Kinetics of greenhouse gas CO2 hydrogenation over K-promoted Cu/ZnO/Cr2O3 catalyst towards sustainable aviation fuel production

In sustainable aviation fuel development, the catalytic approach for CO2 hydrogenation to methanol can introduce side reactions that can significantly influence the process efficiency and final product quality. For process intensification, modeling tools are crucial to predicate and understand the reaction pathways to improve the operating conditions or catalyst design. Herein, we propose a new microkinetic modeling approach that combines the unity bond index-quadratic exponential potential (UBI-QEP) method and the Langmuir-Hin-shelwood-Hougen-Watson (LHHW) technique to examine the conversion of CO2 and H2 to methanol on a Cu(1 1 1)-dominated catalyst. For the mechanism study, the heat of adsorption values for the reaction intermediates and the activation barrier for all the elementary steps are calculated by the UBI-QEP method. The estimation of the pre-exponential parameter is done by fitting the model to the experimental data. This procedure decreases the computational time and enhances the model's accuracy by bypassing complex theoretical calculations. To validate the model, the synthesis of methanol from CO2 and H2 is conducted over a K-promoted Cu/ZnO/Cr2O3 catalyst, using a lab-scale plug-flow fixed-bed reactor (PF-FBR). The computational results suggest that the synthesis of methanol over Cu(1 1 1)-facets preferentially follows the formate pathway, with the hydrogenation of formate acting as a rate-determining step (RDS). The validated model (R2 = 0.99) predicts an activation energy (Ea) of 63.70 kJ.mol-1 for CO2 conversion over the studied catalyst. The proposed microkinetic model can serve as a reliable tool for elucidating the role of active sites that may control the performance of a CO2 hydrogenation catalyst.