Carbon Dioxide Capture by Diethylenetriamine Hydrobromide in Nonaqueous Systems and Phase-Change Formation

Diethylenetriamine hydrobromide ([DETAH]Br) was used for capturing CO2 in polyethylene glycol 200 (PEG200) solution, in which phase change was observed. PEG200 could not only act as a cosolvent but also be involved in CO2 absorption, contributing to biphasic separation and increased CO2 capacity. The potential applications of the mixtures would take advantage of high CO2 capacity (1.184 mol/mol [DETAH]Br), and also less energy consumed when considering the mild regeneration condition and low specific heat of PEG200. This system could be recycled at least for five continuous absorption-desorption cycles without significant loss of CO2 capturing and releasing capability. Spectroscopic analysis revealed a O-H...:N type of H-bonding, and the stabilizing effects of bromide ion would play important roles in stabilizing the system and preventing the biphasic separation by overcoming the electrostatic attractions in the early stage of CO2 absorption. It is estimated that such a simple and inexpensive solution provides an excellent alternative to current CO2 capture technologies.