Exploration of environmentally friendly processes for converting CO2 into propanol through direct hydrogenation

Abstract

This study firstly explores six process configurations for the conversion of CO2 to propanol via direct hydrogenation. The variations in the proposed configurations lie in the technologies used for off-gas treatment (such as pressure swing adsorption, oxyfuel combustion, autothermal reforming, and chemical absorption) and the intensification of separation (including the incorporation of the hydration reaction of ethylene oxide) within the process. Energy efficiency analysis, techno-economic analysis (in minimum required selling price, MRSP), and life cycle assessment (on global warming potential, GWP) were conducted to evaluate all proposed schemes. Overall, this study suggests that enhancing the selectivity towards propanol and implementing a suitable off-gas treatment strategy are crucial for this process. Based on the findings, we recommend Scheme 4, which involves auto-thermal reforming for off-gas treatment, as the optimal configuration. It leads to an energy efficiency of 45.33 %. Despite the higher MRSP (3.12 USD/kg when using grey H2, 7.45 USD/kg when using green H2, commercial process: 1.4 to 1.6 USD/kg), it significantly reduces GWP (3.19 kg-CO2-eq/kg when using grey H2, 1.59 kg-CO2-eq/kg when using green H2) created from the conventional process (6.77 kg-CO2-eq/kg). Given appropriate economic incentives, the proposed process could serve as a more environmentally friendly option for propanol production.