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 CO 2 from gasification syngas consisting of CO 2 , CO, CH 4 , and H 2 . This study investigated the effect of water addition on CO 2 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 CO 2 solubility of ChCl-MEA DES, with the maximum obtained value of 0.5 mol-CO 2 /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 CO 2 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 CO 2 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 CO 2 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 CO 2 solubility. Highest CO 2 /CO selectivity for ChCl-MEA DES 1:5 was found to be around 34.6, CO 2 /CH 4 was 26.7, and CO 2 /H 2 was 4. Water addition was found to have slight reducing effect on the CO 2 selectivity of ChCl-MEA DES.