Optimization of CO 2 hydrogenation for enhanced methanol selectivity: A combined thermodynamic and kinetic assessment

Abstract Gas phase thermodynamic analysis of CO 2 hydrogenation to methanol is conducted using both stoichiometric and Gibbs free energy minimization approaches covering the limiting cases of isothermal and adiabatic conditions followed by optimization of this reaction system in ideal reactor configurations. Results indicate that methanol synthesis from CO 2 hydrogenation exhibits kinetic limitations on Cu/ZnO/Al 2 O 3 catalyst, approaching thermodynamic equilibrium at space times >100 s in the operating range of 2–4 MPa and 450–550 K. Production of methanol is significantly limited by competing reverse water gas shift reactions but the addition of CO in the feed (of CO 2 and H 2 ) suppresses the effect of the latter thereby improving overall methanol selectivity. Special attention was given to analyze the conditions (temperature, pressure and feed mole ratio) using both kinetic and thermodynamic models, at which there is no net CO formation and close to 100% methanol selectivity can be obtained.