Insights on CO2 Utilization through Reverse Water Gas Shift Reaction in Membrane Reactors: A Multi-scale Mathematical Modeling Approach

The rising levels of carbon dioxide (CO2) in the atmosphere significantly contribute to climate change, highlighting the need for effective CO2 mitigation strategies. While capturing and storing CO2 is important, converting it into useful products offers additional environmental and economic benefits. One promising method is the reverse water gas shift (RWGS) reaction, which transforms CO2 into carbon monoxide (CO). Membrane reactors (MR), which integrate selective membranes with equilibrium limited chemical reactions, have the potential to intensify processes based on the RWGS reaction. In such reactors, by-products like water are removed in-situ from the reaction zone, effectively shifting the reaction equilibrium to favor higher CO2 conversion. This study develops a comprehensive multi-scale mathematical model for RWGS membrane reactors. We integrate the microscale permeance model (for LTA-4A membrane) with the RWGS MR unit scale and the system�s scale models. The effectiveness of applying sweep gas has been suggested, and the optimal H2 perm-selectivity is found in the range from 30 to 50. A detailed membrane permeance model for LTA-4A membranes is integrated in the MR model to assess how species permeance changes with varying reactor conditions. We propose a sweep recycle configuration and compare it with the conventional sweeping configuration commonly assumed in most literature. A thermal efficiency analysis is conducted to evaluate the proposed recycling configuration, providing insights into the practical feasibility of membrane reactors for CO2 utilization.