(84d) Formation of Nitrosamines in the Desorber of Tertiary Amine-Based Carbon Dioxide Capture Systems

Post-combustion CO₂ capture is one of the most developed and commonly employed technologies for power plants to reduce greenhouse gas emissions. Amine-based CO₂ absorption technology can be easily retrofitted into existing power plants and especially suitable for the flue gases containing low concentration of CO₂. Tertiary amines are considered as alternatives to the benchmark solvent monoethanolamine for CO₂ absorption, because they provide the benefits of higher absorption capacity and lower heat of reaction. However, public concerns have been raised for amine-based CO₂ capture due to the formation of nitrosamines, which are toxic to human health and ecological systems.

In this work, the influences of amine structural characteristics and desorber conditions on the formation of nitrosamines were investigated. Generally, tertiary amines were less reactive towards nitrosamines comparing with secondary amines. The formation of total nitrosamine from tertiary amine was first-order dependent on nitrite concentration and CO₂ loading, but was not dependent on amine concentration. For tertiary amines with the same number of 2-hydroxyethyl groups, less hindered amines showed faster nitrosamine formation and higher nitrosamine yields based on nitrite consumption. The distribution of specific nitrosamine formation from tertiary alkanolamines implied the preferential cleavage of 2-hydroxyethyl group over methyl group, but comparable to ethyl group, and therefore shed light on the nitrosation mechanisms.