Heats of Reaction and Vapor−Liquid Equilibria of Novel Chemical Absorbents for Absorption/Recovery of Pressurized Carbon Dioxide in Integrated Coal Gasification Combined Cycle−Carbon Capture and Storage Process

There has been increased interest in the development of innovative carbon dioxide (CO2) capture and storage (CCS) applicable to the integrated coal gasification combined cycle (IGCC) equipped with a water−gas shift reaction, to reduce greenhouse gas emissions to almost zero (IGCC-CCS). We studied the heats of reaction (ΔH r) and vapor−liquid equilibria for N-methyldiethanolamine and novel absorbents [1,2-dimethylimidazole, 2-methylimidazole, 1-methylimidazole, imidazole, and 4-(2-hydroxyethyl)morpholine] obtained by the pK a-based screening method in our previous work and found a proportional relationship between pK a and ΔH r values. This allows estimation of ΔH r values by measuring their pK a. Measurements of vapor−liquid equilibria of novel absorbents provided important information on the CO2 capacity per absorption/recovery cycle. 1,2-Dimethylimidazole and 4-(2-hydroxyethyl)morpholine would be nominated as candidates suitable to absorb/recover CO2 with partial pressures at 1.6 MPa or higher without loss of a CO2 pressure level, resulting in saving CO2 compression energy in the CCS process.