Computational analysis of Nitrosamine Formation during Amine- Based CO2 Capture process with different Groups of Nitrosating Agents (NO-X)

In an amine-based CO2 capture from a coal-fired power plant, nitrosamines can be generated as a result of the reaction between impurities such as NOx (an example of a nitrosating agent) in the flue gas with amine solutions in the absorption column. There is the potential that the nitrosamines can be emitted to the atmosphere if adequate control measures are not put in place. As is well known, all amines types (i.e. primary, secondary, and tertiary) can react with nitrosating agents. However, the nitrosamine generated from primary amines (RNH2) will decompose to generate N2 while the tertiary amine (R3N) is degraded when it reacts with nitrosating agents. Only secondary amines (R2NH) can generate stable nitrosamine products. That is why attention is focused on secondary amines such as DMA, PZ and MOR in nitrosamine studies. In the last few years, there has been a lot of interest in reactions for nitrosamine formation with most nitrosating agents. Nitrosating agents can be categorized into two major groups: NO2 related agents, and NO derivatives (NO-X). NO2 and N2O4 belong to the first group while NO, N2O3, NOY, HNO2, NO + and NO2 belong to the second group (which can simply be written as NO-X). There are two important steps in the reaction pathway of NO-X nitrosation, N-NO bond generation and H transfer. Current studies show that the first step is N-NO bond generation before H transfer with nitrosating agents. However, it may also be possible for nitrosation to occur with H transfer occurring before N-NO bond generation depending on the prevailing circumstance. Also, it has been observed from actual process operation that even if all of NO2 is removed from flue gas before entering the amine CO2 capture absorber column, trace amount of nitrosamines can still be detected in the absorber offgas. The circumstance for NO-induced formation of nitrosamine has not yet been elucidated in the literature. Furthermore, the role that CO2 plays in the nitrosation process is not yet clear. While there are indications