Kinetics of carbonyl sulfide reaction with alkanolamines: A review

Carbonyl sulfide represents an undesirable impurity in a variety of industrial gases and it has to be removed down to very low concentrations to meet the required specifications. This can be achieved by chemisorption with alkanolamines. In this article, the kinetics of the reaction of carbonyl sulfide with alkanolamines is reviewed. Different reaction mechanisms used to interpret experimental kinetic data, viz. zwitterion, termolecular and base-catalysed hydration are described in detail. The kinetic behaviour of several conventional, sterically hindered, cyclic amines and diamines proposed in the literature is analysed. Generally, the reaction of carbonyl sulfide with primary, secondary and sterically hindered amines is described by the zwitterion mechanism, whereas the reaction with tertiary amines is described by the base-catalysed hydration of carbonyl sulfide. The same reaction pathways are followed by carbon dioxide which is similar in structure to carbonyl sulfide. While the carbon dioxide reaction with alkanolamines has been comprehensively reviewed, e.g., in our recent paper (P.D. Vaidya, E.Y. Kenig, CO2–alkanolamine reaction kinetics: a review on recent studies, Chem. Eng. Technol. 30 (2007) 1467), an overview on the kinetic behaviour of carbonyl sulfide is still missing. In this paper, an evaluation of the published results is given to close this gap.