Experimental study on the effect of water addition to ChCl-MEA DES towards its performance in CO2 removal from syngas

ChCl-MEA DES was used to absorb CO2 from gasification syngas consisting of CO2, CO, CH4, and H2. This study investigated the effect of water addition on CO2 absorption capabilities of ChCl-MEA DES with different mole ratios of ChCl to MEA, and different absorption temperatures. It was found that water addition had a positive effect on CO2 solubility of ChCl-MEA DES, with the maximum obtained value of 0.5 mol-CO2/mol-DES for aqueous ChCl-MEA DES with 75%vol water at absorption temperature of 40 °C and pressure of 9 bar. In general, water addition increases CO2 solubility and absorption rate of ChCl-MEA DES. ChCl-MEA DES 1:5 mol ratio was able to benefit from water addition up to 75%vol water content. While ChCl-MEA 1:10 had its CO2 solubility increase with water addition up to 50%vol, after which, it declined. Investigation into water addition at different absorption temperatures revealed that water addition at 40 °C produced the most significant CO2 solubility enhancement compared to water addition at 20 °C and 60 °C. This might be caused by the tradeoff between the effects of high temperature in decreasing ChCl-MEA DES viscosity and lowering its CO2 solubility. Highest CO2/CO selectivity for ChCl-MEA DES 1:5 was found to be around 34.6, CO2/CH4 was 26.7, and CO2/H2 was 4. Water addition was found to have slight reducing effect on the CO2 selectivity of ChCl-MEA DES.