Identification of a new C28H14 polycyclic aromatic hydrocarbon as a product of supercritical fuel pyrolysis: Tribenzo[cd,ghi,lm]perylene

Abstract

Tribenzo[cd,ghi,lm]perylene has been identified as a product of the supercritical pyrolysis of both toluene and Fischer-Tropsch synthetic jet fuel. This identification is based on HPLC/UV/MS data, which show that compound I, eluting immediately after five other C28H14 isomers, is also a C28H14 PAH. The UV spectrum of compound I has features of a benzenoid PAH, of which there are only eight C28H14 isomers. Four of these isomers--benzo[a]coronene, phenanthro[5,4,3,2-efghi]perylene, benzo[cd]naphtho[3,2,1,8-pqra]perylene, and benzo[pqr]naphtho[8,1,2-bcd]perylene--have already been identified as supercritical pyrolysis products by matching their UV spectra with those of respective reference standards. A fifth C28H14 PAH--benzo[ghi]naphtho[8,1,2-bcd]perylene, which does not have a reference standard--has also been recently identified through MS and UV data, use of annellation theory to predict UV spectral characteristics, and length-to-breadth ratio/retention time data. Of the remaining three isomers, bisanthene (IUPAC name phenanthro[1,10,9,8-opqra]perylene) has been determined not to be present in our product mixture, as its UV spectrum does not match that of any of our product PAH. Using annellation theory, we predict the UV spectral characteristics of the two remaining C28H14 benzenoid isomers, for which there are no reference standards (tribenzo[cd,ghi,lm]perylene and naphthaceno[3,4,5,6,7-defghij]naphthacene). Results from this analysis show that the predicted UV spectral features of tribenzo[cd,ghi,lm]perylene match those of compound I--and that those of naphthaceno[3,4,5,6,7-defghij]naphthacene are inconsistent with those of compound I. The length-to-breadth ratio of tribenzo[cd,ghi,lm]perylene also agrees with compound I's HPLC elution behavior. This is the first time that tribenzo[cd,ghi,lm]perylene (IUPAC name phenanthro[2,1,10,9,8,7-pqrstuv]pentaphene) has been identified as a product of fuel pyrolysis or combustion.