Regulating crystal structures of EDA-carbamates in solid–liquid phase-changing CO2 capture solutions

To study the relationship between crystal structures of amine-carbamates and regeneration energy consumptions, two new solid–liquid phase-changing solutions of ethylenediamine/N,N-dimethylacetamide (EDA/DMA) and ethylenediamine/N,N-dimethylformamide (EDA/DMF) were prepared to capture CO 2 efficiently and regulate the crystal structures of CO 2 absorption products (EDA-carbamates). The CO 2 absorption capacity and peak absorption rate of EDA/DMA and EDA/DMF solutions were both 30% and 67%, respectively, higher than those of EDA/water solution. EDA-carbamates in EDA/DMA and EDA/DMF solutions had the same molecular structures but different molecular arrangements (they belonged to orthorhombic and monoclinic crystals, respectively). The regeneration heat of EDA-carbamates in EDA/DMF solution (181.28 kJ/mol) was higher than orthorhombic EDA-carbamates in EDA/DMA solution (133.76 kJ/mol), which was attributed to the endothermic process (recrystallization process) during the transition from monoclinic EDA-carbamates to orthorhombic EDA-carbamates.