Influence of ionic liquids in the reverse water-gas shift reaction: a thermodynamic study

Carbon dioxide (CO 2 ) conversion processes can be a promising alternative to replace conventional processes toward a more sustainable industry. The addition of ionic liquids (IL) was reported to increase the performance of related reactions; however, their thermodynamic influence in the reactive chemical equilibrium has been poorly investigated. This study evaluated the effect of the ionic liquids (ILs) [BMIm]BF 4 ], [BMIm][PF 6 ], or [BMIm][NTf 2 ] on the CO 2 hydrogenation to carbon monoxide (CO) chemical equilibrium. Predictive and nonpredictive approaches based on the Predictive Soave-Redlich-Kwong equation of state were applied to represent pure ILs densities and vapor pressure. The nonpredictive approach presented the most suitable representation and was applied to represent binary vapor-liquid and liquid-liquid phase equilibria of ILs + CO 2 , hydrogen (H 2 ), CO, or water (H 2 O). The influence of temperature pressure, and IL content on CO 2 hydrogenation to CO reaction were evaluated. Higher ILs’ molar ratio increased the equilibrium conversion. IL-containing systems are significantly influenced by pressure, and high pressures enhance CO 2 conversion. High temperatures increased the reaction’s conversion of systems containing the hydrophobic ILs [BMIm][PF 6 ] or [BMIm][NTf 2 ], while low temperatures increased the CO production of systems containing the hydrophilic IL [BMIm][BF 4 ]. This effect was attributed to the high influence of temperature on the water sorption in the IL. The hydrophilic IL, [BMIm][BF 4 ], promoted the highest increase in CO 2 conversion. At 348 K and 2.0 MPa, the CO 2 conversion was increased from 1.1–54.1%; roughly an increase of ~ 50 times the original conversion without IL addition.