Liquid-phase CO2 hydrogenation to methanol synthesis: Solvent screening, process design and techno-economic evaluation

This paper focuses on a liquid-phase CO₂ hydrogenation process for methanol synthesis to enhance CO₂ conversion. The feasibility of a liquid-phase CO₂ hydrogenation process is comprehensively evaluated through a techno-economic analysis. The solvent tetraethylene glycol dimethyl ether is identified as one of the most favorable options following an analysis of the solubility data pertaining to various solvents and their influence on the reaction equilibrium of the substances within the system. The influence of process parameters, including temperature, pressure, solvent amount, and gas hourly space velocity (GHSV), on the conversion of CO₂ and the selectivity for methanol is examined and optimized in a liquid-phase CO₂ hydrogenation to methanol process without a gas recycle (Process 1), optimal reaction conditions are determined and a CO₂ conversion of 95.19 % and a CH₃OH yield of 94.77 % with a purity of 99.9 % are achieved. A liquid-phase process with a gas recycle (Process 2) is implemented to enhance the utilization of feed gas, achieving a CO₂ conversion rate of 95.23 % and a methanol yield of 99.69 %. The liquid-phase process is further optimized by incorporating reactive distillation technology (Process 3), to enhance reaction efficiency and reduce energy consumption. Following the techno-economic evaluation, the energy efficiency of Process 3 is 7.79 % and 4.99 % higher than that of Process 1 and Process 2, respectively. The product cost of Process 3 is reduced by 8.75 % compared to Process 1 and by 4.25 % compared to Process 2. This research offers insights into the challenges associated with the development of the liquid-phase method.