Carbon Capture with 4 m Piperazine/4 m 2-Methylpiperazine

Abstract

An equimolar diamine blend of 4 m 2-methylpiperazine (2MPZ) with 4 m piperazine (PZ) is shown to be an attractive solvent for CO2 capture. This blend overcomes the difficulties posed by the narrow solid solubility window of pure 8 m PZ while preserving its benefits. The solid solubility window at 20°C broadens from ▪ to ▪. As the blend viscosity is nearly double that of pure PZ, normalizing the capacity by viscosity shows a practical capacity comparable to MEA at 0.63mol CO2/kg solvent. The CO2 absorption rate of the blend is lower, with ▪ at 40°C, 84% that of PZ. The heats of CO2 absorption of the blend and PZ are equal at ΔHabs=70kJ/mol. While the blend thermal stability is decreased, Tmax = 155 compared to 163°C, oxidative stability is similar. Lastly, their volatilities are nearly equal with amine Henry's constant near 23Pa at 40°C. In short, the equimolar blend of 4 m 2MPZ with 4 m PZ is a competitive solvent for amine scrubbing.