Nathan Marsh | National Institute of Standards and Technology (original) (raw)
Papers by Nathan Marsh
Combustion Science and Technology, 2007
In this work, we investigate the utility of the smoke lamp for evaluating the soot-reducing poten... more In this work, we investigate the utility of the smoke lamp for evaluating the soot-reducing potential of additives, by comparing it to a more complex liquid-fed laminar diffusion flame. The additives, ferrocene (bis(cyclopentadienyl) iron-Fe(C 5 H 5 ) 2 ), ruthenocene (bis(cyclopentadienyl)ruthenium-Ru(C 5 H 5 ) 2 ), iron naphthenate (a 12% iron salt of naphthenic acid, which is a mixture of fatty carboxylic acids, some of which may include a cyclopentane ring), and MMT (Methylcyclopentadienyl manganese tricarbonyl-CH 3 C 5 H 4 Mn(CO) 3 ) are evaluated at various concentrations in the jet fuel JP-8. Although the smoke lamp is a simple, inexpensive, and widely-available test for evaluating the sooting potential of liquid fuels, it does not provide an effective measure of soot suppression by metal-containing additives. The drop-tube reactor more accurately captures the physical conditions and processes-droplet vaporization, ignition, and rich vs. lean operation-typically found in more complex systems. We find in the smoke lamp that ferrocene, and to a lesser degree ruthenocene, are effective soot suppressors when used in JP-8, and that their effectiveness increases with increasing concentration. In the smoke lamp, MMT and iron naphthenate have minimal effect. On the other hand, in the drop-tube reactor, all four additives are quite effective, especially at fuel lean conditions, where soot suppression reaches 90-95%. Under fuel-rich conditions, where in some cases the additives elevate the yield of soot aerosol slightly, we find a significant increase in the production of the soluble organic fraction of the aerosol, i.e., tar. In order to understand why the smoke lamp sometimes fails to indicate a soot suppressing potential (i.e., from MMT and iron naphthenate), soot samples were collected from a wick lamp burning ferrocene and iron naphthenate additives in JP-8. These samples, as well as several from the drop-tube reactor, were analyzed by X-Ray Fluorescence (XRF) in order to determine their metal content, and we find that the soot aerosol produced by the wick lamp using ferrocene-containing fuel had roughly 30 times the iron content of the soot aerosol produced by the wick lamp using iron-naphthenatecontaining fuel. This difference in metal content is not found in samples produced in the drop-tube reactor. We conclude that the poor performance of iron naphthenate in the smoke lamp is likely the result poor vaporization of the additive from the wick, a consequence of its high molecular weight (average 465).
Symposium (International) on Combustion, 1998
ABSTRACT By burning droplets of benzene in a single-droplet combustor and performing phase-discri... more ABSTRACT By burning droplets of benzene in a single-droplet combustor and performing phase-discriminating sampling of the liquid and gas phases of the droplet system, we have found that gas-phase pyrolysis products arise in the liquid phase of the droplet. The experiments are conducted at 1000 K and 21 mol % O2 in the postcombustion gas from an oxygen-rich premixed methane flame. Disruptive burning, which has not previously been reported for a pure hydrocarbon in normal gravity conditions, is observed at the end of the droplet residence time (∼92 ms). Samples of the liquid phase have been taken at various times throughout the combustion lifetime and analyzed by high-pressure liquid chromatography. Compositional analysis using ultraviolet-visible absorbance spectra of the separated components of the samples reveals a wide variety of pure polycyclic aromatic hydrocarbons (PAH), substituted PAH, and cyclopenta-fused PAH. In addition, recent synthesis of new reference standards has enabled identification of cyclopenta-fused PAH—cyclopent[hi]acephenanthrylene, cyclopenta[cd]fluoranthene, and dicyclopenta[cd, jk]pyrene—which have never before been identified as benzene products. Because the droplet remains relatively cold (∼350 K) with respect to the gas phase in the oxygen-deficient zone between the droplet and the flame (∼2000 K), we conclude that these compounds are gas-phase pyrolysis products that are obsorbed into the droplet, rather than products of reactions within the droplet. These heavier species may play a role in observed terminal disruptive burning events by acting as additional droplet components that promote multicomponent effects. Analysis of species concentrations over time reveals the dominance of both ring rupture pyrolysis products such as phenylacetylene, triacetylene, and acenaphthylene, and biaryl pyrolysis products such as biphenyl. These four products in particular represent 70% of the identified mass of absorbed pyrolysis products, which accounts for up to 5% of the droplet mass at the end of its lifetime.
2010 14th International Heat Transfer Conference, Volume 3, 2010
ABSTRACT CHRISTIFIRE (Cable Heat Release, Ignition, and Spread in Tray Installations during FIRE)... more ABSTRACT CHRISTIFIRE (Cable Heat Release, Ignition, and Spread in Tray Installations during FIRE) is a U.S. Nuclear Regulatory Commission Office of Research program to quantify the mass and energy released from burning electrical cables. This type of quantitative information will be used to develop more realistic models of cable fires for use in fire probabilistic risk assessment (PRA) analyses. The experimental program has two main thrusts—bench-scale measurements of small samples of burning cables and full-scale measurements of the heat release and fire-spread rates of cables burning within typical ladder-type trays. The bench-scale measurements include micro-calorimetry of cable components, effluent characterization using absorption spectroscopy, and measurements of the heat release rate using a cone calorimeter. The full-scale measurements include the burning of a variety of cables within a typical tray under radiant panel heating, and full-scale, multiple tray fires. The outcome of the experiments is to be used by a variety of fire models, ranging from simple correlations to computational fluid dynamics.
41st AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2005
Polycyclic Aromatic Compounds, 2000
... NATHAN D. MARSH", MARY J. WORNAT", *, LAWRENCE T. SCOTTb, ATENA NECULAb, ARTHUR L. ... more ... NATHAN D. MARSH", MARY J. WORNAT", *, LAWRENCE T. SCOTTb, ATENA NECULAb, ARTHUR L. LAFLEUR" and ELAINE F. PLUMMER" a Department of Mechanical and Aerospace Engineering, Princeton Merkert Chemistry Center, Boston College, Chestnut Hill, ...
Polycyclic Aromatic Compounds, 2005
Abstract In order to investigate further the polycyclic aromatic hydrocarbons (PAH) produced by b... more Abstract In order to investigate further the polycyclic aromatic hydrocarbons (PAH) produced by benzene droplet combustion, we have obtained and analyzed a highly-concentrated benzene droplet combustion sample, using high pressure liquid chromatography (HPLC) ...
Journal of Analytical and Applied Pyrolysis, 2011
In order to better elucidate the role of thermal decomposition products in the formation of polyc... more In order to better elucidate the role of thermal decomposition products in the formation of polycyclic aromatic hydrocarbons (PAH) from complex fuels, we have performed pyrolysis experiments in a tubularflow reactor, using the model fuel catechol (ortho-dihydroxybenzene), a phenol-type compound representative of structural entities in biomass, coal, and wood. Catechol pyrolysis at temperatures of 700-1000 ЊC and a residence time of 0.4 s produces a range of C 1 -C 6 products, which have been analysed by nondispersive infrared analysis and by gas chromatography with flame-ionization detection. Quantification of product yields versus temperature reveals that the major products are CO, acetylene, 1,3-butadiene, phenol, cyclopentadiene, benzene, and ethylene; minor products are methane, ethane, propyne, propadiene, and propylene. CO is the highest yield catechol pyrolysis product at all temperatures. Among the hydrocarbons, 1,3-butadiene is the highest yield product at temperatures up to 800 ЊC; above 800 ЊC, acetylene is. The structural features of catechol and the experimental product yield data-considered with the established reactions for phenol decomposition-suggest that the major products of catechol decomposition come from the following routes: (1) phenol and benzene from H displacement of OH on catechol and phenol, respectively, (2) cyclopentadiene from unimolecular decomposition of the phenoxy radical, and (3) 1,3-butadiene, acetylene, and CO from decomposition of the hydroxy-substituted phenoxy radical (but with different oxygenated C 5 intermediates). The remaining C 1 -C 3 products appear to arise chiefly from the decomposition of key radicals such as cyclopentadienyl, propargyl, and 1,3-butadienyl. The results presented in this work, in concert with those from a complementary study of the C 7 -C 28 catechol products, provide the basis for the development of a detailed kinetic model for both pyrolytic catechol decomposition and PAH formation and growth.
Energy & Fuels, 2005
JP-8, a surrogate fuel, and several model compounds were used to produce soot aerosols in a drop-... more JP-8, a surrogate fuel, and several model compounds were used to produce soot aerosols in a drop-tube furnace with optical access. The soluble organic fractions (SOF) of soot aerosols were studied with GC, GC-MS, and 13 C NMR. The residue of each aerosol sample was studied with Raman spectroscopy, ESR, and a recently developed technique used to determine the conductivity and extent of turbostratic structure formation in soot. The SOF values from different fuel sources exhibit variations in yield, and carbon aromaticity values, and the latter parameter correlates with the extent of turbostratic structure formation in the aerosol residues. Raman data of the soot residues indicate the presence of highly disordered graphitic structures, but the graphite factor measurements reveal differences among these disordered structures that are not apparent in the Raman data.
![Research paper thumbnail of Yields of Polycyclic Aromatic Hydrocarbons from the Pyrolysis of Catechol [ o rtho -Dihydroxybenzene]: Temperature and Residence Time Effects](https://attachments.academia-assets.com/44099841/thumbnails/1.jpg)
](Energy & Fuels, 2004
To understand in more detail the formation of polycyclic aromatic hydrocarbons (PAH) from complex... more To understand in more detail the formation of polycyclic aromatic hydrocarbons (PAH) from complex fuels, we have performed pyrolysis experiments in a laminar-flow reactor, using the model fuel catechol (ortho-dihydroxybenzene), a phenol-type compound representative of structural entities in tobacco, coal, and wood. Catechol pyrolysis at temperatures of 700 to 1000°C and residence times of 0.4 to 1 s produces a range of aromatic products, which have been analyzed by gas chromatography with flame-ionization detection and by high-pressure liquid chromatography with diode-array ultraviolet-visible absorption detection. Of the 64 aromatic products identified, yields are reported for the 30 species whose yields are at least 0.005% of the mass of fed catechol, over a significant temperature range. The quantified products fall into 8 structural categories: benzene, benzenoid PAH, indene benzologues, fluoranthene benzologues, cyclopenta-fused PAH, ethynyl-substituted aromatics, alkyl-substituted aromatics, and vinyl-substituted aromatics. In general, the more prominent products within a particular structural class are more prominent at all temperatures examined, and the most prominent product in a class is usually 10 times more prevalent than other compounds in the same class. The product quantifications show that at 900-950°C, the aromatic products account for up to 22% of the mass of fed catechol. At these higher temperatures, and all the way up to 1000°C, there are also more quantifiable products that are the result of multiple ring-buildup steps (e.g., the larger benzenoid PAH) as well as an increase in the number and relative quantity of ethynyl-aromatics and cyclopenta-fused PAH. At the lower temperatures, indene is produced at especially high yield, indicative perhaps of a particular facility for the formation of indene from catechol. Also readily formed from catechol is benzene, the aromatic product of highest yield for the entire temperature range investigated. Experiments at different residence times show that at 800°C the 0.4-1 s time interval is one of mostly increasing yields; at 1000°C this same span of residence times sees mostly decreasing yields. The data reported here represent one of the most extensive quantifications of aromatic products from any fuel, and the only one for catechol.
Energy & Fuels, 2002
... Elmer B. Ledesma, Nathan D. Marsh, Alyssa K. Sandrowitz, and Mary J. Wornat*. Princeton Unive... more ... Elmer B. Ledesma, Nathan D. Marsh, Alyssa K. Sandrowitz, and Mary J. Wornat*. Princeton University ... 1984; Vol. 1, pp 41−164. (6) Durant, JL; Busby, WF, Jr.; Lafleur, AL; Penman, BW; Crespi, CL Mutation Res.1996, 371, 123. ...
Combustion Science and Technology, 2007
In this work, we investigate the utility of the smoke lamp for evaluating the soot-reducing poten... more In this work, we investigate the utility of the smoke lamp for evaluating the soot-reducing potential of additives, by comparing it to a more complex liquid-fed laminar diffusion flame. The additives, ferrocene (bis(cyclopentadienyl) iron-Fe(C 5 H 5 ) 2 ), ruthenocene (bis(cyclopentadienyl)ruthenium-Ru(C 5 H 5 ) 2 ), iron naphthenate (a 12% iron salt of naphthenic acid, which is a mixture of fatty carboxylic acids, some of which may include a cyclopentane ring), and MMT (Methylcyclopentadienyl manganese tricarbonyl-CH 3 C 5 H 4 Mn(CO) 3 ) are evaluated at various concentrations in the jet fuel JP-8. Although the smoke lamp is a simple, inexpensive, and widely-available test for evaluating the sooting potential of liquid fuels, it does not provide an effective measure of soot suppression by metal-containing additives. The drop-tube reactor more accurately captures the physical conditions and processes-droplet vaporization, ignition, and rich vs. lean operation-typically found in more complex systems. We find in the smoke lamp that ferrocene, and to a lesser degree ruthenocene, are effective soot suppressors when used in JP-8, and that their effectiveness increases with increasing concentration. In the smoke lamp, MMT and iron naphthenate have minimal effect. On the other hand, in the drop-tube reactor, all four additives are quite effective, especially at fuel lean conditions, where soot suppression reaches 90-95%. Under fuel-rich conditions, where in some cases the additives elevate the yield of soot aerosol slightly, we find a significant increase in the production of the soluble organic fraction of the aerosol, i.e., tar. In order to understand why the smoke lamp sometimes fails to indicate a soot suppressing potential (i.e., from MMT and iron naphthenate), soot samples were collected from a wick lamp burning ferrocene and iron naphthenate additives in JP-8. These samples, as well as several from the drop-tube reactor, were analyzed by X-Ray Fluorescence (XRF) in order to determine their metal content, and we find that the soot aerosol produced by the wick lamp using ferrocene-containing fuel had roughly 30 times the iron content of the soot aerosol produced by the wick lamp using iron-naphthenatecontaining fuel. This difference in metal content is not found in samples produced in the drop-tube reactor. We conclude that the poor performance of iron naphthenate in the smoke lamp is likely the result poor vaporization of the additive from the wick, a consequence of its high molecular weight (average 465).
Combustion and Flame, 2006
Knowledge of the chemical structure of young soot and its precursors is very useful in the unders... more Knowledge of the chemical structure of young soot and its precursors is very useful in the understanding of the paths leading to soot particle inception. This paper presents analyses of the chemical functional groups, based on FT-IR and 1 H NMR spectroscopy of the products obtained in an ethylene inverse diffusion flame. The trends in the data indicate that the soluble fraction of the soot becomes progressively more aromatic and less aliphatic as the height above the burner increases. Results from 1 H NMR spectra of the chloroform-soluble soot samples taken at different heights above the burner corroborate the infrared results based on proton chemical shifts (Ha, Hα, Hβ, and Hγ ). The results indicate that the aliphatic β and γ hydrogens suffered the most drastic reduction, while the aromatic character increased considerably with height, particularly in the first half of the flame.
The use of nanoscale materials as performance additives in polymers may pose significant health a... more The use of nanoscale materials as performance additives in polymers may pose significant health and environmental risks. Although it is unlikely that nanoadditives encapsulated in polymers will be released during normal use, there is the potential for nanoparticle aerosolization when these materials are exposed to heat and fire (either accidentally or during incineration). Furthermore, the nanoparticle morphologies and chemical compositions generated during the combustion of nanocomposite materials may be vastly different than the structures of the pristine nanoadditives due to oxidation and/or interactions with other decomposition products. The potential health and environmental impact of these morphological transformations are unknown.
Computational Fluid Dynamics (CFD) models are used extensively by fire protection engineers for p... more Computational Fluid Dynamics (CFD) models are used extensively by fire protection engineers for performance based design and forensic analysis. The equations of motion describing the gas phase are relatively well known and the approximations in the various gas phase sub-models have been extensively studied. However, coupling of the gas phase and the condensed phase to describe flame spread over a burning solid, has proven to be difficult to model. This is due to a lack of understanding of the underlying physical phenomena that take place during the decomposition of the solid as well as poor characterization of the fundamental material properties that control the burning process.
ISO 16312-1 4 states that the role of a physical fire model for generating accurate toxic effluen... more ISO 16312-1 4 states that the role of a physical fire model for generating accurate toxic effluent composition is to "recreate the essential features of the complex thermal and reactive chemical environment in full-scale fires." These environments vary with the physical characteristics of the fire scenario and with time during the course of the fire, and close representation of some phenomena occurring in full-scale fires may be difficult or even not possible at the small-scale. The accuracy of the physical fire model, then, depends on two features:
Combustion Science and Technology, 2007
In this work, we investigate the utility of the smoke lamp for evaluating the soot-reducing poten... more In this work, we investigate the utility of the smoke lamp for evaluating the soot-reducing potential of additives, by comparing it to a more complex liquid-fed laminar diffusion flame. The additives, ferrocene (bis(cyclopentadienyl) iron-Fe(C 5 H 5 ) 2 ), ruthenocene (bis(cyclopentadienyl)ruthenium-Ru(C 5 H 5 ) 2 ), iron naphthenate (a 12% iron salt of naphthenic acid, which is a mixture of fatty carboxylic acids, some of which may include a cyclopentane ring), and MMT (Methylcyclopentadienyl manganese tricarbonyl-CH 3 C 5 H 4 Mn(CO) 3 ) are evaluated at various concentrations in the jet fuel JP-8. Although the smoke lamp is a simple, inexpensive, and widely-available test for evaluating the sooting potential of liquid fuels, it does not provide an effective measure of soot suppression by metal-containing additives. The drop-tube reactor more accurately captures the physical conditions and processes-droplet vaporization, ignition, and rich vs. lean operation-typically found in more complex systems. We find in the smoke lamp that ferrocene, and to a lesser degree ruthenocene, are effective soot suppressors when used in JP-8, and that their effectiveness increases with increasing concentration. In the smoke lamp, MMT and iron naphthenate have minimal effect. On the other hand, in the drop-tube reactor, all four additives are quite effective, especially at fuel lean conditions, where soot suppression reaches 90-95%. Under fuel-rich conditions, where in some cases the additives elevate the yield of soot aerosol slightly, we find a significant increase in the production of the soluble organic fraction of the aerosol, i.e., tar. In order to understand why the smoke lamp sometimes fails to indicate a soot suppressing potential (i.e., from MMT and iron naphthenate), soot samples were collected from a wick lamp burning ferrocene and iron naphthenate additives in JP-8. These samples, as well as several from the drop-tube reactor, were analyzed by X-Ray Fluorescence (XRF) in order to determine their metal content, and we find that the soot aerosol produced by the wick lamp using ferrocene-containing fuel had roughly 30 times the iron content of the soot aerosol produced by the wick lamp using iron-naphthenatecontaining fuel. This difference in metal content is not found in samples produced in the drop-tube reactor. We conclude that the poor performance of iron naphthenate in the smoke lamp is likely the result poor vaporization of the additive from the wick, a consequence of its high molecular weight (average 465).
Symposium (International) on Combustion, 1998
ABSTRACT By burning droplets of benzene in a single-droplet combustor and performing phase-discri... more ABSTRACT By burning droplets of benzene in a single-droplet combustor and performing phase-discriminating sampling of the liquid and gas phases of the droplet system, we have found that gas-phase pyrolysis products arise in the liquid phase of the droplet. The experiments are conducted at 1000 K and 21 mol % O2 in the postcombustion gas from an oxygen-rich premixed methane flame. Disruptive burning, which has not previously been reported for a pure hydrocarbon in normal gravity conditions, is observed at the end of the droplet residence time (∼92 ms). Samples of the liquid phase have been taken at various times throughout the combustion lifetime and analyzed by high-pressure liquid chromatography. Compositional analysis using ultraviolet-visible absorbance spectra of the separated components of the samples reveals a wide variety of pure polycyclic aromatic hydrocarbons (PAH), substituted PAH, and cyclopenta-fused PAH. In addition, recent synthesis of new reference standards has enabled identification of cyclopenta-fused PAH—cyclopent[hi]acephenanthrylene, cyclopenta[cd]fluoranthene, and dicyclopenta[cd, jk]pyrene—which have never before been identified as benzene products. Because the droplet remains relatively cold (∼350 K) with respect to the gas phase in the oxygen-deficient zone between the droplet and the flame (∼2000 K), we conclude that these compounds are gas-phase pyrolysis products that are obsorbed into the droplet, rather than products of reactions within the droplet. These heavier species may play a role in observed terminal disruptive burning events by acting as additional droplet components that promote multicomponent effects. Analysis of species concentrations over time reveals the dominance of both ring rupture pyrolysis products such as phenylacetylene, triacetylene, and acenaphthylene, and biaryl pyrolysis products such as biphenyl. These four products in particular represent 70% of the identified mass of absorbed pyrolysis products, which accounts for up to 5% of the droplet mass at the end of its lifetime.
2010 14th International Heat Transfer Conference, Volume 3, 2010
ABSTRACT CHRISTIFIRE (Cable Heat Release, Ignition, and Spread in Tray Installations during FIRE)... more ABSTRACT CHRISTIFIRE (Cable Heat Release, Ignition, and Spread in Tray Installations during FIRE) is a U.S. Nuclear Regulatory Commission Office of Research program to quantify the mass and energy released from burning electrical cables. This type of quantitative information will be used to develop more realistic models of cable fires for use in fire probabilistic risk assessment (PRA) analyses. The experimental program has two main thrusts—bench-scale measurements of small samples of burning cables and full-scale measurements of the heat release and fire-spread rates of cables burning within typical ladder-type trays. The bench-scale measurements include micro-calorimetry of cable components, effluent characterization using absorption spectroscopy, and measurements of the heat release rate using a cone calorimeter. The full-scale measurements include the burning of a variety of cables within a typical tray under radiant panel heating, and full-scale, multiple tray fires. The outcome of the experiments is to be used by a variety of fire models, ranging from simple correlations to computational fluid dynamics.
41st AIAA/ASME/SAE/ASEE Joint Propulsion Conference & Exhibit, 2005
Polycyclic Aromatic Compounds, 2000
... NATHAN D. MARSH", MARY J. WORNAT", *, LAWRENCE T. SCOTTb, ATENA NECULAb, ARTHUR L. ... more ... NATHAN D. MARSH", MARY J. WORNAT", *, LAWRENCE T. SCOTTb, ATENA NECULAb, ARTHUR L. LAFLEUR" and ELAINE F. PLUMMER" a Department of Mechanical and Aerospace Engineering, Princeton Merkert Chemistry Center, Boston College, Chestnut Hill, ...
Polycyclic Aromatic Compounds, 2005
Abstract In order to investigate further the polycyclic aromatic hydrocarbons (PAH) produced by b... more Abstract In order to investigate further the polycyclic aromatic hydrocarbons (PAH) produced by benzene droplet combustion, we have obtained and analyzed a highly-concentrated benzene droplet combustion sample, using high pressure liquid chromatography (HPLC) ...
Journal of Analytical and Applied Pyrolysis, 2011
In order to better elucidate the role of thermal decomposition products in the formation of polyc... more In order to better elucidate the role of thermal decomposition products in the formation of polycyclic aromatic hydrocarbons (PAH) from complex fuels, we have performed pyrolysis experiments in a tubularflow reactor, using the model fuel catechol (ortho-dihydroxybenzene), a phenol-type compound representative of structural entities in biomass, coal, and wood. Catechol pyrolysis at temperatures of 700-1000 ЊC and a residence time of 0.4 s produces a range of C 1 -C 6 products, which have been analysed by nondispersive infrared analysis and by gas chromatography with flame-ionization detection. Quantification of product yields versus temperature reveals that the major products are CO, acetylene, 1,3-butadiene, phenol, cyclopentadiene, benzene, and ethylene; minor products are methane, ethane, propyne, propadiene, and propylene. CO is the highest yield catechol pyrolysis product at all temperatures. Among the hydrocarbons, 1,3-butadiene is the highest yield product at temperatures up to 800 ЊC; above 800 ЊC, acetylene is. The structural features of catechol and the experimental product yield data-considered with the established reactions for phenol decomposition-suggest that the major products of catechol decomposition come from the following routes: (1) phenol and benzene from H displacement of OH on catechol and phenol, respectively, (2) cyclopentadiene from unimolecular decomposition of the phenoxy radical, and (3) 1,3-butadiene, acetylene, and CO from decomposition of the hydroxy-substituted phenoxy radical (but with different oxygenated C 5 intermediates). The remaining C 1 -C 3 products appear to arise chiefly from the decomposition of key radicals such as cyclopentadienyl, propargyl, and 1,3-butadienyl. The results presented in this work, in concert with those from a complementary study of the C 7 -C 28 catechol products, provide the basis for the development of a detailed kinetic model for both pyrolytic catechol decomposition and PAH formation and growth.
Energy & Fuels, 2005
JP-8, a surrogate fuel, and several model compounds were used to produce soot aerosols in a drop-... more JP-8, a surrogate fuel, and several model compounds were used to produce soot aerosols in a drop-tube furnace with optical access. The soluble organic fractions (SOF) of soot aerosols were studied with GC, GC-MS, and 13 C NMR. The residue of each aerosol sample was studied with Raman spectroscopy, ESR, and a recently developed technique used to determine the conductivity and extent of turbostratic structure formation in soot. The SOF values from different fuel sources exhibit variations in yield, and carbon aromaticity values, and the latter parameter correlates with the extent of turbostratic structure formation in the aerosol residues. Raman data of the soot residues indicate the presence of highly disordered graphitic structures, but the graphite factor measurements reveal differences among these disordered structures that are not apparent in the Raman data.
Energy & Fuels, 2004
To understand in more detail the formation of polycyclic aromatic hydrocarbons (PAH) from complex... more To understand in more detail the formation of polycyclic aromatic hydrocarbons (PAH) from complex fuels, we have performed pyrolysis experiments in a laminar-flow reactor, using the model fuel catechol (ortho-dihydroxybenzene), a phenol-type compound representative of structural entities in tobacco, coal, and wood. Catechol pyrolysis at temperatures of 700 to 1000°C and residence times of 0.4 to 1 s produces a range of aromatic products, which have been analyzed by gas chromatography with flame-ionization detection and by high-pressure liquid chromatography with diode-array ultraviolet-visible absorption detection. Of the 64 aromatic products identified, yields are reported for the 30 species whose yields are at least 0.005% of the mass of fed catechol, over a significant temperature range. The quantified products fall into 8 structural categories: benzene, benzenoid PAH, indene benzologues, fluoranthene benzologues, cyclopenta-fused PAH, ethynyl-substituted aromatics, alkyl-substituted aromatics, and vinyl-substituted aromatics. In general, the more prominent products within a particular structural class are more prominent at all temperatures examined, and the most prominent product in a class is usually 10 times more prevalent than other compounds in the same class. The product quantifications show that at 900-950°C, the aromatic products account for up to 22% of the mass of fed catechol. At these higher temperatures, and all the way up to 1000°C, there are also more quantifiable products that are the result of multiple ring-buildup steps (e.g., the larger benzenoid PAH) as well as an increase in the number and relative quantity of ethynyl-aromatics and cyclopenta-fused PAH. At the lower temperatures, indene is produced at especially high yield, indicative perhaps of a particular facility for the formation of indene from catechol. Also readily formed from catechol is benzene, the aromatic product of highest yield for the entire temperature range investigated. Experiments at different residence times show that at 800°C the 0.4-1 s time interval is one of mostly increasing yields; at 1000°C this same span of residence times sees mostly decreasing yields. The data reported here represent one of the most extensive quantifications of aromatic products from any fuel, and the only one for catechol.
Energy & Fuels, 2002
... Elmer B. Ledesma, Nathan D. Marsh, Alyssa K. Sandrowitz, and Mary J. Wornat*. Princeton Unive... more ... Elmer B. Ledesma, Nathan D. Marsh, Alyssa K. Sandrowitz, and Mary J. Wornat*. Princeton University ... 1984; Vol. 1, pp 41−164. (6) Durant, JL; Busby, WF, Jr.; Lafleur, AL; Penman, BW; Crespi, CL Mutation Res.1996, 371, 123. ...
Combustion Science and Technology, 2007
In this work, we investigate the utility of the smoke lamp for evaluating the soot-reducing poten... more In this work, we investigate the utility of the smoke lamp for evaluating the soot-reducing potential of additives, by comparing it to a more complex liquid-fed laminar diffusion flame. The additives, ferrocene (bis(cyclopentadienyl) iron-Fe(C 5 H 5 ) 2 ), ruthenocene (bis(cyclopentadienyl)ruthenium-Ru(C 5 H 5 ) 2 ), iron naphthenate (a 12% iron salt of naphthenic acid, which is a mixture of fatty carboxylic acids, some of which may include a cyclopentane ring), and MMT (Methylcyclopentadienyl manganese tricarbonyl-CH 3 C 5 H 4 Mn(CO) 3 ) are evaluated at various concentrations in the jet fuel JP-8. Although the smoke lamp is a simple, inexpensive, and widely-available test for evaluating the sooting potential of liquid fuels, it does not provide an effective measure of soot suppression by metal-containing additives. The drop-tube reactor more accurately captures the physical conditions and processes-droplet vaporization, ignition, and rich vs. lean operation-typically found in more complex systems. We find in the smoke lamp that ferrocene, and to a lesser degree ruthenocene, are effective soot suppressors when used in JP-8, and that their effectiveness increases with increasing concentration. In the smoke lamp, MMT and iron naphthenate have minimal effect. On the other hand, in the drop-tube reactor, all four additives are quite effective, especially at fuel lean conditions, where soot suppression reaches 90-95%. Under fuel-rich conditions, where in some cases the additives elevate the yield of soot aerosol slightly, we find a significant increase in the production of the soluble organic fraction of the aerosol, i.e., tar. In order to understand why the smoke lamp sometimes fails to indicate a soot suppressing potential (i.e., from MMT and iron naphthenate), soot samples were collected from a wick lamp burning ferrocene and iron naphthenate additives in JP-8. These samples, as well as several from the drop-tube reactor, were analyzed by X-Ray Fluorescence (XRF) in order to determine their metal content, and we find that the soot aerosol produced by the wick lamp using ferrocene-containing fuel had roughly 30 times the iron content of the soot aerosol produced by the wick lamp using iron-naphthenatecontaining fuel. This difference in metal content is not found in samples produced in the drop-tube reactor. We conclude that the poor performance of iron naphthenate in the smoke lamp is likely the result poor vaporization of the additive from the wick, a consequence of its high molecular weight (average 465).
Combustion and Flame, 2006
Knowledge of the chemical structure of young soot and its precursors is very useful in the unders... more Knowledge of the chemical structure of young soot and its precursors is very useful in the understanding of the paths leading to soot particle inception. This paper presents analyses of the chemical functional groups, based on FT-IR and 1 H NMR spectroscopy of the products obtained in an ethylene inverse diffusion flame. The trends in the data indicate that the soluble fraction of the soot becomes progressively more aromatic and less aliphatic as the height above the burner increases. Results from 1 H NMR spectra of the chloroform-soluble soot samples taken at different heights above the burner corroborate the infrared results based on proton chemical shifts (Ha, Hα, Hβ, and Hγ ). The results indicate that the aliphatic β and γ hydrogens suffered the most drastic reduction, while the aromatic character increased considerably with height, particularly in the first half of the flame.
The use of nanoscale materials as performance additives in polymers may pose significant health a... more The use of nanoscale materials as performance additives in polymers may pose significant health and environmental risks. Although it is unlikely that nanoadditives encapsulated in polymers will be released during normal use, there is the potential for nanoparticle aerosolization when these materials are exposed to heat and fire (either accidentally or during incineration). Furthermore, the nanoparticle morphologies and chemical compositions generated during the combustion of nanocomposite materials may be vastly different than the structures of the pristine nanoadditives due to oxidation and/or interactions with other decomposition products. The potential health and environmental impact of these morphological transformations are unknown.
Computational Fluid Dynamics (CFD) models are used extensively by fire protection engineers for p... more Computational Fluid Dynamics (CFD) models are used extensively by fire protection engineers for performance based design and forensic analysis. The equations of motion describing the gas phase are relatively well known and the approximations in the various gas phase sub-models have been extensively studied. However, coupling of the gas phase and the condensed phase to describe flame spread over a burning solid, has proven to be difficult to model. This is due to a lack of understanding of the underlying physical phenomena that take place during the decomposition of the solid as well as poor characterization of the fundamental material properties that control the burning process.
ISO 16312-1 4 states that the role of a physical fire model for generating accurate toxic effluen... more ISO 16312-1 4 states that the role of a physical fire model for generating accurate toxic effluent composition is to "recreate the essential features of the complex thermal and reactive chemical environment in full-scale fires." These environments vary with the physical characteristics of the fire scenario and with time during the course of the fire, and close representation of some phenomena occurring in full-scale fires may be difficult or even not possible at the small-scale. The accuracy of the physical fire model, then, depends on two features: