Advanced Design and Comparative Analysis of Methanol Production Routes from CO₂ and Renewable H₂: via Syngas vs. Direct Hydrogenation Processes

In this study, we propose two advanced processes, i.e., advanced syngas-to-methanol (AS2M) and direct CO₂-to-methanol (DC2M) processes, for methanol production using waste CO₂ and renewable H₂ as feedstock. The AS2M process produces methanol from syngas after converting CO₂ to CO via reverse water-gas shift and separating CO from a mixture through pressure swing adsorption. In comparison, the DC2M process directly synthesizes methanol from CO₂ through direct hydrogenation. Different unit processes and recycles were synthesized to determine the optimal process configurations and operating conditions for maximizing the methanol production rate. The technoeconomic and environmental capabilities of the two proposed processes were analyzed with four evaluation criteria (carbon and energy efficiencies, CO₂ reduction, and unit production cost) and compared with conventional CO₂-to-methanol processes. A sensitivity analysis for various utilities and H₂ supply strategies was performed to evaluate the economic feasibility and environmental benefits of the proposed systems with different design options. Our findings showed that both processes could achieve improved technical, economic, and environmental performances compared to conventional processes. In particular, the DC2M process showed the lowest unit production cost at $1.02/kg because of its simple configuration and mild operating conditions.