Piperazine/N-methylpiperazine/ N,N'-dimethylpiperazine as an Aqueous Solvent for Carbon Dioxide Capture

A blend of piperazine (PZ), N-methylpiperazine (MPZ) and N,N’-dimethylpiperazine (DMPZ) is described as a novel CO 2 capture solvent for aqueous absorption-stripping. This blend provides improved solid solubility and heat of absorption compared to concentrated PZ. No insolubility was observed for regions of high CO 2 loading, unlike PZ solvents. The blend performed like concentrated PZ in terms of CO 2 capacity and CO 2 absorption rate, both of which were more than double that of a traditional 7 molal (30 wt%) MonoEthanolAmine (MEA). Thermal equilibrium was established between the three constituent amines that increases the thermal stability compared to traditional blended solvents. The primary drawback of this novel solvent system is enhanced amine volatility at absorber conditions compared with both concentrated PZ and MEA.