Viable Alternative Prospective Option for Liquid Methanol Industry’s Long-Term and Cost-Effective Development: CO2 to Methanol Conversion and Ethylene Glycol Coproduction

The CO2-to-methanol (CTM) process can realize the recycling of carbon resources and mitigate the global greenhouse effect. However, the low CO2 conversion rate is a consequence of the thermodynamic equilibrium, which restricts the direct hydrogenation of CO2 to methanol (CTMI). Furthermore, there exists a state of kinetic competition between the reaction that produces methanol and the reaction that reverses the water–gas shift, which leads to the low selectivity of methanol. To solve these problems, a new process of indirect hydrogenation of CO2 to methanol and the coproduction of ethylene glycol (CTMII) was proposed in this paper. The steady state modeling, energy integration, and technoeconomic evaluation of the new process were carried out. It was found that the carbon and hydrogen utilization rates of the CTMII process were 98.95% and 98.63%, respectively, corresponding to increases of 2.99% and 34.21%, respectively, compared to those of the CTMI process. The selectivities of methanol and ethylene glycol in the CTMII process are 47.44% and 52.56%, respectively. Under the current economic conditions (0.35 CNY/kWh electricity, 1.8 CNY/m3 natural gas, 5000 CNY/t ethylene glycol, and 17.5 CNY/kg H2), the production cost of the CTMII process was 2572 CNY/t-CH3OH, 38.82% lower than that of the CTMI process. The net present value was calculated, and a sensitivity analysis of the relationship between hydrogen and production costs was performed. When the H2 price dropped to 13.6 CNY/kg, the product cost of CTMII could compete with that of the coal-to-methanol process, showing great economic potential for the future. This study presented a novel approach for the utilization of CO2 resources and broadened the path for green and low-carbon production of methanol.