CO2 Conversion Enhancement in a Periodically Operated Sabatier Reactor: Nonlinear Frequency Response Analysis and Simulation-based Study

Conversion of CO2 into synthetic CH4 via thermocatalytic hydrogenation (the Sabatier reaction), has recently gained increasing interest as a possible route for CO2 utilization and energy storage pathway. Herein, we analyze the possibility of increasing the CO2 conversion through periodic operation of the reactor. The analysis is performed by using the Nonlinear Frequency Response (NFR) method, a recently developed analytical technique, suitable for fast evaluation of periodic reactor operations. The NFR analysis predicts a significant conversion gain (up to 50%) for certain frequencies of the feed flow rate modulation. This prediction is validated by numerical simulations with a reaction rate expression obtained by CO2 conversion experiments using a Ni/Al2O3 catalysts. Both the NFR analysis and numerical simulations predict that it is possible to obtain 70% CO2 conversion at 500 K, 5 bar, and average space velocity of 7600 h(-1) by a periodic modulation of the feed flow rate, as compared to the corresponding steady state CO2 conversion of 43%.