Barbara Apicella | Consiglio Nazionale delle Ricerche (CNR) (original) (raw)
Papers by Barbara Apicella
Energies
The present work focuses on the quality of char and primary tar produced from fast pyrolysis in N... more The present work focuses on the quality of char and primary tar produced from fast pyrolysis in N2 and CO2 of lignocellulosic biomasses: walnut shells (lignin-rich), straw (hemicellulose-rich) and pinewood (cellulose-rich). Heat treatments are carried out in a heated strip reactor (HSR) at 1573 and 2073 K for 3 s, with a heating rate of 104 K/s. The equipment allows for quenching the volatiles as soon as they are emitted. Chars are analyzed by thermogravimetric analysis in air. Results are compared with the products obtained from raw lignin, pure cellulose and pure hemicellulose. Cellulose and hemicellulose tars are dominated by anhydrous monosaccharides, which are scarce in straw tar and abundant in walnut shells tar. Polycyclic aromatic hydrocarbons PAHs are present in the primary products, in particular for walnut shells. The most reactive char is the one obtained from straw and the least reactive is the walnut shells char. Severe heat treatment and a CO2 atmosphere generate addi...
Energies
Heavy fractions of petroleum have for long time been bypassed in favour of lighter fractions. Now... more Heavy fractions of petroleum have for long time been bypassed in favour of lighter fractions. Nowadays, in the framework of the “circular economy”, there is a growing interest in residual petroleum heavy fractions. The present work briefly reviews the use and characterization at laboratory scale of some low valuable solid or semi-solid products of the oil refinery industry: asphaltenes (bitumen/asphalt), pet-coke and pitch for use as fuels. The use of solid and semi-solid refinery residues, in particular, of coke as a coal substitute in thermochemical processes and of pitch and asphaltenes as material precursors, requires careful analysis, and an understanding of their structure at the molecular level is mandatory for the development of processing technology. Techniques for the characterization of typical petroleum heavy fractions such as pitches, asphaltenes and cokes are reviewed. An experimental protocol for investigating at the laboratory scale the thermochemical conversion beha...
Studies in Surface Science and Catalysis, 1999
Kinetic and catalytic aspects of the two steps of formation of poly(ethylenterephtalate) (PET) ha... more Kinetic and catalytic aspects of the two steps of formation of poly(ethylenterephtalate) (PET) have been studied in this work using model molecules. Many kinetic runs have been performed using different catalysts. We have made kinetic runs on some catalysts under different operative conditions to evaluate the effect of catalyst concentration and temperature on the reaction rate. All kinetic runs have been interpreted and kinetic parameters determined. Suggestions on the reaction mechanisms conclude the work.
Chemical engineering transactions, 2019
Thermally-induced annealing by furnace in mild conditions and by fast reactor was applied to naph... more Thermally-induced annealing by furnace in mild conditions and by fast reactor was applied to naphthalene pitch, an amorphous carbon, commercially available. The carbonaceous materials obtained with the two systems were characterized by advanced analytical tools for inferring the occurrence of structural improvements under annealing. The applicability of the produced nanomaterials for use in electrodes preparation for energy storage was discussed.
Chemosphere, 2021
Volatile organic compounds (VOC) and polycyclic aromatic hydrocarbons (PAH), emitted in the envir... more Volatile organic compounds (VOC) and polycyclic aromatic hydrocarbons (PAH), emitted in the environment from a wide range of combustion sources, are hazardous to human health and considered important precursors of both primary and secondary particulate pollutants. In the present work, light hydrocarbons up to C9, as main components of combustion-derived VOC, and PAH produced in fuel-rich conditions of premixed ethylene flames were analyzed by implementing a molecular-beam time of flight mass spectrometer (MB-TOFMS), purposely built for on-line fast monitoring of the environmental impact of combustion systems. The reliability of the MB-TOFMS was preliminarily verified on a slightly-sooting flame, comparing the results with those obtained by batch sampling and gas chromatographic techniques. Electron ionization (EI) and multi-photon ionization (MPI) were used as MB-TOFMS sources and tested on combustion gases of a no-sooting premixed ethylene flame where VOC and PAH are present in traces not detectable with batch sampling and conventional analytical techniques. The mass identification accuracy was improved and guaranteed by systematically performing internal mass calibration, exploiting the formation of "in situ" clusters from combustion water in the molecular beam apparatus. Selective and sensitive monitoring of light hydrocarbons and PAH, derived from oxidation and pyrolysis reactions featuring combustion, was shown to be especially effective when using the MB-TOFMS equipped with MPI source. This technique showed to be effective also for the detection of radical species that are important for the risk assessment of aerosol and fundamental understanding of aerosol chemistry at a molecular level.
Combustion and Flame, 2016
Abstract In oxycombustion and gasification processes coal pyrolysis occurs in CO 2 -rich atmosphe... more Abstract In oxycombustion and gasification processes coal pyrolysis occurs in CO 2 -rich atmospheres. The present work investigates the effect of such conditions on the quantity and quality of the submicronic carbon particulate produced. Pyrolysis experiments were carried out in either N 2 or CO 2 atmospheres in a laminar drop tube reactor, with wall temperatures of 1573 K, heating rates of 10 4 –10 5 K/s and residence times below 130 ms, so as to reproduce pyrolysis conditions comparable to those of pulverized coal-fired boilers. The carbon particulate sampled in the reactor was found to have bimodal distribution in the micronic and submicronic ranges. A method based on solvent extraction was applied to carbon particulate for separating the two modes and determining the relative mass contribution of micronic and submicronic fractions. In CO 2 atmosphere the amount of submicronic fraction of carbon particulate, referred to as soot, was found to be up to four times as much as upon N 2 experiments. Beside the larger formation of soot, relevant differences in terms of combustion reactivity, size distribution and chemical structure of the residual carbon particulate produced in CO 2 environment in respect to N 2 environment were observed by means of a large array of techniques including thermogravimetry, microscopy (SEM+EDX), FT-IR, UV–visible and Raman spectroscopy along with XRD and XPS techniques.
Proceedings of the Combustion Institute, 2015
Dehydrogenation of soot formed in premixed sooting flames burning methane and ethylene in similar... more Dehydrogenation of soot formed in premixed sooting flames burning methane and ethylene in similar equivalence ratio and temperature conditions was studied in detail by measuring the type of C-H bonds, as derived from a newly developed FT-IR quantitative method, and the soot absorption coefficient. The measurement of the aliphatic and aromatic hydrogen content of soot has shown to give useful insights in the different dehydrogenation and soot mass growth processes observed for the methane and ethylene flame. In the ethylene flame, aliphatic hydrogen is preferentially and almost completely removed in the early soot formation region and the reduction of soot formation rate was observed after the aliphatic hydrogen decrease. This can be attributed to the decrease of radical sites formation and the consequent loss of surface reactivity toward further carbon addition. Downstream of the soot formation region, coagulation and thermal annealing of the ethylene soot particles, accompanied by a negligible dehydrogenation, become the predominant phenomena. The corresponding steep rise of the absorption coefficient is a signature of the increase of aromatic structures interconnected by conjugated sp 2 bonds, marking the end of soot formation and growth process. In the methane flame, the decrease of aliphatic hydrogen was found to occur to a lower extent and delayed in respect to the maximum soot formation rate. The reduced soot dehydrogenation observed in the methane flame was attributed to the lower [H]/[H 2 ] ratio, as testified by the larger presence of molecular hydrogen, which reduces the number of radical sites necessary for soot dehydrogenation and aromatic growth. In this condition, the later phases of coagulation and internal structural carbon rearrangements did not significantly occur, as demonstrated by the low value and steadiness of the methane soot absorption coefficient.
Proceedings of the Combustion Institute, 2009
Soot growth from inception to mass-loading is studied in a wide range of molecular weights (MW) f... more Soot growth from inception to mass-loading is studied in a wide range of molecular weights (MW) from 10 5 to 10 10 u by means of size exclusion chromatography (SEC) coupled with on-line UV-visible spectroscopy. The evolution of MW distributions of soot is also numerically predicted by using a detailed kinetic model coupled with a discrete-sectional approach for the modeling of the gas-to-particle process. Two premixed flames burning n-heptane in slightly sooting and heavily sooting conditions are studied. The effect of aromatic addition to the fuel is studied by adding n-propylbenzene (10% by volume) to n-heptane in the heavily sooting condition. A progressive reduction of the MW distribution from multimodal to unimodal is observed along the flames testifying the occurrence of particle growth and agglomeration. These processes occur earlier in the aromatic-doped n-heptane flame due to the overriding role of benzene on soot formation which results in bigger young soot particles. Modeled MW distributions are in reasonable agreement with experimental data although the model predicts a slower coagulation process particularly in the slightly sooting n-heptane flame. Given the good agreement between model predictions and experiments, the model is used to explore the role of fuel chemistry on MW distributions. Two flames of n-heptane and n-heptane/n-propylbenzene in heavily sooting conditions with the same temperature profile and inert dilution are modeled. The formation of larger soot particles is still evident in the n-heptane/n-propylbenzene flame with respect to the n-heptane flame in the same operating conditions of temperature and dilution. In addition the model predicts a larger formation of molecular particles in the flame containing n-propylbenzene and shows that soot inception occurs in correspondence of their maximum formation thus indicating the importance of molecular growth in soot inception.
Proceedings of the Combustion Institute, 2007
Mass spectrometric analysis by laser desorption-time of flight-mass spectrometry (LDI-TOF-MS) was... more Mass spectrometric analysis by laser desorption-time of flight-mass spectrometry (LDI-TOF-MS) was exploited to extend the detection of flame-formed polycyclic aromatic hydrocarbons (PAH) up to the mass limit of the first soot particles (>2000 Da) in the soot formation region of a premixed fuel-rich (C/O = 1) ethylene flame. The typical decreasing intensity of PAH ion peaks with increasing mass was found in the mass range m/z 500-1700 although a slight enrichment in the heavier part of PAH could be observed to occur along the flame axis. The separation by means of size exclusion chromatography (SEC) into two different classes of PAH followed by UV-visible spectroscopy corroborated the mass spectral identification of large mass PAH. Critical examination of mass spectral features and SEC separation was the starting point for speculation about the changes occurring in PAH growth from planar to concave structures which could be important for soot inception mechanisms.
Journal of Applied Polymer Science, 1998
Kinetic and catalytic aspects of the formation of poly(ethylene terephthalate) (PET) have been st... more Kinetic and catalytic aspects of the formation of poly(ethylene terephthalate) (PET) have been studied in this work using model molecules such as 2-hydroxyethyl 4-methylbenzoate (MP), 2-hydroxyethyl 4-benzoate (MB), and 2(-hydroxyethyl 4-methylbenzoate) 4-methylbenzoate (DP), synthesized and purified in our laboratories. The methods to obtain these molecules have been described in detail. Many kinetic runs have been performed using different catalysts, such as compounds of Sb, Ti, Zr, Al, Mo (VI), Mn, Zn, Sn (IV), and Ge. We have made kinetic runs on some catalysts under different operative conditions to evaluate the effect of catalyst concentration and temperature on the reaction rate. We have observed that a second-order kinetic law is suitable for both condensation and reverse reaction. All kinetic runs have been interpreted and kinetic parameters determined. Activity can depend on catalyst concentration in a different way for each type of catalyst. Bivalent metals activity is affected by the presence of a substituent in the aromatic ring, unlike tri- and tetravalent metals. Suggestions on the reaction mechanisms conclude the work. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2423–2433, 1998
Energy & Fuels, 2001
Inflame sampling followed by chemical and spectroscopic analysis coupled with laser-induced fluor... more Inflame sampling followed by chemical and spectroscopic analysis coupled with laser-induced fluorescence (LIF) measurements excited in the UV region (266 nm) were performed on a spray combustion system burning a diesel oil and a vegetable aromatic-free fuel like a rapeseed oil. A large fluorescence emission peaked in the UV was found in the spray region of the diesel oil flame attributed to the unburned aromatic species of the fuel. In the rapeseed oil flame, the absence of aromatic species in the fuel justify the lack of the fluorescence emission in the UV region. The comparison of LIF spectra measured in the PAH-formation region with the fluorescence spectra of the high molecular weight species sampled both in the diesel oil flame and in the rapeseed oil flame suggests a relationship between the broad and unstructured fluorescence measured in the visible and these high molecular weight species formed in the pyrolytic regions of spray flames. The visible emission feature could be assigned to flame-formed PAH species contained in the high molecular weight species if their fluorescence spectra are shifted toward the visible for effect of the high temperature flame environment. Alternatively, responsible for visible emission could be the unidentified heavier part of the high molecular weight species that are know to fluoresce mainly in the visible range of the emission spectrum.
Combustion Science and Technology, 2010
... Islas , CA , Suelves , I. , Millan , M. , Apicella , B. , Herod , AA , and Kandiyoti , R. 200... more ... Islas , CA , Suelves , I. , Millan , M. , Apicella , B. , Herod , AA , and Kandiyoti , R. 2003 . ... 26 , 1422 . [CrossRef], [Web of Science ®] View all references; Karaka et al., 200425. Karaka , F. , Islas , CA ., Millan , M. , Behrouzi , M. , Morgan , TJ , Herod , AA , and Kandiyoti , R. 2004 . ...
Combustion Science and Technology, 2002
High molecular weight carbonaceous materials formed in the combustion of ethylene were collected ... more High molecular weight carbonaceous materials formed in the combustion of ethylene were collected from a premixed laminar flame operating under fuel-rich combustion conditions. Particulates collected from the flame were extracted with dichloromethane (DCM) to ...
Combustion and Flame, 2001
ABSTRACT The exploitation of fluorescence techniques for the characterization of aromatic polluta... more ABSTRACT The exploitation of fluorescence techniques for the characterization of aromatic pollutants formed in combustion processes needs a reliable interpretation for the assignment of fluorescence emission to specific products. To this aim, ultraviolet-excited LIF (laser-induced fluorescence) spectra were measured in premixed rich ethylene/oxygen flames having a different PAH mass loading as verified by sampling and chomatographic analysis of the condensed species produced along the flames.Fluorescence emission in the ultraviolet was mainly found in the flames where PAH formation is relatively low indicating that ultraviolet-fluorescence emission is not related to PAH species. On the opposite, broad visible emission features became prevalent in PAH-rich flames suggesting that the fluorescence of PAH species could be shifted toward the visible for effect of the high-temperature flame environment. In alternative to this hypothesis the visible fluorescence could be due to the heavier unidentified part of the condensed species whose fluorescence emission is shifted toward the visible.
SSRN Electronic Journal, 2022
Chemical Engineering Transactions, 2017
The composition of tars, typically derived from coal and heavy fuel processing or formed in fuel-... more The composition of tars, typically derived from coal and heavy fuel processing or formed in fuel-rich combustion, determines their transformation into carbons relevant in combustion and environmental fields as well as for material production. The speciation of the huge number of aromatic components of tars, usually found in form of viscous black liquid or solid, is not straightforward because of the tar complexity and high molecular weight, spanning from few hundreds up to thousands of Da. To this regard, the pre-separation of tar in lighter and heavier fractions simplifies the further characterization of its composition. The present work reports a fractionation method of a typical sample of combustion-formed tar based on moderate heating in high-vacuum conditions (10-6 mbar). It was preliminarily tested on a single polycyclic aromatic hydrocarbon, coronene, and on synthetic mixtures of polycyclic aromatic hydrocarbons, presumed to be the basic aromatic moieties of tar components. L...
Energies
The present work focuses on the quality of char and primary tar produced from fast pyrolysis in N... more The present work focuses on the quality of char and primary tar produced from fast pyrolysis in N2 and CO2 of lignocellulosic biomasses: walnut shells (lignin-rich), straw (hemicellulose-rich) and pinewood (cellulose-rich). Heat treatments are carried out in a heated strip reactor (HSR) at 1573 and 2073 K for 3 s, with a heating rate of 104 K/s. The equipment allows for quenching the volatiles as soon as they are emitted. Chars are analyzed by thermogravimetric analysis in air. Results are compared with the products obtained from raw lignin, pure cellulose and pure hemicellulose. Cellulose and hemicellulose tars are dominated by anhydrous monosaccharides, which are scarce in straw tar and abundant in walnut shells tar. Polycyclic aromatic hydrocarbons PAHs are present in the primary products, in particular for walnut shells. The most reactive char is the one obtained from straw and the least reactive is the walnut shells char. Severe heat treatment and a CO2 atmosphere generate addi...
Energies
Heavy fractions of petroleum have for long time been bypassed in favour of lighter fractions. Now... more Heavy fractions of petroleum have for long time been bypassed in favour of lighter fractions. Nowadays, in the framework of the “circular economy”, there is a growing interest in residual petroleum heavy fractions. The present work briefly reviews the use and characterization at laboratory scale of some low valuable solid or semi-solid products of the oil refinery industry: asphaltenes (bitumen/asphalt), pet-coke and pitch for use as fuels. The use of solid and semi-solid refinery residues, in particular, of coke as a coal substitute in thermochemical processes and of pitch and asphaltenes as material precursors, requires careful analysis, and an understanding of their structure at the molecular level is mandatory for the development of processing technology. Techniques for the characterization of typical petroleum heavy fractions such as pitches, asphaltenes and cokes are reviewed. An experimental protocol for investigating at the laboratory scale the thermochemical conversion beha...
Studies in Surface Science and Catalysis, 1999
Kinetic and catalytic aspects of the two steps of formation of poly(ethylenterephtalate) (PET) ha... more Kinetic and catalytic aspects of the two steps of formation of poly(ethylenterephtalate) (PET) have been studied in this work using model molecules. Many kinetic runs have been performed using different catalysts. We have made kinetic runs on some catalysts under different operative conditions to evaluate the effect of catalyst concentration and temperature on the reaction rate. All kinetic runs have been interpreted and kinetic parameters determined. Suggestions on the reaction mechanisms conclude the work.
Chemical engineering transactions, 2019
Thermally-induced annealing by furnace in mild conditions and by fast reactor was applied to naph... more Thermally-induced annealing by furnace in mild conditions and by fast reactor was applied to naphthalene pitch, an amorphous carbon, commercially available. The carbonaceous materials obtained with the two systems were characterized by advanced analytical tools for inferring the occurrence of structural improvements under annealing. The applicability of the produced nanomaterials for use in electrodes preparation for energy storage was discussed.
Chemosphere, 2021
Volatile organic compounds (VOC) and polycyclic aromatic hydrocarbons (PAH), emitted in the envir... more Volatile organic compounds (VOC) and polycyclic aromatic hydrocarbons (PAH), emitted in the environment from a wide range of combustion sources, are hazardous to human health and considered important precursors of both primary and secondary particulate pollutants. In the present work, light hydrocarbons up to C9, as main components of combustion-derived VOC, and PAH produced in fuel-rich conditions of premixed ethylene flames were analyzed by implementing a molecular-beam time of flight mass spectrometer (MB-TOFMS), purposely built for on-line fast monitoring of the environmental impact of combustion systems. The reliability of the MB-TOFMS was preliminarily verified on a slightly-sooting flame, comparing the results with those obtained by batch sampling and gas chromatographic techniques. Electron ionization (EI) and multi-photon ionization (MPI) were used as MB-TOFMS sources and tested on combustion gases of a no-sooting premixed ethylene flame where VOC and PAH are present in traces not detectable with batch sampling and conventional analytical techniques. The mass identification accuracy was improved and guaranteed by systematically performing internal mass calibration, exploiting the formation of "in situ" clusters from combustion water in the molecular beam apparatus. Selective and sensitive monitoring of light hydrocarbons and PAH, derived from oxidation and pyrolysis reactions featuring combustion, was shown to be especially effective when using the MB-TOFMS equipped with MPI source. This technique showed to be effective also for the detection of radical species that are important for the risk assessment of aerosol and fundamental understanding of aerosol chemistry at a molecular level.
Combustion and Flame, 2016
Abstract In oxycombustion and gasification processes coal pyrolysis occurs in CO 2 -rich atmosphe... more Abstract In oxycombustion and gasification processes coal pyrolysis occurs in CO 2 -rich atmospheres. The present work investigates the effect of such conditions on the quantity and quality of the submicronic carbon particulate produced. Pyrolysis experiments were carried out in either N 2 or CO 2 atmospheres in a laminar drop tube reactor, with wall temperatures of 1573 K, heating rates of 10 4 –10 5 K/s and residence times below 130 ms, so as to reproduce pyrolysis conditions comparable to those of pulverized coal-fired boilers. The carbon particulate sampled in the reactor was found to have bimodal distribution in the micronic and submicronic ranges. A method based on solvent extraction was applied to carbon particulate for separating the two modes and determining the relative mass contribution of micronic and submicronic fractions. In CO 2 atmosphere the amount of submicronic fraction of carbon particulate, referred to as soot, was found to be up to four times as much as upon N 2 experiments. Beside the larger formation of soot, relevant differences in terms of combustion reactivity, size distribution and chemical structure of the residual carbon particulate produced in CO 2 environment in respect to N 2 environment were observed by means of a large array of techniques including thermogravimetry, microscopy (SEM+EDX), FT-IR, UV–visible and Raman spectroscopy along with XRD and XPS techniques.
Proceedings of the Combustion Institute, 2015
Dehydrogenation of soot formed in premixed sooting flames burning methane and ethylene in similar... more Dehydrogenation of soot formed in premixed sooting flames burning methane and ethylene in similar equivalence ratio and temperature conditions was studied in detail by measuring the type of C-H bonds, as derived from a newly developed FT-IR quantitative method, and the soot absorption coefficient. The measurement of the aliphatic and aromatic hydrogen content of soot has shown to give useful insights in the different dehydrogenation and soot mass growth processes observed for the methane and ethylene flame. In the ethylene flame, aliphatic hydrogen is preferentially and almost completely removed in the early soot formation region and the reduction of soot formation rate was observed after the aliphatic hydrogen decrease. This can be attributed to the decrease of radical sites formation and the consequent loss of surface reactivity toward further carbon addition. Downstream of the soot formation region, coagulation and thermal annealing of the ethylene soot particles, accompanied by a negligible dehydrogenation, become the predominant phenomena. The corresponding steep rise of the absorption coefficient is a signature of the increase of aromatic structures interconnected by conjugated sp 2 bonds, marking the end of soot formation and growth process. In the methane flame, the decrease of aliphatic hydrogen was found to occur to a lower extent and delayed in respect to the maximum soot formation rate. The reduced soot dehydrogenation observed in the methane flame was attributed to the lower [H]/[H 2 ] ratio, as testified by the larger presence of molecular hydrogen, which reduces the number of radical sites necessary for soot dehydrogenation and aromatic growth. In this condition, the later phases of coagulation and internal structural carbon rearrangements did not significantly occur, as demonstrated by the low value and steadiness of the methane soot absorption coefficient.
Proceedings of the Combustion Institute, 2009
Soot growth from inception to mass-loading is studied in a wide range of molecular weights (MW) f... more Soot growth from inception to mass-loading is studied in a wide range of molecular weights (MW) from 10 5 to 10 10 u by means of size exclusion chromatography (SEC) coupled with on-line UV-visible spectroscopy. The evolution of MW distributions of soot is also numerically predicted by using a detailed kinetic model coupled with a discrete-sectional approach for the modeling of the gas-to-particle process. Two premixed flames burning n-heptane in slightly sooting and heavily sooting conditions are studied. The effect of aromatic addition to the fuel is studied by adding n-propylbenzene (10% by volume) to n-heptane in the heavily sooting condition. A progressive reduction of the MW distribution from multimodal to unimodal is observed along the flames testifying the occurrence of particle growth and agglomeration. These processes occur earlier in the aromatic-doped n-heptane flame due to the overriding role of benzene on soot formation which results in bigger young soot particles. Modeled MW distributions are in reasonable agreement with experimental data although the model predicts a slower coagulation process particularly in the slightly sooting n-heptane flame. Given the good agreement between model predictions and experiments, the model is used to explore the role of fuel chemistry on MW distributions. Two flames of n-heptane and n-heptane/n-propylbenzene in heavily sooting conditions with the same temperature profile and inert dilution are modeled. The formation of larger soot particles is still evident in the n-heptane/n-propylbenzene flame with respect to the n-heptane flame in the same operating conditions of temperature and dilution. In addition the model predicts a larger formation of molecular particles in the flame containing n-propylbenzene and shows that soot inception occurs in correspondence of their maximum formation thus indicating the importance of molecular growth in soot inception.
Proceedings of the Combustion Institute, 2007
Mass spectrometric analysis by laser desorption-time of flight-mass spectrometry (LDI-TOF-MS) was... more Mass spectrometric analysis by laser desorption-time of flight-mass spectrometry (LDI-TOF-MS) was exploited to extend the detection of flame-formed polycyclic aromatic hydrocarbons (PAH) up to the mass limit of the first soot particles (>2000 Da) in the soot formation region of a premixed fuel-rich (C/O = 1) ethylene flame. The typical decreasing intensity of PAH ion peaks with increasing mass was found in the mass range m/z 500-1700 although a slight enrichment in the heavier part of PAH could be observed to occur along the flame axis. The separation by means of size exclusion chromatography (SEC) into two different classes of PAH followed by UV-visible spectroscopy corroborated the mass spectral identification of large mass PAH. Critical examination of mass spectral features and SEC separation was the starting point for speculation about the changes occurring in PAH growth from planar to concave structures which could be important for soot inception mechanisms.
Journal of Applied Polymer Science, 1998
Kinetic and catalytic aspects of the formation of poly(ethylene terephthalate) (PET) have been st... more Kinetic and catalytic aspects of the formation of poly(ethylene terephthalate) (PET) have been studied in this work using model molecules such as 2-hydroxyethyl 4-methylbenzoate (MP), 2-hydroxyethyl 4-benzoate (MB), and 2(-hydroxyethyl 4-methylbenzoate) 4-methylbenzoate (DP), synthesized and purified in our laboratories. The methods to obtain these molecules have been described in detail. Many kinetic runs have been performed using different catalysts, such as compounds of Sb, Ti, Zr, Al, Mo (VI), Mn, Zn, Sn (IV), and Ge. We have made kinetic runs on some catalysts under different operative conditions to evaluate the effect of catalyst concentration and temperature on the reaction rate. We have observed that a second-order kinetic law is suitable for both condensation and reverse reaction. All kinetic runs have been interpreted and kinetic parameters determined. Activity can depend on catalyst concentration in a different way for each type of catalyst. Bivalent metals activity is affected by the presence of a substituent in the aromatic ring, unlike tri- and tetravalent metals. Suggestions on the reaction mechanisms conclude the work. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 2423–2433, 1998
Energy & Fuels, 2001
Inflame sampling followed by chemical and spectroscopic analysis coupled with laser-induced fluor... more Inflame sampling followed by chemical and spectroscopic analysis coupled with laser-induced fluorescence (LIF) measurements excited in the UV region (266 nm) were performed on a spray combustion system burning a diesel oil and a vegetable aromatic-free fuel like a rapeseed oil. A large fluorescence emission peaked in the UV was found in the spray region of the diesel oil flame attributed to the unburned aromatic species of the fuel. In the rapeseed oil flame, the absence of aromatic species in the fuel justify the lack of the fluorescence emission in the UV region. The comparison of LIF spectra measured in the PAH-formation region with the fluorescence spectra of the high molecular weight species sampled both in the diesel oil flame and in the rapeseed oil flame suggests a relationship between the broad and unstructured fluorescence measured in the visible and these high molecular weight species formed in the pyrolytic regions of spray flames. The visible emission feature could be assigned to flame-formed PAH species contained in the high molecular weight species if their fluorescence spectra are shifted toward the visible for effect of the high temperature flame environment. Alternatively, responsible for visible emission could be the unidentified heavier part of the high molecular weight species that are know to fluoresce mainly in the visible range of the emission spectrum.
Combustion Science and Technology, 2010
... Islas , CA , Suelves , I. , Millan , M. , Apicella , B. , Herod , AA , and Kandiyoti , R. 200... more ... Islas , CA , Suelves , I. , Millan , M. , Apicella , B. , Herod , AA , and Kandiyoti , R. 2003 . ... 26 , 1422 . [CrossRef], [Web of Science ®] View all references; Karaka et al., 200425. Karaka , F. , Islas , CA ., Millan , M. , Behrouzi , M. , Morgan , TJ , Herod , AA , and Kandiyoti , R. 2004 . ...
Combustion Science and Technology, 2002
High molecular weight carbonaceous materials formed in the combustion of ethylene were collected ... more High molecular weight carbonaceous materials formed in the combustion of ethylene were collected from a premixed laminar flame operating under fuel-rich combustion conditions. Particulates collected from the flame were extracted with dichloromethane (DCM) to ...
Combustion and Flame, 2001
ABSTRACT The exploitation of fluorescence techniques for the characterization of aromatic polluta... more ABSTRACT The exploitation of fluorescence techniques for the characterization of aromatic pollutants formed in combustion processes needs a reliable interpretation for the assignment of fluorescence emission to specific products. To this aim, ultraviolet-excited LIF (laser-induced fluorescence) spectra were measured in premixed rich ethylene/oxygen flames having a different PAH mass loading as verified by sampling and chomatographic analysis of the condensed species produced along the flames.Fluorescence emission in the ultraviolet was mainly found in the flames where PAH formation is relatively low indicating that ultraviolet-fluorescence emission is not related to PAH species. On the opposite, broad visible emission features became prevalent in PAH-rich flames suggesting that the fluorescence of PAH species could be shifted toward the visible for effect of the high-temperature flame environment. In alternative to this hypothesis the visible fluorescence could be due to the heavier unidentified part of the condensed species whose fluorescence emission is shifted toward the visible.
SSRN Electronic Journal, 2022
Chemical Engineering Transactions, 2017
The composition of tars, typically derived from coal and heavy fuel processing or formed in fuel-... more The composition of tars, typically derived from coal and heavy fuel processing or formed in fuel-rich combustion, determines their transformation into carbons relevant in combustion and environmental fields as well as for material production. The speciation of the huge number of aromatic components of tars, usually found in form of viscous black liquid or solid, is not straightforward because of the tar complexity and high molecular weight, spanning from few hundreds up to thousands of Da. To this regard, the pre-separation of tar in lighter and heavier fractions simplifies the further characterization of its composition. The present work reports a fractionation method of a typical sample of combustion-formed tar based on moderate heating in high-vacuum conditions (10-6 mbar). It was preliminarily tested on a single polycyclic aromatic hydrocarbon, coronene, and on synthetic mixtures of polycyclic aromatic hydrocarbons, presumed to be the basic aromatic moieties of tar components. L...