Dehydration-Coupled CO2 Hydrogenation to Methanol Process with Enhanced Conversion and Sustainability

Abstract

CO2 hydrogenation to methanol (CTM) represents a crucial carbon-neutral strategy, yet it is hindered by significant thermodynamic limitations. This study presented a breakthrough strategy to overcome the equilibrium constraints by coupling CTM with dehydration reactions, employing propylene oxide (PO) and olefins as dehydrants, as validated by Aspen simulations and experimental evaluations. A systematic investigation of reaction parameters, including reaction temperature, pressure, and space velocity, revealed that feeding PO at 20 mol % of CO2 reached a record high single-pass methanol yield of 16.5%, surpassing conventional processes, while enhancing CTM kinetics by 60-fold at low reaction pressures. Aspen techno-economic analyses demonstrated multiple merits of the proposed process, including a reduced recycle ratio, small reactor volume, low energy consumption, and low carbon footprint. It achieved a net CO2 utilization of 1.03 ton per ton of methanol, outperforming the conventional CTM processes of −0.22 and 0.58 ton at 30 and 60 atm, respectively, and approaching the stoichiometric value of 1.38 ton. It reversed the financial losses associated with conventional methods and became an outstanding example of a greener transient of hydrogen energy. This dehydration-coupled strategy sheds new light on the process intensification for various CO2 hydrogenation technologies to accelerate global carbon neutrality transitions.