CO2 capture using aqueous solutions of K2CO3+2-methylpiperazine and monoethanolamine: Specific heat capacity and heat of absorption

The specific heat capacity, heat of CCO2 absorption, and CCO2 absorption capacity of aqueous solutions of potassium carbonate (K2CO3)+2-methylpiperazine (2-MPZ) and monoethanolamine (MEA) were measured over various temperatures. An aqueous solution of K2CO3+2-MPZ is a promising absorbent for CCO2 capture because it has high CCO2 absorption capacity with improved absorption rate and degradation stability. Aqueous solution of MEA was used as a reference absorbent for comprison of the thermodynamic characteristics. Specific heat capacity was measured using a differential scanning calorimeter (DSC), and heat of CCO2 absorption and CCO2 absorption capacity were measured using a differential reaction calorimeter (DRC). The CCO2-loaded solutions had lower specific heat capacities than those of fresh solutions. Aqueous solutions of K2CO3+2-MPZ had lower specific heat capacity than those of MEA over the temperature ranges of 303-353 K. Under the typical operating conditions for the process (CCO2 loading=0.23mol-CCO2·mol−1-solute in fresh solution, T=313 K), the heat of absorption (−ΔHabs) of aqueous solutions of K2CO3+2-MPZ and MEA were approximately 49 and 75 kJ·mol-CO2, respectively. The thermodynamic data from this study can be used to design a process for CCO2 capture.