The OH initiated gas-phase chemistry of several amines that are potential candidates for use in post-combustion carbon capture (PCCC) plants have been studied by laser flash photolysis with OH monitored by laser induced fluorescence. The rate coefficients for the reaction of OH with N-methylethanolamine (MMEA) and N,N-dimethylethanolamine (DMEA) have been measured as a function of temperature (∼300–500 K): , . The results for DMEA lie between previous values. This is the first kinetic study of the OH + MMEA reaction. At low pressures in the presence of oxygen, OH is recycled in the DMEA reaction as has been observed for other tertiary amines. Branching ratios for OH abstraction with MEA, DMEA and MMEA are dominated by abstraction from the αCH2 group. Abstraction from N–H is determined to be 0.38 ± 0.06 for MEA and 0.52 ± 0.06 for MMEA at 298 K. The impact of these studies has been assessed by using a modified chemical box model to calculate downwind concentrations of nitramines and nitrosamine formed in the photo-oxidation of MEA. Under clear sky conditions, the simulations suggest that current safe guidelines for nitramines may be significantly exceeded with predicted MEA emission rates.

Piperazine [HN(CH2CH2)2NH, 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 k298 K of (2.38 ± 0.28) × 10–10 cm3 molecule–1 s–1. The reaction has a negative temperature dependence parametrized as kOH+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 O2/NO. The result (rN–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).

The OH initiated gas-phase chemistry of several amines that are potential candidates for use in post-combustion carbon capture (PCCC) plants have been studied by laser flash photolysis with OH monitored by laser induced fluorescence. The rate coefficients for the reaction of OH with N-methylethanolamine (MMEA) and N,N-dimethylethanolamine (DMEA) have been measured as a function of temperature (∼300–500 K): , . The results for DMEA lie between previous values. This is the first kinetic study of the OH + MMEA reaction. At low pressures in the presence of oxygen, OH is recycled in the DMEA reaction as has been observed for other tertiary amines. Branching ratios for OH abstraction with MEA, DMEA and MMEA are dominated by abstraction from the αCH2 group. Abstraction from N–H is determined to be 0.38 ± 0.06 for MEA and 0.52 ± 0.06 for MMEA at 298 K. The impact of these studies has been assessed by using a modified chemical box model to calculate downwind concentrations of nitramines and nitrosamine formed in the photo-oxidation of MEA. Under clear sky conditions, the simulations suggest that current safe guidelines for nitramines may be significantly exceeded with predicted MEA emission rates.