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

Abstract

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 293K–313K. 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 (△Ha) 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 1DMA2P 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.