Uv Spectral Identification of Polycyclic Aromatic Hydrocarbon Products of Supercritical 1-Methylnaphthalene Pyrolysis

Somers, Michelle L; Wornat, Mary J.

doi:10.1080/10406630701462940

Cited by 21 publications

(10 citation statements)

References 24 publications

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“…The formation of high molecular weight PAH has been linked to the production of carbonaceous deposits, especially condensation coke, under supercritical fuel pyrolysis conditions. Several studies using both single component and fully formulated fuels have conclusively detected large PAH products in stressed product samples. ,,− , Accordingly, HPLC/UV analyses were performed on the stressed fuel samples of this study for the identification and quantification of PAH, with specific focus on the formation of PAH not present in the parent fuels. Because the parent fuels contain large amounts of alkanes, stressing of the fuels produces large numbers of alkylated PAH, not all of which can be resolved by reversed-phase HPLC alone.…”

Section: Resultsmentioning

confidence: 99%

“…High-pressure liquid chromatography (HPLC) with diode-array ultraviolet–visible (UV) absorption detection was used to identify and quantify PAH products in the stressed fuels. As detailed elsewhere in the analyses of other fuel product mixtures, , products were separated on a reversed-phase HPLC C 18 column with a time-programmed sequence of the mobile-phase solvents water, acetonitrile, and dichloromethane. UV spectroscopy was employed to determine the isomer-specific identities of each of the separated product components.…”

Section: Methodsmentioning

confidence: 99%

“…The formation of aromatics and PAH have been hypothesized to potentially have a dual role, as actual amorphous coke precursors and as an indicator for short living, highly reactive intermediates which participate in coke formation (via free radical growth) . Detailed product analyses have confirmed extensive PAH formation during supercritical fuel pyrolysis, ,− but the PAH distribution is substantially different from that observed at the higher temperatures and lower pressures associated with combustion. − Thus, deposit formation in supercritical fuel pyrolysis superficially resembles soot formation during combustion in that PAH are believed to be primary intermediates or indicators in the formation of high molecular weight carbonaceous products, but the controlling reactions and growth mechanisms appear to be different in the two reaction environments.…”

Section: Introductionmentioning

confidence: 99%

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Effect of Aviation Fuel Type on Pyrolytic Reactivity and Deposition Propensity under Supercritical Conditions

DeWitt

Edwards

Shafer

et al. 2011

Ind. Eng. Chem. Res.

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Development of reusable liquid-hydrocarbon-fueled hypersonic vehicles requires improved understanding of the effect of chemical composition on the controlling reaction chemistry and deposition propensity as the fuel is used to cool the system. In this effort, supercritical pyrolytic stressing studies were performed using two petroleum-derived fuels and a Synthetic Paraffinic Kerosene (SPK) comprised predominantly of normal and branched paraffins. All fuels decomposed via free radical pathways with high yields of unsaturates and lower molecular weight products consistent with pyrolysis at high pressures and moderate temperatures. However, the SPK was significantly more reactive than the petroleum-derived fuels due to a lack of efficient hydrogen donors that act to terminate chain reactions (higher net propagation rate). High-pressure liquid chromatography was used to identify and quantify polycyclic aromatic hydrocarbons (PAH) in the stressed fuels, conclusively determining that these are produced during thermal stressing. A notable observation was the presence of PAH during SPK stressing, as the neat fuel did not contain cyclic precursors for growth to PAH. During stressing with stainless-steel tubing, the formation of filamentous deposits via metal-catalyzed reactions of stressed fuel components with reactor surfaces was observed for all fuels studied. However, the SPK fuel exhibited a much higher pyrolytic deposition rate, which was attributed to higher lateral growth rates of surface filaments via noncatalytic free radical addition pathways. The PAH formed during SPK stressing are indicators of the highly reactive intermediates prone to participating in the surface coke addition pathways. Studies blending benzene with the SPK indicated that low PAH solubility in the paraffinic fuel is not the dominant cause for the high deposition propensity. Testing with the petroleum-derived fuels showed that metal sulfide filament formation can occur under endothermic conditions, and higher fuel sulfur content can increase carbon deposition propensity. Studies with surface passivated tubing (Silcosteel) suppressed filamentous carbon formation and rendered a substantial reduction in SPK deposition to levels similar to the petroleum-derived fuels. Overall, these studies provided guidance regarding the controlling chemistry during supercritical pyrolysis of current and potential synthetic hydrocarbon fuels and insight into prevalent deposition pathways.

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Effect of Aviation Fuel Type on Pyrolytic Reactivity and Deposition Propensity under Supercritical Conditions

DeWitt

Edwards

Shafer

et al. 2011

Ind. Eng. Chem. Res.

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“…Using the reactor of Figure 1, we have conducted supercritical pyrolysis experiments with three model fuels: I -methylnaphthalene, a two-ring aromatic component of jet fuel [ 18]; toluene, a single-ring component of jet fuel [18) and the major dehydrogenation product of the Figure 3 have never before been identified as products of 1-methylnaphthalene pyrolysis or combustion, so before discussing the mechanisms responsible for the formation of the products in Figure 3, we first present the HPLC, UV, and MS evidence [29] that establishes these products' identifications.…”

Section: Resultsmentioning

confidence: 99%

“…These sixteen newly identified products [29] component CI, whose mass spectrum reveals it also to be of molecular mass 280. As Figure 10 illustrates, the UV spectra of components CI and C2 are remarkably similar, separated by only -2 nm.…”

Section: Identification Of Products Of Supercritical 1-methylnaphihalmentioning

confidence: 99%

Supercritical Fuel Pyrolysis

Womat

Somers²,

McClaine³

et al. 2007

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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.

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Polycyclic Aromatic Hydrocarbons and Combustion

Fetzer

2010

Handbook of Combustion

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The polycyclic aromatic hydrocarbons (PAHs) are ubiquitous in any incomplete combustion; that is, one that does not generate only water and carbon dioxide. A huge variety of PAHs can be produced in combustion; the unsubstituted forms differ in ring number, ring isomerization, degree of condensation, and whether there are only six‐member carbon rings or some with five carbons. Substitution can be as simple as alkylation limited only to methylation. Various conditions can produce hydroxyl, carboxyl, and nitro substitutions. This chapter will mainly focus on the unsubstituted PAHs, as they are the prevalent type found in combustion products. This variety depends on combustion conditions such as the fuel and its concentration, residence time, and combustion temperature. Numerous reactions are involved that involve a multitude of production pathways, and to understand this complexity modern analytical tools must be used. Such tools include gas chromatography‐mass spectrometry and liquid chromatography with UV spectral detection, and are used to differentiate and identify specific PAHs. How these techniques work, and what types of information they provide, will be highlighted.

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Uv Spectral Identification of Polycyclic Aromatic Hydrocarbon Products of Supercritical 1-Methylnaphthalene Pyrolysis

Cited by 21 publications

References 24 publications

Effect of Aviation Fuel Type on Pyrolytic Reactivity and Deposition Propensity under Supercritical Conditions

Effect of Aviation Fuel Type on Pyrolytic Reactivity and Deposition Propensity under Supercritical Conditions

Supercritical Fuel Pyrolysis

Polycyclic Aromatic Hydrocarbons and Combustion

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