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

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, in-cluding 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 de-tected compared with previous studies of methylamine and ethylamine. HCN, NH3, N-2 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 pyroly-sis 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 C-alpha position of NPA, are the major consumption pathways of NPA. In addition, unimolecular reaction breaking C-alpha-C-beta 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 C-alpha (NPA + H = CH3CH2CHNH2 + H-2) plays a leading role for NPA consumption at 760 Torr. The reactions, CH3 + CH3= C2H5 + H and CH3CHCHNH2 + H = CH2CHCHNH2 + H-2 , 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. (C) 2021 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Automated summary

The pyrolysis of n-propylamine (NPA) was studied using tunable synchrotron photoionization and molecular-beam mass spectrometry techniques. A comprehensive kinetic model with 405 species and 2668 reactions was developed. Results indicate that H-abstractions play a major role in NPA consumption, while reactions CH3 + CH3 = C2H5 + H and CH3CHCHNH2 + H = CH2CHCHNH2 + H-2 tend to have inhibiting effects on NPA consumption.