Study on the pyrolysis characteristics of a series of fluorinated cyclopentenes and implication of their environmental influence

Article abstract of DOI:10.1016/j.cplett.2020.138213

3,3,4,4,5,5-hexafluorocyclopentene (6FE), 1,3,3,4,4,5,5-heptafluorocyclopentene (7FE) and octafluorocyclopentene (8FE) are considered as new generation of potential chlorofluorocarbons substitutes. To investigate the thermostabilities, tubular furnace experiments were designed over temperature range of 500-850℃. The results show that 6FE, 7FE and 8FE are all stable below 650 ℃, thus have good stabilities in common storage and practical use condition. Furthermore, considering the short atmospheric lifetimes (several months), low global warming potentials (GWPs, less than 119) and zero ozone depletion potentials (ODPs), the compounds seem no big influences on the climate change.

Full text of DOI:10.1016/j.cplett.2020.138213

Chemical Physics Letters 764 (2021) 138213
Contents lists available at ScienceDirect
Chemical Physics Letters
journal homepage: www.elsevier.com/locate/cplett
Research paper
Study on the pyrolysis characteristics of a series of fluorinated
cyclopentenes and implication of their environmental influence
,
,c
Zhenhai Wua, Yuanyuan Jia b, Hong Lia, Fang Bia, Yanqin Rena, Rui Gaoa, Chenfei Liua
,
,
,
,*
Ling Lia, Hao Zhanga d, Xin Zhanga e, Xuezhong Wanga
a State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China
b College of Earth Sciences. Jilin University, Changchun 130061, China
c School of Science, China University of Petroleum, Beijing 102249, China
d School of Science, China University of Geosciences, Beijing 100083, China
e Environmental Research Institute, Shandong University, Jinan 250100, China
A R T I C L E I N F O
A B S T R A C T
Keywords:
3,3,4,4,5,5-hexafluorocyclopentene
(6FE),
1,3,3,4,4,5,5-heptafluorocyclopentene
(7FE)
and
octa-
Cyclic-HFOs
fluorocyclopentene (8FE) are considered as new generation of potential chlorofluorocarbons substitutes. To
investigate the thermostabilities, tubular furnace experiments were designed over temperature range of 500-
850℃. The results show that 6FE, 7FE and 8FE are all stable below 650 ℃, thus have good stabilities in common
storage and practical use condition. Furthermore, considering the short atmospheric lifetimes (several months),
low global warming potentials (GWPs, less than 119) and zero ozone depletion potentials (ODPs), the compounds
seem no big influences on the climate change.
Pyrolysis decomposition
Pyrolysis mechanisms
Environmental influence
1. Introduction
applicable at a small scale. Several experimental studies were performed
and proved that the polymer film deposition rate in c-C5F8 is higher than
Chloridated and bromided materials were once used widely in the
fields of fire extinguishing, cleaning, refrigerating and foam making
[1,2]. But due to the stratospheric ozone depletion potentials (ODPs)
and high global warming potentials (GWPs), the Montreal Protocol and
its amendments has banned the use of these materials [3,4]. For
example, the atmospheric concentration of trichlorofluoromethane
(CFC-11), which ranks the second-most abundant chlorofluorocarbon,
has declined substantially since the mid-1990 s [5]. However, recent
reports pointed that the decline of the atmospheric concentration of
CFC-11 was slowdown after 2012, suggests global emissions have
increased [6,7]. The replacements of the ozone depletion substances
(ODS) seem to be urgent under this situation. Unsaturated fluorinated
alkenes [8,9] and fluorinated ketone [10,11] have been proposed as
potential etching agent, refrigerants and extinguishant. For example,
perfluoro-2-methyl-3-pentanone (PFMP), marketed as Novec 1230 by 3
M, has been proposed as a fire extinguishing replacement for chloro-
fluorocarbons (CFCs) and Halons [12]. Octafluorocyclopentene (8FE) is
used as an etching and cleaning gas in semiconductor processing in place
of CF4, C2F6, NF3, SF6, and c-C4F8 [13], which has been industrially
in c-C4F8 about 50% and leads to higher selectivity and better perfor-
mance of c-C5F8 [14,15]. Moreover, 3,3,4,4,5,5-hexafluorocyclopentene
(6FE) and 1,3,3,4,4,5,5-heptafluorocyclopentene (7FE), which have the
same structure, are now being exploited the use as heat pump fluids,
etching agents and important industrial intermediate materials [16,17].
Hence prior to large-scale commercial application, environmental
influence, toxicity and thermal stability should be considered first.
Environmental influences, such as stratospheric ozone depletion po-
tentials, global warming potentials, formation of secondary noxious or
toxic degradation products, should be considered in the commercial
employing of chemical materials [18]. The atmospheric lifetime of 6FE
is shown to be 107 days and the global warming potentials (GWPs) for
20, 100, and 500 years were 54, 15, and 4, respectively [19]. As for 8FE,
the atmospheric lifetime and the 100-year time horizon global warming
potentials value of 8FE (c-C5F8) have been estimated to be 104 days and
28 [20]. They all show no big influence on the environment. In-
vestigations of the acute inhalation and oral toxicity values of these
materials have shown nowhere. 1,1,2,2,3,3,4-heptafluorocyclopentane
(7FA) which has a similar carbon skeleton and elements, seems have
* Corresponding author.
E-mail address: wangxz@craes.org.cn (X. Wang).
https://doi.org/10.1016/j.cplett.2020.138213
Received 9 September 2020; Received in revised form 15 November 2020; Accepted 21 November 2020
Available online 28 November 2020
0009-2614/© 2020 Published by Elsevier B.V.

Z. Wu et al.
Chemical Physics Letters 764 (2021) 138213
and the pyrolysis products were discussed.
Table 1
Chemical parameters and principal/probable uses of 6FE, 7FE and 8FE.
2. Materials and methods
Chemical
6FE
Formula
CAS NO.
Concentration
(%)
Principal/Probable
use
2.1. Materials
1005–73-
99.65
Refrigerant, heat
pump fluids
8
Reactants (purity > 99%) and high purity nitrogen (purity >
99.99%) were all purchased from commercial companies (Table 1).
7FE
8FE
1892–03-
99.57
Refrigerant
1
2.2. Methods
559–40-0
99.14
Etching agent,
Luminescent
material
Experiments were carried out in the described system in Fig. 1, which
mainly consists of a tubular pyrolysis furnace (tubular constant tem-
perature zone about 40 cm in length, 1.0 cm inner diameter), a reactant
flow control system, an exhaust gas treatment system and an analysis
system.
intermediate
Moreover, a premixing system (consisted of a 250 ml mixing cham-
ber and pipelines) convolved by heater bands was designed to pro-
gressively evaporate and mix the chemicals and nitrogen (N2) to
homogeneous gaseous state before into the reactor tube. The flow rates
of the chemicals and N2 were controlled by peristaltic pump and gas
mass flowmeter, respectively. The accuracies of the liquid and gas flow
rates were around 0.5%.
negligible (LC50 = 14213 ppm, LD50＞2g/kg) toxicity, as tested by the
Ecological Toxicology and Environmental Safety Lab of Microbiological
Analysis Inspection Center of Guangdong Province in China [21].
Thermal stability is an important issue in investing the properties of
these chemicals especially when directly related to storage ability and
durability. Knowing the products during the pyrolysis process would be
helpful for understanding the working mechanisms, as well. 7FA has
been recommended as a new generation of cleaning agent with property
of zero ODPs and low GWPs [22]. It also shows good fire extinguish
ability with the fire extinguishing concentration of 8.4% (volume)
measured by the Cup Burner [23]. The pyrolysis temperature of 7FA is
580 ℃, and it shows bigger influence on the decomposition with the
temperature increasing. 2H-heptafluoropropane (HFP), used as fire-
extinguishing agent, decomposes at about 640 ◦C and markedly
breaks down at 700 ◦C, exhibits intense decompositions at 800 ◦C;
meanwhile, coke and HF formations were observed during the process,
and the amounts of them highly depend on reaction temperature and
time. But for 6FE, 7FE and 8FE relevant works are very limited. Further
studies on their toxicity and pyrolysis characteristics are still needed.
For exploring the extension application potentials of the materials,
pyrolysis characteristics and environmental influences are studied in
this paper. Pyrolysis experiments were performed at different temper-
atures (500–850 ℃) with residence time of 30 s and the kinds of the
products formed during the experiment were detected. The products at
different temperatures of the materials thermal decompositions were
analyzed and the kinetic mechanisms of the thermal decompositions
were proposed. Moreover, the environmental influences of the materials
Prior to each experiment, the tubular reactor was cleaned by acetone
and heated up to 800 ℃ for 30 min with N2 blowing in to remove
contaminants in the device. Then the furnace was reset to the target
experimental temperatures ranging from 500–850 ℃. Mixture of the
reactant pumped by a peristaltic pump and nitrogen carrier gas was
continuously flew into the tubular reactor during the pyrolysis process.
Flow rate of the mixture (reactant concentration 20%) was controlled at
60 ml/min to maintain the residence time to be 30 s. During the ex-
periments, three repeated samples were taken and analyzed in situ at
every target temperature after removing particulates and acid gases
generated. Analysis of the products collected by the sampling probe was
accomplished by gas chromatography (GC-FID) and gas chromatog-
raphy mass spectrometry (GC–MS). Concentrations of the compounds
were obtained by excluding the abnormal sample and averaging the
remaining ones. GC-FID (Beifen-RuiliSP-3420A) used DB-5 (30.0 m,
0.25 mm, 0.25 μm) capillary with the following temperature program-
ming: initial temperature was 35 ℃, then raised to 180 ℃ at 4 ℃ /min,
and held for 5 min. Helium was used as carrier gas with a flow rate of 6
ml/min. GC–MS analysis was performed on a GC–MS (Shimadzu
QP2010) instrument equipped with Rtx-5 ms column (30.0 m, 0.25 mm,
0.25 μm). Carrier gas flow rate was set to 2 ml/min and ion source
Fig. 1. The schematic of the pyrolysis experimental apparatus.
2

Z. Wu et al.
Chemical Physics Letters 764 (2021) 138213
Fig. 3. Concentrations of main pyrolysis productions of 6FE.
Fig.2. Relationships between pyrolysis temperature and concentration
of reactants.
temperature was set to 200℃ with a scan range of 35–500 m/z. Iden-
tifications of the pure reactants were performed by GC-FID and GC–MS
through the retention times and molecules peaks masses. Normalization
method were used to quantify the reactants and the products by GC–MS.
More detail conditions please see the research we took before [21].
3. Results and discussion
3.1. Pyrolysis temperatures of 6FE, 7FE and 8FE
Pyrolysis reactions of 6FE, 7FE and 8FE were carried out in a tubular
furnace reactor described in Section 2.2 at the different target reaction
temperatures. According to the results obtained by GC-FID and GC–MS,
concentrations of the raw reactants as a function of temperature at
residence time of 30 s are detected and presented in Fig. 2.
Fig. 4. Concentrations of the organic gaseous products of the pyrolysis of 7FE.
processes, we step closer to the relationships between gaseous products
and pyrolysis temperature by GC-FID and GC–MS analysis methods at
the same experimental condition.
As shown in Fig. 2, no obvious conversions of the reactants were
observed below the temperature of 650 ℃ even at a residence time of 30
s. That is to say, the chemicals are stable at normal situation, thus have a
good storability. With the temperature increasing from 650 ℃, 6FE
began to decompose slightly first. By further elevated the temperature
under the same condition, there came the decompositions of 7FE and
8FE around 700 ℃, about 50 ℃ higher than that of 6FE. From the curves
we can see that the more fluorides contained in the chemicals, the more
stable it is and the higher temperature it needs to decompose. This may
3.2.1. Pyrolysis products of 6FE
Comparing the results of GC-FID and GC–MS, four main primary
–
–
–
2
–
products were analyzed and proposed to be CF CH CH CF (m/z =
–
2
126), cyclo-CF2CHFCF2- (m/z = 132), 1,2,3,3,4,6,6-heptafluorocyclo-
–
– – –
) C CFCF CF CF
–
2 2 2
hexa-1,4-diene (m/z = 206) and cyclo-(CHF2
(m/z = 244), respectively, as shown in Fig. 3.
–
be due to the dissociation energy of C F bond (452–531 kJ/mol) is
In the experiment, yields of the four organic gaseous products nearly
–
bigger than that of C H (410 kJ/mol) bond [24], and the number of C-F
–
–
–
–
–
unchanged, including the amount of CF CH CH CF (which was
first to emerge) below 700℃ even under a residence time2of 30 s. Once
the decomposition temperature came up higher than 700℃, the raw
material would undergo unimolecular decomposition first.
2
bond in 7FE and 8FE is more than that of 6FE, resulting in 7FE and 8FE
harder to break. With the increasing of pyrolysis temperature from the
beginning of 750 ℃, decomposition rates and degrees of 6FE, 7FE and
8FE were accelerated and concentrations of these chemicals decreased
significantly. Typically, when the temperature reached to 850 ℃, con-
centrations of 6FE, 7FE and 8FE in the exhaust decreased to the mini-
mum of 18.1%, 40.4% and 53.7%, respectively.
–
–
–
–
–
2
cyclo-CH CHCF CF CF -→CF CH CH CF +∙CF
(1)
–
–
2
2
2
2
2
–
–
–
2
–
The amount of CF CH CH CF was relatively high and
–
2
increasing rapidly with the increasing of pyrolysis temperature and the
yields of other gaseous products increased as well, including HF, cyclo-
CF2CHFCF2, 1,2,3,3,4,6,6-heptafluorocyclohexa-1,4-diene and cyclo-
During the experiments, we could obviously notice that when the
temperature increased to around 700 ℃, there was a small amount of
white smoke (identified to be HF) with pungent smell began to emerge
during 6FE and 7FE experimental processes, while we did not find this
phenomenon in the 8FE experiment. Moreover, with the pyrolysis
temperature proceeding, more HF emerged in the exhaust, which was
consistent with the decomposition degrees of 6FE and 7FE. It is to say
that HF is an important product and could not be ignored when the
compounds applied in high temperature conditions.
–
–
(CHF2)
C CFCF CF CF -. Note that cyclo-CF CHFCF can isomerize to
–
2 2 2 2 2
–
–
generate CF CH CF under high temperature condition due to the high
reactivity a3nd instability, but considering they are isomers and the
molecular ion peaks we could not separate clearly by GC-FID and
GC–MS, we concluded them as one component. Possible pyrolysis
decomposition pathways obtained by experimental results and refer-
ences are shown in (2)~(8) below [21,25,26]:
2
3.2. Degradation products analysis
CF2 → CF + F → C + 2F
(2)
To further investigate the mechanisms of 6FE, 7FE and 8FE pyrolysis
3

Z. Wu et al.
Chemical Physics Letters 764 (2021) 138213
Fig. 5. Possible pyrolysis pathways of 6FE and 7FE.
Fig. 7. Pyrolysis products of the reactants.
when the temperature came to 700 ℃), cyclo-CF2CHFCF2 and HF are the
Fig. 6. Concentrations of the organic gaseous products of the pyrolysis of 8FE.
–
–
–
cyclo-CH CHCF CF CF -+F → cyclo∙CH CHFCF2CF2CF2 →cyclo-
–
2
2
2
–
–
CF2CHFCF2 + CHCF2
–
cyclo-CF CHFCF → CF CH CF
–
2
(3)
(4)
(5)
–
–
–
2
–
major gaseous products; (2) the amount of CF CH CH CF
–
2
decreased unexpectedly with the temperature reaching above 800 ℃
may be due to the generation of coke and new cyclized or polymerized
substances.
2
2
3
–
– –
C
– –
cyclo-CH CHCF CF CF -→cyclo-CH
CFCF CF -+HF
–
2
2
2
2
2
–
cyclo-CH CHCF CFCF -+CF → 1,2,3,3,4,6,6-heptafluorocyclohexa-1,4-
–
2
2
3.2.2. Pyrolysis products of 7FE
diene
(6)
(7)
As shown in Fig. 4, four main primary products were proposed to be
–
–
–
2
–
–
–
–
= 131), CF CH CF CF (m/z = 144),
–
cyclo-CF2CHFCF2-(m/z
cyclo-CH CHCF CF CF -+F → cyclo-CH CFCF CF CF -+H
–
perfluorocyclohexa-1,4-diene (m/z 2
=
2
2
2
2
2
2
–
224) and cyclo-(CF3)
–
–
cyclo-CH CFCF CF CF -+∙CF → cyclo-(CHF )
–
2
2
2
2
2
–
– – – –
–
C
CF CF2 CF2 CF2 (m/z = 262) at the same experimental con-
–
–
–
CFCF CF CF
2
C
(8)
2
2
dition. The 7FE behaved stable under the temperature of 650 ℃, and
decomposition began at 750 ℃. With the temperature increasing, the
concentrations of the four main products were basically equal to each
Unexpectedly, when the temperature came to 800 ℃ the amount of
–
–
–
–
–
CF CH CH CF decreased during the process. It should be
mentioned that so2me fluoroalkene products may also undergo sub-
degradations to form hydrogen fluoride and hydrogen-free fluo-
roalkenes in the high temperature condition [27]. And considering the
high temperature, the reactive unsaturated olefin and free radicals can
also undergo some complex sub-reactions, like cyclization and poly-
merization reactions that generate large molecules which can be proved
by the lightly yellow oily substances emerged in the exhaust pipeline.
For example, cyclopentene which is a source of cyclopentadienyl
methylene radicals which in turn are expected to easily isomerizes to
give benzene [28].
2
–
–
–
–
2
–
other under 800 ℃. The amounts CF CH CF CF ranked behind
–
2
–
of
those
of
cyclo-CF2CHFCF2
and
cyclo-(CF3)
–
– – – –
C
CF CF2 CF2 CF2
,
while
the
concentration
–
perfluorocyclohexa-1,4-diene increased slow above 800 ℃. Along with
the process, the amounts of other products accelerated at 800 ℃ and
reached their maximum at 850 ℃. The pyrolysis reaction pathways of
7FE and 6FE are similar, which can be concluded in Fig. 5. The main
products are shown in red form.
–
It could be concluded that: (1) cyclo-CF2CHFCF2
and
– –
2– –
CF CH CF are the major gaseous products; (2) the amount of cyclo-
2
–
–
– – –
C CF CF2 CF2 CF2-(as the second major organic product)
–
(CF3)
–
–
–
–
2
–
It could be concluded that: (1) CF CH CH CF (emerged first
2
increased relatively rapid with the temperature proceeding above 750
4

Z. Wu et al.
Chemical Physics Letters 764 (2021) 138213
maximum at 850℃.
Table 2
Comparison of products of the three chemicals.
For the pyrolysis reactions of hydrofluorocarbons, hydrogen fluoride
(HF) is usually generated due to the eliminations of H and F atoms from
the molecule, and it can not only damage the health of human, but also
corrode facilities [27]. Therefore, formation of HF and its variation
trends at different temperatures during the thermal decompositions
should be paid attention to.
Reactants
Products
6FE
7FE
8FE
C
√
√
√
√
√
√
√
√
√
√
√
√
√
√
√
√
√
HF
–
CF2 CF2
√
√
-(CF2-CF2-)n-
In all the three chemicals experiments, a great amount of flavescent
oily liquids (color deepened from light-yellow to nut-brown with the
increasing of temperature, Fig. 7) with a pungent smell were observed in
the exist pipeline and the filter cell when the temperature rose to 700 ℃
(6FE) or 750 ℃ (7FE and 8FE) at residence time of 30 s. Black solid
particles generated in the pyrolysis tube also emerged when the tem-
perature came up near 800℃, which proved to be coke. White powders
which were found attached to the outlet pipelines after the experiments,
could not be dissolved in hydrochloric acid, alkali solution or ethyl ac-
etate. Considering the generation of ⋅CF2 radicals in the pyrolysis pro-
cesses, C2F4 would be dimerized rapidly by the ⋅CF2 recombination [29].
We suggest those to be polyfluoroolefins due to the polymerization of
tetrafluoroethylene or hexafluoropropylene under high temperature
condition [30,31]. These all mean that the cyclic chemicals could only
cyclo-CF2CHFCF2-
–
–
CF3CH CF2
–
–
–
–
CF2 CXCX CF2
√
√
√
√
X = H or F
–
–
take simple unimolecular decomposition (such as C C and C F bond
ruptures) which generated the relatively small molecular weight prod-
ucts, but undergo some complex reactions involving isomerization,
recombination and rearrangement of the radicals that generate large
molecules under high temperature condition.
℃, while the increase of perfluorocyclohexa-1,4-diene slowed down
above 800 ℃. Besides the foregoing main gaseous products, the amount
of other trace products increased with the temperature increasing,
especially the coke formation, cyclized and polymerized reactions
products.
The main products and the slight aromatic chemicals detected in the
experiments are summarized in Table 2 and Table 3.
3.2.3. Pyrolysis products of 8FE
3.3. Environmental influences
As shown in Fig. 6, two main primary products were suggested at the
same experimental condition based upon the GC and GC–MS results as
–
–
–
2
Prior to the large-scale industrial usage an assessment of the atmo-
spheric chemistry, and hence environmental impact, of chemic materials
is needed. Climate change, stratospheric ozone loss, and formation of
noxious or toxic degradation products should be considered when it
comes to environmental influence [32]. With no Cl and Br atoms con-
tained in, 6FE, 7FE and 8FE show no ozone depletion potential. Re-
–
followed
by
CF CF CF CF
(m/z
=
162)
and
–
2
–
–
– – –
C CF CF2 CF2 CF2- (m/z = 262). The yields of the two
–
CF3
organic gaseous products nearly approach to zero below 700 ℃. When
the pyrolysis temperature rose higher than 750 ℃ at the same condition,
–
–
–
2
–
–
the amounts of CF CF CF CF together with cyclo-(CF3)
–
2
–
–
– – –
C
CF CF2 CF2 CF2- were significantly increased and reached their
–
–
actions with OH radicals due to the C C double bonds contained in the
Table 3
Aromatic compounds detected in the products of the three chemicals.
5

Z. Wu et al.
Chemical Physics Letters 764 (2021) 138213
Fig. 8. Possible degradation routes of 7FE in the atmosphere.
carbon skeleton, show haloalkenes have reactive activities in the
troposphere, thus have shorter lifetimes than the corresponding hal-
oalkanes [18,32]. As mentioned above, 6FE and 8FE have an atmo-
spheric lifetime of 107 days and 104 days, respectively, and low 100-
year time horizon GWPs (15,28) [19,20], thus have negligible climate
change influence. According to Ni Zhang etc., the atmospheric lifetimes
of cyc-CF2CF2CF2CHFCH2 and trans-cyc-CF2CF2CF2CHFCHF with OH
radicals were 2.8, 3.2 years and the 100-year time horizon global
warming potentials were estimated to be 211, 241, respectively [33].
What is more, the electron withdrawing effect of the halogen atoms in
alkenyl halide results in a reduced reactivity [32]. 7FE should have
relative shorter lifetime than the trans-cyc-CF2CF2CF2CHFCHF, and the
lifetime seems to be around 100 days. Furthermore, the atmospheric
which could react with ∙OH radicals would undergo ring-opening re-
action to generate aldehydes [38] and H2O. Peroxy nitrates are ther-
mally unstable and decompose to reform acetyl peroxyradicals and NO2
in a balance circle [38,39]. Moreover, in the water vapour sufficient
condition, the peroxynitrates could hydrolyze to generate HNO3 and
–
carboxylic acid to some extent [38]. The -CXO, COOH contained
products and COF2 also have relative short atmospheric lifetimes form
several days to months, which could undergo heterogeneous processes
or degraded by the H abstraction of ∙OH radicals in atmospheric envi-
ronment [1,40-42]. Taking 7FE as example, the probable main degra-
dation routes of the fluorinated cyclopentenes are shown in Fig. 8.
4. Conclusions
–
–
–
–
2
–
lifetimes of CF CX CX CF would be shorter than that of CF CF-
–
–
2
2
–
CF CF (1.1 days) [20] due to the high reactivity, analogous structure
Pyrolysis decompositions of 6FE, 7FE and 8FE are investigated
experimentally under combinative conditions of 500–850℃ and resi-
dence time of 30 s in a corundum tubular reactor by GC-FID and GC–MS.
Insignificant temperature effect on the chemicals which shows that 6FE,
7FE and 8FE are all stable below 650℃ and have a good stability in
common storage and practical use condition. Concentrations and kinds
of the products generated during the process varied from the increasing
of temperature. Toxicity of the products is mainly caused by HF and
quantification research need to be further studied in the future. Coke
and yellow oily liquids were observed in the reactor and the exhaust
pipelines over 750 ℃, which demonstrated that all the three chemicals
–
2
and elements (especially the number of H and F atoms) contained in.
They may strongly depend on local and seasonal conditions, thus make
no significant contribution to the radiative forcing of climate change
[20,32].
In the atmosphere degradation, the most feasible reaction channel
for the cycloolefins were the reactions with ∙OH radicals [34]. Then the
∙OH added radicals would react with active oxidants or radicals, such as
O2 (OH, NOx, HO2, etc.) to form peroxy alkyl radicals [35,36], which
could react with NO to generate NO2 and cycloalkyl radicals or perox-
ynitrates at the second step [37]. Generally, the cycloalkyl radicals
6

Z. Wu et al.
Chemical Physics Letters 764 (2021) 138213
[12] D.A. Jackson, C.J. Young, M.D. Hurley, T.J. Wallington, S.A. Mabury, Atmospheric
degradation of perfluoro-2-methyl-3-pentanone: photolysis, hydrolysis and
hydration, Environ. Sci. Technol. 45 (2011) 8030–8036.
not only take unimolecular decompositions, but also undergo cyclized
and polymerized reactions under high temperature condition.
The short atmospheric lifetime, low GWPs and zero ODPs show the
chemicals have no big influence on the climate change, as with all other
fluorinated alkenes studied to date [43,44]. 6FE has been proposed as
useful refrigerant or heat transfer fluid in the process of producing
cooling or heat [45]. 8FE have been proved to be ideal electronic etching
agent with more efficiency and better selectivity property [20,21]. More
applicable usages are still being exploited till now. Fluorinated car-
boxylic acids and secondary organic aerosols are expected to be poten-
tial pollutants which could be transported over distances that could
affect the biosphere [8,45] (depending on the scale of usage).
[13] J.I. Bing, M.S. Andrew, S.R. George, P.R. Badowski, K.E.J. Jr, W.H.P. Jr, P.R.
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CRediT authorship contribution statement
Zhenhai Wu: Conceptualization, Investigation, Data curation,
Writing - original draft. Yuanyuan Ji: Data curation, Visualization.
Hong Li: Funding acquisition, Writing - review & editing. Fang Bi:
Resources, Investigation. Ren Yanqin: Writing - review & editing. Rui
Gao: Visualization, Supervision. Chenfei Liu: Methodology, Investiga-
tion. Ling Li: Resources, Software. Hao Zhang: Investigation, Re-
sources. Xin Zhang: Investigation, Resources. Xuezhong Wang:
Conceptualization, Methodology, Project administration, Writing - re-
view & editing.
[20] T.J. Wallington, M.D. Hurley, Atmospheric chemistry of hexafluorocyclobutene,
octafluorocyclopentene, and hexafluoro-1,3-butadiene, Chem. Phys. Lett. 507
(2011) 19–23.
[21] X. Zhou, D. Lu, M. Chao, W. Chen, Experimental and theoretical studies on the
thermal decomposition of 1,1,2,2,3,3,4-heptafluorocyclopentane, J. Fluorine
Chem. 164 (2014) 70–77.
[22] W. Chen, J. He, Y. Jiang, H. Zhang, X. Zhou, Experimental and theoretical studies
on the atmospheric degradation of 1, 1, 2, 2, 3, 3, 4-heptafluorocyclopentane,
Atmos. Environ. 196 (2019) 38–43.
[23] D. Lu, M. Chao, X. Zhou, Theoretical Studies on the Reactions of 1,1,2,2,3,3,4-
Heptafluorocyclopentane with Hydroxyl and Hydrogen Free Radicals, Chin. J.
Chem . 32 (2014) 897–908.
Declaration of Competing Interest
[24] M. Zhang, Z. Lin, Ab initio studies of the thermal decomposition pathways of 1-
bromo-3,3,3-trifluoropropene, J. Mol. Struct.-Theochem. 899 (2009) 98–110.
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The authors declare that they have no known competing financial
interests or personal relationships that could have appeared to influence
the work reported in this paper.
Acknowledgements
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