Author(s)

H. Yamada, T. Higashii, F. A. Chowdhury, K. Goto & S. Kazama

Abstract

We investigated the solubility of CO2 in aqueous solutions of alkanolamines at 40C and 120C over CO2 partial pressures ranging from a few kPa to 100 kPa to evaluate the potential for CO2 capture from flue gas. CO2 capacities were compared between monoethanolamine, N-ethyl ethanolamine and N-isopropyl ethanolamine. Speciation analyses were conducted in the alkanolamine solutions at different CO2 loadings by accurate quantitative 13C nuclear magnetic resonance spectroscopy. N-isopropyl ethanolamine showed a large capacity for CO2 because of the formation of bicarbonate. However, we also found that at a lower CO2 loading a significant amount of carbamate was present in the aqueous N-isopropyl ethanolamine solutions. Keywords: carbon capture, amine absorbent, CO2 solubility, vapour-liquid equilibrium, nuclear magnetic resonance. 1 Introduction Carbon capture and storage is of central importance for the reduction of anthropogenic CO2 emissions in the atmosphere. Amine scrubbing is the most promising and currently applicable technology used in an industrial scale for the capture of CO2 from a gas stream [1]. To maximise the capture efficiency and to reduce energy costs we previously developed CO2 capture systems and high performance CO2 absorbents [2–5]. Recently, we demonstrated that hindered amino alcohols for the promotion of CO2 capture can be developed by rational molecular design and by the placement of functional groups [4, 5]. For aqueous solutions of primary and secondary amines the CO2 absorption proceeds by the formation of a carbamate anion or a bicarbonate anion. It is well

Keywords

carbon capture, amine absorbent, CO2 solubility, vapour-liquid equilibrium, nuclear magnetic resonance.