Formation Of Polyaromatic Hydrocarbons Research Articles

THE EFFECT OF ASPHALTENES QUANTITY ON THERMAL AND CATALYTIC CRACKING PRODUCT YIELD OF HEAVY OIL FROM KARMALSKOYE FIELD

The study investigated the composition of products resulting from thermal and catalytic cracking of mixtures of deasphaltenized oil from the Karmalskoye field with asphaltenes content of 0.0, 5.2, and 10.4wt.%. The experiments were conducted at a temperature of 450 °C for a duration of 100 min. The catalyst used was a mixture of tungsten carbide and nichrome powders (NiCrWC), in an amount of 0.1%wt. The presence of the NiCrWC additive during cracking of mixtures of deasphaltenized oil with different asphaltenes content has been shown to increase the yield of oils, gasoline, and diesel fractions while reducing the yield of coke and asphaltenes compared to thermal cracking. During the catalytic cracking of all the mixtures studied, the combined yield of gasoline and diesel fractions exceeds 70%wt. It is important to note that an increase in asphaltenes content during catalytic cracking results in a decrease in the yield of gasoline fractions and an increase in the yield of diesel fractions. Studies have demonstrated that the thermal cracking of heavy oil mixtures with different asphaltene contents results in a decrease in the contents of saturated and monoaromatic hydrocarbons, while the contents of biaromatic and triaromatic hydrocarbons increase. Additionally, the presence of asphaltenes has been found to impact the formation of polyaromatic hydrocarbons. During catalytic cracking, the content of saturated, monoaromatic, and biaromatic hydrocarbons increases, while the content of triaromatic and polyaromatic hydrocarbons decreases. During catalytic cracking, the average structure of asphaltene molecules undergoes significant changes. The molecules become smaller, more aromatic, and monoblock, with fewer carbon atoms in the saturated moieties. This catalyst also helps reduce the amount of heteroatoms in the resulting asphaltenes. For citation: Sviridenko N.N., Urazov Kh.Kh., Sergeyev N.S. The effect of asphaltenes quantity on thermal and catalytic cracking product yield of heavy oil from Karmalskoye field. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 8. P. 76-84. DOI: 10.6060/ivkkt.20246708.6t.

Toward Elimination of Soot Emissions from Jet Fuel Combustion.

Soot from jet fuel combustion in aircraft engines contributes to global warming through the formation of contrail cirrus clouds that make up to 56% of the total radiative forcing from aviation. Here, the elimination of such emissions is explored through N2 injection (containing 0-25 vol % O2) at the exhaust of enclosed spray combustion of jet fuel that nicely emulates aircraft soot emissions. It is shown that injecting N2 containing 5 vol % of O2 enhances the formation of polyaromatic hydrocarbons (PAHs) that adsorb on the surface of soot. This increases soot number density and volume fraction by 25 and 80%, respectively. However, further increasing the O2 concentration to 20 or 25 vol % enhances oxidation and nearly eliminates soot emissions from jet fuel spray combustion, reducing the soot number density and volume fraction by 87.3 or 95.4 and 98.3 or 99.6%, respectively. So, a judicious injection of air just after the aircraft engine exhaust can drastically reduce soot emissions and halve the radiative forcing due to aviation, as shown by soot mobility, X-ray diffraction, Raman spectroscopy, nitrogen adsorption, microscopy, and thermogravimetric analysis (for the organic to total carbon ratio) measurements.

Experimental Investigation of the Formation of Polyaromatic Hydrocarbons and Soot during the Pyrolysis of Ethylene with the Addition of Dimethyl and Diethyl Ethers and Dimethoxymethane

Experimental Investigation of the Formation of Polyaromatic Hydrocarbons and Soot during the Pyrolysis of Ethylene with the Addition of Dimethyl and Diethyl Ethers and Dimethoxymethane

Experimental Investigation of the Formation of Polyaromatic Hydrocarbons and Soot during Pyrolysis of Ethylene with Additives of Dimethyl, Diethyl Ether, and Dimethoxymethane

Experimental Investigation of the Formation of Polyaromatic Hydrocarbons and Soot during Pyrolysis of Ethylene with Additives of Dimethyl, Diethyl Ether, and Dimethoxymethane

Sooting propensities of novel cage hydrocarbon propellants

The absolute sooting propensities of three bishomocubane-based cage hydrocarbon fuels– bis(nitratomethyl)-1–3-bishomocubane (DNMBHC), 1,3-Bishomocubane dimer (BHCD), and diazido-dimethyl-bishomocubane (DADMBHC) having potential for propulsive applications were estimated using the full field light extinction technique (LE). The results were compared against relative soot volume fraction measurements obtained using color-ratio pyrometry (CRP). The Rayleigh assumption used in this study was validated by TEM (transmission electron microscopy) measurements. The experiments were conducted using the tethered droplet combustion technique in ambient air under normal gravity conditions. The sooting propensities of 10% w/w blends of the novel BHC fuels with an RP-1 surrogate fuel (RP-1-s) were also studied along with other fuels, includingn-dodecane, methylcyclohexane, isocetane, and dicyclopentadiene (DCPD), which was the starting fuel for the synthesis of the novel BHC compounds. Results indicate an excellent match in the sooting propensities estimated using the two methods despite considerable differences in the estimation methodologies. The novel BHC fuels were extremely sooty compared to RP-1-s and its constituent components on account of their caged molecular structure that favoured the formation of polyaromatic hydrocarbons (PAHs). The assumption of a constant soot dispersion exponent in CRP was judged as having consequences similar to the assumption of a constant soot refractive index in the LE method. The LE technique was assessed as more robust in comparison to CRP as it could capture soot emissions outside the luminous flame zone and had significantly lower uncertainties than CRP for sooty fuels..

PAH formation in the pyrolysis of benzene and dimethyl ether mixtures behind shock waves

In this work the laser-induced fluorescence (LIF) method was used to study the formation of polyaromatic hydrocarbons (PAHs) in the pyrolysis of benzene C6H6 and dimethyl ether C2H6O (DME) mixtures diluted with argon behind reflected shock waves within a temperature range of 1300–2000 K and pressures of 3.5–5.7 bar. To monitor the volume fraction of the condensed phase, laser extinction at a wavelength of 633 nm at the temperature range 1600–2500 K was measured. The LIF spectra of PAHs formed at varying temperatures and at different times relative to the onset of the pyrolysis process were recorded. It was found that the LIF spectra shift toward longer wavelengths with increasing temperature and reaction time. It has been shown that PAHs with four or more aromatic rings are the precursors of the appearance of the condensed phase. In mixtures with DME, greater amounts of small aromatics (consisting of one-two rings and fewer larger PAHs) were detected relative to benzene pyrolysis. Besides, the DME presence significantly reduced the optical density of the mixture at 633 nm, indicating a decrease in the soot yield. Modeling of PAHs and soot growth for the conditions of experiments using the modern sectional kinetic mechanism was carried out. The simulation results have demonstrated a change in PAH formation pathways that depend on fuel composition and temperature. The effect of DME on the growth of PAHs in benzene pyrolysis is both a decrease in temperature due to heat consumption during the decomposition of DME and the appearance of additional pathways for small PAHs formation and, at the same time, a decrease in the yield of heavier compounds consisting of four or more aromatic rings.

Experimental and kinetic modeling study of benzyl alcohol pyrolysis

The pyrolysis of benzyl alcohol (A1CH2OH) at 30 and 760 torr was studied in a flow tube reactor. The synchrotron radiation photoionization and molecular-beam mass spectrometry (MBMS) techniques were used to identify and quantify 35 intermediates and products including some small species, several monophenyl ring species, and a large number of polyaromatic hydrocarbons (PAHs). A comprehensive chemical kinetic reaction model involving 376 species and 2171 reactions was developed with reasonable prediction. According to the rate-of-production analysis, the consumption of A1CH2OH is mainly proceeded with the H-abstraction reactions with H atoms and OH radicals under both pressures. H-abstractions and unimolecular dissociation dehydrogenation reactions also play important roles in the subsequent formation of PAHs. Phenyl radicals, benzene (A1), and benzyl (A1CH2) radicals are important intermediates in the pyrolysis of A1CH2OH, which provide various ways for the formation of PAHs. Sensitivity analysis presents that the most significant sensitive reaction of A1CH2OH consumption is the unimolecular initiation reaction by the CO bond breaking from A1CH2OH under both pressures. The combination of A1CH2 radicals with H atoms to form toluene (A1CH3) has the most inhibiting influence on the A1CH2OH consumption under both pressures, while it has little sensitive effects for the oxidation process of A1CH2OH consumption. The comparison of the A1CH2OH pyrolysis and oxidation results show that the peak mole fractions of A1 increase, while the peak mole fractions of phenol (A1OH) decrease with the increase of equivalence ratio (φ) under the same pressure. It should be noted that the peak mole fractions of benzaldehyde (A1CHO) are relatively stable with various conditions. These results provide a theoretical basis for further study of the combustion chemical kinetics of A1CH2OH and its application in bio alternative fuel.

SOLVING THE PROBLEM OF CONTAMINATING SMOKED FOOD WITH CARCINOGENIC COMPOUNDS OF SMOKE

Meat and fish smoked products, widely produced nowadays, occupy a permanent place in the mass diet. The consumption of smoked meat is estimated by FAO at 15.6 million tons in 2019 (+40 % growth over the past ten years). This is due to the increased incomes of consumers in many countries, which made meat and fish smoked products, once classified as "premium" delicacies, more accessible to the majority. There has been a shortage of high-quality raw materials, which, combined with a highly competitive food market, forces manufacturers to reduce their costs by using non-traditional raw materials. The latter leads to increased use of processing raw materials with smoke to effectively mask individual defects in taste, appearance and consistency of products. As a result, there is a carcinogenic contamination problem because of polyaromatic hydrocarbons (PAHs) presented in the smoke and smoking liquids, and the growth of cancer. PAHs are formed as a result of pyrolysis of wood during smoke generation at temperatures above 450-480 °C. Currently used smoke generators and schemes for cleaning smoke from PAHs are not effective enough, so they do not eliminate the main cause of PAH formation, uncontrolled pyrolysis. The principal solution to the problem is to develop methods and equipment for producing smoke at temperatures below carcinogenic peaks. A successful solution is the method for producing smoke with an infrared power supply, implemented in the design of IR smoke generator (IRSG). The device allows to reliably maintain the pyrolysis temperature of wood below 450 °C. The effectiveness of the method and apparatus is confirmed by studies of products smoked with IR-SG, in which the content of Benzo(a)pyrene is less than 0.0002 mcg/kg, which is lower than the maximum permissible concentrations of this compound in food.

Theoretical Study of the Reaction of Hydrogen Atoms with Three Pentene Isomers: 2-Methyl-1-butene, 2-Methyl-2-butene, and 3-Methyl-1-butene.

This paper presents a comprehensive potential energy surface (PES) for hydrogen atom addition to and abstraction from 2-methyl-1-butene, 2-methyl-2-butene, and 3-methyl-1-butene and the subsequent ß-scission and H atom transfer reactions. Thermochemical parameters for species on the Ċ5H11 potential energy surface (PES) were calculated as a function of temperature (298-2000 K), using a series of isodesmic reactions to determine the formation enthalpies. High-pressure limiting and pressure-dependent rate constants were calculated using Rice-Ramsperger-Kassel-Marcus theory with a one-dimensional master equation. A number of studies have highlighted the fact that C5 intermediate species play a role in polyaromatic hydrocarbon formation and that a fuel's chemical structure can be key in understanding the intermediate species formed during fuel decomposition. Rate constant recommendations for both Ḣ atom addition to, and H-atom abstraction by Ḣ atoms from, linear and branched alkenes have subsequently been proposed by incorporating our earlier work on 1- and 2-pentene, and these can be used in mechanisms of larger alkenes for which calculations do not exist. The current set of rate constants for the reactions of Ḣ atoms with both linear and branched C5 alkenes, including their chemically activated pathways, are the first available in the literature of any reasonable fidelity for combustion modeling and are important for gasoline mechanisms. Validation of our theoretical results with pyrolysis experiments of 2-methyl-1-butene, 2-methyl-2-butene, and 3-methyl-1-butene at 2 bar in a single pulse shock tube (SPST) were carried out, with satisfactory agreement observed.

Polyaromatic hydrocarbons in biochars and human health risks of food crops grown in biochar-amended soils: A synthesis study

Soil amendment with biochars is currently being studied worldwide as a sustainable agricultural practice to improve soil and water quality, increase crop productivity, and augment soil carbon storage. However, the formation of polyaromatic hydrocarbons (PAHs) during biochar production is inevitable. Therefore, it is crucial to assess the risks in food safety and human health of crops grown in biochar-amended soils. This paper performed a synthesis study of PAH concentrations in biochars and estimated the risks of soils amended with biochars, based on refereed articles published between 2012 and 2018. The PAH concentrations in biochars ranged greatly, with the dominant proportion being 2–3 ringed PAHs (40%–71%). Biochar application increased the PAH levels in soils at drastically varying extents (0.02–3574 μg/kg), which led to a broad range of PAH concentrations in food crops grown in biochar-amended soils. A five-step method was then introduced to assess the toxicity of biochar-borne PAHs to human health. The total mean incremental lifetime cancer risk for adults was estimated to range between 2.0 × 10−6–1.9 × 10−5 via direct contact with and ingestion (inhalation) of contaminated soils or consumption of tainted crops. These results indicated that biochar amendment in soils might pose potential risks to food safety and human health, but the overall cancer risks through exposure to biochar-borne PAHs in soils and food crops were low. Higher application rates (e.g. ≥20 t/ha) of biochars with high PAH contents can be avoided to minimize human cancer risks. Although biochar application in arable farmlands has many environmental and agronomic benefits, holistic and systematic approaches are required to fully assess the benefits and risks before their large-scale adoption. PAHs in biochar may be reduced by improving the biochar production process and developing a cost-effective post-manufacturing treatment.

Understanding the role of soot oxidation in gasoline combustion: A numerical study on the effects of oxygen enrichment on particulate mass and number emissions in a spark-ignition engine

The production of increasingly clean engines has become imperative. More stringent regulations for internal combustion engines are constantly proposed, and recent number-based regulations have become a new challenge, since historically only a mass-based regulation needed to be met. It is known that soot particles detectable at the exhaust of an engine are the results of the competition between the formation of soot precursor species and their oxidation. However, the attention is mainly focused on inhibiting soot precursors formation, and much less research is dedicated at elucidating the benefits achievable from enhancing soot oxidation rates. Soot oxidation can be enhanced by increasing the in-cylinder oxygen content. Oxygenated fuels, which are often added to gasoline in order to achieve more efficient combustion, can represent a possible way in the pursuit of this goal. However, chemical mechanisms are still uncertain for practical fuels, and ambiguous results can be produced when the effect of oxygenated fuels on gasoline engine combustion and soot emissions is considered. In the present study, 3-D Computational Fluid Dynamics simulations were performed and the numerical results were compared with existing experimental data, in which load increases were achieved by pure oxygen addition within the intake manifold of a single-cylinder Spark-Ignition (SI) engine. Studying the effects that an addition of 5% and 10% by volume (with respect to air) of additional oxygen produces on the combustion process, allowed to provide basic additional information on soot formation and oxidation, avoiding the uncertainties associated with chemistry models. A semi-detailed soot model and a chemical kinetic model, including poly-aromatic hydrocarbon formation, were coupled with the G-equation flame propagation model for the SI engine simulations and for predicting soot mass and particulate number density. Improvements in the modeling of gasoline premixed combustion were achieved, as well. Specifically, different approaches in the evaluation of the laminar flame speed of gasoline (which is a key factor for obtaining reliable SI engine simulations) were critically compared and analyzed. The numerical results showed aspects that were not possible to appreciate by only referring to the experimental results on which this work was based. It was possible to observe that the higher soot concentrations were located in regions characterized by lower temperatures and lower OH concentrations. Oxygen addition favored a faster burning velocity and produced higher in-cylinder temperatures. However, the production rates of both OH radicals and soot precursor species resulted enhanced. The analysis of these concurrent phenomena allowed to explain why in the experiments the soot mass per kg of fuel was lower for the oxygenated combustion cases.

Identification, Quantification and <i>In-Vitro</i> Genotoxicity of Major Polyaromatic Hydrocarbons Produced by Sugarcane Fly Ash Emitted from Sugarmill

Sugarcane burning during harvest and non-harvest season emits various pollutants like volatile organic compounds (VOCs), alkanes, and PAHs (Polyaromatic hydrocarbons) in the surrounding environment. Among these pollutants, PAHs are of uttermost concern due to their high level of toxicity. Burning of sugarcane bagase in sugar mill results in the production of fly ash. Fly ash is produced as a result of sugarcane bagasse burning in sugar mills. In present study, fly ash that comes out from the sugar mill chimney was collected from Western Uttar Pradesh, India and used for further analysis. High temperature and incomplete combustion inside chimney lead to the formation of PAHs. Extraction of PAHs present in fly ash samples was done by ultrasonication method and was identified with GC-FID (gas chromatography-flame ionization detector). Results exhibit the presence of eight PAHs in fly ash samples where the Benzo(a)pyrene and Naphthalene were found to be in high concentration. Furthermore, we have evaluated toxic effects of fly ash and Polyaromatic hydrocarbons (Standard of BaP & Nap) through different methods i.e. MTT, ROS and comet assay. Significant reduction (p < 0.001) in cell viability was noted in cells treated with fly ash as compared to control. Fly ash samples were also found to induce significant oxidative stress in HeLa cells, which ultimately causes DNA damage. Therefore, it may be concluded that the fly ash samples are toxic to the environment due to the presence of PAHs. Hence, the present study plays an important role in determining the harmful effects of PAHs and their source of occurrence.

Tocopherols and Polyphenols in Pumpkin Seed Oil Are Moderately Affected by Industrially Relevant Roasting Conditions

Traditionally, pumpkin seed oil is obtained by pressing the seeds after a roasting pretreatment, at temperatures up to 150 °C. However, the appropriate temperatures and roasting times are under discussion. In this study, oils from seeds roasted at different temperatures (60–150 °C) are compared with oil from non‐roasted seeds. At higher roasting temperatures, lower roasting times are required to release the oil. Both, for tocopherols and phenolic compounds, no decreasing trend with the increasing roasting temperature are observed. In contrast, the oil from non‐roasted seeds have relatively low levels of tocopherols and phenolics and lacked the typical aroma. Levels of polyaromatic hydrocarbons (PAHs) are very low, ranging from not detected in oil from non‐roasted seeds to 13.8 μg kg−1 in the oil from seeds roasted at 150 °C. Therefore, the choice between the studied roasting conditions may depend rather on sensory evaluations than on the content of antioxidants or of PAHs. Practical Applications: The process of the production of virgin pumpkin oil is based on a thermal treatment of the ground seeds, favoring the separation of the lipid fraction, and giving a typical aroma of the roasted oil. Results of this research provide important information regarding the influence of roasting conditions on the quality and safety of the oil. Roasting pumpkin seeds increased the tocopherol and phenols content in the pumpkin oil, with no significant formation of PAHs. The information will be valuable and important for not only for the pumpkin oil production, but also for all the seeds submitted to a roasting treatment before extraction.Pumpkin seed oil is traditionally produced in several European countries and commonly used in salad dressing. The production of pumpkin seed oil frequently includes roasting of the seeds at high temperatures, which may influence the amount of phenolic compounds and the final nutritional quality of the oil. The roasting of the pumpkin seeds is necessary to obtain the desired color, flavor, and taste characteristics. At higher roasting temperatures, lower roasting times are required to release the oil. Both, for tocopherols and phenolic compounds, no decreasing trend with the increasing roasting temperature is observed.

Investigation of n-pentane pyrolysis at elevated temperatures and pressures in a variable pressure flow reactor

Thermally cracking fuel in a fuel processing facility or undergoing pyrolysis in the anode channel of a fuel cell can lead to coke deposition. The formation of coke occurs via chemical kinetic pathways that are largely dependent on poly aromatic hydrocarbons (PAHs). The formation of PAH⿿s largely depends on species which include ethylene, acetylene, butadiene, benzene and toluene. Pentane is a relatively simple structure for modeling purposes, yet large enough that it produces some of the relevant chemistry of real fuels. Experiments were conducted in a newly designed variable pressure flow reactor (VPFR) built to process both liquid and gaseous reactants at pressures to 4.0MPa and temperatures to 1373K. The VPFR was initially validated via ethane pyrolysis experiments and comparing the results with existing literature data. Pentane experiments were done over a range of temperatures (923⿿1073K), pressures (1⿿2.0MPa) and residence times (30ms⿿40s). The product selectivity appeared to be greatest influenced by pressure and level of fuel conversion. Pressure increases ethylene production but has an inverse effect on ethane production. Soot precursors appeared at higher levels of conversion. The results of the experiments were compared to an existing chemical kinetic mechanism with good agreement.

PAHs formation simulation in the premixed laminar flames of TRF with alcohol addition using a semi-detailed combustion mechanism

Abstract Toluene reference fuel (TRF) is a kind of surrogate fuel for diesel. Clarifying the combustion mechanism of TRF is a key to understand the combustion of diesel. Alcohols are added into diesel to reduce the soot emission from engines. The formation mechanism of soot precursors, i.e., polyaromatic hydrocarbons (PAHs), in the premixed laminar flames of TRF, methanol-TRF blend, ethanol-TRF blend, and n- butanol-TRF blend were investigated experimentally and theoretically. A partly reduced n- butanol combustion mechanism, including the sub-mechanism of methanol and ethanol, and a partly reduced soot formation mechanism were merged into a partly reduced mechanism of TRF to simulate the combustion of the TRF-alcohol blends. Additions of methanol, ethanol, and n- butanol can reduce the mole fractions of the PAHs in TRF flames at an equivalence ratio of 2.0. The mole fractions of the PAHs in the flames are in the order of n- butanol-TRF

Kinetic model of gas-phase reactions in the chemical vapor deposition of propane

The chemical kinetics of propane pyrolysis in chemical vapor deposition (CVD) is investigated in 1074 reactions consisting of 285 species to understand chemistry of CVD from propane. The reaction mechanism is modeled in a perfectly stirred reactor and a continuous tubular reactor, to produce a 0-D and a 1-D propane pyrolysis model, respectively. The concentration profiles of gas-phase products in the axial direction of the reactor as functions of temperature and residence time are computed with the DETCHEM software package designed for computing time-dependent homogeneous reactions. Comparison between simulated and experimental results shows that the mechanism gives the formation pathway for all major products and can predict the concentration profiles of minor products. Main reaction paths and crucial reaction steps have been determined at 1248 K for 1s by analyzing the flux of the main products. The significant roles of radicals such as propargyl, cyclopentadienyl and indenyl in the formation of polyaromatic hydrocarbons were discussed. [New Carbon Materials 2013, 29(1): 67–77]

Formation of carcinogenic PAHs (polyaromatic hydrocarbons) in the turbulent diffusive flame

The paper is devoted to the investigation of forming the PAH spectrum in the process of turbulent diffusion combustion of a propane butane mixture. The parameters that influence the oxidation of hydrocarbons and basic PAHs are generalized in terms of the process of mixing, diffusion, chemical kinetics. Areas of intensive formation of the PAH spectrum are revealed.

Development of an n-heptane/toluene/polyaromatic hydrocarbon mechanism and its application for combustion and soot prediction

A chemical reaction mechanism has been developed for modeling the combustion process and polyaromatic hydrocarbon formation of diesel and n-heptane/toluene fuels. A reduced n-heptane/polyaromatic hydrocarbon mechanism was applied and updated to better predict the formation of polyaromatic hydrocarbon up to four rings (A4) in ethylene and n-heptane premixed flames. In addition, a reduced toluene mechanism was updated and combined with the n-heptane/polyaromatic hydrocarbon mechanism to predict the combustion and polyaromatic hydrocarbon formation of diesel and n-heptane/toluene fuels. The final mechanism consists of 71 species and 360 reactions. This mechanism was validated with experimental ignition delay data in shock tubes, premixed flame species concentration profiles, homogeneous charge compression ignition combustion and direct injection spray combustion data. A practical multistep soot model was integrated with the polyaromatic hydrocarbon kinetic model to predict soot emissions of diesel and n-heptane/toluene direct injection engine data. Constant-volume combustion vessel simulations were also conducted and the effects of combustion parameters, such as temperature and equivalence ratio, together with the n-heptane/toluene ratio on polyaromatic hydrocarbon and soot formation are discussed. The results show that the present mechanism provides promising agreement in terms of polyaromatic hydrocarbon prediction for various fuels in premixed flames and highlights the importance of aromatics on the polyaromatic hydrocarbon formation and soot emissions. Homogeneous charge compression ignition combustion and direct injection spray combustion simulation results confirm that the present mechanism gives reliable predictions of combustion and soot emissions for both diesel and n-heptane/toluene fuels under various conditions.

Composition of in situ burn residue as a function of weathering conditions

Troll B crude oil was weathered under Arctic conditions with different ice coverage: open water, 50% ice and 90% ice. Samples (100mL) were taken during the experiment and tested for ignitability in a burning cell. From each burning a residue sample was taken for analysis. The burning process removed the light compounds eluting before C13. No effect from the prior weathering time or the different ice coverage was seen in the burn residue composition. The content of selected Poly Aromatic Hydrocarbons (PAHs) was determined and it was noted that the concentration of PAHs with more than 4 rings were increased. The source origin of the PAHs was investigated by use of relative ratios of PAH isomers and indicated that some formation of PAHs was additionally taking place during burning.

Effect of ethanol on the chemistry of formation of precursors of polyaromatic hydrocarbons in a fuel-rich ethylene flame at atmospheric pressure

The effect of the addition of ethanol (EtOH) to the initial combustible mixture on the concentration of various compounds, in particular, those preceding the formation of polyaromatic hydrocarbons in a fuel-rich (equivalence ratio of fuel ϕ = 1.7) flat premixed ethylene/oxygen/argon flame at atmospheric pressure was studied experimentally and by numerical modeling using a detailed mechanism of chemical reactions. Concentrations of various stable and labile species, including reactants, major combustion products, and intermediates in C2H4/O2/Ar and C2H4/EtOH/O2/Ar flames were measured along the height above the burner using molecular beam mass spectrometry. Experimental mole fraction profiles were compared with those calculated using the previously proposed mechanisms of chemical reactions. This mechanism was analyzed to determine the cause of the ethanol effect on the flame concentration of propargyl, the main precursor of polyaromatic hydrocarbons.