Oxidation study of n-propylamine with SVUV-photoionization molecular-beam mass spectrometry

Abstract

This work reports the experimental results of n-propylamine (NPA) oxidation in a jet-stirred reactor at 1 atm within 625–875 K, equivalence ratios from 0.5 to 2.0. Oxidation products and intermediates were identified and quantified with synchrotron vacuum ultraviolet photoionization mass spectrometry. Apart from various hydrocarbons, oxygenated and nitrogenous species reported in previous studies of amines, several intermediates were newly detected, including formamide (H2NCHO), nitromethane (CH3NO2), nitrous acid (HNO2), 2-propen-1-ol (C3H5OH) and 2-propenal (C2H3CHO). A detailed kinetic model consisting of 277 species and 2314 reactions was developed with reasonable predictions against the measured data. The rate-of-production and sensitivity analyses results show that NPA oxidation at low temperatures is dominated by the reaction with HO2. Particular attention was paid to the main oxidation product HCN, because its formation is affected by both fuel structure and reaction temperature. The equivalence ratio changes have an opposite effect on HCN concentration in NPA oxidation compared with the pyrrole oxidation and ethylamine flame. In the current study, the peak mole fraction of HCN decreases with increasing equivalence ratio, because the formation of CN triple bond in HCN requires successive H-abstractions, dominantly controlled by the concentrations of OH/HO2 radicals and O2. In addition, a comparison between the experimental results of NPA oxidation and pyrolysis was performed to illustrate the effect of O2 concentration on reaction routes. Current results provide a preliminary insight into the combustion kinetics of more complicated aliphatic amines.