Influence of formaldehyde on N-nitrosopiperazine formation from nitrite and piperazine in CO2 capture

Piperazine (PZ) based amine blends are promising solvents for post-combustion CO2 capture, but PZ can form potential carcinogenic nitrosamines from nitrite. In this work, the kinetics of the reaction between nitrite and PZ to form N-nitrosopiperazine (MNPZ) was determined in 0.1-0.5 mol L−1 PZ in the presence of 17-170 mmol L−1 formaldehyde at 60-135 °C. The nitrosation of PZ can be catalyzed by formaldehyde, a primary degradation product of PZ. And the reaction involving nitrite and PZ is first order in nitrite, formaldehyde, and hydronium ion. A kinetic model was established, and the activation energy is 33.6 ± 1.8 kJ mol−1 with a rate constant of 2.3 × 103 ± 0.4 × 103 L2 mol−2 s−1 at 100 °C. The kinetics will be helpful to develop strategies to reduce nitrosamine formation and accumulation in PZ based CO2 capture systems.