Experimental study on CO₂ solubility in aqueous Piperazine/alkanolamines solutions at stripper conditions

Vapor liquid equilibrium (VLE) experiments using pressurized vessel operated at wide range of temperatures from 40 °C to 120 °C were conducted with four binary solutions of Piperazine (PZ) and alkanolamines, which are 2- Isopropylaminoethanol (IPAE), Monoethanolamine (MEA), Diethanolamine (DEA) and Methyldiethanolamine (MDEA). Effective CO₂ loadings of some PZ based binary solutions, which meant the difference between the CO ₂ loadings at the consistent absorber and stripper conditions, increased in comparison with the PZ only solution and especially, PZ/MDEA showed the largest effective CO₂ loading. CO₂ loadings at the stripper condition did not depend on additive amount of MDEA to PZ and was the same CO₂ loading as PZ only solution, while those increased with increase in MDEA concentration at the absorber condition. According to the reaction products analysis for PZ/MDEA samples operated at different temperature by using ¹³C-NMR spectroscopy, the bicarbonate in the solution decreased significantly with increase in temperature, but the PZ carbamate dissociated CO₂ much less than the carbamate even at 120 °C.