Abstract
To thoroughly understand low-temperature oxidation of dimethylamine (DMA), the reaction kinetics of triplet ground state O 2 addition to DMA radicals ( CH 3 NH C ˙ H 2 and CH 3 N ˙ CH 3 ) are theoretically investigated. In CH 3 NH C ˙ H 2 + O 2 , the direct H-abstraction reaction is significant due to its extremely low energy barrier, and the dominant channels involving intermediates, CH 3 NHCH 2 O O ˙ = CH 3 NCH 2 + H O ˙ 2 , CH 3 NHCH 2 O O ˙ = C ˙ H 2 NHCH 2 OOH and C ˙ H 2 NHCH 2 OOH = CH 2 NH + CH 2 O + O ˙ H , also have much lower barriers than those in reaction system CH 3 CH 2 C ˙ H 2 + O 2 . In CH 3 N ˙ CH 3 + O 2 , the O 2 addition to N atom has a tight transition state, hindering radical consumption at low temperatures. The second O 2 addition to C ˙ H 2 NHCH 2 OOH is further investigated because of its comparable production at low temperatures and elevated pressures. The temperature- and pressure-dependent rate constants are calculated; CH 3 NCH 2 + H O ˙ 2 and CH 2 NCH 2 OOH + H O ˙ 2 are the dominant products for the first and second O 2 addition reactions, respectively, but the formation of formamides/O-heterocycles + O ˙ H is less important. Our results reveal different reaction pathways of DMA radicals from those of alkyls, and shed light on low-temperature oxidation mechanisms of N-containing fuels.
Published Version
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