomes a key step in conversion.

[1] F. Koschany, D. Schlereth, and O. Hinrichsen, “On the kinetics of the methanation of carbon dioxide on coprecipitated NiAl(O)x,” Appl. Catal. B Environ., vol. 181, pp. 504–516, 2016.