(769f) Influence of Amine Structural Characteristics On N-Nitrosamine Formation in Post-Combustion Carbon Dioxide Capture Systems

Amine-based CO₂ capture technology is the prime contender for implementing post-combustion CO₂ capture in the near future.  Increasing attention has been paid to develop amines with structural characteristics featuring improved CO₂ absorption performance.  However, the influence of amine structural characteristics on their environmental impacts has not been evaluated.  Specifically, the formation of carcinogenic N-nitrosamines by NO_x reactions with amines within the capture unit and the possible contamination of downwind air and water by the release of these compounds are of great concern.  In this study, 17 amines with systematically varied structural characteristics were selected and tested in a lab-scale CO₂ capture reactor for their N-nitrosamine formation potential.  The order of the amine is a major factor affecting their total N-nitrosamine formation in the absorber unit.  Primary amines formed total N-nitrosamines at 1-2 orders of magnitude lower rates compared to secondary and tertiary amines.  The steric hindrance and alkyl chain length of primary amines had no significant impacts on N-nitrosamine formation in the absorber.  When considering the total N-nitrosamine accumulation rates in the water wash unit, a parameter bearing direct environment relevance, amines with alcohol functional groups gave rise to lower total N-nitrosamine levels in the water wash unit, regardless of the order of the amino group.  The influence of amine structural characteristics should be considered in the search for an “ideal” solvent for CO₂ capture to minimize environmental and health impacts related to N-nitrosamines.