Kinetic and modeling studies on ETBE pyrolysis behind reflected shock waves

Article abstract of DOI:10.1016/j.cplett.2007.11.097

The high temperature pyrolysis of ethyl tert-butyl ether (ETBE) was studied behind reflected shock waves coupled with the single-pulse method and UV (195 nm) absorption spectroscopy in the temperature range 1000-1500 K at total pressures ranging between 1.0 and 9.0 atm. The energies of ETBE and transition states for the reactions ETBE = iso-C₄H₈ + C₂H₅OH (1) and ETBE = C₂H₄ + tert-C₄H₉OH (2) were calculated at the MP4/cc-pVTZ//MP2/cc-pVTZ level of theory. A 170-reaction mechanism was constructed to explain the product distribution. From the UV absorption experiment, the rate coefficient k₁ = 1.7 × 10¹⁴exp(-254.0 kJ mol^-1/RT) s^-1 was found to reach its high-pressure limit.

Full text of DOI:10.1016/j.cplett.2007.11.097

Available online at www.sciencedirect.com
Chemical Physics Letters 451 (2008) 192–197
www.elsevier.com/locate/cplett
Kinetic and modeling studies on ETBE pyrolysis behind reflected
shock waves
Kenji Yasunaga a, Yuma Kuraguchi b, Yoshiaki Hidaka b,*, Osamu Takahashi c,
Hiroshi Yamada a, Tohru Koike a
a Department of Chemistry, National Defense Academy, Hashirimizu, 239-8686 Yokosuka, Japan
b Departments of Chemistry and Biology, Graduate School of Science and Engineering, Ehime University, Bunkyo-cho, 790-8577 Matsuyama, Japan
c Department of Chemistry, Graduate School of Science, Hiroshima University, Kagamiyama, 739-8526 Higashihiroshima, Japan
Received 12 October 2007; in final form 30 November 2007
Available online 8 December 2007
Abstract
The high temperature pyrolysis of ethyl tert-butyl ether (ETBE) was studied behind reflected shock waves coupled with the single-pulse
method and UV (195 nm) absorption spectroscopy in the temperature range 1000–1500 K at total pressures ranging between 1.0 and
9.0 atm. The energies of ETBE and transition states for the reactions ETBE = iso-C4H8 + C2H5OH (1) and ETBE = C2H4 + tert-
C4H9OH (2) were calculated at the MP4/cc-pVTZ//MP2/cc-pVTZ level of theory. A 170-reaction mechanism was constructed to explain
the product distribution. From the UV absorption experiment, the rate coefficient k1 = 1.7 ꢀ 1014exp(ꢁ254.0 kJ molꢁ1/RT) sꢁ1 was
found to reach its high-pressure limit.
Ó 2007 Elsevier B.V. All rights reserved.
1. Introduction
ETBE = C2H4 + tert-C4H9OH (TBA) (2) was found by
detecting TBA produced by the pyrolysis of ETBE. The
pressure dependence of the rate coefficient for reaction
(1) was examined by UV absorption experiments.
Recently, biofuels have been expected to function as new
energy resources. In particular, bioethanol prevails as a
fuel in several countries. In the United States and Brazil,
bioethanol itself is used as an automobile fuel. In Europe,
on the other hand, ethyl tert-butyl ether (ETBE) synthe-
sized from C2H5OH and iso-C4H8 is used. In Japan, a ten-
tative sale of ETBE began in April 2007.
The gas-phase oxidation of pure ETBE has previously
been investigated using a static reactor [1] and jet-stirred
reactors [2,3]. Previous works concluded that the dominant
initial thermal decomposition step of ETBE was the
unimolecular elimination reaction, ETBE = iso-C4H8 +
C2H5OH (1). In the present study, shock tube study of
ETBE pyrolysis was performed at temperatures above
1000 K. A 170-reaction ETBE pyrolysis mechanism was
constructed in order to explain the product distributions.
The evidence for the new unimolecular elimination reaction
2. Experimental
All experiments were performed behind reflected shock
waves. In the gas-analyzing experiments, the initial
pressure (P1) was fixed at 50 torr, while in the UV absorp-
tion experiments, it ranged between 100 and 300 torr. The
Ar (Teisan Co. and Iwatani), specified to be 99.999% pure,
was used without further purification. The ETBE (Sigma–
Aldrich, Inc.), specified to be 99% pure, was frozen,
degassed a number of times, and purified by trap-to-trap
distillation before use.
Two shock tubes were used in this study. The first was a
magic-hole-type with 4.1 cm i.d. [4]. The reacted gas mix-
tures were extracted into a pre-evacuated vessel (50 cm3)
through the valve near the end plate and analyzed by three
serially connected gas-chromatographs, each with a TCD.
The gas-chromatographic analysis, which was similar to
*
Corresponding author. Fax: +81 89 927 9590.
E-mail address: hidaka@dpc.ehime-u.ac.jp (Y. Hidaka).
0009-2614/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved.
doi:10.1016/j.cplett.2007.11.097

K. Yasunaga et al. / Chemical Physics Letters 451 (2008) 192–197
193
that in the study conducted by Hidaka et al. [5], was used
to determine the concentrations of reactant and products.
The amounts of reactant and products were determined
within an uncertainty of 4%. The effective heating time te
(reaction time), which was defined as the amount of time
between the arrival point of the reflected shock front and
the 80% point in the fall from the reflected shock front
pressure as shown in Fig. 1, was determined using the
method described previously [6,7]. The modeling method-
ology for this comparison is shown in detail in previous
reports [8,9].
The second was a standard-type shock tube connected
to a UV absorption system. This tube consisted of three
sections [10]. The high-pressure section was made of a steel
tube 1.5 m long and with an inner diameter of 10 cm. The
low-pressure section was made of stainless steel and had a
rectangular cross-section of 7.2 by 3.8 cm. For smooth flow
of the driver gas from the round high-pressure section to
the low-pressure section, we employed a conversion section
of 30 cm in length. Observation windows were located
3.8 m downstream from the diaphragm positioned between
the high-pressure section and the conversion section. The
end plate for the reflected shock wave was located 1 cm
from the observation windows. The total length of low-
pressure section was 3.8 m. UV light obtained from a deu-
terium lamp passed through a path of 7.2 cm in length in
the shock tube at the observation station and was dispersed
into 195 nm by a monochromator (half-width = 1.6 nm). It
was detected by a photo-multiplier (R208, Hamamatsu
photonics). The UV absorption profile that we observed
was analyzed using absorbance, log(If/It). The extinction
coefficients at 195 nm were measured for several com-
pounds expected to be the main products of UV absorption
under our experimental conditions. We found that iso-
C4H8 and ETBE only contributed to the UV absorption
profile at 195 nm. The equations for the extinction coeffi-
cients of iso-C4H8 and ETBE were eUV(iso-C4H8) =
3.44 ꢀ 106 cm2 molꢁ1 and
e
UV(ETBE) = ꢁ2.83 ꢀ 106 +
2770 ꢀ T (K) cm2 molꢁ1, respectively. The extinction coef-
ficient of C2H4 was about 1/30 that of iso-C4H8 at 1300 K.
The influence of C2H4 concentration on the UV absorption
profile at 195 nm was negligible.
Thermochemical data for H2O were adopted from the
JANAF table [11]. The heat of formations of ETBE,
TBA, C2H5 and OH were adopted from tables reported
by Dunphy et al. [12], NIST [13], Brouard et al. [14] and
Ruscic et al. [15], respectively. Thermochemical data for
H, H2, CH3, CH4, C2H4, CH2O and CH3CHO were
adopted from NIST [13]. Thermochemical data for
C2H5O, C2H5OH, C2H6O (acetone), iso-C4H8 and tert-
C4H9 were adopted from Burcat [16]. Thermochemical
data for r1ETBE(C2H5OC(CH3)2CH2), r2ETBE(CH2-
CH2OC(CH3)3), r3ETBE(CH3CHOC(CH3)3), r4ETBE-
(C2H5OC(CH3)2), tert-C4H9O, rdMTBE(CH2OC(CH3)3),
r1TBA(HOC(CH3)2CH2) and r2TBA(HOC(CH3)2) were
estimated using group values shown in [17] and group addi-
tivity method reported by Benson [17]; Cp values at 1500 K
not found in [17] were assumed from those in similar
species. Thermochemical data of ETBE and associated rad-
icals are shown in Table 1. Shock temperature was calcu-
lated by the measured velocity, assuming no chemical
reactions and full relaxation of the chemical species.
The computer calculations used in this study were essen-
tially the same as those described by Hidaka et al. [18]. We
used a computer routine consisting of the Gear-type inte-
gration of the set of differential equations describing the
chemical kinetics under constant density conditions for
the reflected shock waves. Reverse reactions were automat-
ically included in the computer program through equilib-
rium constants computed from the thermochemical data.
Sensitive spectra (pS) were calculated in order to deter-
mine the importance of each reaction. The pS adopted was
defined as pSij = log[(computed quantity)j0/(computed
quantity)j]/log[(parameter)i0/(parameter)i], where the primes
denote the parameters i and computed quantities j for a
computer simulation in which the value of one parameter
Table 1
Thermochemical data
DHꢂf 298
(kJ/mol) (J/mol K)
Sꢂ298
300 K Cp
(J/mol K)
1000 K 1500 K
500 K
ETBE
ꢁ325.1
ꢁ144.9
ꢁ149.3
ꢁ155.6
ꢁ123.0
386.4
406.5
399.3
401.0
351.1
309.2
393.9
322.4
149.3 232.3
147.0 227.6
147.1 225.5
141.8 219.8
120.0 185.6
106.6 160.9
134.7 198.3
82.8 126.3
348.9
335.1
336.0
330.7
293.0
240.3
287.0
202.9
403.9
378.6a
384.4
382.9
357.9a
273.6
324.4a
240.1
r1ETBE
r2ETBE
r3ETBE
r4ETBE
tert-C4H9O ꢁ86.9
rdMTBE
tert-C4H9
a
ꢁ116.0
55.0
Fig. 1. A typical pressure profile with the definition of effective heating
time.
Assumed value.

194
K. Yasunaga et al. / Chemical Physics Letters 451 (2008) 192–197
has been changed from a reference value (unprimed quan-
tity and parameter) [19]. The computed quantity and
parameter were the concentration of reactant or products
obtained by simulation and the rate coefficient,
respectively.
4.2. Product distribution
The reactant and product distributions obtained by the
pyrolysis of 3% ETBE diluted in Ar are shown in Fig. 3a.
In this Letter, the distributions of ETBE, iso-C4H8,
C2H6O(acetone), C2H5OH, TBA, H2, CH4 and CH3CHO
are shown to estimate rate coefficients relating to ETBE
pyrolysis. The distributions of C2H2, C2H4, C2H6, a-C3H4-
(allene), p-C3H4(propyne), C3H6 and C3H8, on the other
hand, depend mainly on the subsequent reactions, so they
are not shown in this Letter.
3. Theoretical calculations
All quantum chemical calculations were performed
using the GAUSSIAN 03 program package [20]. The geome-
tries of the reactant, products, and transition states were
optimized at the MP2/cc-pVTZ level of approximation.
Vibrational frequencies were calculated using the analytical
second derivatives at the same level of the geometry optimi-
zation in order to confirm the stationary structures and
correct for the zero-point vibrational energy. Single point
energy calculations were performed at the MP4/cc-
pVTZ//MP2/cc-pVTZ level in order to estimate the energy
of the compounds.
4.3. UV absorption at 195 nm
The typical time-dependent absorbance at 195 nm,
log(If/It), is shown in Fig. 4a. Under the conditions of
our UV absorption experiments, the main absorbers were
iso-C4H8 and ETBE, as shown in Fig. 4a.
5. Discussion
4. Results
5.1. Construction of an ETBE pyrolysis mechanism
4.1. Theoretical calculations
An ETBE pyrolysis mechanism, which included 170-
reactions, was constructed in order to reproduce the reac-
tant and product distributions obtained by the single pulse
method. The mechanism constructed is shown in Table 2.
The distributions of C2H5OH and TBA are sensitive to
reactions (1) and (2), as seen in Fig. 3b. C2H5OH and
TBA are produced only via unimolecular elimination reac-
tions (1) and (2), respectively. The activation energies of the
rate coefficients for reactions (1) and (2) were adopted from
the E0 obtained from quantum chemical calculations.
Those pre-exponential factors were estimated to reproduce
the distributions of C2H5OH and TBA. The distribution of
The transition states of reactions (1) and (2), TS1 and 2,
which form a four-centered structure, were found by quan-
tum chemical calculations. The relative energies of TS1 and
2 calculated from the reactant are shown in Fig. 2 along
with a concise optimized structural diagram. The relative
energies calculated were over 70 kJ molꢁ1 lower than the
DHꢂ0 of reactions (3)–(6), estimated from heats of formation
as described in Table 2. This suggests that the dominant
initial decomposition steps of ETBE were unimolecular
elimination reactions.
Fig. 2. Potential energy diagrams of ETBE unimolecular elimination reactions with geometries of TS1 and 2.

K. Yasunaga et al. / Chemical Physics Letters 451 (2008) 192–197
195
Table 2
Elementary reactions and rate coefficient expressions
No.
Reaction
A
n
Ea
DH0
55,200
Reference
(1)
(2)
(3)
(4)
(5)
(6)
(7)
(8)
ETBE = iso-C4H8 + C2H5OH
ETBE = C2H4 + TBA
ETBE = r4ETBE + CH3
1.70 ꢀ 1014
5.00 ꢀ 1013
2.50 ꢀ 1016
8.00 ꢀ 1015
8.00 ꢀ 1015
8.00 ꢀ 1015
3.00 ꢀ 1014
1.00 ꢀ 1014
7.00 ꢀ 1013
3.00 ꢀ 1012
1.00 ꢀ 1012
7.00 ꢀ 1011
5.00 ꢀ 1014
5.00 ꢀ 1014
1.00 ꢀ 1012
1.00 ꢀ 1012
2.50 ꢀ 1014
8.00 ꢀ 1013
2.50 ꢀ 1016
3.00 ꢀ 1014
3.00 ꢀ 1012
1.00 ꢀ 1012
5.00 ꢀ 1014
1.32 ꢀ 1020
5.43 ꢀ 1015
5.66 ꢀ 1011
1.59 ꢀ 1022
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
0.00
254,000
265,000
337,000
334,000
344,000
348,000
49,000
49,800
22,600
65,700
66,500
39,300
116,000
98,300
26,400
12,600
82,800
266,000
337,000
49,000
65,700
104,000
140,000
86,800
93,000
141,000
70,500
This work
This work
This work
This work
See text
See text
See text
See text
See text
See text
See text
See text
Assume
Assume
Assume
Assume
[20]
See text
See text
See text
See text
Assume
Assume
[21]
56,900
337,000
334,000
344,000
348,000
–64,100
–50,600
–54,800
–58,200
–43,900
–48,100
116,000
98,300
26,400
12,600
45,600
42,700
342,000
–42,300
–35,600
104,000
140,000
40,200
60,700
140,000
16,300
ETBE = tert-C4H9O + C2H5
ETBE = rdMTBE + CH3
ETBE = tert-C4H9 + C2H5O
ETBE + H = r1ETBE + H2
ETBE + H = r2ETBE + H2
ETBE + H = r3ETBE + H2
ETBE + CH3 = r1ETBE + CH4
ETBE + CH3 = r2ETBE + CH4
ETBE + CH3 = r3ETBE + CH4
r1ETBE = iso-C4H8 + C2H5O
r2ETBE = tert-C4H9O + C2H4
r3ETBE = tert-C4H9 + CH3CHO
r4ETBE = C2H6O + C2H5
rdMTBE = tert-C4H9 + CH2O
TBA = iso-C4H8 + H2O
TBA = r2TBA + CH3
TBA + H = r1TBA+H2
TBA + CH3 = r1TBA + CH4
r2TBA = H + C2H6O
r1TBA = OH + iso-C4H8
C2H5O = CH3 + CH2O
C2H5O = CH3CHO + H
tert-C4H9 = iso-C4H8 + H
tert-C4H9O = C2H6O + CH3
(9)
(10)
(11)
(12)
(13)
(14)
(15)
(16)
(17)
(18)
(19)
(20)
(21)
(22)
(23)
(24)
(25)
(26)
(27)
–2.02
–0.69
0.70
[21]
[21]
[21]
–2.55
Rate coefficients in the form, ATnexp(ꢁEa/RT), in cm, mol, J and K units. Heat of reactions, DHꢂ0, in J/mol unit.
C2H6O was sensitive to reactions (1), (3), (4), (8) and (9).
The radicals r4ETBE and tert-C4H9O produced by reac-
tions (3) and (4) unimolecularly decomposed to produce
C2H6O via reactions (16) and (27). The radical r2ETBE
produced by reactions (8) and (11) also produced C2H6O
via reactions (14) and (27). The rate coefficients for reac-
tions (3) and (4) were determined by fixing those for reac-
tions (1) and (2) to the value estimated above. The
activation energies were adopted from the heat of reactions
at 0 K. The pre-exponential factors were estimated in order
to reproduce C2H6O distribution, and the difference
between their pre-exponential factors was determined
based on the number of CH3 groups contributing to reac-
tions (3) and (4). The uncertainties of the rate coefficients
for reactions (3) and (4) were within 5% in the case of reac-
tion (8) with uncertainty of 50%. The rate coefficients for
reactions (5) and (6) were adopted by assuming values sim-
ilar to those of reactions (3) and (4), because none of the
experimental data had any sensitivity to them. The product
distributions of H2, CH4 and CH3CHO were sensitive to
the secondary reactions of ETBE, as seen in Fig. 3b. The
rate coefficients for reactions (7)–(12) were estimated to
reproduce the product distributions of H2, CH4 and
CH3CHO. They seemed to be much more sensitive to
experimental results in the oxidation system. We will deter-
mine the rate coefficients of the secondary reaction of
ETBE accurately in the near future in our work that
includes the oxidation mechanism. The rate coefficient for
reaction (18) was estimated by a shock tube study coupled
with UV absorption spectroscopy conducted at 195 nm
using 0.01–0.08% TBA in Ar and ab initio calculation,
and the details of this experiment will be published in the
near future. The same rate coefficient values as in reactions
(3), (7) and (10) were adopted for reactions (19), (20) and
(21), respectively. No experimental data was sensitive to
the rate coefficients for reactions (13)–(16), (22) and (23),
so we assumed those rate coefficients. We adopted the pub-
lished values of Curran [21] as the rate coefficients for reac-
tions (24)–(27).
From the ETBE pyrolysis mechanism that we con-
structed, we saw that 50% of the ETBE was consumed
by 70 ls at 1300 K under the gas-chromatographic exper-
imental condition. About 85% of the ETBE decomposed
unimolecularly, while about 15% of the ETBE reacted
with H and CH3. C2H5OH and TBA were each only pro-
duced directly via reaction (1) or (2). About 82% of the
iso-C4H8 was produced via reaction (1), and about 17%
was produced via reactions (6), (7), (9), (10) and (12).
About 82% of the C2H6O was produced via reactions (3)
and (4), and about 15% was produced via reactions (8)
and (11). About 15% of the CH4 was produced via reac-
tions (10)–(12), while about 85% was produced by subse-
quent reactions. About 63% of the CH3CHO was
produced via reactions (6), (7), (9), (10) and (12), and
about 37% was produced via the secondary reactions of
C2H5OH. About 55% of the H2 was produced via reac-
tions (7)–(9), while about 45% was produced by subse-
quent reactions.

196
K. Yasunaga et al. / Chemical Physics Letters 451 (2008) 192–197
1
a
ETBE
iso C4H8
C2H5OH
0.5
TBA
0
1
CH4
0.5
0
H2
CH3CHO
C2H6O
1500
1000
1000
1500
T5 / K
T5 / K
b
1.5
0.5
0
1200 K
t = 1270 μs
1200 K
t = 1270 μs
0
1
1
1
2
2
3
3
3
4
9
12
1
1
2
3
7
9
1
0
2
0
1200 K
1200 K
t = 1270 μs
t = 1270 μs
2
3
9
18
9
12
1
0
1
0
1200 K
1200 K
t = 1270 μs
t = 1270 μs
9
12
1
1
3
2
4
8
9
0.5
0
1
0
1200 K
1200 K
t = 1270 μs
t = 1270 μs
1
2
3
4
12
3
12 15
Reaction Number
Fig. 3. (a) Product distribution measured with 3% ETBE diluted in Ar at P1 = 50 torr. Solid lines are the simulated results using ETBE pyrolysis
mechanism constructed in the present study. The effective heating times are 1410 ls (900 K), 1360 ls (1000 K), 1310 ls (1100 K), 1270 ls (1200 K), 1230 ls
(1300 K), 1180 ls (1400 K) and 1130 ls (1500 K), respectively. (b) Sensitive spectra (pS) [19] for ETBE, iso-C4H8, C2H5OH, TBA, H2, C2H6O, CH4 and
CH3CHO concentration at 1200 K and 1270 ls for 3% ETBE diluted in Ar.
5.2. Pressure dependence of the rate coefficient for reaction
(1)
the conditions of UV absorption experiments that we ana-
lyzed the pyrolysis of ETBE using simple first order equa-
tions, as shown below, coupled with the Lambert–Beer
equation,
The pressure dependence of the rate coefficient for reac-
tion (1) was examined by monitoring the ETBE pyrolysis at
195 nm under the condition ranging from 0.0167% to
0.05% ETBE in Ar. As seen in Fig. 4a, absorption was
measured from the initial part of the ETBE pyrolysis.
From the ETBE pyrolysis mechanism that we constructed,
93% of the ETBE was consumed by reactions (1)–(6), and
the remaining 7% of the ETBE was consumed by reactions
(7)–(12) at 200 ls under the conditions shown in Fig. 4a.
The influence of secondary reactions was so small under
½ETBEꢃ ¼ ½ETBEꢃ0 expfꢁðkðiso-C4H8Þ þ kðothersÞtÞ
½iso-C4H8ꢃ ¼ ꢁkðiso-C4H8Þ=ðkðiso-C4H8Þ
þ kðothersÞÞ½ETBEꢃ0
½1 ꢁ expfꢁðkðiso-C4H8Þ þ kðothersÞÞtgꢃ;
where k(iso-C4H8) and k(others) signify the rate coefficients
producing iso-C4H8 and other products, respectively. The
estimated rate coefficients are shown in Fig. 5, with the

K. Yasunaga et al. / Chemical Physics Letters 451 (2008) 192–197
197
We compared our k1 value with that of Glaude et al. at
750–1150 K and 10 atm [2] and confirmed good agreement,
as shown in Fig. 5. In UV absorption experiments,
k(others) was also estimated simultaneously with k(iso-
C4H8), but none of the reactions not producing iso-C4H8,
namely reactions (2)–(5), were sensitive enough to the
production of iso-C4H8 to be estimated accurately, as
shown in Fig. 4b.
a
b
6. Conclusion
We constructed a 170-reaction mechanism including the
new reaction (2). From the UV absorption experiments, we
found that the rate coefficient for reaction (1) reached its
high-pressure limit at 1 atm. The rate coefficient for reac-
tion (1) estimated in the present study showed good agree-
ment with the findings of Glaude et al. [2]. Detailed
modeling for ETBE oxidation will be performed in the near
future.
Fig. 4. (a) A typical absorbance profile in ETBE pyrolysis at 195 nm;
shock conditions, 0.0167% ETBE diluted in Ar, T5 = 1231 K, P5 =
8.1 atm, P5 = 8.1 ꢀ 10ꢁ5 mol cmꢁ3
. Sensitive spectra (pS) [19] for
iso-C4H8 concentration in 200 ls and 800 ls at 1231 K for 0.0167%
ETBE diluted in Ar.
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[13] Data from NIST Standard Reference Database 69, June 2005
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445.
Fig. 5. Arrhenius plots for k(iso-C4H8) (s; P1 = 100 torr, P5 = 2.5–
3.0 atm, 0.05% ETBE diluted in Ar, h; P1 = 200 torr, P5 = 5.0–6.1 atm,
0.025% ETBE diluted in Ar, D; P1 = 300 torr, P5 = 8.1–8.9 atm, 0.0167%
ETBE diluted in Ar) and k (others) (d; P1 = 100 torr, P5 = 2.5–3.0 atm,
0.05% ETBE diluted in Ar, j; P1 = 200 torr, P5 = 5.0–6.1 atm, 0.025%
ETBE diluted in Ar, N; P1 = 300 torr, P5 = 8.1–8.9 atm, 0.0167% ETBE
diluted in Ar), , k1 = 1.7 ꢀ 1014exp(ꢁ254.0 kJ molꢁ1/RT) sꢁ1, estimated
by gas chromatographic result, -----, k1 = 1.6 ꢀ 1014exp(ꢁ251.0 kJ
molꢁ1/RT), proposed by Glaude et al. [1], ꢄꢄꢄꢄꢄꢄ, the sum of k2–k5
estimated by gas chromatographic result.
[15] B. Ruscic et al., J. Phys. Chem. A 106 (2002) 2727.
[16] A Burcat, B. Ruscic, Third Millennium Ideal Gas and Condensed
Phase Thermochemical Database for Combustion with updates from
Active Thermochemical Tables. ANL-05/20 TAE 960 2005.
[17] S.W. Benson, Thermochemical Kinetics, second edn., Wiley, New
York, 1976.
[18] Y. Hidaka, T. Higashihara, N. Ninomiya, H. Oshita, H. Kawano, J.
Phys. Chem. 97 (1993) 10977.
[19] W.C. Gardiner Jr., J. Phys. Chem. 81 (1977) 2367.
[20] J.C. Brocard, F. Baronnet, H.E. O’Neal, Combust. Flame 52 (1983)
25.
Arrhenius expression of reaction (1) estimated by gas chro-
matographic results. At 200 ls under the conditions shown
in Fig. 4a, 90% of the iso-C4H8 was produced via reaction
(1). The k(iso-C4H8) obtained was approximately k1, and
good agreement between UV absorption experiments at
2.5–8.9 atm and gas-chromatographic results was con-
firmed. The experimental results did not show pressure-
dependence, so we concluded that the rate coefficient for
reaction (1) reached its high-pressure limit at 1 atm.
[21] H.J. Curran, Int. J. Chem. Kinet. 38 (2005) 250.