Atmospheric Oxidation of Piperazine by OH has a Low Potential To Form Carcinogenic Compounds

Piperazine [HN(CH 2 CH 2 ) 2 NH, PZ] is widely recognized as an efficient solvent for carbon capture (CC). We present the first determination of the rate coefficient, k, and the branching ratios for the reaction of OH with PZ in the gas phase using the technique of pulsed laser photolysis with detection of OH by laser-induced fluorescence giving k 298 K of (2.38 ± 0.28) × 10 –10 cm 3 molecule –1 s –1 . The reaction has a negative temperature dependence parametrized as k OH+PZ = (2.37 ± 0.03) × 10 –10 ( T /298) −(1.76±0.08) . The high rate coefficient suggests that gas phase processing in the atmosphere will compete with uptake onto aerosols. The branching ratios, abstraction from C–H versus N–H, have been determined by analysis of OH temporal profiles obtained in the presence of O 2 /NO. The result ( r N–H = 0.09 ± 0.06) shows that the potential for forming the carcinogenic nitrosamines or nitramines from PZ oxidation is smaller than for the oxidation of the benchmark CC solvent monoethanolamine (MEA).