Oxidative degradation mechanisms for amines in flue gas capture

Abstract

The use of amines for CO2 capture from flue gases involves one distinct difference and challenge from traditional amine acid gas capture: the presence of dioxygen and its role in the oxidative degradation of the amine. Insights on mechanisms of degradation in flue gas CO2 capture can be obtained from observations of other gas treating processes–primarily trace O2 contamination in “traditional” gas treating amine units as well as the autoxidation of amino acids during oxidative dehydrosulfurization using iron chelates. Three distinct pathways for degradation initiation will be discussed: thermal, direct metal ion oxidation and dioxygen reduction intermediate reactions (most likely generated from metal ions). Possible mechanisms will be tied together within a framework of varied amine plant process conditions, pointing out where each mechanism may be an important contributor to the overall amine degradation. The ultimate goal of these considerations is to predict and control amine degradation in CO2 capture systems.