Toward rational selection of amine solutions for PCC applications: CO₂ absorption kinetics and absorption heat in tertiary aqueous solutions

The CO₂ absorption kinetics in aqueous 1-(2-hydroxyethyl)-piperidine (1-(2-HE)PP), 1-(2-hydroxyethyl)pyrrolidine (1-(2-HE)PRLD) and 3-diethylamino-1,2-propanediol (DE-1,2-PD) solutions have been studied using the stopped-flow technique over the temperature range of 293 K-313 K. In order to analyze the kinetics results, the base-catalyzed hydration mechanism and artificial neural network (ANN) models were employed to represent the kinetics results of those three solvents, and all gave acceptable ADDs less than 10%. In addition, the reaction rate constants (k₂) and protonation constants (K₁) of amines also were presented. The Brønsted plots between protonation constant (K₁) and kinetics parameter (k₂) have been established to understand the relationship between protonation constant and kinetics. The CO₂ absorption heats (ΔH_a) of those three solvents were also obtained by using the Gibbs Helmholtz equation. Based on a comparison with other amines such as MEA, MDEA and 1DMA2 P with respect to kinetics and absorption heat, the order is as follows: kinetics (MEA > DEA > DEAB > DE-1,2-PD > 1-(2-HE)PRLD > 1-(2-HE)PP > DMMEA > 1DMA2P > MDEA.) and CO₂ absorption heat (MEA > DEA > MDEA > DEAB > DE-1,2-PD >1-(2-HE)PRLD > 1-(2HE)PP > 1DMA2P). The overall evaluation of amines for application CCS in terms of absorption and desorption is discussed, providing helpful information for the screening of novel amines.