Nitrosamine Formation in the Desorber of Tertiary Alkanolamine-Based Carbon Dioxide Capture Systems

Tertiary amines are being considered as absorption solvents for post-ombustion CO₂ capture, but their potential to form harmful byproducts nitrosamines is yet to be evaluated. This study investigated the factors influencing the formation of nitrosamines from tertiary alkanolamines under simulated desorber conditions and the effects of amine structural characteristics. Total nitrosamine formation from tertiary alkanolamine was determined to be first-order with respect to nitrite concentration and the absorbed CO₂, but was zero-order with respect to amine concentration in the range of 0.5-2.5 M. Tertiary alkanolamines formed less nitrosamine than their secondary amine analogues. For tertiary alkanolamines with the same number of 2-hydroxyethyl groups, smaller steric hindrance resulted in more nitrosamine formation and higher yields based on nitrite consumption. The analysis of specific nitrosamines revealed that the cleavage of 2-hydroxyethyl group was preferred over demethylation, but comparable to de-ethylation. Reaction pathways were proposed to account for the experimental observations.