Pyrolysis investigation of n-propylamine with synchrotron photoionization and molecular-beam mass spectrometry

Abstract

With biofuels market expanding, amines, as an important compound class in biofuels, are attracting increasing attention. The pyrolysis of n-propylamine (NPA) was studied in a flow tube using tunable synchrotron photoionization and molecular-beam mass spectrometry techniques. 28 and 30 species, including nitrogenous compounds and hydrocarbons, were identified and quantified at 30 and 760 Torr, respectively. 1,3-Cyclopentadiene, 1,4-pentadiene, 2-methyl-1,3-butadiene and benzene, were newly detected compared with previous studies of methylamine and ethylamine. HCN, NH3, N2 and methanimine were detected as the dominant nitrogenous products. Moreover, minor aliphatic and unsaturated amines were also identified, such as methylamine, ethylamine and acetaldimine. Ethylene achieved at the highest level among hydrocarbon products. With the pressure increasing, the onset temperature of NPA pyrolysis shifts towards low temperature region and NPA decomposes faster. A comprehensive detailed kinetic model involving 405 species and 2668 reactions was developed with reasonable predictions. According to rate-of-production analysis, H-abstractions, especially at Cα position of NPA, are the major consumption pathways of NPA. In addition, unimolecular reaction breaking Cα-Cβ bond is the important consumption channel of NPA at 30 Torr, while its positive effect is seriously weakened at 760 Torr. The H-abstraction at Cα (NPA+HCH3CH2CHNH2+H2) plays a leading role for NPA consumption at 760 Torr. The reactions, CH3+CH3=C2H5+H and CH3CHCHNH2+HCH2CHCHNH2+H2, tend to present inhibiting effects on NPA consumption at 30 and 760 Torr, respectively. These results could provide a theoretical basis for further combustion kinetic studies of biofuels and amine fuels.