Supercritical Fuel Pyrolysis

Abstract

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the tane for reviewing instnictons. searching existing data sources, gathering and maintaining the data needed, and comnpleting and reviewing this coltlction of information. SPONSORING I MONITORING AGENCY NAME(S) AND ADDRESS(ES) SPONSOR/MONITOR'S ACRONYM(S)AFOSR SUPPLEMENTARY NOTES ABSTRACTSupercritical pyrolysis experiments were conducted with three model fuels at temperatures up to 585 °C and pressures up to 110 atm. The products were analyzed by gas chromatography and high-pressure liquid chromatography with diode-array ultraviolet-visible absorbance and mass spectrometric detection, a technique ideally suited for the isomer-specific analysis of polycyclic aromatic hydrocarbons (PAH), which can serve as precursors to carbonaceous solids. Thirty-nine individual 2-to 9-ring PAH were identified in the supercritical 1-methylnaphthalene pyrolysis products-seventeen of which, for the first time.Reaction pathways involving l-naphthylmethyl, methyl, and naphthyl radicals were developed to account for the formation of the observed PAH products and explain why unobserved PAH were not formed in the supercritical I -methylnaphthalene pyrolysis environment. Likewise, reaction pathways involving benzyl, methyl, and phenyl radicals were developed that accounted for the formation of the forty-four individual PAH identified as supercritical toluene pyrolysis products and explained why unobserved PAH were not formed. The PAH product distribution from methylcyclohexane was extremely similar to that of toluene, indicating that the PAH formation mechanisms devised for toluene applied to supercritical methylcyclohexane as well.

Reaction Mechanisms Governing the Formation of Polycyclic Aromatic Hydrocarbons in the Supercritical Pyrolysis of Toluene: C28H14Isomers

“…For this effort, use of a model fuel (such as a single component of jet fuel) allows reaction mechanisms to be more easily determined; these reaction pathways can then be extended for multicomponent systems. Supercritical pyrolysis experiments with methylcyclohexane, toluene, , and 1-methylnaphthalene have led to the identification of more than 35 2- to 10-ring PAH products for each individual fuel. Many of the PAH identified as products of these model fuels have also been found in the supercritical pyrolysis products of jet fuel .…”

“…Figure shows an HPLC/UV chromatogram of the products of supercritical toluene pyrolysis 7 at 535 °C, 100 atm, and a residence time of 140 s−conditions representative of those predicted for fuel lines of hypersonic aircraft. Depicted in Figure are the structures of over 40 2- to 10-ring PAH that have been identified , in this product mixture by high-pressure liquid chromatography (HPLC) coupled with ultraviolet−visible (UV) diode-array detection and mass spectrometry (MS). There are three features of the HPLC/UV chromatogram shown in Figure that characterize the supercritical pyrolysis of toluene: (1) 3 times as many benzenoid PAH (PAH composed of only six-carbon rings) have been identified in this product mixture relative to PAH containing a five-membered ring; (2) all benzenoid PAH products are fully aromatic; and (3) none of the PAH identified have a cove or fjord region (concave faces of five or six carbons, respectively).…”