Theoretical Study on the Kinetics of Thermal Decomposition of

Subscriber access provided by LAURENTIAN UNIV

Article

Theoretical Study on the Kinetics of Thermal Decomposition of Guaiacol and Catechol Yuki Furutani, Yuki Dohara, Shinji Kudo, Jun-ichiro Hayashi, and Koyo Norinaga J. Phys. Chem. A, Just Accepted Manuscript • DOI: 10.1021/acs.jpca.7b08112 • Publication Date (Web): 10 Oct 2017 Downloaded from http://pubs.acs.org on October 11, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

The Journal of Physical Chemistry A is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

The Journal of Physical Chemistry

Theoretical Study on the Kinetics of Thermal Decomposition of Guaiacol and Catechol Yuki FURUTANI1, Yuki DOHARA1, Shinji KUDO2, Jun-ichiro HAYASHI2,3, and Koyo NORINAGA*4 1 Interdisciplinary Graduate School of Engineering Sciences, Kyushu University, 6-1, Kasuga-koen, Kasuga, Fukuoka, 816-8580, Japan. 2 Institute for Materials Chemistry and Engineering, Kyushu University, 6-1, Kasuga-koen, Kasuga, Fukuoka, 816-8580, Japan. 3 Research and Education Centre of Carbon Resources, Kyushu University, 6-1, Kasugakoen, Kasuga, Fukuoka, 816-8580, Japan. 4 Department of Chemical Systems Engineering, Graduate School of Engineering, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8603, Japan. *Corresponding author: Koyo NORINAGA, Tel +81 52 789 3618, Fax +81-52-789-3272 Email: [email protected] Abstract The theoretical aspects of the development of a chemical kinetic model for guaiacol and catechol pyrolysis are presented to describe the pyrolysis behaviors of the individual lignin-derived components. The possible pyrolysis pathways involving both unimolecular and bimolecular decomposition were investigated by the potential energy surfaces (PES) calculated at CBS-QB3 level. The high-pressure limiting rate constants of each elementary reaction step were evaluated based on the transition state theory (TST) to determine the dominant pyrolysis pathways. The kinetic analysis results predicted the most favorable catechol unimolecular decomposition pathways, where catechol isomerization to 2-hydroxycyclohexa-2,4-dien-1-one occurred via migration of the hydroxyl H atom, followed by decomposition into 1,3-butadiene, acetylene, and CO. In the case of the bimolecular reaction of catechol, a hydrogen radical is coupled to the carbon atom in the benzene ring, leading to the formation of phenol and a hydroxyl radical through dehydroxylation. On the other hand, guaiacol is likely to form catechol and phenol via the O-CH3 homolysis and coupling of a hydrogen radical to the carbon atom with the methoxyl group, respectively.

1 ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

1. Introduction Lignin has received broad attention as a sustainable source of aromatic polymers composed of three phenyl propane monomers (guaiacyl, syringyl, and p-hydroxylphenyl units).1,2 Their compositions are quite different in softwood and hardwood lignins; softwood lignins have only guaiacyl-type unit, whereas hardwood lignins have both types.3,4 Pyrolysis-based technologies (fast pyrolysis and gasification) are promising methods for converting lignin into gas, liquid fuels, and valuable aromatic compounds.5– 11 A better understanding of the mechanism underlying lignin pyrolysis at the molecular level is crucial for optimizing these methods. Our group has established a detailed chemical kinetic model (DCKM) consisting of thousands of elementary reaction steps and hundreds of chemical species, which predicts the vapor-phase reactions of volatiles derived from the fast pyrolysis of biomass at the molecular level and provides detailed information on the molecular composition of the products.12–15 However, empirical kinetic parameters estimated to minimize the gaps between the simulation and experimental results has been used in the DCKM because of the lack of a kinetic database on the elementary decomposition steps of several ligninderived compounds such as catechol, guaiacol, syringol, and their derivatives.12 Thus, the DCKM was not sufficient to adapt to the change in operation parameters, such as temperature, gasifying agent and lignin type. In order to exclude the empirical parameters and enhance the versatility of the DCKM, it is necessary to estimate the rate constants of elementary decomposition steps of individual lignin-derived compounds. Since guaiacol is the predominant species generated from lignin pyrolysis16–19, many experimental studies have focused on identifying the molecular products derived from the thermal decomposition of catechol20–25 and guaiacol.4,26–32 For instance, Ledesma et al.22 carried out the pyrolysis of catechol in a tubular flow reactor to quantify the pyrolytic products ranging from gases (especially CO and CH4) to heavy polyaromatic hydrocarbons. Hosoya et al.31 revealed that the main products generated from guaiacol pyrolysis at 600 °C were phenolic compounds, such as catechol and o-cresol. In addition to experimental studies, theoretical investigations using first-principles computational chemistry have been conducted to analyze the thermal decomposition pathways of catechol33–37 and guaiacol.32,38 For instance, Altarawneh et al.35 investigated unimolecular decomposition pathways of catechol leading to the formation of experimentally reported major products (CO, 1,3-C4H6, and cyclo-C5H6) based on the potential energy surfaces (PES) calculated with the density functional theory (DFT). Liu 2 ACS Paragon Plus Environment

Page 2 of 27

Page 3 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


et al.38 theoretically predicted that the most energetically favorable thermal decomposition pathway of guaiacol involved coupling a hydrogen radical to the carbon atom with the methoxyl group, followed by demethoxylation. However, to date, the rate constants of the individual decomposition steps have not yet been estimated theoretically. In this study, the high-pressure limiting rate constants for the elementary steps of catechol and guaiacol decomposition are evaluated using highlevel ab initio methods. First, we proposed possible unimolecular and bimolecular decomposition pathways on the PES calculated with a suitably accurate method, i.e., “complete basis set” CBS-QB3 method. Second, the high-pressure limiting rate constants for each elementary reaction step were calculated using the transition state theory (TST) to assess the feasibility of the proposed reaction pathways. The theoretically determined rate constants of these elementary reaction steps will aid the development of a DCKM that can describe the behavior of lignin pyrolysis.

2. Computational Method Ab initio calculations were performed with the Gaussian09 (G09) software package.39 In this study, PES along the selected pathways were calculated using the CBS-QB3 method40, which offers greater accuracy within 1 kcal/mol. This highly accurate method includes a ﬁve-step calculation starting with a geometry optimization and frequency calculation at B3LYP/6-311G(2d,d,p) level of theory41,42, followed by a single-point calculation at CCSD(T)/6-31+G(d’), MP4SDQ/CBSB4 and MP2/CBSB3 level, and a complete basis set extrapolation to correct the total energy. Analytical frequency calculations at the same level of theory, namely, B3LYP/6-311G(2d,d,p), were performed to verify one imaginary frequency for a transition structure and all positive frequencies for a stable structure. Subsequently, intrinsic reaction coordinate (IRC) calculations43 were carried out to establish the correct connections between the reaction intermediates. High-pressure limiting rate constants were calculated based on the TST using the GPOP program.44 The partition functions and the density/sum of states for internal degrees of freedom were calculated at B3LYP/6-311G(2d,d,p) level by assuming harmonic vibrational frequencies. The internal rotation of the hydroxyl and methoxyl groups in catechol and guaiacol was treated as hindered internal rotors by using the Pitzer–Gwinn approximation.45,46 In this program, the 1D semiclassical tunneling effects were corrected by assuming the asymmetric Eckart potential.47 The variational TST (VTST) was used for the calculation of rate constants for barrierless channels.44



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

3. Results and Discussion 3.1. Proposal of Pyrolysis Pathways on Potential Energy Surfaces Altarawneh et al.34,35 investigated the unimolecular decomposition pathways of catechol (o-C6H4(OH)2) based on the PES calculated at the B3LYP/6-311+G(3df,2p)//B3LYP/6311+G(d,p) level. Following the theoretical study of Altarawneh et al.34,35, we provided the unimolecular decomposition pathways of o-C6H4(OH)2, involving both singlet and doublet states, as shown in Figure 1. All energy values on the PES were calculated at the CBS-QB3 level and are given relative to o-C6H4(OH)2. According to Figure 1, there exist five possible initial decomposition channels of C6H4(OH)2 (Rxn-1, Rxn-2, Rxn-5, Rxn-7, and Rxn-16). Rxn-1 corresponds to concerted dehydrogenation of the two hydroxyl H atoms, resulting in the production of o-benzoquinone with H2 release via the transition state TS1. Previous studies have suggested that o-benzoquinone decomposes into carbon monoxide (CO) and cyclopentadienone (C5H4O) via a ring-opening reaction.35,36,48,49 Direct self-expulsion of H2 and H2O (Rxn-2 and Rxn-5) forms intermediates IM1 and IM3, which decomposes into cyclopentadienone (C5H4O) and cyclopenta-1,2,4-triene (C5H4), with the release of CO by decarbonylation (Rxn-3, Rxn-4 and Rxn-6), respectively.50 It is expected that C5H4O contracts to form a fused bicyclic compound with a four-membered and three-membered ring and dissociates into 1,3-butadiene (C4H4), acetylene (C2H2), and CO32,51–53, whereas C5H4 captures a H radical in the gas phase to form either naphthalene or cyclopentadiene.54,55 Rxn-7 contributes to the formation of intermediate IM4 through the migration of the hydroxyl H to a carbon bearing a H atom via TS5. IM4 can branch into three channels (Rxn-8, Rxn-9, and Rxn-13). Rxn-8 associated with the O–H bond dissociation might be energetically unfavorable due to its exceedingly high potential barrier of 78.1 kcal/mol. Hydroxycyclopentadienyl radical (C5H4OH) might be formed with CO release as a result of the condensed ring reaction (Rxn-9 -> Rxn-10 -> Rxn-11 -> Rxn-12) or ring-opening reaction (Rxn-13 -> Rxn-14 -> Rxn-15). C5H4OH is converted into C5H4O via homolysis of the O–H bond56, followed by decomposition into 1,3-butadiene (C4H4), acetylene (C2H2), and CO as described earlier. After the O–H bond dissociation at Rxn-16, there exist four possible doublet state routes (Rxn-17, Rxn-22, Rxn-26, and Rxn-27). Rxn-17 and Rxn-22 involve intramolecular transfer of the hydroxyl H to the carbon site via TS11 and TS16 to form intermediates IM11 and IM14, respectively, both of which are capable of converting to a 1,3-butadiene radical (CH2CHCHCH) or propenal radical (CHCHCHO) with the release of CO. The fate of CH2CHCHCH is characterized by its dissociation into C2H2 + C2H357,58, whereas 4 ACS Paragon Plus Environment

Page 4 of 27

Page 5 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


the fate of CH2CHCHO is characterized by its dissociation into CO + C2H259. The intermediate IM17 containing an aldehyde radical is formed through an aromatic ring contraction to a five-membered ring at Rxn-27, subsequently decomposing into C5H4OH via the expulsion of CO.60



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 1: Reaction pathways for the unimolecular decomposition of catechol (oC6H4(OH)2) on singlet and doublet PES. All energy values are in kcal/mol computed relative to o-C6H4(OH)2 at 0 K with the CBS-QB3 method. 6 ACS Paragon Plus Environment

Page 6 of 27

Page 7 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


The inclusion of bimolecular reactions, either with the radical pool (mostly H in pyrolysis) or with intermediates, could provide more facile routes for the formation of experimentally detected major products, such as phenol (C6H5OH) and benzene (C6H6).22,23 Figure 2 depicts the possible pathways for the H-addition reaction with catechol on the doublet PES. After coupling of a H radical to the carbon atom in the sixmembered ring (via Rxn-28, Rxn-29, and Rxn-30), the added H atom is transferred to a carbon-bearing hydroxyl group to form intermediate IM20, which converts to C6H5OH and OH radical by dehydroxylation (via Rxn-33). C6H5OH is expected to decompose into c-C5H6 and CO through the isomerization to 2,4-cyclohexadienone 50,61–64 or convert to C6H6 by the displacement of an OH species with H.22

Figure 2: Reaction pathways for H-addition with catechol (o-C6H4(OH)2) on doublet PES. All energy values are in kcal/mol computed relative to o-C6H4(OH)2 + H at 0 K with the CBS-QB3 method.

Figure 3 shows the H-abstraction channels for catechol by several radicals (H, CH3, OH, and IM10) on doublet PES. The self-reaction of catechol leading to the formation of IM4 on singlet PES is presented in Figure 4. Note that the PES for Rxn-37 and Rxn-38 had to be calculated with B3LYP/6-311++G(d,p) level in order to shorten the single-point calculation time for large transition structures TS30 and TS31 as depicted in Figure 5.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 3: H-abstraction channels for catechol (o-C6H4(OH)2) by radicals (H, CH3, OH, IM10) on doublet PES. Energy values for Rxn-37, Rxn-38, and Rxn-39 in kcal/mol are computed relative to the reactant states at 0 K with the CBS-QB3 method, otherwise at the B3LYP/6-311++G(d,p) level.

Figure 4: Self-reaction of catechol on singlet PES. Energy values in kcal/mol are computed relative to o-C6H4(OH)2 + o-C6H4(OH)2 at 0 K at the B3LYP/6-311++G(d,p) level.


Page 8 of 27

Page 9 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 5: Optimized structures for the transition state of (a) TS30 and (b) TS31 calculated at the B3LYP/6-311++G(d,p) level. Distances are measured in Å. The possible pyrolytic pathways of guaiacol (CH3OC6H4OH) were proposed with an emphasis on the reactivity of the methoxyl group, as shown in Figure 6. Rxn-39 corresponds to the O–C bond scission reactions in the methoxyl group, which leads to the formation of IM10 and CH3 radicals. The hydroxyl H atom is transferred to a carbonbearing methoxyl group through Rxn-41 to form intermediate IM21, which results in its decomposition into phenoxy (C6H5O) and methoxyl radicals (OCH3) by demethoxylation through Rxn-41. At Rxn-42 and Rxn-43, the formation of intermediate IM22 is achieved by coupling a hydrogen radical to the carbon atom in the benzene ring through Rxn-42, and then, it is converted to C6H5OH and methoxyl radical (OCH3) through demethoxylation via TS34. Rxn-44 represents the methoxyl CH3 abstraction by a H radical.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 6: Reaction pathways of guaiacol pyrolysis on PES. All energy values are in kcal/mol computed at 0 K with the CBS-QB3 method.

3.2.

High-Pressure Limiting Rate Constants Calculated With Transition State Theory As shown in Figure 7, the high-pressure limiting rate constants of Rxn-1, Rxn-2, Rxn-5, Rxn-7, and Rxn-16 were calculated with TST in the range of 300–1500 K to determine the dominant unimolecular channel of catechol. Since Rxn-16 involves barrierless O–H bond fission in catechol (as shown in Figure S1 in Supporting Information), the VTST was applied to obtain its rate constant. Figure 7 indicated that Rxn-7 has a large rate constant at all temperatures; thus, hydroxyl H migration to a carbon site bearing a H atom is probably the most facile channel. With increasing temperature, the rate constants of Rxn-5 and Rxn-7 approach one another, but do not intersect one another. Even in the lowpressure limiting rate constants obtained with Rice-Ramsperger-Kassel-Marcus (RRKM) theory65–68, Rxn-7 has larger values as shown in Figure S3 of the Supporting Information. Horn et al.69 also concluded from time-resolved measurements with a shock tube that catechol decomposition was initiated by the hydroxyl H migration to the carbon site. 10 ACS Paragon Plus Environment

Page 10 of 27

Page 11 of 27

40 Rxn-1

0

ln (k [1/s])

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Rxn-2 -40

Rxn-5

-80

Rxn-7 Rxn-16

-120 -160 0

1

2

3

4

1000/T [1/K] Figure 7: High-pressure limiting rate constants for Rxn-1, Rxn-2, Rxn-5, Rxn-7, and Rxn16 calculated with TST in the temperature range of 300−1500 K.

Figure 8 shows a comparison of the high-pressure limiting rate constants among the three channels (Rxn-8, Rxn-9, and Rxn-13) and indicated that Rxn-21 and Rxn-25, both of which lead to the formation of C4H4, C2H2, and CO as described in the previous section, were likely to be the major channels. Thus, the unimolecular decomposition pathways would be pass through the singlet state (Rxn-7 -> Rxn-9 -> Rxn-10 -> Rxn-11 -> Rxn-12 or Rxn-7 -> Rxn-13 -> Rxn-14 -> Rxn-15). Ledesma et al. 22 also supported the formation of C4H4, C2H2, and CO from catechol pyrolysis based on an experimental observation with a quartz tubular-flow reactor.



ln (k [cm3/mol/s])

20 0

Rxn-8

-20

Rxn-9

-40

Rxn-13

-60 -80 -100 -120 0

1

2

3

4

1000/T [1/K] Figure 8: High-pressure limiting rate constants for Rxn-8, Rxn-9 and Rxn-13 calculated with TST in the temperature range of 300−1500 K.

In order to evaluate if the H radical contributes to Rxn-28, Rxn-29, Rxn-30, or Rxn-34, the high-pressure limiting rate constants of these channels were plotted in Figure 9. According to this figure, H-addition into a carbon site with the hydroxyl group, namely, Rxn-30, was least likely to occur at all temperatures. Thus, it is reasonable to conclude that H-addition into a carbon bearing a H atom (Rxn-28 and Rxn-29) or H-abstraction (Rxn-34) tends to take place more easily. 35

ln (k [cm3/mol/s])

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 12 of 27

Rxn-28

30

Rxn-29 25

Rxn-30

20

Rxn-34

15 10 0

1

2

3

4

1000/T [1/K] Figure 9: High-pressure limiting rate constants for Rxn-28, Rxn-29, Rxn-30, and Rxn-34 12 ACS Paragon Plus Environment

Page 13 of 27

in the temperature range of 300−1500 K.

Figure 10 illustrates the calculated high-pressure limiting rate constants for the initial channels of guaiacol unimolecular decomposition (Rxn-39 and Rxn-40). A comparison of these two rate constants suggested that Rxn-39, which produces precursor IM10 for the formation of catechol, has a higher rate constant and plays an important role in guaiacol pyrolysis. Hosoya et al.31 reported that a large amount of catechol was observed from the guaiacol pyrolysis experiment with total-ion chromatograms in the GC–MS analysis. 40 Rxn-39

ln (k [1/s])

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


0

Rxn-40

-40 -80 -120 0

1

2

3

4

1000/T [1/K] Figure 10: High-pressure limiting rate constants for Rxn-39 and Rxn-40 calculated with TST in the temperature range of 300−1500 K. Figure 11 is a graphic representation for comparing the high-pressure limiting rate constants between Rxn-42 and Rxn-44. As indicated in this figure, H-addition (Rxn-42) would be more susceptible than H-abstraction (Rxn-44) when focusing on the bimolecular reaction of guaiacol with a H radical.



30

ln (k [cm3/mol/s])

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 14 of 27

Rxn-42

20

Rxn-44 10 0 -10 -20 0

1

2

3

4

1000/T [1/K] Figure 11: High-pressure limiting rate constants for Rxn-42 and Rxn-44 calculated with TST in the temperature range of 300−1500 K. Modified Arrhenius parameters for all reaction channels, including both the forward and reverse rate constants, are given in Table 1.


Page 15 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47


Table 1: Modified Arrhenius Parameters (k=ATnexp(-E/RT)) for Each Elementary Channel, Forward (f) ((cm3/mol)/s and kcal/mol) and Reverse (r) ((cm3/mol)/s and kcal/mol) Channel

Reaction

A(f)

n(f)

E(f)

A(r)

n(r)

E(r)

10.54

65.33

7.73×10-28

11.32

20.16

1.44×105

2.65

57.93

0.00

2.88

Rxn-1

o-C6H4(OH)2

→

o-C6H4O2

+ H2

1.61×10-23

Rxn-2

o-C6H4(OH)2

→

IM1

+ H2

5.94×108

Rxn-3

IM1

→

IM2

Rxn-4

IM2

→

C5H4O

Rxn-5

o-C6H4(OH)2

→

IM3

Rxn-6

IM11

→

C5H4

Rxn-7

o-C6H4(OH)2

→

IM4

Rxn-8

IM4

→

IM10

Rxn-9

IM4

→

IM5

5.54×10

Rxn-10

IM5

→

IM6

2.89×1012

Rxn-11

IM6

→

IM7

+ CO

6.31×10

11

Rxn-12

IM7

→

C5H4OH

+ H

3.40×108

Rxn-13

IM4

→

IM8

Rxn-14

IM8

→

IM9

Rxn-15

IM9

→

C5H4OH

Rxn-16

o-C6H4(OH)2

→

IM10

Rxn-17

IM10

→

IM11

8.50×10

Rxn-18

IM11

→

IM12

7.50×1011

Rxn-19

IM12

→

IM13

12

0.35

Rxn-20

IM13

→

CH2CHCHCH + CO

1.87×1012

0.13

+ CO

6.43×10

16

1.13×109

2.28 109.38

15

0.00

93.11

6.46×10

1.14

2.69

8.62×107

1.63

79.41

1

3.22

46.93

0.00

0.00

17.74

19.98

+ H2O

1.02×10

12

1.18

82.22

7.82×10

+ CO

3.76×1015

0.00

77.65

2.62×1017

1.15×10 + H

5.69×106 8

17.60

35.21

1.51×10

2.18

78.90

8.61×105

2.30

15.39

1.18

38.14

9

0.96

7.22

0.05

8.16

3.97×10

3.58×1012

0.05

4.72

3

3.86

52.37

1.46

1.42

0.12

4.06

0.61

27.58

1.37×10

1.66

77.81

7.62×107

0.67

44.19

8.99×10

1.76×1012

0.31

35.39

8.67×104

+ H

8.33×10

13

0.00

+ H

1.95×1014

0.00

+ CO

-48

11

2.90×10 + CO

-47

4.91×10


-55

10

3.98

66.20

77.10

2.43×10

12

0.00

1.56

84.42

1.40×1013

0.00

7.50

19.72

4.33

-55

19.90

40.22

2.39×10

0.54

36.07

2.45×1011

0.10

4.33

7.20

1.61×10

5

3.45

16.59

7.18

6.95×105

3.73

4.80


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47

IM14

→

Rxn-22

IM10

→

IM14

2.59×10

Rxn-23

IM14

→

IM15

3.66×1012

Rxn-24

IM15

→

IM16

+ CO

6.25×10

12

Rxn-25

IM16

→

CHCHCHO

+ C2H2

2.58×1011

Rxn-26

IM10

→

o-C6H4O2

Rxn-27

IM10

→

IM17

Rxn-28

o-C6H4(OH)2

+ H

→

Rxn-29

o-C6H4(OH)2

+ H

→

+ H

Rxn-21

2.20×108

IM11

+ H

-12

1.30 7.40

61.81

0.18

2.13

0.62

27.89

4.25

3.14×109

1.24

27.31

1.75

6.08

8

1.48

25.75

18.98

14.74

2.56×10-52

18.98

14.60

16.63

19.69

1.54×10

-44

16.68

16.30

18.88

17.29

2.41×104

2.33

-0.96

1.63

3.82

1.96×10

5

2.36

29.57

4.01

1.75

2.34×10-3

5.03

27.67

IM19

2.63×10-52 -44

5.45×10-52

Rxn-32

IM19

→

IM20

Rxn-33

IM20

→

C6H5OH

Rxn-34

o-C6H4(OH)2

+ H

→

IM10

+ H2

1.00×10

Rxn-35

o-C6H4(OH)2

+ CH3

→

IM10

+ CH4

9.51×10-2

1.54×10

8

Rxn-36

o-C6H4(OH)2

+ OH

→

IM10

+ H2O

1.97×10

Rxn-37

o-C6H4(OH)2

+ IM10

→

IM10

+ IM4

1.23×10-8

+ o-C6H4(OH)2

→

o-C6H4(OH)2

+ IM4

2.58×10

-2

IM10

+ CH3

1.61×1014

Rxn-41

IM21

→

C6H5O

Rxn-42

CH3OC6H4OH

→

IM22

Rxn-43

IM22

→

C6H5OH

6.06×10 + OCH3

4

-69

1.42×1013 5.09×10

+ OCH3

1.84

1.30

1.73×10

IM21

1.61

1.76×10

IM20

→

2.81

4.68

→

CH3OC6H4OH

2.50

8

16.98

7

Rxn-40

4.39×104

0.34

1.57

→

284.18

9

1.87×108

→

7

4.02×1012


5.51

3.66

5.36×10

1.02×1011

IM18

6.99

14.80

61.20

Rxn-31

40.73

0.07

0.87

o-C6H4(OH)2

1.53

4

1.04×1011

IM19

CH3OC6H4OH

1.64×1011

2.87×10

1.62

Rxn-39

5.38×10

-12

72.77

1.02×10

o-C6H4(OH)2

2.98×107

1.55

1.17×10

IM18

Rxn-38

34.52

1.11 321.99

8

+ OH

6.25

10

Rxn-30

+ H

Page 16 of 27

2.91×10

1

2.29

0.30

5.48×10

5.65

20.05

2.02×10-9

5.94

6.90

3.20

27.20

4.23×10

-3

3.50

14.06

0.00

50.65

3.11×1011

0.00

0.00

24.05

16.72

-69

3.08 4763.39

24.00

44.34

1.55×10

0.00

41.72

175×1011

0.00

0.00

1.62

5.08

7.84×10

8

1.35

25.83

0.29

16.28

1.11×10-1

3.51

2.54

Page 17 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47


Rxn-44

CH3OC6H4OH

+ H

→

IM10

+ CH4

2.16×102


3.38

21.76

7.74×10-7

5.60

67.66


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

4. Conclusions The possible pathways of catechol and guaiacol pyrolysis, including bimolecular reaction and unimolecular decomposition, were proposed. Subsequently, PES were calculated by the CBS-QB3 method. The high-pressure limiting rate constants for the proposed pyrolysis channels were estimated based on the TST. The kinetic analysis suggested that the catechol unimolecular decomposition starts with H migration to a carbon site bearing a H atom to produce 2-hydroxycyclohexa-2,4-dien-1-one, which finally decomposes into C4H4, C2H2, and CO. On the other hand, guaiacol unimolecular decomposition seems to give rise to homolysis of the O–CH3 bond, followed by the formation of catechol. In the case of bimolecular reaction with a H radical, the formation of phenol is kinetically the most favorable in both the catechol and guaiacol pyrolysis pathways. In order to establish the capability of the DCKM for describing the complex phenomena related to lignin pyrolysis more accurately, further work is required so that the rate constants for the elementary decomposition steps of other individual lignin-derived compounds, such as syringol, coniferyl, sinapyl, and p-coumaryl alcohols, can be determined. Supporting Information Geometries, frequencies, spin multiplicities, and Gaussian outputs of all stable structure and transition state are described in Supporting Information. Acknowledgements This research was in part financially supported by KAKENHI (Grant-in-Aid for Scientific Research (B): 17H03454). The authors are also grateful to the support by the Cooperative Research Program of “Network Joint Research Center for Materials and Devices”. All the computations in this study were performed on the PC cluster systems in our group and the high-performance computing system at the Research Institute for Information Technology, Kyushu University. References: (1)

Kawamoto, H.; Saka, S. Role of Side-Chain Hydroxyl Groups in Pyrolytic Reaction of Phenolic β-Ether Type of Lignin Dimer. J. Wood Chem. Technol. 2007, 27 (2), 113–120.

(2)

Kawamoto, H.; Horigoshi, S.; Saka, S. Pyrolysis Reactions of Various Lignin Model Dimers. J. Wood Sci. 2007, 53 (2), 168–174. 18 ACS Paragon Plus Environment

Page 18 of 27

Page 19 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(3)

Vivas, N.; Nonier, M. F.; Pianet, I.; Vivas de Gaulejac, N.; Fouquet, E. Structure of Extracted Lignins from Oak Heartwood. Comptes Rendus Chim. 2006, 9 (9), 1221–1233.

(4)

Dorrestijn, E.; Mulder, P. The Radical-Induced Decomposition of 2Methoxyphenol. J. Chem. Soc., Perkin Trans 1999, 0, 777–780.

(5)

Czernik, S.; Bridgwater, A. V. Overview of Applications of Biomass Fast Pyrolysis Oil. Energy and Fuels 2004, 18 (2), 590–598.

(6)

Bridgwater, A. V. Review of Fast Pyrolysis of Biomass and Product Upgrading. Biomass and Bioenergy 2012, 38, 68–94.

(7)

Kawamoto, H. Lignin Pyrolysis Reactions. J. Wood Sci. 2017, 63 (2), 117–132.

(8)

Goyal, H. B.; Seal, D.; Saxena, R. C. Bio-Fuels from Thermochemical Conversion of Renewable Resources: A Review. Renew. Sustain. Energy Rev. 2008, 12 (2), 504–517.

(9)

Collard, F. -X.; Blin, J. A Review on Pyrolysis of Biomass Constituents: Mechanisms and Composition of the Products Obtained from the Conversion of Cellulose, Hemicelluloses and Lignin. Renew. Sustain. Energy Rev. 2014, 38, 594–608.

(10) Naqvi, M.; Yan, J.; Dahlquist, E. Black Liquor Gasification Integrated in Pulp and Paper Mills: A Critical Review. Bioresour. Technol. 2010, 101 (21), 8001– 8015. (11) Mu, W.; Ben, H.; Ragauskas, A.; Deng, Y. Lignin Pyrolysis Components and Upgrading-Technology Review. Bioenergy Res. 2013, 6 (4), 1183–1204. (12) Yang, H.; Appari, S.; Kudo, S.; Hayashi, J.-I.; Norinaga, K. Detailed Chemical Kinetic Modeling of Vapor-Phase Reactions of Volatiles Derived from Fast Pyrolysis of Lignin. Ind. Eng. Chem. Res. 2015, 54 (27), 6855–6864. (13) Thimthong, N.; Appari, S.; Tanaka, R.; Iwanaga, K.; Kudo, S.; Hayashi, J. -I.; Shoji, T.; Norinaga, K. Kinetic Modeling of Non-Catalytic Partial Oxidation of Nascent Volatiles Derived from Fast Pyrolysis of Woody Biomass with Detailed Chemistry. Fuel Process. Technol. 2015, 134, 159–167. (14) Norinaga, K.; Yang, H.; Tanaka, R.; Appari, S.; Iwanaga, K.; Takashima, Y.; Kudo, S.; Shoji, T.; Hayashi, J. -I. A Mechanistic Study on the Reaction Pathways Leading to Benzene and Naphthalene in Cellulose Vapor Phase Cracking. Biomass and Bioenergy 2014, 69, 144–154. 19 ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(15) Norinaga, K.; Shoji, T.; Kudo, S.; Hayashi, J. -I. Detailed Chemical Kinetic Modelling of Vapour-Phase Cracking of Multi-Component Molecular Mixtures Derived from the Fast Pyrolysis of Cellulose. Fuel 2013, 103, 141–150. (16) Hosoya, T.; Kawamoto, H.; Saka, S. Pyrolysis Behaviors of Wood and Its Constituent Polymers at Gasification Temperature. J. Anal. Appl. Pyrolysis 2007, 78 (2), 328–336. (17) Nakamura, T.; Kawamoto, H.; Saka, S. Pyrolysis Behavior of Japanese Cedar Wood Lignin Studied with Various Model Dimers. J. Anal. Appl. Pyrolysis 2008, 81 (2), 173–182. (18) Brodin, I.; Sjöholm, E.; Gellerstedt, G. The Behavior of Kraft Lignin during Thermal Treatment. J. Anal. Appl. Pyrolysis 2010, 87 (1), 70–77. (19) Brebu, M.; Vasile, C. Thermal Degradation of Lignin – A Review. Celluose Chem. Technol. 2010, 44 (9), 353–363. (20) Khachatryan, L.; Adounkpe, J.; Maskos, Z.; Dellinger, B. Formation of Cyclopentadienyl Radical from the Gas-Phase Pyrolysis of Hydroquinone, Catechol, and Phenol. Environ. Sci. Technol. 2006, 40 (16), 5071–5076. (21) Thomas, S.; Wornat, M. J. Polycyclic Aromatic Hydrocarbons from the CoPyrolysis of Catechol and 1,3-Butadiene. Proc. Combust. Inst. 2009, 32 I (1), 615–622. (22) Ledesma, E. B.; Marsh, N. D.; Sandrowitz, A. K.; Wornat, M. J. An Experimental Study on the Thermal Decomposition of Catechol. Proc. Combust. Inst. 2002, 29, 2299–2306. (23) Yang, H.; Furutani, Y.; Kudo, S.; Hayashi, J. -I.; Norinaga, K. Experimental Investigation of Thermal Decomposition of Dihydroxybenzene Isomers: Catechol, Hydroquinone, and Resorcinol. J. Anal. Appl. Pyrolysis 2016, 120, 321–329. (24) Thomas, S.; Ledesma, E. B.; Wornat, M. J. The Effects of Oxygen on the Yields of the Thermal Decomposition Products of Catechol under Pyrolysis and FuelRich Oxidation Conditions. Fuel 2007, 86 (16), 2581–2595. (25) Wornat, M. J.; Ledesma, E. B.; Marsh, N. D. Polycyclic Aromatic Hydrocarbons from the Pyrolysis of Catechol (Ortho-Dihydroxybenzene), a Model Fuel Representative of Entities in Tobacco, Coal, and Lignin. Fuel 2001, 80 (12), 1711–1726. 20 ACS Paragon Plus Environment

Page 20 of 27

Page 21 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


(26) Vuori, A. I.; Bredenberg, J. B. -S. Thermal Chemistry Pathways of Substituted Anisoles. Ind. Eng. Chem. Res. 1987, 26 (2), 359–365. (27) Vuori, A. Pyrolysis Studies of Some Simple Coal Related Aromatic Methyl Ethers. Fuel 1986, 65 (11), 1575–1583. (28) Suryan, M. M.; Kafafi, S. A.; Stein, S. E. The Thermal Decomposition of Hydroxy- and Methoxy-Substituted Anisoles. J. Am. Chem. Soc. 1989, 111, 1423–1429. (29) Lawson, J. J. R.; Klein, M. M. T. Influence of Water on Guaiacol Pyrolysis. Ind. Eng. Chem. Fundam. 1985, 24 (2), 203–208. (30) Asmadi, M.; Kawamoto, H.; Saka, S. Thermal Reactions of Guaiacol and Syringol as Lignin Model Aromatic Nuclei. J. Anal. Appl. Pyrolysis 2011, 92 (1), 88–98. (31) Hosoya, T.; Kawamoto, H.; Saka, S. Role of Methoxyl Group in Char Formation from Lignin-Related Compounds. J. Anal. Appl. Pyrolysis 2009, 84 (1), 79–83. (32) Scheer, A. M.; Mukarakate, C.; Robichaud, D. J.; Nimlos, M. R.; Ellison, G. B. Thermal Decomposition Mechanisms of the Methoxyphenols: Formation of Phenol, Cyclopentadienone, Vinylacetylene, and Acetylene. J. Phys. Chem. A 2011, 115 (46), 13381–13389. (33) Alsoufi, A.; Altarawneh, M.; Dlugogorski, B. Z.; Kennedy, E. M.; Mackie, J. C. A DFT Study on the Self-Coupling Reactions of the Three Isomeric Semiquinone Radicals. J. Mol. Struct. THEOCHEM 2010, 958 (1–3), 106–115. (34) Altarawneh, M.; Dlugogorski, B. Z.; Kennedy, E. M.; Mackie, J. C. Thermochemical Properties and Decomposition Pathways of Three Isomeric Semiquinone Radicals. J. Phys. Chem. A 2010, 114 (2), 1098–1108. (35) Altarawneh, M.; Dlugogorski, B. Z.; Kennedy, E. M.; Mackie, J. C. Theoretical Study of Unimolecular Decomposition of Catechol. J. Phys. Chem. A 2010, 114 (2), 1060–1067. (36) Khachatryan, L.; Asatryan, R.; McFerrin, C.; Adounkpe, J.; Dellinger, B. Radicals from the Gas-Phase Pyrolysis of Catechol. 2. Comparison of the Pyrolysis of Catechol and Hydroquinone. J. Phys. Chem. A 2010, 114 (37), 10110–10116. (37) McFerrin, C. A.; Hall, R. W.; Dellinger, B. Ab Initio Study of the Formation and Degradation Reactions of Semiquinone and Phenoxyl Radicals. J. Mol. Struct. 21 ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

THEOCHEM 2008, 848 (1–3), 16–23. (38) Liu, C.; Zhang, Y.; Huang, X. Study of Guaiacol Pyrolysis Mechanism Based on Density Function Theory. Fuel Process. Technol. 2014, 123, 159–165. (39) Frisch, M. J.; Trucks, G. W.; Schlegel, H. B.; Scuseria, G. E.; Robb, M. A.; Cheeseman, J. R.; Scalmani, G.; Barone, V.; Mennucci, B.; Petersson, G. A. . et al. Gaussian 09, Revision A.1; Gaussian, Inc.: Wallingford, CT, 2009. (40) Montgomery, J. A.; Frisch, M. J.; Ochterski, J. W.; Petersson, G. A. A Complete Basis Set Model Chemistry. VII. Use of the Minimum Population Localization Method. J. Chem. Phys. 2000, 112 (15), 6532–6542. (41) Raghavachari, K. Perspective on “Density Functional Thermochemistry. III. The Role of Exact Exchange.” Theor. Chem. Accounts 2000, 103 (3–4), 361–363. (42) Lee, C.; Yang, W.; Parr, R. G. Development of the Colle-Salvetti CorrelationEnergy Formula into a Functional of the Electron Density. Phys. Rev. B 1988, 37 (2), 785–789. (43) Gonzalez, C.; Schlegel, H. B. An Improved Algorithm for Reaction Path Following. J. Chem. Phys. 1989, 90 (4), 2154–2161. (44) Miyoshi, A. GPOP software, Home Page: http://www.frad.t.utokyo.ac.jp/~miyoshi/gpop/. (45) Pitzer, K. S.; Gwinn, W. D. Energy Levels and Thermodynamic Functions for Molecules with Internal Rotation I. Rigid Frame with Attached Tops. J. Chem. Phys. 1942, 10 (7), 428–440. (46) Knyazev, V. D. Density of States of One-Dimensional Hindered Internal Rotors and Separability of Rotational Degrees of Freedom. J. Phys. Chem. A 1998, 102 (22), 3916–3922. (47) Garrett, B. C.; Truhlar, D. G. Semiclassical Tunneling Calculations. J. Phys. Chem. 1979, 83 (22), 2921–2926. (48) Frank, P.; Herzler, J.; Just, T.; Wahl, C. High-Temperature Reactions of Phenyl Oxidation. Symp. Combust. 1994, 25 (1), 833–840. (49) Alzueta, M. U.; Glarborg, P.; Dam-Johansen, K. Experimental and Kinetic Modeling Study of the Oxidation of Benzene. Int. J. Chem. Kinet. 2000, 32 (8), 498–522. (50) Scheer, A. M.; Mukarakate, C.; Robichaud, D. J.; Nimlos, M. R.; Carstensen, H. -H.; Barney Ellison, G. Unimolecular Thermal Decomposition of Phenol and D 22 ACS Paragon Plus Environment

Page 22 of 27

Page 23 of 27

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


5-Phenol: Direct Observation of Cyclopentadiene Formation via Cyclohexadienone. J. Chem. Phys. 2012, 136 (4), 044309. (51) Wang, H.; Brezinsky, K. Computational Study on the Thermochemistry of Cyclopentadiene Derivatives and Kinetics of Cyclopentadienone Thermal Decomposition. J. Phys. Chem. A 1998, 102 (9), 1530–1541. (52) Chambreau, S. D.; Lemieux, J.; Wang, L.; Zhang, J. Mechanistic Studies of the Pyrolysis of 1, 3-Butadiene, 1, 3-Butadiene-1, 1, 4, 4-d 4, 1, 2-Butadiene, and 2Butyne by Supersonic Jet/Photoionization Mass Spectrometry. J. Phys. Chem. A 2005, 109 (10), 2190–2196. (53) Woodin, R. L.; Meyer, C. F.; Kajkowski, K. A. Laser Powered Homogeneous Pyrolysis of 1,3-Butadiene. Spectrochim. Acta 1987, 43 (2), 241–242. (54) Melius, C. F.; Colvin, M. E.; Marinov, N. M.; Pit, W. J.; Senkan, S. M. Reaction Mechanisms in Aromatic Hydrocarbon Formation Involving the C5H5 Cyclopentadienyl Moiety. Symp. Combust. 1996, 26 (1), 685–692. (55) Cavallotti, C.; Polino, D. On the Kinetics of the C5H5 + C5H5 Reaction. Proc. Combust. Inst. 2013, 34 (1), 557–564. (56) Robinson, R. K.; Lindstedt, R. P. On the Chemical Kinetics of Cyclopentadiene Oxidation. Combust. Flame 2011, 158 (4), 666–686. (57) Dean, A. M. Predictions of Pressure and Temperature Effects upon Radical Addition and Recombination Reactions. J. Phys. Chem. 1985, 89 (21), 4600– 4608. (58) Weissman, M. A.; Benson, S. W. Rate Parameters for the Reactions of C2H3 and C4H5 with H2 and C2H2. J. Phys. Chem. 1988, 92 (14), 4080–4084. (59) Jen, S.-H.; Chen, I.-C. Production of HCO from Propenal Photolyzed near 300 Nm: Reaction Mechanism and Distribution of Internal States of Fragment HCO. J. Chem. Phys. 1999, 111 (18), 8448-8453. (60) Furutani, Y.; Kudo, S.; Hayashi, J. -I.; Norinaga, K. Theoretical Study on Reaction Pathways Leading to CO and CO2 in the Pyrolysis of Resorcinol. J. Phys. Chem. A 2017, 121 (3), 631–637. (61) Xu, Z. F.; Lin, M. C. Ab Initio Kinetics for the Unimolecular Reaction C6H5OH → CO + C5H6. J. Phys. Chem. A 2006, 110 (4), 1672–1677. (62) Liu, R. F.; Morokuma, L.; Mebel, A. M.; Liu, M. C. Ab Initio Study of the Mechanism for the Thermal Decomposition of the Phenoxy Radical. J. Phys. 23 ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Chem. 1996, 100 (22), 9314−9322. (63) Carstensen, H. -H.; Dean, A. M. A Quantitative Kinetic Analysis of CO Elimination from Phenoxy Radicals. Int. J. Chem. Kinet. 2011, 44 (1), 75–89. (64) Zhu, L.; Bozzelli, J. W. Kinetics and Thermochemistry for the Gas-Phase KetoEnol Tautomerism of Phenol ↔ 2,4-Cyclohexadienone. J. Phys. Chem. A 2003, 107 (19), 3696–3703. (65) Wardlaw, D. M.; Marcus, R. A. RRKM Reaction Rate Theory for Transition State of Any Looseness. Chem. Phys. Lett. 1984, 110 (3), 230–234. (66) Mokrushin, V.; Bedanov, V.; Tsang, W.; Zachariah, M.; Knyazev, V. ChemRate, ver. 1.5.8; NIST: Gaithersburg, 2009. (67) Hippler, H.; Troe, J.; Wendelken, H. J. Collisional Deactivation of Vibrationally Highly Excited Polyatomic Molecules. II. Direct Observations for Excited Toluene. J. Chem. Phys. 1983, 78 (11), 6709–6717. (68) Barker, J. R. Energy Transfer in Master Equation Simulations: A New Approach. Int. J. Chem. Kinet. 2009, 41 (12), 748–763. (69) Horn, C.; Roy, K.; Frank, P.; Just, T. Shock-Tube Study on the HighTemperature Pyrolysis of Phenol. Symp. Combust. 1998, 27 (1), 321–328.


Page 24 of 27

Page 25 of 27


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47

TOC graphic


Page 26 of 27

Page 27 of 27

TOC Graphic 40 Rxn-1 0

ln (k [1/s])

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42


Rxn-2 -40

Rxn-5 Rxn-7

-80

Rxn-16

-120 -160 0

1

2

1000/T [1/K] ACS Paragon Plus Environment

3

4

Theoretical Study on the Kinetics of Thermal Decomposition of

Recommend Documents