Preparation of trifluoroiodomethane via vapour-phase catalytic reaction between pentafluoroethane and iodine

Article abstract of DOI:10.14233/ajchem.2013.14398

A new route for preparing C3₃I has been developed via a reaction between C2HF5 and I2. The influence of reaction temperature and active components of the catalysts on the amount of C3₃I was investigated. The result suggests that the selectivity of the C3₃I can be controlled by reaction conditions and active component of catalyst. The process for the formation of C3₃I and by-products is also discussed.

Full text of DOI:10.14233/ajchem.2013.14398

Asian Journal of Chemistry; Vol. 25, No. 8 (2013), 4640-4642
http://dx.doi.org/10.14233/ajchem.2013.14398
Preparation of Trifluoroiodomethane via Vapour-Phase Catalytic
Reaction Between Pentafluoroethane and Iodine
1
,2,3
1
1
1
1,*
AIQIN MAO , HUA WANG , LINHUA TAN , XIANGYANG NIN and RENMING PAN
1
2
3
School of Chemical Engineering, Nanjing University of Science and Technology, Xiao Ling Wei Street 200, Nanjing 210094, Jiangsu, P.R. China
School of Materials Science and Engineering, Anhui University of Technology, Hudonglu 59, Ma'anshan 243002, Anhui Province, P.R. China
Anhui Key Laboratory of Metal Materials and Processing, Anhui University of Technology, Hudonglu 59, Ma'anshan 243002, Anhui, P.R. China
*
Corresponding author: Tel/Fax: +86 25 84315511; E-mail: panrenming@sohu.com; maoaiqinmaq@163.com
(
Received: 4 August 2012;
Accepted: 18 February 2013)
AJC-13031
A new route for preparing CF
components of the catalysts on the amount of CF
by reaction conditions and active component of catalyst. The process for the formation of CF
3
I has been developed via a reaction between C
I was investigated. The result suggests that the selectivity of the CF
I and by-products is also discussed.
2
HF
5
and I
2
. The influence of reaction temperature and active
3
3
I can be controlled
3
Key Words: Trifluoroiodomethane, Vapour-phase catalytic, Pentafluoroethane, Difluorocarbene, Trifluoromethyl radical.
2 5 2
via the reaction between C HF and I suggested the reaction
INTRODUCTION
Trifluoroiodomethane (CF I) possesses a short atmos-
proceeds also via carbenes formed on the catalyst surface as
3
1,2
intermediates. Based on this investigation, a new route for
pheric lifetime and low global warming potential , which
makes it become the preferred alternative for halon and other
halohydrocarbons in the application of fire extinguishing agent.
preparing CF
reaction between C
study on the effect of catalytic activities especially the selec-
tivity of the CF I to reaction conditions and catalysts, and the
3
I was developed via a vapour-phase catalytic
2
HF and I . We reported here the detailed
5
2
3-6
3
Of note, CF I is expected for various other applications , such
3
as freezing medium, etching gas and raw materials for
fluorochemicals, etc.
3
process for the formation of CF I and by-products is also
7,8
discussed.
Nagasaki et al. have reported a continuous vapour-phase
catalytic process for the manufacture of CF I via the reaction
between trifluoromethane (CHF ) and iodine (I ), which makes
the CF I industrialization possible (Scheme-I). Yang et al.
have investigated the above mentioned synthetic mechanism
of CF I and by products, and suggested that the reaction
proceeds via difluorocarbenes (CF carbenes) formed on the
catalyst surface as intermediates, followed by CF carbene
disproportionation to trifluoromethyl (CF ) radicals, further-
more CF radical react with I to form CF I (Scheme-II). But
the raw material CHF will be stopped little by little based on
the montreal protocol, because the global warming potential
of CHF is as high as 12000 and the atmospheric lifetime is as
long as 250 years. The raw material pentafluoroethane (C HF
possesses a low global warming potential and the atmospheric
3
cat
.
3CHF
3
+ I
2
3
→ 2CF I + 3HF + C
3
2
9
,10
Scheme-I
3
3
2
2
3
3
2
3
3
3
2
5
)
11
lifetime is only 33 years .
12
In our previous report , a consideration of the reaction
mechanism for the formation of pentafluoroethyl iodide (C I)
F
2 5
Scheme-II

Vol. 25, No. 8 (2013)
Preparation of Trifluoroiodomethane via Vapour-Phase Catalytic Reaction 4641
GC-MS (EI, 70 eV) spectra were measured using the
Shimazu GCMS-QP2010 system equipped with GC-2010. The
EXPERIMENTAL
Preparation of catalyst: A commercial wooden AC
TanxinActivated Carbon Co. Ltd., Shanghai; specific surface
column was CP-PoraPLOT Q with 0.32 mm i.d. and 30 m
length from J &W Scientifc Inc. The column was programmed
as above-mentioned GC conditions. Injection port temperature,
(
2
area 1322 m /g) was used as the catalyst support in this study.
After HF (2 M) washing, the AC had an ash content lower
than 1.2 wt %, thenAC was subjected to 2 M HCl for about 24
h at room temperature in order to decompose the carboxyl
and lactone groups, increase the relative amounts of the
3
2
00 ºC; the carrier gas rate, 4.1 cm He/min.
RESULTS AND DISCUSSION
13-15
Synthesis of CF
the reaction temperature on product distribution in the gas-
phase catalytic reaction for the synthesis of CF I between
HF and I in the presence of K CO /AC catalyst was
3
I on different temperature: Effect of
phenolic and carbonyl groups , and then theAC was washed
with distilled water and dried in air at 103-105 ºC overnight.
After that, the sample was added to the aqueous metal salts
solution, impregnated at room temperature for about 6 h and
dried by a rotary evapourator at about 80 ºC for 4 h. The pre-
dried catalyst was then calcined at 600 ºC for 2 h under nitrogen
flow.
3
C
2
5
2
2
3
examined. The results were shown in Fig. 1 and the product
distribution was listed in Table-2.
Synthesis of CF
fixed bed reactor and were heated to 550 ºC under nitrogen.
Then nitrogen flow was stopped and C HF was introduced to
reactor at a rate of 60 mL/min. After 2 h, I was provided by
bubbling C HF into molten I which was placed in a stainless
steel evaporator and heated up to 190 ºC in an oil bath. The
products were neutralized by Ca(OH) solution, dried with
3
I: 15 mL catalysts were packed into a
2
5
2
2
5
2
2
CaCl
2
and analyzed by GC-MS. The results were listed as follows:
+
, m/z: 69, CF
+
; 50, CF
+
; 31, CF; 19, F.
–
1
. CF
4
3
2
+
, m/z: 119, CF
+
+
2
. CF CF
3
3
3 2 2 2 3
CF ; 100, CF CF ; 69, CF ;
+
+
5
0, CF
2
; 31, CF.
. CHF , m/z: 69, CF
. CF CF CF , m/z: 169, CF
; 69, CF3; 50, CF
+
+
+
; 31, CF.
3
4
3
3
; 51, CHF
2
+
+
; 119, CF
3
2
3
3
CF CF
2
2
3
CF ; 100,
2
+
CF
+
+
+
2
CF
2
2
; 31, CF.
+
+
+ +
I ; 127, I; 69, CF
–
5
3 3
. CF I, m/z: 196, CF I; 177, CF
2
3
;
Time (min)
+
1, CF;
3
Fig. 1. GC spectrum of gas products; a-reaction at 500 ºC, b- reaction at
550 ºC, c- reaction at 600 ºC
+
I, m/z: 246, CF
+
I; 227, CF
6
. CF
+
3
CF
+
2
3
CF
2
2
CF
2
I; 177,
+
–
+
I ; 158, CFI; 127, I; 119, CF
+
; 100, CF
CF
2
3
CF
2
CF ; 69,
2 2
+
CF
+
; 50, CF
+
TABLE-2
EFFECT OF REACTION TEMPERATURE
ON PRODUCT DISTRIBUTION
3
2
; 31, CF.
Characterization of samples: Products were analyzed
by means of GC-1002 produced by Beijing analytical instru-
ment factory. The capillary column was a CP-PoraPLOTQ with
Temperature
ºC)
Ratio of relative volume of products (%)
(
C HF
2
CHF3
-
CF3I
-
C F I
2 5
Others
5
0
.32 mm diameter and 30 m length from J & WScientific Inc.
4
50
00
100
-
-
The column was programmed as follows: the initial tempe-
rature was set at 60 ºC for 6 min; then the temperature was
increased at the rate of 40 ºC/min and finally reached to 200 ºC
and held for 11 min. The instrumental parameters were set up
as follows: injection port temperature, 200 ºC; FID detector,
5
79.4
68.7
68.2
1.4
0.4
1.2
8.4
17.2
8.9
10.1
13.7
19.8
0.7
-
550
600
1.9
-
-no products detected
2
50 ºC; the carrier gas was N
2
(0.1 MPa). The products were
The conversion of C
reaction temperature and when the reaction temperature was
450 ºC, reaction did not occur and only raw material C HF
was detected in gas product. When the reaction temperature
was 550 ºC, the conversion of C HF reached 31.3 % and CF
was produced in 17.2 % relative volume of the gaseous products
for 4 h, accompanying with CF , CHF , C , C and C
as by-products. But the ratio of CF I formed gradually decreased
when the reaction temperature was 600 ºC, the concentration
of CF I reached only in 8.4 % (Table-2). It is suggested that
the selectivity of the CF I is controlled by reaction conditions.
Synthesis of CF I on different catalysts: The tested
2 5
HF increased with the increasing
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 and retention time of each compound
are given in Table-1.
2
5
2
5
3
I
4
3
F
2 6
3
F
8
2 5
F I
3
TABLE-1
RELATIVE RESPONSE COEFFICIENTS
3
(kI/kstd) DETERMINED BY GC-FID
3
Sample
CHF3
Retention time/min
k /
I kstd
3
8.3
8.5
3.6
1.0
catalysts were made from various alkali metal salts and alkaline
earth metal salts withAC as a supporter. The catalytic activities
of these catalysts were tested after 4 h reaction (Table-3).
CF CHF
3
2
CF3I
9.5
1.45
1.29
2 5
C F I
10.4

4
642 Mao et al.
Asian J. Chem.
TABLE-3
EFFECTS OF ALKALI METAL AND ALKALINE EARTH METAL
SALT CATALYSTS ON THE REACTION OF C HF AND I
2
5
2
C HF
CF3I
conversion (%) selectivity (%) selectivity (%)
C F I
2 5
2
5
Component
NaNO3
KNO3
RbNO3
CsNO3
KF
11.2
18.7
30.4
17.3
22.0
18.5
<1
0
0
53.5
44.0
36.5
49.5
34.0
0
29.0
40.0
32.5
48.7
51.3
0
Scheme-III: Suggested process for the formation of CF
3
I and by-products
RbF
CsF
Conclusion
K CO3
2
31.3
5.9
54.9
13.6
20.1
43.8
12.4
11.9
Mg(NO3)2
A new method for the preparation of CF I has been
3
Ba(NO3)
2
9.8
developed via a reaction between C HF and I . The effect of
2
5
2
-1
Reaction temperature: 550 ºC; C HF /I (mol ratio):1.5; SV: 130 h
2 5 2
the temperature on the synthesis of CF
3
I was studied and the
HF increased with
the increasing reaction temperature, but the radio of CF
formed gradually decreased.Also the conversion of C HF and
the selectivity of CF I reached 46.5 % and 53.1 % respectively
when the reaction was conducted in the presence of Rb-K/AC
catalyst with the mass ratio of 3:1 (RbNO :KF). The results
suggest that the selectivity of the CF I can be controlled by
reaction conditions and active component of catalyst. Further-
more, the catalyst promotes disproportionation of CF carbene
to form CF I.
results indicated that the conversion of C
2
5
As shown in Table-3, alkali metal salts shows a higher
3
I
catalytic activity than the alkaline earth metal salts. This is
because the electronegativity of alkali metal is less than the
alkaline earth metal and the basicity of the alkali metal oxide
decomposing from alkaline metal is better than alkali earth
metal oxide decomposing from alkaline earth metal. Zhu
2
5
3
3
3
16
et al. have reported that the decomposition of alkaline earth
metal nitrates becomes more difficult with the atomic number
increases. The highest activity of the alkali metal catalysts is
2
to generate CF
3
radical, which reacts with I
2
3
RbNO
3
and the highest selectivity is potassium such as KF
CO . While the anions, counterion to the metal cations,
and K
2
3
REFERENCES
–
have also effect on the reaction rate, NO
–
and F with high activity.
3
with high selectivity
1
.
R.A. Levy, V.B. Zaitsev, K.Aryusook, C. Ravindranath, V. Sigal, A. Misra,
S. Kesari, D. Rufin, J. Sees and L. Hall, J. Mater. Res., 13, 2643 (1998).
Based on exhaustive studies, it is found that the most
suitable catalyst for this reaction is the synergistic combination
2. L.G. Christophorou and J.K. Olthoff, J. Phys. Chem. Ref. Data, 29,
53 (2000).
J.C.Yang, I.Vazquez, C.I. Boyer, M.L. Huber and L. Weber, Int. J. Refrig.,
0, 96 (1997).
5
3
.
of KF with high selectivity and RbNO
especially the mass ratio of RbNO and KF is 3:1(Table-4).
I is also controlled
3
with high activity,
2
3
4. A. Misra, J. Sees, L. Hall, R.A. Levy, V.B. Zaitsev, K. Aryusook, C.
This ensures that the selectivity of the CF
3
Ravindranath, V. Sigal, S. Kesari and D. Rufin, Mater. Lett., 34, 415
(
1998).
S. Ait-Mohand, N. Takechi, M. Medebielle and W.R. Dolbier, Tetrahedron
Lett., 43, 4317 (2002).
by active component of catalyst.
5
.
TABLE-4
EFFECT OF THE RATIO OF TWO ACTIVE COMPONENTS
ON CATALYTIC ACTIVITY
6
7
.
.
N. Lu and J.S. Thrasher, J. Fluorine Chem., 117, 181 (2002).
N. Nagasaki, N. Suzuki, S. Nakano and N. Kunihiro, US Patent 5892136
(1999).
8. N. Nagasaki, Y. Morikuni, K. Kawada and S. Arai, Catal. Today, 88,
121 (2004).
KF/RbNO3
mass ratio)
C HF5
CF3I
conversion (%) selectivity (%) selectivity (%)
C F I
2
2 5
(
9
1
1
.
G.C. Yang, L. Shi, R.M. Pan and H.D. Quan, J. Fluorine Chem., 130,
31 (2009).
0. G.C. Yang, X.Q. Jia, R.M. Pan and H.D. Quan, J. Mol. Catal. A, 309,
84 (2009).
1. G. Aiello, M. Enea, G. Galante and G. La Scalia, Fire Technol., 45,
05 (2009).
1
1
2
1
3
:1
:2
:1
:3
:1
34.6
46.0
40.0
46.5
38.3
50.2
42.4
43.8
53.1
51.2
32.5
41.2
39.3
28.3
32.8
2
1
4
-1
Reaction temperature: 550 ºC; C F H /I (mol ratio):1.5; SV: 130 h
2
5
2
12. A.Q. Mao, H. Wang, L.H. Tan, X.Y. Lin and R.M. Pan, J. Fluorine
Chem., 132, 548 (2011).
1
1
1
3. Z.M. Gao and Y. Wu, React. Kinet. Catal. Lett., 59, 359 (1996).
4. S.B. Wang and Z.H. Zhu, Dyes Pigments, 75, 306 (2007).
5. Z.H. Zhu, L.R. Radovic and G.Q. Lu, Carbon, 38, 451 (2000).
The compounds containing CF
, C , C I and CF
following process for the formation of CF
As shown in Scheme-III, C HF is decomposed to form the
intermediates CF carbene. Then CF carbene is absorbed on
the surface of the catalysts and disproportionation to CF
radicals, furthermore CF radical react with I to form CF I,
whereas with H and F to form CHF and CF
maybe comes from carboxyls and phenols on the AC surface
3
group such as CHF
3
, CF
4
,
C
2
F
6
3
F
8
2
F
5
3
I were formed. We propose the
I and by products.
3
16. Y.X. Zhu, W. Zhuang, D.E. Jiang and Y.C. Xie, Chinese J. Catal., 21,
2 (2000).
5
2
5
1
1
7. X.L. Zheng, S.J. Zhang, J.X. Xu and K.M. Wei, Carbon, 40, 2597 (2002).
8. Y.Y. Xue, G.Z. Lu,Y. Guo,Y.L. Guo,Y.Q. Wang and Z.G. Zhang, Appl.
Catal. B, 79, 262 (2008).
2
2
3
3
2
3
19. H.S. Jazeyi and T. Kaghazchi, J. Ind. Eng. Chem., 16, 852 (2010).
1
7-19
3
4
. H radical
9
and F radical comes from the decomposing of CF
on heat. Alternatively, CF radical reacts with CF carbene to
form CF CF radical, which generates C I, C and C
2
carbene
3
2
3
2
F
2 5
F
2 6
3 8
F .