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Extended Detailed Chemical Kinetic Model for Benzene Pyrolysis with New Reaction Pathways Including Oligomer Formation Akihiro Kousoku,† Koyo Norinaga,*,‡ and Kouichi Miura§ †

Mitsubishi Chemicals, Co. Ltd, 3-10 Ushiodori, Kurashiki 712-8054, Japan Institute for Materials Chemistry and Engineering, Kyushu University, Kasuga, Fukuoka 816-8580, Japan § Institute of Advanced Energy, Kyoto University, Gokasyo, Uji, Kyoto 611-0011, Japan ‡

S Supporting Information *

ABSTRACT: The detailed chemical kinetic model based on elementary reactions was developed by adding reactions associated with the formations of benzene oligomers such as quaterphenyl (C24H18) and quinquephenyl (C30H22) and the overall reactions on coke formation to the available model reported previously [Norinaga, K.; et al. J. Anal. Appl. Pyro., 2009]. This extended model was critically evaluated by comparisons of the computed results with experimental data on the benzene pyrolysis performed with an atmospheric flow reactor at temperature ranging from 1123 to 1223 K, residence time up to 4 s, and benzene partial pressure of 10.1 kPa [Kousoku, A.; et al. J. Chem. Eng. Jpn.; accepted for publication]. The extended model showed improved capabilities in predicting product distribution in the benzene pyrolysis, including the yields of unreacted benzene as well as primary products such as benzene oligomers, low molecular weight gaseous products such as hydrogen and methane, and soot/coke. In contrast, the original model significantly underpredicted the conversion of benzene and could not predict the formations of benzene oligomers larger than terphenyl and coke. Acceptable agreements in oligomer yields obtained theoretically and experimentally indicate that the higher oligomer formations that had been ignored in the previous research are important reaction pathways leading to polycyclic aromatic hydrocarbons in the primary stage of benzene pyrolysis.

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INTRODUCTION

PAHs and coke from benzene or toluene were discussed qualitatively on the basis of the pyrolysis products obtained experimentally. As briefly reviewed above, it seems that the smallest aromatic compound, benzene, plays a crucial role to form PAHs and coke. The reactions of benzene following the PAC mechanism, the MAC mechanism, and the HACA mechanism are reported to be dominant to form large PAHs, coke, and soot. Most of the works, however, have qualitatively discussed the reaction mechanisms based on the experimentally identified products and focused on the benzene pyrolysis chemistry at relatively high temperatures above 1300 K. Quantitative examinations for the chemistry and kinetics of the benzene pyrolysis at more primary stage are very likely essential for better understanding of PAHs growth and the subsequent formation of coke molecules or soot particles. It has been reported by the authors of this study that the benzene oligomers including biphenyl (C12H10), terphenyl (C 18 H 14 ), quaterphenyl (C 24 H 18 ), and quinquephenyl (C30H22) were primary products and important intermediates of the coke in the benzene pyrolysis at temperature ranging from 1123 to 1223 K.19 The oligomer formations were not focused in the previous studies on the benzene pyrolysis and, consequently, were not understood at the mechanistic level. There are few kinetic models for hydrocarbon pyrolysis available that include reaction pathways for benzene oligomer formations.

Liquid fuels have been supporting our society through various applications such as electricity generation, fuels for automobiles, and so on. Combustion of liquid fuels is a core technology of most of such applications. It is, therefore, essential to combust liquid fuels efficiently and cleanly.1−3 One of the significant problems encountered in combustion of liquid fuels is the formation of soot particles that not only decrease the combustion efficiency but also cause serious environmental problems.4−6 So, it is a big challenge to develop the technologies that suppress the soot formation during the combustion. To do so, the mechanism of soot formation must be clarified. It has been reported that pyrolysis of hydrocarbons under high temperature combustion atmosphere produces polycyclic aromatic hydrocarbons (PAHs) in the process of producing soot particles.7−11 One of the important reactions to understand reaction mechanisms for producing PAHs is considered to be the pyrolysis of benzene and benzene derivatives because they are the smallest aromatic units included in most of liquid fuels. There has been a great discussion about the pyrolysis of benzene. Shukla and Koshi12 clarified the importance of the hydrogen abstraction and acetylene addition (HACA) mechanism,13,14 the phenyl addition/cyclization (PAC) mechanism, and the methyl addition/cyclization (MAC) mechanism by analyzing the products of gas phase pyrolysis of toluene with and without addition of benzene and acetylene. The HACA mechanism explains the successive growth of PAHs. The repetition of the reaction based on the HACA mechanism leads to condensed aromatic structures with a number of rings and high molecular weight. Several researchers13,1516−18 have focused on the thermal decomposition of benzene or toluene. Reaction paths forming © 2014 American Chemical Society

Received: Revised: Accepted: Published: 7956

December 29, 2013 March 22, 2014 April 14, 2014 April 14, 2014 dx.doi.org/10.1021/ie4044218 | Ind. Eng. Chem. Res. 2014, 53, 7956−7964

Industrial & Engineering Chemistry Research

Article

Figure 1. Effects of temperature and residence time on the yields on carbon the basis of the unreacted fraction of benzene as simulated with the model reported by Norinaga et al.,26 and their comparison with experimental data reported in ref 19.

Figure 2. Effects of temperature and residence time on the yields on carbon the basis of biphenyl (P2) and terphenyl isomers (P3) and the yields on a hydrogen basis of hydrogen simulated by the previous model reported by Norinaga et al.26 compared with experimental data reported in ref 19.

The detailed chemical kinetic modeling is a powerful approach for understanding reaction mechanisms of both conversion of feedstock and formations of products. Some studies have been done to construct the pyrolysis model consisting of elementary reactions, of which raw materials included hydrocarbons such as methane, ethylene, acetylene, propane, propylene, and butane,20−25 whereas it is very difficult to construct the detailed model based on elementary reactions added in growth reactions of aromatic compounds in gas phase. One of the authors in this research has reported that the detailed model based on elementary reactions was constructed and it was possible for

the model to predict the formation characteristics of PAHs such as benz[a]anthracene, chrysene, and benz[a]pyrene in ethylene, acetylene, and propylene pyrolysis at high accuracies.24,26 However, no study has been done to apply the detailed model for predicting benzene pyrolysis, especially because it has been little studied to evaluate the validity of the model, compared with the yields of a wide variety of products. The purpose of this work is, thus, to add the reaction pathways to account the productions of quaterphenyl and quinquephenyl and the overall reactions on the production of coke to the abovementioned detailed model on benzene pyrolysis kinetics. 7957

dx.doi.org/10.1021/ie4044218 | Ind. Eng. Chem. Res. 2014, 53, 7956−7964


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Table 1. Thermodynamic Physical Properties of Terphenyl (C18H14) (Abbreviated to P3) and Compounds from Which Hydrogen Radicals Are Abstracted (Abbreviated to P3-)a species

T (K)

Cpl (cal/mol/K)

Cp2 (cal/mol/K)

H1 (kcal/mol)

H2 (kcal/mol)

S1 (cal/mol/K)

S2 (cal/mol/K)

P3 P3 P3 P3P3P3-

300 1000 2000 300 1000 2000

57.67 134.3 160.8 56.85 130.4 155.9

56.17 142.1 170.1 55.73 137.7 164.6

66.73 139.8 290.4 126.8 197.9 344

66.14 143.2 301.5 127 202.1 355.4

111.6 228 331.3 112.7 226.2 326.4

121.7 243.4 352 124.6 243.4 348.5

a 1 is written as a subscript to represent thermodynamic physical properties following the database used in the previous model of Norinaga et al.26 2 is written as a subscript to represent those based on Benson’s method.28

Table 2. Additions to Reaction Mechanism Reported by Norinaga et al.26 Where k = ATn exp(−Ea/RT) number 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19

reaction P3- + C6H5 P3- + C6H5 P3 + C6H5 P3- + C6H6 P2 + P2P4- + C6H5 P4- + C6H5 P4 + C6H5 P4- + C6H6 P4 + H P4- + H P3- + P2P3- + P2P3 + P2P3- + P2 P5 + H P5- + H P2- + P2P2- + P2-

= = = = = = = = = = = = = = = = = = =

A (s−1 or m3 mol−1s−1)

n

Ea (kJ/mol)

5.94 × 10 8.60 × 1013 1.00 × 1077 1.00 × 1077 1.80 × 1077 5.94 × 1042 8.60 × 1013 1.00 × 1077 1.00 × 1077 3.23 × 1007 1.17 × 1033 1.78 × 1043 2.58 × 1013 3.00 × 1077 1.00 × 1077 6.46 × 1007 2.34 × 1033 3.56 × 1043 5.16 × 1014

−8.83 0.5 −18.9 −18.9 −18.9 −8.83 0.5 −18.9 −18.9 2.095 −5.57 −8.83 0.5 −18.9 −18.9 2.095 −5.57 −8.83 0.5

57.9 145.7 165.2 165.2 165.2 57.9 145.7 165.2 165.2 66.3 36.7 57.9 145.7 165.2 165.2 66.3 36.7 57.9 145.7

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P4 P4- + H P4 + H P4 + H P4 + H P5 P5- + H P5 + H P5 + H P4- + H2 P4 P5 P5- + H P5 + H P5 + H P5- + H2 P5 P4 P4- + H

performed with a tubular flow reactor. Gas and condensing products were collected by a gasbag and filter/cold traps, respectively, and analyzed by using gas chromatographs and a mass spectrometer. Benzene oligomers up to C24 (quaterphenyl) were detected by the GC and, thus, quantitatively analyzed. The descriptions for the whole experimental setup and procedure are also provided in the Supporting Information. In the previously reported model, biphenyl and terphenyl isomers are considered as benzene oligomer compounds. Figure 1 shows the yields on carbon the basis of the unreacted fraction of benzene against residence time, tR, at three pyrolysis temperatures of 1123, 1173, and 1223 K. In Figures presented in this paper, the plot shows the experimental data, and the solid line shows the simulated results. Figure 1 indicates that the simulated results on the benzene conversion underestimated overall. Similarly, Figure 2 shows the yields on a carbon basis of biphenyl and terphenyl isomers and the yields on a hydrogen basis of hydrogen against tR at three pyrolysis temperatures. In the case of biphenyl, the simulated results fairly reproduce the production behavior at 1123 K (Panel a), on the other hand, the simulated results seemed to overestimate at 1173 (Panel d) and 1223 K (Panel g). In the case of terphenyl isomers, the simulation underpredicted the experimentally obtained yield at three temperatures (Panels b, e, and h). With respect to hydrogen, the simulated results seemed to underestimate the experimental values similarly (Panels c, f, and i). In the original model previously reported, two reasons are mainly considered concerning the low accuracy of estimations of

In addition, the newly extended model is critically evaluated by comparing the simulation results with experimental data from the detailed product analysis in the benzene pyrolysis experiments.19

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NUMERICAL SIMULATION The original mechanism consisted of 241 species and 902 elementary step-like reactions, 798 of which were reversible.26 This model is going to be extended to account formations of the higher benzene oligomers and coke. Calculations were performed using the gas-phase reaction mechanism using the BATCH code in the DETCHEM program package (DETCHEMBATCH).27 DETCHEMBATCH is capable of simulating homogeneous gas-phase reactions in a batch reactor. Numerical simulations were performed under isothermal and isobaric conditions for reproducing the flow reactor experiments. The system of equations was solved using a differential algebraic equation solver. The governing equations and numerical methods used for this simulation are given in detail in the user’s manual of the DETCHEM.27

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COMPARISON OF EXPERIMENTAL DATA19 WITH SIMULATED RESULTS BY THE ORIGINAL MODEL First, for an overview of the prediction capability of the previously reported detailed kinetic model,26 results simulated by the model were compared with experimental data19 concerning the effects of reaction temperature and residence time on benzene conversion. The experiments for benzene pyrolysis were 7958



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Figure 3. Effects of temperature and residence time on carbon basis yields of triphenylene simulated with the previous model reported by Norinaga et al.26 and their comparison with experimental data reported in ref 19.

Table 3. Hydrogen to Carbon Atomic Ratios (H/C) and Compositional Formula of Coke-1 and Coke-2 Obtained from Benzene Pyrolysis at 1123, 1173, and 1223 K 1123 K coke-1 coke-2

1173 K

1223 K

H/C

compositional formula

H/C


H/C


0.56 0.28

C18H10 C18H5

0.44 0.22

C18H8 C18H4

0.22 0.11

C18H4 C18H2

similar reactions associated with the phenyl radical (C6H5), benzene, P2, P2-, P3, and P3- included in the original model (Table 2). All newly added reactions are reversible. The rate constants of the backward reactions can be estimated because thermodynamic physical properties of P4, P4-, P5, and P5- are available, as the above subsection mentioned. Addition of Overall Coke Production Reactions. Figure 3 shows the carbon basis yield of triphenylene against residence time, tR, at the pyrolysis temperatures of 1123, 1173, and 1223 K.19 Triphenylene is the dominant products in the benzene pyrolysis. In Figure 3, the results simulated by the original model26 were also provided. Figure 3 indicates that the formation of triphenylene is overestimated. This is likely because the reactions of triphenylene to larger PAHs, including coke, are not considered in the original model. In the present study, the reaction of triphenylene converting to coke (expressed as coke-1) and the reaction of coke-1 converting to heavier coke (expressed as coke-2) are considered. Because the pyrolysis temperature should affect the quality of coke formed, we analyze the elemental compositions of coke-1 and coke-2 obtained at 1123, 1173, and 1223 K. Table 3 lists hydrogen to carbon atomic ratios (H/C) and compositional formula of coke-1 and coke-2. The H/C values of both coke-1 and coke-2 decrease with increasing the pyrolysis temperature, as expected. According to the varied compositions of coke-1 and coke-2 with temperature, we formulate the following overall reactions at each temperature for coke deposition. At 1123 K

the fraction of unreacted benzene, benzene oligomer compounds, and hydrogen. One is that reactions associated with benzene oligomer compounds, except biphenyl and terphenyl isomers, are not considered in the model at all. This means that it is possible to estimate the consumption of biphenyl and the production of terphenyl isomers with better accuracy by considering reactions associated with quaterphenyl and quinquephenyl isomers, which were experimentally identified as primary oligomers produced in the benzene pyrolysis.19 In addition, the model is expected to improve the underestimation on the yield of hydrogen by adding the reaction paths to another major product like coke. In our previous experimental study,19 the coke deposited the quartz wool placed at the bottom of the reactor, and the coke formed on the reactor wall during the experiment were distinguished and classified into coke-1 and coke-2, respectively. The development of a new model was then attempted by extending the present reaction mechanisms to account for the formations of quaterphenyl, quinquephenyl isomers, and coke.

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EXTENSION OF REACTION MECHANISM Estimation of Thermodynamic Physical Properties of Benzene Oligomer Compounds. Thermodynamic physical properties of terphenyl (hereafter abbreviated as P3) and the compound from which hydrogen radical is abstracted (P3-) on the basis of the database used in the previous model were compared with thermodynamic physical properties based on Benson’s method.28 Table 1 shows that there is little difference between the two kinds of thermodynamic physical properties based on the database and on Benson’s method. Similarly, quaterphenyl (P4), quaterphenyl radical (P4-), quinquephenyl (P5), and quinquephenyl radical (P5-) were estimated based on Benson’s method and the thermodynamic physical properties used for the simulation in the NASA polynomial format are provided in the Supporting Information. Addition of Reactions Associated with Benzene Oligomer Compounds. Elementary reactions associated with P4, P4-, P5, and P5- were newly added in the original model. These reactions and rate constants of them were estimated by

Triphenylene(C18H12) → coke‐1(C18H10) + H 2

(a)

coke‐1(C18H10) → coke‐2(C18H5) + 5H

(b)

3Benzene(C6H6) → coke‐2(C18H5) +

13 H2 2

(c)

At 1173 K

7959

Triphenylene(C18H12) → coke‐1(C18H8) + 2H 2

(a′)

coke‐1(C18H8) → coke‐2(C18H4) + 4H

(b′)



Article

3Benzene(C6H6) → coke‐2(C18H4) + 7H 2

PAHs included in the reaction model. In Figure 4, the plot shows the experimental data, and the solid line shows the simulated results. Likewise, Figure 5 shows the yields on hydrogen basis of hydrogen, methane, and acetylene, which are considered as the main gaseous products, and Figure 6 shows that the yields on carbon the basis of P2, P3, P4, and triphenylene. Concerning the unreacted fraction of benzene, the simulated behavior by the newly constructed model seems to agree with the experimental results (Figure 4). The yield of tar is judged to be estimated by the model, especially Figure 4 (Panel b) indicates that the simulated result is possible to estimate the behavior of increasing, reaching a maximum, and then decreasing gradually with increasing residence time. The yields of coke-1 and coke-2 also seem to be approximately estimated by the model. Especially, the unique behavior of coke-1 can be estimated. The unique behavior means that the yield of coke-1 is almost zero at small residence time and starts to increase at a certain threshold residence time. The yield of hydrogen seems to be overestimated slightly, whereas the behavior of increasing of the yield with increasing residence time seems to be estimated. The behavior of the yield of methane seems to be estimated, whereas the yield is underestimated. Concerning acetylene, the order of the yield value seems to be estimated, whereas the behavior of increasing, reaching a maximum, and then decreasing gradually with increasing residence time seems not to be estimated in the current model. This is because the consumption of acetylene via the HACA mechanism leading to larger PAHs than coronene (C24H12) is not considered in the current model, although the reactions of acetylene to PAHs leading up to coronene via the HACA mechanism are considered. In addition, another reason is that the deposition of acetylene on the surface of soot or coke is not considered in the model. Shown in Figure 6, the yields of P2, P3, and P4 indicate that the simulated results estimate the behavior of increasing, reaching a maximum, and then decreasing with increasing residence time. The trends are captured well in such a way by the developed kinetic model, whereas the yields are underestimated at longer residence time. A good agreement is obtained for the triphenylene yield. Comparison at Pyrolysis Temperatures of 1123 and 1223 K. A comparison of the experimental data with the simulated results obtained using the developed model at pyrolysis temperatures of 1123 and 1223 K is shown in Figures 7, 8, and 9. As shown in Figure 7, the fraction of unconverted benzene is well estimated at 1123 K (Panel a), though it is slightly overestimated at 1223 K (Panel e). In Panel b, at 1123 K, the yield of tar increases gradually with increasing residence time, whereas the

(c′)

At 1223 K Triphenylene(C18H12) → coke‐1(C18H4) + 4H 2

(a″)

coke‐1(C18H4) → coke‐2(C18H 2) + 2H

(b″)

3Benzene(C6H6) → coke‐2(C18H 2) + 8H 2

(c″)

As shown above, in addition to two kinds of global reactions for the formation of coke-1 and coke-2, a global reaction for the formation of coke-2 from benzene is also added based on the dominating reaction pathways proposed by our previous study.19 The rate parameters for the reactions of formations of coke-1 and coke-2 and direct conversion of benzene into coke-2 are summarized in Table 4. In the determination of the rate Table 4. Rate Parameters for the Reactions of Formations of Coke-1 and Coke-2 and a Direct Conversion of Benzene into Coke-2 reaction coke-1 formation (a) (a′) (a″) coke-2 formation (b) (b′) (b″) direct conversion of benzene into coke-2 (c) (c′) (c″) a

frequency factor

activation energy, kJ/mol

1.5 × 106c 1.0 × 104c 1.0 × 107c

105a 105a 217b

Based on ref 19. bBased on ref 29. cOptimized.

parameters, the activation energies for reactions a, b, and c are based on the references of Kousoku et al.19 and Li et al.,29 respectively, whereas the frequency factors were optimized to reproduce the results because currently no experimental basis to validate them is available. The activation energies of reactions a and b were determined by the numerical fitting to the experimental results obtained at the early stage of the benzene pyrolysis based on the overall consecutive reaction model.19

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COMPARISON OF EXPERIMENTAL DATA WITH SIMULATED RESULTS OBTAINED USING DEVELOPED MODEL Comparison at Pyrolysis Temperature of 1173 K. Figure 4 shows the carbon basis yields the unreacted fraction of benzene, tar, coke-1, and coke-2 against residence time, tR, at 1173 K for comparing the experimental data19 with the results obtained using the developed simulation model. The complete set of elementary reactions and kinetic parameters included in the extended model is given in the Supporting Information. The numerically obtained tar yield corresponds to the total yield of

Figure 4. Effects of residence time on carbon basis yields of the unreacted fraction of benzene, tar, coke-1, and coke-1 + coke-2 at 1173 K of reaction temperature simulated with the model developed in this study and their comparison with experimental data reported in ref 19. 7960



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Figure 5. Effects of residence time on hydrogen basis yields of unreacted fraction of benzene, tar, coke-1, and coke-2 at reaction temperature of 1173 K simulated with the model developed in this study and their comparison with experimental data reported in ref 19.

Figure 6. Effects of residence time on carbon basis yields of biphenyl (C12H10, P2), terphenyl isomers (C18H14, P3), quaterphenyl (C24H18, P4), and triphenyleneat reaction temperature of 1173 K simulated with the model developed in this study and their comparison with experimental data reported in ref 19.

Figure 7. Effects of residence time on carbon basis yields of unreacted fraction of benzene, tar, coke-1, and coke-1 + coke-2 at reaction temperature of 1123 and 1223 K simulated with the model developed in this study and their comparison with experimental data reported in ref 19.

behavior of the yield simulated by the model increases, reaches a maximum at around 1.5 s of residence time, and then decreases gradually with increasing residence time. The model fairly estimates the yield of coke-1 and coke-2 (Panels c and d).

Figure 8 indicates that the yields of hydrogen, methane, and acetylene can be estimated approximately, whereas at 1223 K,the trend of the acetylene profile is difficult to estimate (Panel f in Figure 8), as is the case at 1173 K. 7961



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Figure 8. Effects of residence time on hydrogen basis yields of hydrogen, methane, and acetylene at reaction temperature of 1123 and 1223 K simulated with the model developed in this study and their comparison with experimental data reported in ref 19.

Figure 9. Effects of residence time on carbon basis yields of biphenyl (C12H10, P2), terphenyl isomers (C18H14, P3), quaterphenyl (C24H18, P4), and triphenylene at reaction temperature of 1123 and 1223 K simulated with the model developed in this study and their comparison with experimental.

Figure 9 indicates that at 1123 K the yields of P2, P3, P4, and triphenylene simulated by the model’s increase, reach a maximum, and then gradual decrease with increasing residence time, whereas in the experimental data, the yields increase gradually. It was found that the kinetic constants for the reactions associating with both formations and consumptions of P3 and P4

have no significant sensitivities for the P3 and P4 concentration profiles, suggesting that the thermodynamic parameters are important to capture the trend more accurately for the benzene oligomers at 1123 K. At 1223 K, the behaviors of the yields of P2, P3, and P4 were estimated with high accuracy (Panels e, f, and g in Figure 9); on the other hand, the yield of triphenylene seems 7962



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to be underestimated (Panel h in Figure 9). This is likely because the reaction rate of triphenylene to coke-1 (Reaction a) is overestimated at 1223 K, suggesting that optimization of activation energies for reactions a and b to avoid overestimation of triphenylene conversion, underestimation of coke-1 formation, and overestimation of coke-2 formation should be a possible solution. More accurate estimations of thermodynamic properties for the benzene oligomers and their radicals should also contribute to improving the predictive capability of the kinetic model. Although there are slight disagreements with some of the experimental observations, overall the modified kinetic model succeeded in predicting benzene pyrolysis behaviors considering the complexity involved in the development of elementary gas-phase reactions.

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SUMMARY

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ASSOCIATED CONTENT

S Supporting Information *

The reaction mechanism that was used for the benzene pyrolysis simulations and the experimental procedure for the benzene pyrolysis are shown. This material is available free of charge via the Internet at http://pubs.acs.org/.

AUTHOR INFORMATION

Corresponding Author

*K. Norinaga. Fax: +81 92 583 7793. E-mail: norinaga@cm. kyushu-u.ac.jp. Author Contributions

The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. Notes

The authors declare no competing financial interest.

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REFERENCES

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Thermodynamic physical properties of benzene oligomers such as quaterphenyl (C24H18) and quinquephenyl (C30H22), as well as their radical compounds, were estimated by Benson’s method. Elementary reactions in the gas phase associated with quaterphenyl, quinquephenyl, and their radical compounds were newly added to the original model reported previously.26 Rate constants of the elementary reactions newly added were estimated based on similar prototype reactions included in the original model. In addition, the overall reactions on the production of coke were added to the original model. Therefore, the model is now available for estimating the behavior of pyrolysis products derived from benzene pyrolysis. The experimentally observed characteristics for the consumption of benzene as well as formations of primary products such as benzene oligomers and coke are reproduced by the extended kinetic model within accuracies demonstrated in this study. Nevertheless, the perfect reproductions of the observed dependency of reaction temperature require further explorations such as through evaluating thermodynamic data for benzene oligomers more accurately.

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ACKNOWLEDGMENTS

The part of this work is supported by Grant-in-Aid for Young Scientists (A), Japan Society for the Promotion of Science (JSPS). The authors are grateful to Mr Ryota Tanaka (Kyushu University) for his useful comments in the kinetic modeling. 7963



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(24) Norinaga, K.; Deutschmann, O. Detailed kinetic modeling of gasphase reactions in the chemical vapor deposition of carbon from light hydrocarbons. Ind. Eng. Chem. Res. 2007, 46 (11), 3547−3557. (25) Norinaga, K.; Janardhanan, V. M.; Deutschmann, O. Detailed chemical kinetic modeling of pyrolysis of ethylene, acetylene, and propylene at 1073−1373 K with a plug-flow reactor model. Int. J. Chem. Kinet. 2008, 40 (4), 199−208. (26) Norinaga, K.; Deutschmann, O.; Saegusa, N.; Hayashi, J. i. Analysis of pyrolysis products from light hydrocarbons and kinetic modeling for growth of polycyclic aromatic hydrocarbons with detailed chemistry. J. Anal. Appl. Pyrolysis 2009, 86 (1), 148−160. (27) Deutschmann, O.; Tischer, S.; Kleditzsch, S.; Janardhanan, V. M.; Correa, C.; Chatterjee, D.; Mladenov, N.; Minh, H. D. DETCHEM software package, Version 2.2, www.detchem.com: Karlsruhe, Germany, 2008. (28) Benson, S. W. Thermochemical Kinetics: Methods for the Estimation of Thermochemical Data and Rate Parameters, 2nd ed.; John Wiley & Sons: New York, 1973. (29) Li, A.; Norinaga, K.; Zhang, W.; Deutschmann, O. Modelling and simulation of materials synthesis: chemical vapor deposition and infiltration of pyrolytic carbon. Composite Sci. Technol. 2008, 68 (5), 1097−1104.

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