Modeling the CO2 capture and in situ conversion to CH4 on dual function Ru-Na2CO3/Al2O3 catalyst

Abstract

Abstract A dynamic kinetic model is proposed to describe the CO2 adsorption and in situ hydrogenation to CH4 on a 4%Ru-10%Na2CO3/Al2O3 catalyst. One dimensional isothermal heterogeneous plug flow reactor model with axial dispersion is considered. The reaction network and kinetic equations are deduced from experimental data analysis. The molecular modeling includes competitive adsorption of CO2 and H2O on same adsorption site. During CO2 storage period, CO2 is adsorbed onto Na2O species to form Na2CO3. Alternatively, CO2 can be also adsorbed onto NaOH species releasing H2O to the gas phase, which can further be adsorbed onto free adsorption sites located downstream. It was needed to consider formation of unstable bicarbonates to fit the experimental data. During CO2 hydrogenation step, adsorbed carbonates are decomposed, promoted by the presence of H2. CH4 is then formed through the Sabatier’s reaction and the as-formed H2O interacts with regenerated adsorption sites. Temporal evolution of CO2, CH4 and H2O during CO2 storage and hydrogenation cycles is accurately predicted by the model, for a wide range of reactant concentrations and temperature (250−400 °C), gaining understanding on mechanisms and dynamics of the process on dual function materials.