Amine-based CO2 capture has been proposed as a way of mitigating climate change. In this work, the fundamental processes governing the atmospheric gas phase chemistry of amines released from CO2 capture have been studiedusing computational and experimental methods.
The reactions of amines, amides and imines with OH radicals have been studied with computational methods. The reactions are all characterized by strongly bound pre-reaction complexes and submerged barriers to hydrogen abstraction. Rate coefficients calculated from statistical rate theory show negative temperature dependencies and are in good agreement with experimental results where available.
It has been suggested that the climate effect of amine based CO2 capture may be counteracted by the formation of N2O as a minor product in the photo-oxidation of methylamine. Calculations in this work unambiguously show that N2O is not a product in the photo-oxidation of methylamine.
The reaction rate coefficients for the OH radical reactions of N-methylformamide and N,N-dimethylformamide have been measured as a function of temperature and pressure by using the flash photolysis laser-induced fluorescence technique. The reactions are significantly slower than the corresponding amine reactions and show a negative temperature dependence. The study further reveals that the amides have a higher potential for nitramine and nitrosamine formation and that they may therefore constitute a previously undisclosed health risk.
Kinetic isotope effects for the OH radical reaction of HCN have been measured in a smog chamber through the use of FTIR spectroscopy. The measured values and calculated results confirm that the reaction, unlike the other reactions in this work, mainly occur through an addition channel. The present work has contributed significantly to our understanding of the atmospheric reactions of the intermediates in the atmospheric degradation of methyl amines.
List of papers. All papers except paper II. are removed due to publisher copyright.
I. Onel, L.; Thonger, L.; Blitz, M. A.; Seakins, P. W.; Bunkan, A. J. C.; Solimannejad, M.; Nielsen, C. J. Gas-Phase Reactions of OH with Methyl Amines in the Presence or Absence of Molecular Oxygen. An Experimental and Theoretical Study. The Journal of Physical Chemistry A 2013, 117, 10736-10745. DOI:10.1021/jp406522z
II. Nicovich, J. M.; Mazumder, S; Laine, P. L.: Wine, P. H.; Tang, Y.; Bunkan, A. J. C.; Nielsen, C. J. An experimental and theoretical study of the gas phase kinetics of atomic chlorine reactions with CH3NH2, (CH3)2NH, and (CH3)3N. Physical Chemistry Chemical Physics 2014. Submitted. Published version DOI:10.1039/C4CP03801K
III. Bunkan, A. J. C; Hetzler, J; Mikoviny, T; Wisthaler, A; Nielsen, C. J.; Olzmann, M. Experimental and theoretical study of the OH radical reactions with N-methylformamide and N,N -dimethylformamide. Manuscript in preparation
IV. Bunkan, A. J. C.; Tang, Y. and Sellevåg, S. R. and Nielsen, C. J. Atmospheric Gas Phase Chemistry of CH2=NH and HNC. A First-Principles Approach. The Journal of Physical Chemistry A 2014, 118, 5279-5288. DOI:10.1021/jp5049088
V. Maguta, M. M.; Aursnes, M. Bunkan, A. J. C.; Edelen, K.; Mikoviny, T; and Nielsen, C. J.; Stenstrøm, Y; Tang, Y; Wisthaler, A. Atmospheric Fate of Nitramines: An Experimental and Theoretical Study of the OH Reactions with CH3NHNO2 and (CH3)2NNO2. The Journal of Physical Chemistry A 2014, 118, 3450-3462. DOI:10.1021/jp500305w
VI. Bunkan, A. J. C.; Liang, C.-H.; Pilling, M. J.; Nielsen, C. J. Theoretical and experimental study of the OH radical reaction with HCN. Molecular Physics 2013, 111, 1589-1598. DOI:10.1080/00268976.2013.802036