Formation Of Aromatic Hydrocarbons Research Articles

Real Gas Effects in High-Pressure Ignition of n-Dodecane/Air Mixtures.

This work studies the real gas effects on the autoignition of hydrocarbon fuels under high pressures, using normal dodecane (n-dodecane) as the representative fuel and the Redlich-Kwong equation of state (EoS) as the real gas description. It is demonstrated that the real gas description yields a shorter ignition delay time (IDT) compared with the ideal gas description, especially in low-temperature regimes which could encompass the negative temperature coefficient (NTC) phenomena and has a stronger dependence on the molecular volume than the attractive potential. The study further shows that high pressure facilitates low-temperature reaction pathways, where the compressibility factors of key reactants contribute to real gas effects. Moreover, the results suggest that accounting for real gas behavior leads to an increase in the formation of polycyclic aromatic hydrocarbons (PAHs), which, in turn, promotes soot generation.

Mechanism, Formation and Transport of Polycyclic Aromatic Hydrocarbons (PAHs) in Fruits, Vegetables and Fresh Fish Species in Africa: A Systematic Review of its Health Risk

Mechanism, Formation and Transport of Polycyclic Aromatic Hydrocarbons (PAHs) in Fruits, Vegetables and Fresh Fish Species in Africa: A Systematic Review of its Health Risk

Relationship between Flavonoid Chemical Structures and Their Antioxidant Capacity in Preventing Polycyclic Aromatic Hydrocarbons Formation in Heated Meat Model System.

The relationship between the chemical structures of six flavonoids and their abilities to inhibit the formation of polycyclic aromatic hydrocarbons (PAHs) in a heated meat model system was investigated. The PAH8 forming in samples was analyzed by using QuEChERS coupled GC-MS. Inhibitory effects of PAHs were myricetin (72.1%) > morin (55.7%) > quercetin (57.3%) > kaempferol (49.9%) > rutin (32.7%) > taxifolin (30.2%). The antioxidant activities of these flavonoids, assessed through (1, 1-diphenyl-2-picrylhydrazyl) free radical scavenging activity assay (DPPH), [2,2'-azinobis (3-ethylbenzothiazoline-6-sulphonic acid)] free radical scavenging activity assay (ABTS) and ferric ion reducing antioxidant power assay (FRAP) assays, exhibited a significant negative correlation with PAH reduction. Notably, myricetin that contained three hydroxyl groups on the B-ring, along with a 2,3-double bond in conjugation with a 4-keto moiety on the C-ring, demonstrated strong antioxidant properties and free radical scavenging abilities, which significantly contributed to their ability to inhibit PAH formation. However, rutin and taxifolin, substituted at the C-3 position of the C-ring, decreased the PAH inhibitory activity. The ABTS assay proved the most effective in demonstrating the correlation between flavonoid antioxidant properties and their capacity to inhibit PAH formation in heated meat model systems. Thus, the inhibition of PAHs can be achieved by dietary flavonoids according to their chemical structures.

Depolymerization of PMMA-Based Dental Resin Scraps on Different Production Scales

This research explores the depolymerization of waste polymethyl methacrylate (PMMAW) from dental material in fixed bed semi-batch reactors, focusing on three production scales: laboratory, technical and pilot. The study investigates the thermal degradation mechanism and kinetics of PMMAW through thermogravimetric (TG) and differential scanning calorimetry (DSC) analyses, revealing a two-step degradation process. The heat flow during PMMAW decomposition is measured by DSC, providing essential parameters for designing pyrolysis processes. The results demonstrate the potential of DSC for energetic analysis and process design, with attention to standardization challenges. Material balance analysis across the production scales reveals a temperature gradient across the fixed bed negatively impacting liquid yield and methyl methacrylate (MMA) concentration. Reactor load and power load variables are introduced, demonstrating decreased temperature with increased process scale. The study identifies the influence of temperature on MMA concentration in the liquid fraction, emphasizing the importance of controlling temperature for efficient depolymerization. Furthermore, the research highlights the formation of aromatic hydrocarbons from the remaining char, indicating a shift in liquid composition during the depolymerization process. The study concludes that lower temperatures below 450 °C favor liquid fractions rich in MMA, suggesting the benefits of lower temperatures and slower heating rates in semi-batch depolymerization. The findings contribute to a novel approach for analyzing pyrolysis processes, emphasizing reactor design and economic considerations for recycling viability. Future research aims to refine and standardize the analysis and design protocols for pyrolysis and similar processes.

Превращение комбинированного сырья на цеолитсодержащих катализаторах

The article discusses the ways of rational use of hydrocarbon raw materials in order to obtain isoparaffin and aromatic hydrocarbons. The possibilities of joint processing of the 75-100°C fraction have been studied from gas condensate and propane-butane fraction (PBF) in an anhydrous environment and in the presence of a modified zeolite-containing catalyst. The regularities of the yield of aromatic and isoparaffinic hydrocarbons of the anhydrous process of catalytic conversion of combined hydrocarbon raw materials on a zeolite-containing Pt/Beta catalyst modified by 0.5% wt have been established platinum. So, when converting a fraction of 75-100°C. With a temperature range of 300-350°C, the content of isoparaffins in liquid products increases by more than 20% by weight. A further increase in temperature is accompanied to a greater extent by the formation of aromatic hydrocarbons. The total content of benzene, toluene, xylenes is about 20% by weight. Similar trends are observed when testing the propane-butane fraction. The greatest increase in isoparaffin hydrocarbons is also observed at a temperature of 300°C. Their content in liquid and gaseous products increases by an average of 10%. The main share in this process is accounted for by iso-butane. Accordingly, an increase in the reaction temperature by 100°C increases the formation of benzene and toluene by 11% by weight. More significant results were obtained during the joint transformation of the 75-100°C fraction and the propane-butane fraction. At a reaction temperature of 300°C, a high content of iso-butane is observed in gaseous products, which allows them to be involved in petrochemical processes. The content of isoparaffins in liquid products increases by 50% by weight, which makes them valuable as a high-octane component of motor fuels. Favorable temperatures for the production of aromatic hydrocarbons are 400°C and above.

Investigation of flame structure and emission production: Combustion modeling of co-flow interaction with spray

Using a validated computational approach, the present study examines the flame structure and emission production by spray combustion in an unconfined, swirl-free lab burner. Some species, such as acetylene, a precursor to the formation of polycyclic aromatic hydrocarbons, are generated within the fuel-rich region. A smaller area of the enclosed region reduces the mass concentration of emissive species. This can be accomplished by modifying the operating conditions, such as the spray characteristics, macro-flow velocity, and nozzle geometry. Increasing the co-flow velocity has a significant effect on transforming the flame structure from a single-reaction regime to a double-structure regime. The fuel-rich area shrinks as the co-flow velocity increases, resulting in a decrease in emissive species but a fall in total heat generation. In terms of air passage design, it appears that altering the air passage area has a noticeable impact on the flame structure, where a reaction zone can be established within the flame core. Depending on the equivalence ratio, the total heat generation and output emissions can be modified through the burner air passage improvement, resulting in a 90% decrease in the production of emissive species and an 18% increase in total heat production.

A systematic study on the chemical model of polycyclic aromatic hydrocarbons formation from nutrients (glucose, amino acids, fatty acids) in food

Polycyclic aromatic hydrocarbons (PAHs), prominent carcinogens formed during food processing, pose health risks through long-term consumption. This study focuses on 16 priority PAHs in the European Union, investigating their formation during pyrolysis. Glucose, amino acids and fatty acids are important food nutrients. To further explore whether these nutrients in food form PAHs during heating, a single chemical model method was used to heat these nutrients respectively, and GC–MS/MS was used to identify and quantify the obtained components. Glucose is the most basic nutrient in food, so the influence of water, pH, temperature and other factors on the formation of PAHs was studied in the glucose model. At the same time, the models of amino acids and fatty acids were used to assist in improving the entire nutrient research system. According to our results, some previously reported mechanisms of PAHs formation by fatty acids heating were confirmed. In addition, glucose and amino acids could also produce many PAHs after heating, and some conclusions were improved by comparing the intermediates of PAHs from three types of nutrients.

Experimental and modeling study of fuel-rich oxidation of gasoline surrogate components/dimethyl carbonate blends in an atmospheric flow reactor

Fuel-rich oxidation of blending fuels consisting of three typical gasoline surrogate components (n-heptane, iso-octane, and toluene) and dimethyl carbonate (DMC) was investigated in an atmospheric-pressure flow reactor at mean gas temperatures from 1000 to 1350 K, equivalence ratio of 9.0, and residence time of 1.2 s. Blending ratios of DMC were 35 and 70 % on a molar basis. The mole fractions of not only polycyclic aromatic hydrocarbons (PAHs) up to 3 ring structure but also small intermediate species from C1 to C5 contained in sampled gas were experimentally quantified. A kinetic model that includes not only oxidation mechanism of gasoline surrogate components and DMC but also PAH growth reactions was developed to reproduce the experimental data. The experimental and simulated results showed that the blending effect of DMC on PAH production was different according to gasoline surrogate components. By blending DMC with n-heptane and iso-octane, the mole fractions of PAHs were generally reduced with an increase of the DMC blending ratio in the temperature range studied here. On the other hand, when DMC was blended with toluene, PAH production in the blending fuels was larger than that in pure toluene at a temperature below 1150 K, while the mole fractions of PAHs in pure toluene were identical to or larger than those in the blending fuels at a temperature above 1200 K. Because a reactivity of DMC is higher than toluene, toluene conversion was facilitated at a low temperature, leading to the promoted PAH production in the blending fuels compared to pure fuel. However, such a promoting effect of DMC was diminished at an elevated temperature, explaining the identical or large PAH production in neat toluene compared to the blending fuels. On the other hand, n-heptane and isooctane can be easily reacted even at a low temperature, suggesting that the promoting effect of DMC cannot be observed. This study reasonably succeeded in explaining the different DMC blending effects on PAH formation depending on the gasoline surrogate components. Novelty and significance statementExperiments and kinetic modeling for the mixtures consisting of dimethyl carbonate (DMC) and gasoline surrogate components, such as n-heptane, iso-octane, and toluene, were conducted to reveal the blending effect of DMC on polycyclic aromatic hydrocarbon (PAH) formation under the fuel-rich environment. It was found that DMC had a dilution effect in n-heptane/DMC and iso-octane/DMC blends, resulting in a reduction in PAH production with an increase of a DMC blending ratio. On the other hand, while DMC had the dilution effect in the toluene/DMC blend at an elevated temperature similar to other blends, toluene conversion was facilitated in the presence of DMC at a low temperature, resulting in the enhanced PAH production in the toluene/DMC blends compared to pure toluene.

Effect of lignin on the formation of polycyclic aromatic hydrocarbons in smoked and grilled meat products

In order to explore the influence of wood types on formation of polycyclic aromatic hydrocarbons (PAHs) in traditional smoked and grilled meat products, the effect of lignin in woods on formation of PAHs was investigated in meat model systems. The results showed that PAHs formation was much dependent on the heating conditions. The addition of lignin led to significantly increased PAHs, which being connected with lignin structure. In comparison, the formation of PAHs was more facilitated by lignin with G structure than that with G/S structure. However, further study of adding lignin precursors demonstrated that lignin precursors with S structure were more favorable to the formation of PAHs than those with G structure. It was proposed that the relative content and activity of G/S structure of lignin in wood played a significant role in the formation of PAHs, which might provide theoretical reference for inhibition of PAHs fundamentally.

Compact and accurate chemical mechanism for methane pyrolysis with PAH growth

A reliable and compact chemical mechanism of gas-phase methane pyrolysis leading to formation of large polycyclic aromatic hydrocarbon (PAH) molecules has been developed. This model is designed for studies of carbon nanostructure synthesis such as carbon black and graphene flakes, including soot growth kinetics. Methane pyrolysis with carbon nanostructure synthesis is a two-stage process where conversion of CH4 to C2H2 precedes the growth of PAH molecules from acetylene. We present a single chemical mechanism that accurately describes both stages. We have constructed a compact and accurate chemical mechanism capable of modeling both stages of methane pyrolysis based on the ABF [1] mechanism which was expanded with the most prominent reaction pathways from the mechanism by Tao [2] for small PAH molecules and HACA pathways for larger PAH molecules, up to 37 aromatic rings. The resulting mechanism was validated through comparison to multiple available sets of experimental data. Good agreement with the experimental data for both processes was obtained. Performance of the mechanism was tested for pyrolysis of methane-rich mixtures under long residence times leading to abundant formation of PAH molecules. It is shown that the inclusion of larger PAH species (up to A37) in the chemical mechanism is important for accurate prediction of the fraction of carbon converted to PAH molecules and, correspondingly, the residual fraction of acetylene in the mixture. The mechanism file is available upon request.

External standard calibration method for high-repetition-rate shock tube kinetic studies with synchrotron-based time-of-flight mass spectrometry.

The signal levels observed from mass spectrometers coupled by molecular beam sampling to shock tubes are impacted by dynamic pressures in the spectrometer due to rapid pressure changes in the shock tube. Accounting for the impact of the pressure changes is essential if absolute concentrations of species are to be measured. Obtaining such a correction for spectrometers operated with vacuum ultra violet photoionization has been challenging. We present here a new external calibration method which uses VUV-photoionization of CO2 to develop time-dependent corrections to species concentration/time profiles from which kinetic data can be extracted. The experiments were performed with the ICARE-HRRST (high repetition rate shock tube) at the DESIRS beamline of synchrotron SOLEIL. The calibration experiments were performed at temperatures and pressures behind reflected shock waves of 1376 ± 12 K and 6.6 ± 0.1 bar, respectively. Pyrolytic experiments with two aromatic species, toluene (T5 = 1362 ± 22 K, P5 = 6.6 ± 0.2 bar) and ethylbenzene (T5 = 1327 ± 18 K, P5 = 6.7 ± 0.2 bar), are analyzed to test the method. Time dependent concentrations for molecular and radical species were corrected with the new method. The resulting signals were compared with chemical kinetic simulations using a recent mechanism for pyrolytic formation of polycyclic aromatic hydrocarbons. Excellent agreement was obtained between the experimental data and simulations, without adjustment of the model, demonstrating the validity of the external calibration method.

Experimental and kinetic modeling of soot formation in counterflow non-premixed flames of surrogate fuel components: n-dodecane and iso-dodecane

Normal dodecane (n-C12) and iso-dodecane (i-C12) are often used as components for surrogate mixtures of aviation and diesel fuels. Although studies have been performed to understand the combustion and spray behavior of dodecane isomers, the soot formation from the combustion of n- and i-C12 in non-premixed flames is not well studied. In this work, soot volume fraction (SVF) profiles of n- and i-C12 were measured across a wide range of strain rates and mixture conditions in a counterflow burner facility at the University of Connecticut. Neat and binary mixtures of n- and i-C12 were investigated to study the influence of alkane branching on soot formation. A soot model was developed and validated in this study by extending the detailed kinetic model developed at the Lawrence Livermore National Laboratory (LLNL) for the formation of polycyclic aromatic hydrocarbons (PAHs) to simulate soot formation and growth based on the discrete sectional method. Additional gas phase reactions forming pyrene and ring enlargement reactions were added to the existing PAH model. The LLNL kinetic model was validated with SVF data obtained in this work for n-C12 and i-C12 flames along with data available in literature for ethylene, iso-butene, n-heptane, and iso-octane. The soot precursor reactions added in this work were found to play a critical role in simulating the experimentally observed non-linear trend of the peak SVF with increased branched alkanes. Reaction path analysis was conducted to illustrate the fuel structure effects on soot formation pathways in n- and i-C12 mixtures. In view of the satisfactory agreement between modeling results and experimental data, as well as capturing the non-linear variation in peak SVF with the alkane branching for the first time, further investigation within the framework of the soot model is discussed and critical insights are provided into the reaction pathways which require further attention.

Bio-Oil Upgrading over ZSM-5 Catalyst: A Review of Catalyst Performance and Deactivation

Due to population explosion and industrialization, waste biomass and polymer conversion into biofuel has attracted the interest of researchers. The application of the ZSM-5 catalyst for bio-oil upgrading into renewable biofuels has attracted researchers’ efforts as an excellent catalyst. The need for improved biofuel quality with reduced oxygenates has further necessitated the application of catalyzed upgrading techniques. The catalytic performance of the ZSM-5 catalyst was attributed to its exceptional pore structure and window architecture and when it is incorporated with some selected transition metals to improve aromatic hydrocarbon formation. The review revealed that the development of coke deposit on the microspores of the ZSM-5 catalyst hindered the effective transport of large molecular compounds into the active sites for an easy deoxygenation process. Hence, the introduction of mesoporosity, hybrid catalyst development, and tailored crystal growth on the ZSM-5 catalyst could address several hindrances associated to conventional ZSM-5. Therefore, the need for catalyst modification is paramount for ZSM-5 performance during bio-oil upgrading.

Cellulose pyrolysis under NH3 atmosphere for levoglucosan and pyrrole: An experimental and theoretical study

Cellulose pyrolysis for valuable levoglucosan (LG) can improve the value of cellulose utilization. Here, NH3 was introduced into cellulose pyrolysis by a fixed-bed system to investigate the effect of NH3 on the formation of LG and pyrrole, and the reaction pathways of LG and pyrrole formation were explored by combining experimental results with DFT calculations. Results showed that the highest CO yield reached 147.66 mL/g at 800 °C. The yields of H2 and CH4 significantly increased, while CO2 yield decreased. NH3 increased the content of oxygen-containing substances while inhibiting the formation of aromatic and aliphatic hydrocarbons. In addition, some nitrogen-containing products were generated, and their content increased with increasing temperature, among which, the nitrogen-containing products were mainly pyrroles. The content of LG increased about two times, and its absolute yield reached 10.96 wt% at 600 °C, which was about 4.6 times that of direct pyrolysis. DFT calculations showed that NH3 had a promoting effect on cellulose pyrolysis to produce LG, and the reaction energy barrier of the optimal pathway is 194.05 kJ/mol. Cellobiose is transferred to the glycosidic bond O-site by hydrogen transfer from the C2-site to break the glycosidic bond to form the intermediate a4-i1 and glucose. The intermediate a4-i1 was combined with NH3 to form LG via hydrogen transfer, while the resulting glucose was dehydrated to form LG by combining with NH3. For the pathway of cellulose pyrolysis to form pyrrole, NH3 promoted the deoxidation of FF to form furan, and the combination of NH3 with furan promoted furan to undergo a ring-opening reaction more than that of H2O. After the ring opening, the C2 position amino group was linked to the C5 position to form a ring, and the O atom was removed by dehydration with the formation of a hydroxyl group to form pyrrole. The reaction energy barrier for cellulose pyrolysis to form pyrrole under an NH3 atmosphere was 280.08 kJ/mol. It provided a new approach for the preparation of LG and pyrrole from cellulose.

Pyrolysis–gas chromatography of hybrid rocket fuel comprising low-melting-point thermoplastics

Solid fuels comprising low-melting-point thermoplastics (LTs) have been developed as hybrid rocket fuels. However, it is necessary to improve the regression rate of such fuels for practical application. In this study, the pyrolysis mechanism of an LT fuel in the absence of oxygen was investigated and the combustion-inhibition species among the gaseous pyrolysis products were identified. Pyrolysis–gas chromatography was used to analyze the hydrocarbon compounds produced from the pyrolysis of the LT fuel and its constituents. Detailed chemical reaction simulations were performed to dissect the pyrolysis mechanism of paraffin oil, the principal constituent of the LT fuel. The results revealed that the pyrolysis and evaporation of the fuel components yield aromatic hydrocarbons and polycyclic aromatic hydrocarbons (PAHs), which reduces fuel combustion. Notably, the C2H4 generated during paraffin pyrolysis considerably amplified the formation of aromatic hydrocarbons and PAHs, further inhibiting combustion. C2H4 was also identified as one of the potential chemical species that inhibit combustion. The C2H4 ratio in the fuel pyrolysis gas can be considered as an indicator for evaluating fuel compositions that enhance the fuel regression rate.

Effect of beef patties fortification with black garlic on the polycyclic aromatic hydrocarbons (PAHs) content and toxic potency.

Nine different black garlic samples aged at varying temperatures and durations were added to the patties at 0.5% and 1% ratios and compared with raw garlic in terms of polycyclic aromatic hydrocarbons (PAHs) formation. The results showed that black garlic caused a reduction in the patties' content of ∑PAH8 by 38.17% to 94.12% compared to raw garlic, with the highest reduction percent in the patties fortified with 1% black garlic aged at 70°C for 45days. Beef patties fortified with black garlic reduced human exposure to PAHs from beef patties (from 1.66E to 01 to 6.04E-02ng-TEQBaP kg-1 bw per day). The negligible cancer risk associated with exposure to PAHs through the consumption of beef patties was confirmed by very low ILCR (incremental lifetime cancer risk) values of 5.44E-14 and 4.75E-12. Finally, patty fortification with black garlic could be suggested as an effective way to reduce PAHs formation and exposure from patties.

Catalytic and non-catalytic low-pressure hydrothermal liquefaction of pinewood sawdust, polyolefin plastics and their mixtures

Hydrothermal co-liquefaction of biomass and polyolefin plastic feedstocks offers the advantage of potential synergistic reaction environments for producing liquid products of high fuel quality. In this present study, hydrothermal liquefaction and co-liquefaction of sawdust, low-density polyethylene and high-density polyethylene were investigated in a batch reactor from 350 °C to 450 °C and autogenic pressures below 30 bar. The novel low-pressure hydrothermal processing method was carried out with and without low-cost Ni–Cu/Al2O3 bimetallic catalyst. Thermal degradation of the sawdust started at 350 °C, whereas the plastics could only completely degrade at 450 °C, which was then chosen as the optimum reaction temperature. The catalysed process led to an increase in oil yield from the sawdust, with carbon enrichment by 16.3% and 22% deoxygenation. Furthermore, the catalyst promoted the formation of ketones and aromatic hydrocarbons, while consuming phenols and furfural in the sawdust-derived bio-oils. For the plastics, the catalyst, gave slight decreases in oils yield in favour of gas and/or char formation, with the promotion of in situ hydrogenation to enhance the yields of alkanes over alkenes. Results from hydrothermal co-liquefaction tests showed that synergistic interactions occurred between the degradation products of sawdust and the plastics. The observed synergy was further promoted by the presence of the catalyst, leading to dramatic deoxygenation of the oil products to produce hydrocarbon-rich fuels with less than 4 wt% oxygen contents (≈90% deoxygenation). This low-pressure hydrothermal co-liquefaction process is an efficient and cost-effective pathway for single-loop conversion of widely available biomass and plastics feedstocks into highly deoxygenated oils for use as sustainable fuels.

Astrochemical Modeling of Propargyl Radical Chemistry in TMC-1

Recent detections of aromatic species in dark molecular clouds suggest that formation pathways may be efficient at very low temperatures and pressures, yet current astrochemical models are unable to account for their derived abundances, which can often deviate from model predictions by several orders of magnitude. The propargyl radical, a highly abundant species in the dark molecular cloud TMC-1, is an important aromatic precursor in combustion flames and possibly interstellar environments. We performed astrochemical modeling of TMC-1 using the three-phase gas-grain code NAUTILUS and an updated chemical network, focused on refining the chemistry of the propargyl radical and related species. The abundance of the propargyl radical has been increased by half an order of magnitude compared to the previous GOTHAM network. This brings it closer in line with observations, but it remains underestimated by 2 orders of magnitude compared to its observed value. Predicted abundances for the chemically related C4H3N isomers within an order of magnitude of observed values corroborate the high efficiency of CN addition to closed-shell hydrocarbons under dark molecular cloud conditions. The results of our modeling provide insight into the chemical processes of the propargyl radical in dark molecular clouds and highlight the importance of resonance-stabilized radicals in polycyclic aromatic hydrocarbon formation.

Inhibitory effects of longan seed extract on polycyclic aromatic hydrocarbons formation and muscle oxidation in baked mutton kebabs

Longan seeds, rich in phenolic compounds with antioxidant properties, are an underestimated by-product of longan processing. Polycyclic aromatic hydrocarbons (PAHs), which are carcinogenic and mutagenic, are produced during the cooking of meat products at high temperatures. The effects of different concentrations of longan seed extract (LSE, 0.2, 0.6, 1.0 mg/mL) on the formation of PAHs and muscle oxidation in mutton kebabs were investigated. Mutton kebabs were baked at 150, 200, 250 °C for 20 min, respectively, and the contents of PAHs, the degree of lipid and protein oxidation were evaluated. The results showed that LSE exhibited positive effects in inhibiting total PAHs formation (range from 14.9 to 48.8 %), decreasing the thiobarbituric acid reactive substances (TBARS) values (range from 17.1 to 39.1 %), reducing carbonyl content (range from 22.0 to 51.2 %) and increasing sulfhydryl content (range from 18.6 to 51.8 %). This study provided a guidance and potential solution for reducing the content of PAHs and muscle oxidation levels in baked meat.

Analysis of key intermediates in the growth of polycyclic aromatic hydrocarbons using the parameter-selected merged model

Soot, a by-product of incomplete combustion of organic fuels, can cause engine exhaust blockage, affect engine performance, and increase fuel consumption. Regulations have been introduced to reduce soot emissions, and studying the formation and growth of polycyclic aromatic hydrocarbons (PAHs) is essential to achieve this. Having a sub-model with sufficient PAH targets and understanding the key intermediates in the growth paths of PAHs is important for constructing a comprehensive model from fuel to PAHs. This enables the fuel pyrolysis or oxidation sub-models to interface effectively with the PAHs generation. The species in the 6 basic models, which target toluene, o-xylene, xylenes, trimethylbenzenes, indene, and α-methyl-naphthalene, were represented using the IUPAC Standard InChI (InChI) and their structural features were extracted using RDKit in Python. Then, 6 merged models were created by merging the same species and reactions in the 6 basic models based on 6 different parameter selection orders, resulting in a sub-model with 1376 species that includes 11 priority PAHs. The DRGEP method was used to simplify the 6 merged models and identify the key intermediates involved in the generation of benzene, which is considered as the key aromatic compound in the growth pathway of PAHs. A total of 91 species were obtained, present in both the 6 basic models and the 6 simplified models, and the performance of the merged models was evaluated based on the peak concentration results of these species. The selected merged model was further simplified using the DRGEP method with different targets to identify the key intermediates involved in the generation of the 11 priority PAHs. Through a comprehensive analysis of species based on 6 basic models, a conclusion was drawn that 32 C2-C4 hydrocarbon species are essential intermediates in the growth pathway of 11 discussed priority PAHs.