This study assesses the feasibility of using H-2-containing streams, such as biomass gasification product gas, as a source of H-2 for the thermocatalytic conversion of CO2 to renewable natural gas (RNG). A heat-exchanger type, molten salt-cooled membrane reactor is analyzed using a transient mathematical model that accounts for dynamic catalyst deactivation. The effect of the distributed H-2 supply via a H-2-selective membrane on the catalyst deactivation was investigated in comparison to the non-membrane reactor. The simulation results showed significantly lower catalyst deactivation rates in the membrane reactor due to the distributed H-2 supply that results in a more uniform temperature distribution. Space velocity and cooling rate are crucial parameters and there is a trade-off between positive and negative effects of these parameters on the membrane reactor performance. The model predicts that, with a proper selection of operating parameters, it is possible to achieve CO2 conversion and CH4 yield of 97% during an extended period of operation of 10,000 h.