ABSORPTION OF CARBON DIOXIDE INTO STERICALLY HINDERED AMINES: KINETICS ANALYSIS AND THE INFLUENCE OF PROMOTERS

The sterically hindered amines 2-amino-2-methyl-1-propanol (AMP) and 2-piperidineethanol (PE) are promising candidate absorbents for CO2 capture. Although reaction kinetics of the CO2-AMP system is extensively studied, there exists some deviations in the reported kinetic parameters and there is some uncertainty about the reaction mechanism. Contrarily, kinetic data on the CO2-PE reaction system is scarce. In this work, these reaction systems were revisited to set right the discrepancy of previous works and facilitate and deepen fundamental understanding of these reaction systems. Kinetic data were obtained experimentally at 298, 303, and 308K by using a stirred-cell reactor. The molarities of AMP and PE in the aqueous solutions were varied from 1 to 3M and 0.05 to 0.25M. Second order rate constants for the reactions with AMP and PE were equal to 809 and 899m(3)/(kmols) at 303K. The increase in temperature and amine concentration caused the expected increase in the values of the observed pseudo-first order reaction rate constants. Finally, it was found that the investigated reactions were accelerated by the addition of two sterically hindered secondary amines comprising an alkyl group, viz., N-methyl- and N-ethyl-monoethanolamine, even at low additive concentrations (0.05-0.1M).