Equilibrium model for CO₂ absorption in an aqueous solution of 2‐amino‐2‐methyl‐1‐propanol

Abstract

A semi-empirical gas-liquid equilibrium model for the absorption of CO, in aqueous 3M AMP (2-amino-2-methyl-I-propanol) is presented. It applies to high CO, loadings (y > 0.5) in the temperature range between 20 and 50 "C, and is based on experimental solubility and pH determinations. For a given amine concentration, it yields the equilibrium partial pressure of CO, as a function of only two variables: the CO, loading and temperature. The model correlates the expressions for the chemical equilibria involved as follows: pco, = m y x lo", where pco, is the equilibrium partial pressure, x = logK -pH, m is the amine molarity, y the CO, loading, and K is a parameter involving Henry's law constant, H, and the first dissociation constant, K,, of carbonic acid. pH is found to depend on both temperature and CO, loading while logK depends only on the CO, loading. Correlations for pH and logK are presented. The model fits own data for 3M AMP very well as well as the equilibrium data found in recent literature.