Pyrolysis of Organic Molecules Relevant to Combustion as Monitored by Photoionization Time-of-Flight Mass Spectrometry
Flash pyrolysis coupled to molecular beam extraction and single photon ionization time-of-flight mass spectrometry along with quantum chemical calculations are employed to study the pyrolysis of organic molecules with relevance to combustion processes. Branching ratios for the molecular elimination and bond fission pathways was achieved for ethyl and propyl iodides providing information about the nature of the mechanism with relation to chemical structure. Similarly, the decompositions of a series of alkyl methyl ethers, whose anti-knock ability in commercial fuels is attributed to the molecular elimination pathway, was investigated to examine the competition of primary and subsequent homolyses at higher temperatures, which tend to promote "knock". The isomerization/decomposition of isoprene was looked at in detail with special attention to the formation of soot precursor, most notably the "first ring" benzene. Cyclopentadiene and methylcyclopentadiene are known to be highly sooting fuels and were pyrolyzed to study the initial steps in aromatization. The pyrolysis of cyclohexene, cyclopentene, and 1,4-cyclohexadiene were conducted to facilitate interpretation of aromatic formation and to compare experimental results with well established mechanisms. Finally, the pyrolysis of methylcyclohexane, an important component some jet fuels, was studied.