Thermodynamic analysis and kinetics studies of CO2 hydrogenation to alcohols by reverse water--gas shift and Fischer-Tropsch reactions

Carbon dioxide (CO 2 ) is the primary contributor to the greenhouse effect. Its emissions have increased in recent years, primarily due to the burning of fossil fuels for energy production and transportation. Therefore, developing processes capable of converting CO 2 into value-added products that can serve as alternative fuels is crucial. As thermodynamic equilibrium analysis offers key insights into species stability, reactant conversion, and product selectivity, a thermodynamic equilibrium study of the RWGS reaction, CO 2 methanation, CO 2 hydrogenation to methanol, ethanol and ethylene glycol was conducted using Aspen Plus V12.1 simulation software, with the Peng-Robinson equation of state as the thermodynamic model. The influence of temperature, pressure and H 2 :CO 2 ratio on reaction equilibrium was assessed via an RGIBBS reactor model. This research evaluated the thermodynamic behavior of ethanol and ethylene glycol synthesis via CO 2 hydrogenation, as these compounds have not yet received significant attention in literature. While the hydrogenation of CO 2 to ethanol is thermodynamically feasible over a wide range of temperatures and pressures, the production of ethylene glycol is only favorable at temperatures below 200 °C. Kinetic studies indicated that most catalysts operated near thermodynamic equilibrium; however, the catalyst for the RWGS and for the CO 2 hydrogenation to methanol were likely operating under kinetic control rather than being close to thermodynamic equilibrium.