Preparation of trifluoroiodomethane via vapor-phase catalytic reaction between hexafluoropropylene oxide and iodine

Article abstract of DOI:10.1016/j.jfluchem.2009.06.010

Based on our previous investigation on the reaction mechanism to produce difluorocarbene and subsequent CF₃I starting with CHF₃ and I₂, a new route for preparing CF₃I at a relative low temperature, 200 °C, has b

Full text of DOI:10.1016/j.jfluchem.2009.06.010

Journal of Fluorine Chemistry 130 (2009) 985–988
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Journal of Fluorine Chemistry
journal homepage: www.elsevier.com/locate/fluor
Short communication
Preparation of trifluoroiodomethane via vapor-phase catalytic reaction
between hexafluoropropylene oxide and iodine
a
a
a
b,
Guang-Cheng Yang , Xiao-Qing Jia , Ren-Ming Pan , Heng-Dao Quan *
a
School of Chemical Engineering, Nanjing University of Science and Technology, Nanjing 210094, China
b
National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8565, Japan
A R T I C L E I N F O
A B S T R A C T
Article history:
Based on our previous investigation on the reaction mechanism to produce difluorocarbene and
Received 26 March 2009
Received in revised form 17 June 2009
Accepted 18 June 2009
subsequent CF
3
I starting with CHF
3 2 3
and I , a new route for preparing CF I at a relative low temperature,
200 8C, has been developed via a vapor-phase catalytic reaction between hexafluoropropylene oxide
with I
2
in the presence of KF supported on activate charcoal as a catalyst. The influence of reaction
I was investigated. In the reaction process, coke-
formation was suggested on the surface of catalysts by means of BET, XPS and TG-DTA analysis. The
process for the formation of CF I and by-products is also discussed.
ß 2009 Elsevier B.V. All rights reserved.
Available online 25 June 2009
temperature and reaction time on the amount of CF
3
Keywords:
3
CF
CF
3
I
2
carbene
Hexafluoropropylene oxide
Disproportionation
1
. Introduction
sources employing at below 200 8C. Especially, HFPO is useful
because of its commercial availability [4].
Trifluoroiodomethane (CF
3
I) has drawn growing attention as a
Based on our former research on mechanism for the formation
promising replacement for halon and other halohydrocarbons in
the application of fire extinguishing agent, freezing medium and
etching gas since its short atmospheric lifetime and low global
warming potential (GWP). In our previous report, we summarized
of CF
temperature around 200 8C, was developed via a vapor-phase
catalytic reaction between HFPO with I in the presence of KF
catalyst on AC (KF/AC). We reported here the detailed study on
characterization of the catalysts to demonstrate the disproportio-
3 3
I, a new route for preparing CF I at a relatively low
2
the properties and synthetic methods of CF
synthetic routes, the continuous vapor-phase catalytic process via
the reaction between CHF and I in the presence of O at 550 8C
makes the CF I industrialization possible [2]. With the help of
experiments, the mechanism for the formation of CF I was
attributed to that CF carbene produced in the pyrolysis process
of CHF is transferred into CF radical, which converts to CF I in the
presence of catalyst, I and O [1]. According to the report, a quite
high temperature is required for the formation of CF carbene in
the pyolysis process. However, high temperature in the presence of
would cause not only the destruction of the supporter of
3
I [1]. Among the
2
nation of CF carbene.
3
2
2
3
2. Experimental
3
2
2.1. Materials
3
3
3
2
2
AC was obtained from Shanxi Taiyuan Activated Carbon
Factory. HFPO was provided by Shandong Dongyue Chemical
2
2
Co., Ltd., China. I was purchased from Nanjing Yicheng Chemical
O
2
Co., Ltd., China.
catalyst, activated carbon (AC), but also the coke-formation on the
surface of catalyst and deactivation of the catalyst [3].
In order to decrease the reaction temperature, structurally
strained fluorocarbons containing three-membered ring instead of
2.2. Instrument and apparatus
Products were analyzed by means of Shimadzu GC-17A. The
2 3 2
CHF Cl and CHF were selected as thermal sources of CF carbene
capillary column was a CP-Pora PLOT Q with 0.32 mm diameter
and 30 m length from J&W Scientific Inc. The column was
programmed as follows: the initial temperature was set at 60 8C
for 6 min; then the temperature was increased at the rate of 40 8C/
min, and finally reached to 200 8C and held for 11 min. The
instrumental parameters were set up as follows: injection port
temperature, 200 8C; TCD detector, 200 8C; the carrier gas rate,
under milder conditions. Perfluorocyclopropane and hexafluor-
opropylene oxide (HFPO) have been used as difluorocarbene
*
Corresponding author. Tel.: +81 298 614196; fax: +81 298 614657.
E-mail address: Hengdao-quan@aist.go.jp (H.-D. Quan).
0022-1139/$ – see front matter ß 2009 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2009.06.010

9
86
G.-C. Yang et al. / Journal of Fluorine Chemistry 130 (2009) 985–988
Table 1
at 210 8C for 2 h. The products passed through a KOH solution.
Then the washed products were collected in a gas bag and analyzed
by GC and GC–MS. The data of MS are listed as follows:
Relative response coefficients (kI/kstd
)
deter-
mined by GC-TCD.
kI/kstd
+
+
+
1
.
CHF
2. CF CHF
3. HFPO, m/z: 119, CF
3
, m/z: 69, F
3
C ; 51, CHF
2
; 31, FC .
CHF
CF CHF
HFPO
3
1
+
+
+
+
, m/z: 119, CF
3
CF
2
; 101, CF
2
CHF
CF; 69, F
CF 55 CF ; 100, CF
2 3 2
; 69, F C ; 51, CHF .
3
2
0.90
0.74
0.72
0.69
0.73
3
2
+
+
+
+
3
CF
2
; 100, CF
+
3
3 2
C ; 50, F C
CF
CF
CF
3
3
3
CF5CF
2
+
+
4
.
CF
3
+
CF 55 CF
2
, m/z: 150, M ; 131, CF
2
2
2
55 CF
2
; 69,
I
+
3
F C ; 31, FC .
2
CF I
+
+
+
5
6
.
.
CF
CF
3
3
I, m/z: 196, M ; 127, I ; 69, F C .
std = CHF
3
.
+
+
+
+
+
3
CF
2
I, m/z: 246, M ; 127, I ; 119, C
2
F
5
; 100, C
2
F
4
; 69, F
3
C ;
+
2
50, F C .
4
.1 ml He/min. The products were identified by comparison of
their GC retention times and mass spectra with authentic samples.
Quantitative analysis of the product standard ratios was obtained
by comparison with mixtures prepared for calibration purposes.
The relative response coefficients of each compound are given in
Table 1.
3. Results and discussion
3
CF I was produced in 59% relative volume of the gaseous
products obtained by the reaction between HFPO and iodine in the
MS (EI, 70 eV) spectra were measured using the Shimadzu
GCMS-QP2010 system equipped with GC-17A. The column was CP-
Pora PLOT Q with 0.32 mm diameter and 30 m length from J&W
Scientific Inc. The column was programmed as above-mentioned
GC conditions. Injection port temperature, 200 8C; the carrier gas
rate, 4.1 ml He/min.
presence of KF/AC catalyst at 210 8C for 2 h, accompanying with
CHF , CF CHF , CF CF 55 CF , CF CF I as by-products. The conversion
of HFPO reached 99%, as shown in Table 1. When the reaction
3
3
2
3
2
3
2
temperature was 170 8C, HFPO remained in 58% in the mixture of
gaseous products, and CF I was formed only in 5.4%. When the
3
reaction temperature was 120 8C, reaction did not occur and only
The BET surface area of AC was measured by means of low
raw material of HFPO was detected in gas product (Table 2).
Effect of the reaction time at 210 8C was also examined. The
results are shown in Fig. 1. The concentration of HFPO decreased
with the increase in reaction time and closed to zero when reaction
temperature adsorption of nitrogen using a micromeritics ASAP
À5
2
5
010. Samples were degassed under vacuum (P < 10 torr) at
73 K for 3 h before measurement.
Thermogravimetry and Differential Thermal Analysis (TG-DTA)
time reached to 100 min. At the same time, the ratio of CF I formed
3
was conducted on NTEZSCH STA 449C instrument. The experi-
ments were performed under the conditions of 25–350 8C at a heat
rate of 10 8C/min with air at flow rate of 100 ml/min. About 20 mg
of sample was placed inside of an uncovered Pt pan. Samples of
used AC were pretreated by heating at 500 K under vacuum to
remove iodine that accumulated on the surface.
gradually increased. When the reaction time was over 100 min, the
concentration of CF I reached over 50%.
3
The BET surface area and pore volume of the fresh and used
catalysts were measured. As shown in Table 3, the fresh KF/AC
2
catalyst had a large surface area of 879 m /g and a pore volume of
3
0.40 cm /g. Depending on longer reaction time, the surface area of
The XPS instrument was a Thermo VG ESCALAB 250 which uses
catalysts decreased. When the reaction was conducted at 210 8C
2
a mono-chromatic Al K
of 500 m.
a
(1486.6 eV) X-ray source with a plot size
for 2 h, the surface area of the catalyst was reduced to 72 m /g and
3
m
pore volume was to 0.04 cm /g, respectively, possibly caused by
coke-formation during the reaction. When the reaction tempera-
2
2
.3. Reaction procedure
ture was lowered to 170 8C, the surface area and pore volume of the
2
3
used catalyst were 377 m /g and 0.18 cm /g, respectively. In this
case, due to the lower conversion of HFPO, the coke-formation was
quite small compared with that at 210 8C. As for the catalyst that
was used in the reaction at 120 8C, the reduction in surface area and
pore volume would be explained by the absorbed compounds
containing fluorine on the surface of the catalyst. Therefore, XPS
analysis was carried out to characterize the elemental content on
the surface of the fresh and used catalysts. As shown in Table 4, it
was found that after the reaction, fluorine content increased and
potassium content decreased on the surface of catalyst. These
results possibly indicated that the KF surface is covered with
products derived from generated CF2 carbene. As for the catalyst
that used in the reaction at 210 8C, XPS study also revealed that the
carbon content reached 43.5%, which was far higher than that of
.3.1. Preparation of catalyst
Twenty grams of AC was added into a KF solution which was
prepared by dissolving 5 g of KF into 100 ml of de-ionized water
and the mixture was kept at room temperature for 1 h. The catalyst
was dried at around 100 8C for 3 h under atmospheric conditions
and then at around 200 8C for 2 h under nitrogen flow condition.
2.3.2. Synthesis of CF
3
I
About 2 ml of the above mentioned catalyst and 2 g of I
2
were
placed in a stainless steel reactor with 80 ml volume. The reactor
was cooled to À196 8C, then 10 mmol of HFPO was introduced into
the reactor. The reactor was placed in an oil bath and the reaction
mixture was stirred by a magnetic stirrer. The reactor was heated
Table 2
a
Effect of reaction temperature on product distribution .
b
Entry
Temperature (8C)
Distribution of products (%)
HFPO
CHF
3
CF
3
CHF
2
CF
3
CF5CF
2
CF
3
I
3
CF CF
2
I
Others
c
c
c
c
c
c
1
2
3
120
170
210
100
–
–
–
–
–
–
58.1
<0.1
20.4
24.9
4.0
5.3
10.0
4.2
5.4
1.7
3.2
0.4
3.3
59.1
a
Reaction time: 2 h.
b
c
Ratio of relative volume of gaseous compound.
Not detected.

G.-C. Yang et al. / Journal of Fluorine Chemistry 130 (2009) 985–988
987
Fig. 2. TG curves of fresh and used catalysts (a: fresh catalyst, b: catalyst used at
20 8C, c: catalyst used at 170 8C, and d: catalyst used at 210 8C).
1
3
Fig. 1. Effect of reaction time on the ratio of HFPO and CF I at 210 8C.
the catalysts used in the reaction at 120 and 170 8C. The increase of
coke-formation resulted in the increase of carbon content on the
surface of used catalyst.
The coke-formation on the used catalysts was characterized by
means of TG-DTA technique under air flow (Fig. 2). Magnoux found
that coke oxidation and evolution of carbon dioxide generally start
at the temperature from 250 to 350 8C [5]. As shown in Fig. 2, line a,
within the range of 150–350 8C, the fresh catalyst was relatively
stable under air flow and there was no obvious weight loss
observed. However, within the same temperature range, the TG
curves of the used catalysts showed weight loss due to removal of
coke by oxidation. The rates of weight loss for the samples used in
the reactions at 210 8C (line d), 170 8C (line c) and 120 8C (line b)
were 34%, 29% and 12%, respectively. These results indicated that
the amount of coke-formation on the surface of the catalysts
increased with the elevation of reaction temperature raising. It
3
Scheme 1. Suggested process for the formation of CF I and by-products.
mechanism of CF
We propose the following process for the formation of CF
products. As shown in Scheme 1, HFPO is decomposed by heating
to form the intermediate of CF carbene. Then, CF carbene is
absorbed on the surface of the catalysts and disproportionation
reaction takes place to generate CF radical. CF radical reacts with
to form CF I, whereas with H radical to form CHF . H radical
maybe comes from carboxyls and phenols on the AC surface.
2
carbene disproportionation to form CF
3
radical.
3
I and by-
2
2
3
3
revealed that the reaction of HFPO with I
2
to prepare CF
3
I will lead
I
2
3
3
coke-formation and the amount of coke increases with the increase
of HFPO conversion.
Alternatively, CF
3
radical reacts with CF
2
carbene to form CF
3
CF
2
2
The compounds containing CF
3
group such as CHF
3
, CF
3
I,
radical, which generates CF
3
CF I and CF CHF
2
3
2
. In the process of CF
CF
3
2
CF I were formed. These results were in accordance with the
carbene disproportionation, carbon is formed as coke on the
Table 3
a
BET surface area and pore volume of the fresh and used catalysts .
2
3
Reaction temperature (8C)
BET surface area (m /g)
Pore volume (cm /g)
Fresh catalyst
879
0.40
Used catalysts
120
591
377
72
0.28
0.18
0.04
1
2
70
10
a
Reaction time: 2 h.
Table 4
a
Element concentration on the surface of the fresh and used catalysts .
Reaction temperature (8C)
Content (at.%)
C
1s
K
2p
F
1s
I
3d
Fresh catalyst
36.9
30.4
32.7
Used catalysts
120
17.4
17.9
43.5
21.5
22.8
11.7
58.7
58.0
46.6
2.4
1.4
2.2
1
2
70
10
a
Reaction time: 2 h.

9
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G.-C. Yang et al. / Journal of Fluorine Chemistry 130 (2009) 985–988
surface of the catalysts. It caused the reduction of surface area for
the used catalysts.
promotes disproportionation of CF
2
carbene to generate CF
3
radical, which reacts with I
2
to form CF I.
3
4
. Conclusion
References
3
A new method for the preparation of CF I has been developed
[
[
[
1] G.C. Yang, L. Shi, R.M. Pan, H.D. Quan, J. Fluorine Chem. 130 (2009) 231–235.
2] N. Nagasaki, N. Suzuki, S. Nakano, N. Kunihiro, US Patent 5,892,136 (1999).
3] R. Romelaer, V. Kruger, J.M. Baker, R. William, Dolbier Jr., J. Am. Chem. Soc. 123
(2001) 6767–6772.
4] D.L. Brahms, W.P. Dailey, Chem. Rev. 96 (1996) 1585–1632.
5] P. Magnoux, M. Guisnet, Appl. Catal. 38 (1988) 341–352.
via a reaction between HFPO and I
catalyst. The ratio of CF I in the gaseous products reached over
0% when the reaction was conducted at 210 8C for 100 min.
2
in the presence of KF/AC
3
5
[
[
During the reaction, surface area and pore volume of the catalyst
decreased due to coke-formation. Furthermore, the catalyst