Pyrolysis Of N-decane Research Articles

Kinetic study of H-abstraction and preliminary pyrolysis of n-decane in post-injection fuels

The combustion and pyrolysis process of n-decane was investigated via quantum chemical method to enhance the understanding of post-injection fuels. The hydrogen abstraction reactions were the main reactions that initiated combustion and pyrolysis of n-decane via H atoms and CH3/OH/NO2 radicals. The potential energy surface of hydrogen abstraction and preliminary pyrolysis was determined via high precision CBS-QB3 and M06–2X/6–311++G (d,p) methods. RRKM - Master Equation theory had been utilized to calculate the rate constants of isomerization and β-dissociation reactions in the temperature range of 300–2000 K. In this PES, the ε-site was the most advantageous site in contrast with others and the α-site has the highest energy barrier and was the most challenging hydrogen abstraction site. The isomerisation reactions of decyl radicals play a crucial role in the combustion and pyrolysis of n-decane at low temperature, particularly via 1,5-H shift and 2,5-H shift reaction. At high temperatures, the scission of the CC bond becomes the primary mechanism. Additionally, modified information was incorporated into the detailed model of n-decane combustion and pyrolysis. The modified model exhibited good agreement with experimental measurements of the mole fractions of various significant products in Jet-stirred reactor (JSR) experiments. The research provides a foundation for future investigations of n-decane combustion and pyrolysis support.

A theoretical calculation and kinetic modeling analysis of H-abstraction from 1-octene for subsequent isomerization and [formula omitted]-dissociation

As a main component of alkenes, 1-octene is the key important intermediate in the process of oxidation or pyrolysis of n-decane or higher alkanes. In this work, quantum chemistry calculations of the 1-octene combustion and pyrolysis were illustrated for the potential energy surface, including the H-abstraction reactions and subsequent isomerization and β-dissociation reactions. The primary β-dissociation reactions after the H-abstraction reaction involving H atoms and CH3/NH2/NO2 radicals are detailed description with kinetic calculation. The rate constants of the primary pyrolysis reaction of 1-octene from 300 to 2000K were determined with the RRKM theory combined with CTST. The results indicated the H-abstraction reactions adhere to the Evans-Polanyi principle within the calculation uncertainty 1 kcal/mol. The 3-site exhibited the highest competitiveness in the 1-octene H-abstraction process and dominated, whereas the 1-site is lack of competitiveness due to overcome higher energy barriers (2–4 kcal/mol). The five-membered or six-membered ring in the H atom transfer process served as the most favorable structure for the isomerization reaction of 1-octenyl because of the lowest transition state energy. The dissociation channel for converting 1-octenyl to various octadienes and H atoms consumed the least 1-octenyl in the dissociation process. Following temperatures exceeding 570K, INT6 exhibits a preeminent 1-octenyl consumption ratio, attributed to the synergy between the enthalpy and entropy effects. The modified kinetic data of 1-octene H-abstraction reactions by four radicals and the subsequent isomerization and β-dissociation was expanded from 300 to 2000K, 0.01–100 atm. The modified model shows the better experimental prediction capabilities.

Numerical analysis of flow and heat transfer characteristics of supercritical endothermic hydrocarbon fuel in taper tube

To enhance the cooling performance of the scramjet regenerative cooling system, a novel taper tube is proposed. Under supercritical pressure, the flow characteristics and heat transfer characteristics of endothermic hydrocarbon fuel (EHF) in taper tube, narrow cylindrical tube, and wide cylindrical tube are numerical investigated and compared. The results of the investigation of flow and heat transfer processes in the above three tubes indicate that the taper tube effectively facilitates the pyrolysis of n-decane and the n-decane conversion is increased by 3.94%, compared with narrow cylindrical tube. Compared with wide cylindrical tube, the taper tube enhances cooling effect and the wall temperature near the outlet is reduced by 50.16 K. The taper tube contributes to the cooling structure optimization and promotion of regenerative cooling system performance.

Heat and mass transfer correlations of supercritical n-decane considering the influence of pyrolysis reaction by simplifying internal heat and mass sources as pseudo-wall fluxes

The convective heat and mass transfer characteristics of the supercritical pressure (SCP) fuel in the regenerative cooling channel of hypersonic vehicles are significantly affected by pyrolysis reactions. In this study, we proposed a novel method to develop the Nusselt number (Nu) and Sherwood number (Sh) correlation of SCP fuel that considers the influence of pyrolysis reaction by simplifying internal heat and mass sources as pseudo-wall fluxes based on the differential global reaction (DGR) model of pyrolysis. The convective heat and mass transfer and pyrolysis characteristics of n-decane were investigated experimentally and numerically in a vertical downward-flow heated tube at pressures of 3-7 MPa. Theoretical analysis of the experimental conditions was conducted sequentially according to the partial differential equations (PDEs) of species continuity and energy, in which the internal source terms of heat and mass due to pyrolysis reactions were simplified and predicted using the DGR model of n-decane pyrolysis. A semi-empirical Sh correlation for predicting the radial distribution of fuel conversion was proposed associated with computational fluid dynamics (CFD) data by equivalently simplifying the internal mass source as pseudo-wall mass flux. A Nu correlation for convective heat transfer was proposed using the same methodology considering the influences of pyrolysis. The correction terms consider pyrolysis endothermicity and thermophysical property variation due to the conversion differences between the pipe wall and the bulk flow. Finally, the Nu correlation was compared to the experimental data, and the influence of heat transfer deterioration (HTD) due to pyrolysis coking was also analyzed quantitatively and empirically.

Inhibitory mechanisms of ammonia addition on soot formation during n‑decane pyrolysis

Soot formation during the imperfect combustion or pyrolysis of fuels is harmful to engine efficiency·NH3 has been proved to reduce soot emission effectively in flames. In this work, the effect of NH3 addition on soot inhibition during n-decane pyrolysis was systematically investigated from a theoretical principle. The MD simulations indicate that the coking phenomenon is weakened with the NH3 addition. Besides, the NH3 additives make the concentration peak of the dominant gas products lag. Thus, the concentrations of crucial precursors (acetylene and propargyl) are reduced by NH3 addition. Moreover, the NH3 additives can also influence the PAH growth process through the PAHs with N atoms (N-PAHs). Then, the chemical kinetic analysis shows that proper addition of NH3 additives can meet the heat absorption demand of fuel cracking. Furthermore, the mass fractions of PAHs and soot particles decrease with NH3 addition, which is consistent with the results from MD simulations. The formation of the main carbonitride species originates from the reaction of CH3 and C2H5 with NH2 followed by the dehydrogenation or C-C bond breaking reaction. The carbon source directly involved in the formation of soot particle will be reduced and the growth of the soot particle will be inhibited by preventing the formation of the key reactants, such as the acetylene molecule.

Effects of n-decane pyrolytic products on heat transfer in regenerative channels under supercritical pressure

The study of the heat transfer process in the regenerative cooling channel of the scramjet engine is always one of the main focuses on highlighting the heat transfer characteristics caused by the pyrolysis of n-decane under supercritical pressure. The heat transfer is simulated in detail using the standard k-ε two-equation turbulent model and pseudo-detailed chemical kinetics mechanism. The results indicate that the dramatic changes in density and dynamic viscosity could lead to heat transfer deterioration at the beginning of the heated channel. The change rate of density and dynamic viscosity can reach up to 75 % and 97.4 %, separately. At the same time, the physical heat sink takes the lead because of the changes in the mixture’s specific heat capacity near the pseudo-critical region which are mainly contributed by C5 (pentane and pentene), and the proportion in total heat sink can reach up to 17.4 % when the conversion is below 15.0 %. The advantage of the endothermic cracking reaction is not reflected in the heat transfer process when the conversion of the fuel is lower than 25.0 % in this work. For practical applications, the effects of the pyrolytic products’ types and properties on the pyrolytic mechanism and heat sink should be performed to maximize the cooling capacity of n-decane in the cooling channel.

Online analysis method for pyrolysis products with large volatility difference at high temperature and pressure: Pyrolysis kinetics of supercritical pressure n-decane

Pyrolysis is widely applied in industrial fields including waste-to-energy conversion and hypersonic-vehicle cooling technology. Traditional offline analysis methods for fluid products based on cooling, depressurization, and separation processes often impart measurement uncertainties. Here, we propose a novel online analysis method for fluid pyrolysis products with significant volatility differences. High-frequency sampling based on instant cooling–flashing was used to avoid gas–liquid separation, where the fluid mixture is directly transported into an online-GC system as a vapor through a preheated vacuum tube. The method reliability was evaluated experimentally. Pyrolysis of supercritical-pressure n-decane (3–7 MPa) in a mini-tubular reactor was analyzed using both the proposed online method and an offline method. The gas yield measured using the offline method is significantly lower than that measured online due to the dissolution and volatilization loss of gaseous products during gas–liquid separation. The mass fraction of C3–C4 products measured using the offline method was 40–80% less than the online results. The maximum deviation in the mass fraction of the main products obtained offline was reduced to 20–25% after dissolution-loss correction. The kinetic constants of n-decane pyrolysis were determined based on product-yield data, and the calculated residence time was experimentally verified using particle image statistics. The proposed model was implemented in a computational fluid dynamics model. The deviation between the predicted conversion and experimental results was below 11%, while the deviations of the predicted mass fraction of typical products was significantly higher based on the offline model than the online model.

Effect of methanol and ethanol on n-decane pyrolysis process by ReaxFF simulation and experiment validation

Alcohol assisted hydrocarbon fuels regenerative cooling is a promising method to deal with scramjet engine heat management of hypersonic flight vehicle. To reveal the effect of alcohol on hydrocarbon fuels pyrolysis pathway, ReaxFF molecular dynamics simulation was done to investigate the variation of intermediate fragments in methanol/ethanol assisted n-decane pyrolysis process. Results shows that, two alcohols increase the initial cracking temperature of n-decane. Two alcohols turn the first-step cracking products of n-decane from C3H7 + C7H15 to C5H11 + C5H11, and make n-decane cracking into C2H5 + C8H17 possible. Initial pyrolysis of n-decane with methanol and ethanol can be coupled by CH3 and C2H5 free radical respectively. In the subsequent pyrolysis process, C10 are completely consumed within 10 ps. C7-C9 fragments are transient intermediates and can hardly accumulate. Experiment indicates that 450–500 °C is the decisive temperature range for n-decane cracking, and adding methanol or ethanol increase the initial cracking temperature of n-decane pyrolysis.

Inhomogeneity Effects on Reactions in Supercritical Fluids: A Computational Study on the Pyrolysis of n-Decane.

Supercritical fluids exhibit peculiar inhomogeneity, which strongly affects reaction behaviors in them. However, explanations for inhomogeneity and its effect on reactions are both ambiguous so far. Here, we provide an atomic-level understanding of inhomogeneity effects on reactions via the computational method, with the example of n-decane pyrolysis under supercritical conditions. We describe the characteristic pyrolysis behaviors through collective variable-driven hyperdynamics (CVHD) simulations and explain the inhomogeneity of supercritical n-decane as the coexistence of gas-like and liquid-like atoms by a trained machine learning classifier. Due to their specific local environment, the appearance of liquid-like atoms under supercritical conditions significantly increases the type and frequency of bimolecular reactions and eventually causes changes in product distributions. Future research with this method is expected to extend the effect of inhomogeneity on other reactions under supercritical conditions or other condensed phases.

Inhibition mechanism of electric field on polycyclic aromatic hydrocarbon formation during n-decane pyrolysis: A ReaxFF MD and DFT study

Polycyclic aromatic hydrocarbon (PAH) is the soot precursor in hydrocarbon fuel pyrolysis process, which results in serious combustion and environmental issues. This work investigated the process of n-decane pyrolysis and PAHs formation under electric field using ReaxFF molecular dynamics and density functional theory (DFT) method. The results demonstrated that the electric field increased the decomposition reaction rate constant (k) from 5.15 × 109 s−1 to 9.01 × 109 s−1 and decreased the reaction activation energy (Ea) from 59.47 to 54.79 kcal/mol of n-decane pyrolysis at 0.20 V/Å. DFT calculation validated that the enthalpy change (ΔH) of bonds cracking was decreased and the polarization of n-decane was enhanced by electric field. A priority selective effect was performed on the initial cracking path and validated by the potential energy surfaces (PES). With products distribution statistics, C2 precursors of ring formation were decreased by the field, resulting in the inhibition of largest molecular size growth. The development of the largest molecule structure revealed clearly that the 5-member ring was unstable and the growth of 6-member ring was inhibited under electric field. This work supplies the n-decane pyrolysis and PAH formation mechanism modified by electric field, which provides a wide application in fuel clean combustion and environmental pollution researches.

Effect of Methanol Addition on Soot Inhibition During N-Decane Pyrolysis

Effect of Methanol Addition on Soot Inhibition During N-Decane Pyrolysis

Impact of Pyrolysis Products on n-Decane Laminar Flame Speeds Investigated through Experimentation and Kinetic Simulations

Jet fuels used in regenerative cooling are often pyrolyzed into gaseous and liquid products, which changes their burning properties. The effects of primary pyrolysis products, namely, hydrogen, methane, ethylene, and ethane, on the laminar flame speeds of n-decane/air were investigated at atmospheric pressure and 405 K using a Bunsen burner and chemical kinetics. The experimental results showed that methane inhibited the laminar flame speeds, whereas hydrogen, ethylene, and ethane promoted them. However, the laminar flame amplitude with ethane was about 40% of that with ethylene. Additionally, the enhanced flame speeds with ethylene and ethane were more evident under fuel-rich conditions than under fuel-deficient conditions. The effect of n-decane pyrolysis conversion on flame speeds can be approximated as the superposition of the separate effects of four gases within 26% conversion. Kinetic analyses indicated that laminar flame speeds are sensitive to the generation and consumption of H and OH, where the total molarity of these species determines the laminar flame speeds. The hydrogen absorption reactions of methane consumed large amounts of H and OH, and generated CH₃ enhanced this consumption. The addition of ethylene significantly increased the mole fraction of HCO, the main precursor of H generation, which then generated OH and HO₂. C₂H₅ generated by ethane produced H through a decomposition reaction, which was the major reason for the increase in laminar flame speeds of n-decane.

Atmospheric and high pressures pyrolysis study of n-decane in a flow reactor with online GC-MS/FID analysis: Experiments and modeling

The atmospheric and high-pressure pyrolysis of n-decane was studied in a flow tube reactor combined with online GC–MS/FID at 723−1123 K, 0.1–3.0 MPa (highly diluted in helium). Compared with 0.1 MPa, the conversion of n-decane and mole fraction of alkenes clearly increased at 3.0 MPa at the fixed temperature, and more aromatics were observed including toluene, styrene, ethylbenzene, indene and naphthalene, suggesting that the secondary reactions are more intense under high pressure. To account for these differences, a detailed kinetic model with 191 species and 1117 reactions was constructed by incorporating the aromatics subset to a n-decane model developed in previous low-pressure work, and further validated against literature data covering a wide pressure range (0.004–7.2 MPa) with reasonable reproducibility. The current model was compared against three literature kinetic models (LLNL, JetSurf 2.0 and Rev1stGen) and showed a better accordant with the conversion of n-decane and the selectivity of major products. Based on the rate of production and sensitivity analysis using the current model, the results show that although the total consumption of n-decane is weakly pressure-dependent at fixed temperature and residence time under the investigated conditions, the formation and consumption pathways of primary products change significantly attributed to the enhanced bimolecular abstraction and combination reactions at higher pressures. For the formation of benzene, the combination of 1,3-butadien-2-yl with ethylene is the main pathway at both 0.1 and 3.0 MPa, while the additional combination reactions: propargyl with allyl and cyclopentadienyl (c-C5H5) with CH3 become dominant at 0.1 MPa and 3.0 MPa, respectively. For the formation of larger aromatic naphthalene, the self-recombination of c-C5H5 is the most important channel at all investigated pressures.

A novel global reaction modeling approach considering the effects of pressure on pyrolysis of n-decane at supercritical pressures

Pressure is one of the key factors in pyrolysis of hydrocarbon fuels at supercritical pressures, which changes the relation between the product distribution and fuel conversion. However, reaction model with both high accuracy and efficiency to predict pressure effects is lacking. A comprehensive experimental investigation of pressure effects on supercritical pyrolysis of n-decane in the pressure range of 3–7 MPa and temperature range of 560–670 °C is presented. The formation of liquid products is preferred at higher pressures. Gas and liquid products of n-decane pyrolysis can be categorized into three and four types, respectively, according to the formation characteristics. Results show that pressure had more profound effects on the formation of most products without C–C double bonds or benzene rings in their molecular structures (i.e., C3–C9 n-paraffins or cycloparaffins). A novel global reaction modeling approach was presented to solve the effects of both pressure and secondary reactions on pyrolysis of hydrocarbon fuels, in which the stoichiometric coefficients of each product are expressed as binary functions of fuel conversion and pressure. The proposed model was implemented in a computational fluid dynamics (CFD) simulation to predict the n-decane pyrolysis coupled with flow and heat transfer. The results show that the model predicts n-decane pyrolysis more accurately at both low and high pressures. This study can help design regenerative cooling systems with high accuracy and efficiency for engineering applications.

Soot formation of n-decane pyrolysis: A mechanistic view from ReaxFF molecular dynamics simulation

The chemical-kinetic mechanism of soot formation for the n-decane pyrolysis was comprehensively investigated from theoretical perspective. We found the formation of carbonaceous nanoparticle with a multi-layer closed cylindrical structure needs four processes including initial rings formation, PAH growth, particle nucleation via coalescence of PAH and particle growth by coagulation or surface reactions. The mechanisms of HACA, CAHM and CHRCR play crucial roles in the processes of the formation and growth of PAH molecules. In addition, the temperature effect was discussed and found the higher temperature can accelerate the formation of soot particle, which is in agreement with the experiment findings.

Reaction pathways of molecular growth for bay-region methyl-substituted polycyclic aromatic hydrocarbons during supercritical pyrolysis of n-decane, as determined from experiments with 4-methylchrysene dopant

To investigate the molecular-growth reactions of bay-region methyl-substituted polycyclic aromatic hydrocarbons (PAH) in the supercritical n-alkane-fuel pyrolysis environment, we have performed supercritical n-decane pyrolysis experiments with and without the dopant 4-methylchrysene (dopant concentration, 0.684 mg/g n-decane), in an isothermal, silica-lined stainless-steel flow reactor at 568 °C, 94.6 atm, and 133 s, conditions of rapid PAH growth. Analyses of the reaction products by high-pressure liquid chromatography with diode-array ultraviolet-visible absorbance and mass-spectrometric detection reveal that in the supercritical n-decane pyrolysis environment—where the aliphatic growth species methyl, ethylene, propene, and 1-butene are abundant—molecular growth of the four-ring 4-methylchrysene to high-ring-number PAH occurs chiefly through two routes, both of which take advantage of the bay-region position of 4-methylchrysene's methyl substituent. In the first route, 4-methylchrysene's resonance-stabilized arylmethyl radical 4-chrysenylmethyl attacks the aryl carbon just across the bay of 4-methylchrysene's structure to form the C19H12 methylene-bridged PAH 4H-cyclopenta[def]chrysene, whose resonance-stabilized radical 4-cyclopenta[def]chrysenyl reacts with methyl and ethylene in ring-expansion reactions that selectively produce the five-ring C20H12 benzo[a]pyrene and its derivatives 4- and 5-methylbenzo[a]pyrene. The arylmethyl radicals 4- and 5-benzo[a]pyrenylmethyl then undergo a series of reactions with n-decane's high-yield C2C4 1-alkenes to selectively produce particular six- to nine-ring peri‑condensed benzenoid PAH such as dibenzo[a,e]pyrene, benzo[a]naphtho[2,3-e]pyrene, dibenzo[e,ghi]perylene, benzo[a]coronene, and naphtho[8,1,2-abc]coronene—all of whose yields increase dramatically with 4-methylchrysene doping. In 4-methylchrysene's second major route of molecular growth, 4-chrysenylmethyl's attack of the aryl carbon across the bay is followed by an intramolecular rearrangement that produces 4H-benzo[cd]fluoranthene, a non-fully aromatic C19H12 PAH with an internal five-membered ring. Reactions of the resonance-stabilized benzo[cd]fluoranthenyl radicals with methyl, propene, and 1-butene selectively produce the six-ring C22H12 indeno[1,2,3-cd]pyrene and four particular seven-ring C26H14 benzindeno[1,2,3-cd]pyrenes—each of which contains an internal five-membered ring, evidencing the distinctive molecular-growth pathways of bay-region methyl-substituted PAH in the supercritical n-alkane-fuel pyrolysis environment.

Kinetic modeling with automatic reaction network generator, an application to naphtha steam cracking

Abstract Accurate process simulation models of naphtha steam cracking are significant for improving product yields, reducing energy consumption, and process control. However, the complete mechanistic model for steam cracking of naphtha feedstock is not available in the literature. It is a challenging task to build large-scale detailed kinetic models of such complex mixtures. The application of automatic reaction network generation is a possible way to solve this problem efficiently. An open-source automatic reaction network generator RMG is used to construct the detailed mechanistic model of naphtha steam cracking. A step-by-step construction methodology that starts with automatic reaction network generation for a single hydrocarbon and then merges reaction networks of all considered hydrocarbons according to specific merging rules is proposed. The final merged model contains 1947 species and 82130 reactions. The pyrolysis of n-decane in the literature and a set of naphtha steam cracking experiments are used to verify the accuracy of the generated reaction network for single hydrocarbon and naphtha mixture, respectively. The results show that the simulated yields of major products are in overall agreement with experiments, and the deviations of minor products are within an acceptable range.

Experimental Investigation on Pyrolysis of n-Decane Initiated by Nitropropane under Supercritical Pressure in a Miniature Tube

Adding an initiator is an effective method of promoting hydrocarbon pyrolysis and improving the heat sink of fuels. Nitropropane was proposed as an initiator with good performance, owing to its lower reaction activation energy for C–N bond cleavage. To study the effects of this initiator on hydrocarbon pyrolysis, a miniature tube reactor that can simulate a real heating procedure in an aeroengine was used to investigate the n-decane pyrolysis with and without nitropropane under experimental supercritical conditions. The results demonstrate that the nitropropane initiator promotes the pyrolysis of fuel as it flows through a tube with a large length–diameter ratio within a certain temperature range. The initial decomposition temperature of n-decane is reduced by approximately 100 K, and the increase in the conversion leads to a higher heat sink for n-decane, which can result in decreases in the fuel and reactor temperatures under the same heating condition and within the effective temperature range. A stronger promoting effect can be achieved by increasing the concentration of the nitropropane initiator. The variation laws for the n-decane pyrolysis reaction rate along the flow reactor are changed by the initiator, the presence of nitropropane greatly accelerates the pyrolysis reaction of fuel at a lower temperature, and the opposite tendency appears as the fuel temperature increases, which is caused by the consumption of the initiator. In addition, the selectivity of methane, propane, and alkenes, especially ethylene, increases because of the propyl radical generated by the C–N dissociation of nitropropane before the initiator is consumed.

The performance comparison in predicting n-decane pyrolysis process between three ANNs methods: MLP, RBFN and GRNN

In this work, three kinds of ANNs are employed to predict the pyrolysis behavior of n-decane. Six-fold cross validation method is adopted to optimize the key parameter of ANNs and evaluate the performance of ANNs. The results indicate that RBFN has best performance in predicting the species distribution and all ANNs have good performance in predicting the bulk temperature. Meanwhile, these results reveal that all ANNs are more suitable for predicting products with high mass fraction than those with less mass fraction, whose errors are also acceptable.

Polycyclic aromatic hydrocarbons formation and growth during the supercritical pyrolysis of 1-octene

To better understand the roles of larger 1-alkenes in reactions leading to the production of polycyclic aromatic hydrocarbons (PAH) and solids in the supercritical pre-combustion environments of future-high-speed-aircraft fuels, supercritical pyrolysis experiments have been conducted with the model fuel 1-octene, a representative 1-alkene product of supercritical n-alkane-fuel pyrolysis. The 1-octene pyrolysis experiments are performed in an isothermal, silica-lined stainless-steel flow reactor at 94.6 atm, 133 s, and ten temperatures in the range 440–535 °C. Straight-chain aliphatics—particularly n-alkanes, 1-alkenes, and 2-alkenes—are the highest-yield products at all temperatures. At temperatures ≤500 °C, high yields of the C8 product 2-octene and the C16 product 6-hexadecene evidence 1-octene's facile formation of the resonance-stabilized alkylallylic radical 1-octen-3-yl, whose resonance structure 2-octen-1-yl not only abstracts H to produce 2-octene but also reacts with 1-octene to produce, with high selectivity, 6-hexadecene—establishing that, at low temperatures, a long-chain alkene with an interior CC double bond can result from alkylallyl-radical addition to a 1-alkene. Gas-chromatographic analyses of 1-octene's aromatic products show that one- and two-ring aromatics are produced at temperatures ≥ 475 °C. High-pressure-liquid-chromatographic analyses reveal the identities of 180 three- to nine-ring PAH products—178 of which have never before been identified as pyrolysis products of a large 1-alkene and all of which are produced from supercritical n-decane pyrolysis as well. As in the case for n-decane, the high levels of methyl-substituted PAH in the 1-octene products provide a ready source for resonance-stabilized arylmethyl radicals and (after reaction with ethylene) phenalenyl-type radicals. Reactions of these arylmethyl and phenalenyl-type radicals with C2C4 1-alkenes lead to the sequential PAH growth that accounts for 1-octene's production of PAH as large as nine rings at temperatures as low as 500 °C and the dramatic increases in the PAH-product yields as temperature approaches 535°C, 1-octene's temperature of incipient solids formation.