Computational Exploration on Coupling Formic Acid Production with Propylene Synthesis via Catalytic Transfer Hydrogenation: The Role of CO2 beyond Reverse Water Gas Shift Reaction.

Abstract

CO2-assisted propane dehydrogenation (CO2-ODHP) is emerging as an alternative route to the direct dehydrogenation of propane. Previous studies on CO2-ODHP have shown that the role of CO2 is to shift the reaction equilibrium toward the product side by consuming the produced H2 molecules via reverse water gas shift (RWGS) reaction. Since the ultimate fate of CO2 is to get reduced, we herein propose another pathway of CO2 reduction in the realm of CO2-ODHP─CO2 hydrogenation to formic acid (FA). With the objective of investigating the feasibility of this process, we, for the first time, carry out a computational investigation on coupling propane dehydrogenation with CO2 hydrogenation using a Ti-alkoxide-functionalized UiO-67 metal-organic framework. Analysis using the distortion/interaction model confirms that CO2 hydrogenation to FA is a preferred pathway over the RWGS reaction and hence can be realized in practice. Our study also highlights the importance of intersystem crossing, which provides an opportunity to access nonground state potential energy surfaces while undergoing chemical transformations. Again, subsequent addition of water molecules has shown to ease product desorption by 41 kcal/mol. Our study, therefore, hints at an unexplored role of CO2 beyond the RWGS reaction in oxidative propane dehydrogenation.