Solvent-catalyst optimization of ionic liquid-based CO2 conversion to propylene carbonate: Laboratory validation and techno-economic analysis

Abstract

Ionic liquids (ILs) have been widely suggested as efficient catalysts to produce propylene carbonate (PC) from CO2 and propylene oxide (PO). Recently, the use of liquid-liquid extraction (LLE) has been proposed to efficiently separate ILs from PC since it reduces energy consumption, with fatty alcohols when selecting hydrophobic ILs. However, the study of this reaction-separation system at experimental level is scarce. In addition, the solvent-catalyst system design to improve the global process performance is a current challenge. This work develops an integrated experimental-computational multiscale approach to improve the PC production process by CO2 cycloaddition to PO using the IL [P66614][Br] as catalyst. Reaction yield and liquid-liquid equilibrium measurements were carried out for the experimental validation of the proposed catalytic/separation systems using different solvents (fatty alcohol and water). Process modelling and techno-economic analysis were performed using Aspen Plus for solvent-catalyst optimization, proceeding with an integrated iterative experimental-computational approach to decrease energy requirements and operating costs. It was found that the presence of solvents in the reaction affects conversion and selectivity of the reaction, with fatty alcohols increasing PC yield and enabling IL/PC separation, while water reduces PC selectivity. On the other hand, the presence of water in the process allows reducing electricity demands as well as vacuum requirements. It was possible to modulate fatty alcohol and water dosages to minimize energy consumption, vacuum requirements and utility costs. Optimal configurations have an energy consumption of approximately 0.6 kWh/kgPC and utility costs of 6.6 $/tPC.