The effects of pressure on the yields of polycyclic aromatic hydrocarbons produced during the supercritical pyrolysis of toluene

Evolution of in-cylinder polycyclic aromatic hydrocarbons in a diesel engine fueled with n-heptane and n-heptane/toluene

“…This phenomenon may be attributed to two main factors. First, it is known that active reactants such as methane, benzene, and phenyl are formed in relatively high concentrations upon the breakdown of toluene [1,25,26], which is conducive to the growth from small PAHs to larger PAHs and/or soot by different reaction mechanisms such as phenyl addition/cyclization (PAC) and methyl addition/cyclization (MAC) mechanisms [27,28]. Second, the co-oxidation reaction between n-heptane and toluene, as reported by Andrae et al [29], promotes the growth of PAHs to form larger PAHs and soot.…”

Supercritical Fuel Pyrolysis

“…Distinctions between the supercritical phase and gas phase are particularly pronounced for the reactions of PAH formation and growth. Studies in our laboratory with toluene demonstrate that acetylene-addition mechanisms [13][14][15]--widely applicable to high-temperature gas-phase combustion systems-do not hold for the lower temperatures and higher pressures of the supercritical fuel pyrolysis environment, as no acetylene is formed [16,17]. We thus see that reaction pathways and reaction kinetics in the supercritical phase are substantially different from those in the gas or liquid phase.…”

“…The reactor system [16,17,20] is illustrated in Figure 1. Prior to an experiment, liquid fuel is sparged with nitrogen for three hours [I I] to remove any dissolved oxygen that could introduce auto-oxidative effects [21].…”

“…Figure 22 presents the HPLC chromatogram [17] of supercritical toluene pyrolysis products from experiments in the reactor of Figure 1, at conditions of 535 'C, 100 atm, and 140 sec. Since large PAH can be precursors [16] to carbonaceous solids in the supercritical fuel pyrolysis environment, of particular interest is the set of six 8-ring C 28 H1 4 PAH, whose structures are shown in red in Figure 22 as well as in Table 2 Figure 25 shows interference from a UV spectral peak of benzo[a]coronene, and the UV spectrum of the product component in Figure 26 shows interference from the UV spectrum of phenanthro [5,4,3,2-efghi]perylene. Once these interferences from co-eluting compounds are taken into account, however, the UV spectra of Figures 25 and 26 Table 2), has ever before been identified as a product of fuel pyrolysis or combustion, and since reference standards of neither exist, the analyses of the chromatographic and spectral evidence documenting each of these two products' identities are very extensive and appear in two…”

“…Because of the critical role that PAH play in the formation of carbonaceous solid deposits [16] and the need to discern PAH reaction pathways with as much specificity as possible, we have analyzed the products of the model fuel experiments by high-pressure liquid chromatography with diode-array ultraviolet-visible absorbance and mass spectrometric detection (HPLC/UV/MS), a technique ideally suited to the isomer-specific analysis of PAH. We have also employed HPLC/UV/MS in the compositional analysis of stressed Fischer-Tropsch synthetic jet fuel samples provided to us by Dr.…”