Preparation of 1,1,1,2-tetrafluoroethane by the vapor-phase catalytic reaction of 1,1,1-trifluoro-2-chloroethane with anhydrous hydrogen fluoride

Article abstract of DOI:10.1016/S0022-1139(01)00453-5

1,1,1,2-Tetrafluoroethane was prepared in 97% selectivity by the vapor-phase catalytic reaction of 1,1,1-trifluoro-2-chloroethane with anhydrous hydrogen fluoride (AHF) over a metal fluoride catalyst (CrF₃ and CoF₂) supported on porous aluminum fluoride (PAF). The relationship between the crystalline phase transition of porous aluminum fluoride and temperature from 100 to 640°C was investigated by X-ray diffraction.

Full text of DOI:10.1016/S0022-1139(01)00453-5

Journal of Fluorine Chemistry 111 +2001) 193±199
Preparation of 1,1,1,2-tetra¯uoroethane by the vapor-phase
catalytic reaction of 1,1,1-tri¯uoro-2-chloroethane with
anhydrous hydrogen ¯uoride
Heng-Dao Quan*, Hui-e Yang, Zhong Li, Jian-Zhang Ren, Hui-Li Li
Á Á
Xõan Modern Chemistry Research Institute, Xõan 710061, China
Received 26 March 2001
Abstract
1,1,1,2-Tetra¯uoroethane was prepared in 97% selectivity by the vapor-phase catalytic reaction of 1,1,1-tri¯uoro-2-chloroethane with
anhydrous hydrogen ¯uoride +AHF) over a metal ¯uoride catalyst +CrF3 and CoF2) supported on porous aluminum ¯uoride +PAF). The
relationship between the crystalline phase transition of porous aluminum ¯uoride and temperature from 100 to 6408C was investigated by
X-ray diffraction. # 2001 Elsevier Science B.V. All rights reserved.
Keywords: 1,1,1,2-Tetra¯uoroethane; 1,1,1-Tri¯uoro-2-chloroethane; Metal ¯uoride; Porous aluminum ¯uoride
1. Introduction
In this contribution, we ®nd a new type of catalyst which
consists of metal ¯uorides +CrF3, CoF2) supported on PAF
which exhibits a high catalytic activity, which taken the
conversion of HCFC-133a and selectivity of HFC-134a to 25
and 97%, respectively. The PAF was prepared by reaction
of g-Al2O3 with AHF. The investigation of the crystalline
phase of PAF by X-ray diffraction spectroscopy +XRD)
indicates PAF is thermally stable over the temperature range
from 100 to 5408C.
1,1,1,2-Tetra¯uoroethane +HFC-134a), having a zero
ozone depletion potential +ODP) in the stratosphere, a low
global warming potential +GWP), and similar physical prop-
erties to chloro¯uorocarbons +CFCs), has been proposed as
a major CFC-alternative refrigerant. Possible synthetic routes
to prepare HFC-134a are reported in the literature [1±5].
One of the practical routes is by vapor-phase catalytic ¯uor-
ination of 1,1,1-tri¯uoro-2-chloroethane +HCFC-133a) with
anhydrous hydrogen ¯uoride +AHF) using chromia catalyst
[6±9], or metal ¯uoride catalysts supported on porous alu-
minum ¯uoride +PAF) or magnesium ¯uoride [10±14].
To reduce the cost of producing HFC-134a, studies
focused on the improvement of the catalytic technology
[15±18], especially on the investigation of catalyst support.
Previously, we reported some results on the use of PAF as
catalyst support for preparing HFC-134a [10], and also the
¯uorination of n-dodecane and halogano-ethers adsorbed on
porous aluminum ¯uoride +PAF) by gaseous ¯uorine
[19,20], and Al+OH)mF3-m used as a reagent in organic
synthesis has been reported [21]. PAF becomes active
catalyst support in more areas due to its porous properties,
and inertness to gaseous ¯uorine and AHF.
2. Results and discussion
The analytical results show that while the main product
of the reaction was HFC-134a +Scheme 1), trace amounts
of CF3CH3, CF2=CHCl, and CF3CF2H were produced.
The CF2=CHCl is not only toxic, but also easily forms an
azeotropic mixture with HFC-134a, which makes the pur-
i®cation of product more dif®cult. So, the formation of
CF2=CHCl in the reaction should be avoided by optimizing
the catalyst. Some related factors were investigated as
follows.
2.1. Relationship between crystalline phase transition
of PAF and temperature
* Corresponding author. Present address: National Institute of Advanced
Industrial Science and Technology RITE/AIST, Tsukuba Central 5, 1-1-1,
Higashi, Tsukuba, Ibaraki 305-8565, Japan. Tel.: ‡81-298-51-3791;
fax: ‡81-298-51-3791.
By measuring the crystalline phase of PAF at different
temperatures by XRD +Fig. 1), the results of crystalline
phases transition of PAF with temperature indicate that PAF
E-mailaddress : hengdao-quan@aist.go.jp +H.-D. Quan).
0022-1139/01/$ ± see front matter # 2001 Elsevier Science B.V. All rights reserved.
PII: S 0 0 2 2 - 1 1 3 9 + 0 1 ) 0 0 4 5 3 - 5

194
H.-D. Quan et al. / Journal of Fluorine Chemistry 111 12001) 193±199
Scheme 1.
Fig. 1. XRD Pattern of porous aluminum fluoride and a-AlF3.
has excellent thermostability in the temperature range from
100 to 5408C. When the temperature rises to 5408C, part of
the PAF starts to transform into a-AlF3 and the peak strength
of a-AlF3 increases. When the temperature increases to
6008C, almost all of PAF becomes a-AlF3. Formation of
a-AlF3 indicated the PAF was sintered, and the surface area
of PAF decreased. So the preparation temperature of PAF
should be controlled strictly at less than 5008C. When PAF
was used as catalyst support in the preparation of HFC-134a,
the reaction temperature should be lower than 5008C.
the ¯uorination falls in the sequence: +CrF3 ‡ CoF2)/
PAF > CrF3=PAF > CoF2=PAF>NiF2=PAF>ZnF2=PAF
> InF3=PAF.
2.3. Effect of crystalline phase and surface area of
PAF on catalytic activity
When PAF was prepared under different conditions, it
exhibits different crystalline phases and surface area. The
metal ¯uoride supported on different kinds of PAF shows
remarkable differences in catalytic activities in the reaction
of HCFC-133a with AHF. The results are shown in Table 1.
When PAF was treated at 8008C, the surface area of PAF is
only 1 m2/g, the conversion of HCFC-133a and selectivity of
HFC-134a were 7.8 and 71.6%, respectively +Table 1, No.1).
With increasing amount of PAF and amorphous phase PAF,
the conversion of HCFC-133a and selectivity of HFC-134a
increases +Table 1, No. 2±7).
2.2. Effect of different metalful oride on
catalytic activity
Different metal chlorides were supported on PAF, and
were ¯uorinated by AHF. The prepared catalyst was used in
¯uorination reactions. The results are listed in Figs. 2a±7b.
Comparing the conversion of HCFC-133a and selectivity of
HFC-134a, the complex catalyst composed of CrF3 and
CoF2 supported on PAF exhibits the highest catalytic activ-
ity. The amount of by-products, CF3CH3, CF2=CHCl, and
CF3CF2H, can be controlled at a low level. The results
indicate that the ef®cacy of the catalysts with respect to
2.4. Possible reaction mechanism
The reaction mechanism can be explained as shown in the
Scheme 2: MFm promoted by PAF works as a strong Lewis

H.-D. Quan et al. / Journal of Fluorine Chemistry 111 12001) 193±199
195
Fig. 2. +a) Catalyst +CoF2/PAF); +b) catalyst +CoF2/PAF).
Fig. 3. +a) Catalyst +CrF3 ‡ CoF2/PAF); +b) catalyst +CrF3 ‡ CoF2/PAF).

196
H.-D. Quan et al. / Journal of Fluorine Chemistry 111 12001) 193±199
Fig. 4. +a) Catalyst +CrF3/PAF); +b) catalyst +CrF3/PAF).
Fig. 5. +a) Catalyst +InF3/PAF); +b) catalyst +InF3/PAF).

H.-D. Quan et al. / Journal of Fluorine Chemistry 111 12001) 193±199
Fig. 6. +a) Catalyst +NiF2/PAF); +b) catalyst +NiF2/PAF).
Fig. 7. +a) Catalyst +ZnF2/PAF); +b) catalyst +ZnF2/PAF).
197

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H.-D. Quan et al. / Journal of Fluorine Chemistry 111 12001) 193±199
Table 1
Effect of crystalline phase and surface area of PAF on catalytic activitya
No.
a-AlF3
PAF
Amorphous
phase PAF
Surface area
+m2/g)
Conversion of
133a +%)
Selectivity of
134a +%)
1
2
3
4
5
6
7
98
97
5
2
3
0
0
1.3
8.3
7.8
9.0
72.0
72.3
91.9
96.3
96.2
96.2
96.6
73
62
73
68
5
12
30
25
30
95
34.0
40.3
48.0
55.0
69.4
12.6
16.8
18.7
24.6
27.9
8
2
2
0
a Reaction temperature 3758C, molar ratio +HF:133a ˆ 10:1), catalyst +Cr ‡ Co)/PAF, Cr 3 wt.%, Co 1 wt.%.
heated tubular nickel reactor, 2 cm in diameter and 40 cm
in length equipped with an inner nickel tube for inserting
type-K thermocouples with diameter 1 mm. Two thermo-
couples enter the reactor through a type-316 stainless-
steel CAJON ®tting and penetrate to the catalyst bed to
measure the temperature change of different position of
the reactor.
XRD was used to determine the bulk crystalline phase of
aluminum ¯uoride. The pattern of aluminum ¯uoride was
recorded by Dmax-2400. For XRD using Cu Ka
+0.1504 nm) radiation, the X-ray tube was operated at
50 kV and 100 mA. The aluminum ¯uoride was put into
the sample cell, heated to 1008C and kept at that the
temperature for 1 h, then heated at a rate of 20 to 7008C/
min. The XRD patterns of aluminum ¯uoride from 100 to
6408C are shown in Fig. 1.
The BET surface area of AlF3 were measured by means of
low temperature adsorption of nitrogen using a micromeri-
tics ASAP 2000. Sample were outgassed under vacuum
+P < 10À5 torr) at 523 K for 5 h before measurement.
A SQ-203 gas chromatograph +produced by Beijing Ana-
lytic Instrument Factory) was used to analyse products,
Scheme 2.
acid in the reaction. The metal ion in MFm coordinates to the
chlorine atom of HCFC-133a to make the neighboring car-
bon more positive. Nucleophilic attack of ¯uorine in MFm on
the neighboring carbon atom gives HFC-134a and MFm-1Cl.
MFm was regenerated by reaction of MFm-1Cl with AHF.
Ê
which were dried by molecular sieve +4 A) after being
washed by H2O, then by NaOH aqueous solution to remove
HF and HCl. The GC column was packed with GDX-401.
Operating conditions were as follows: column temperature,
1008C; TCD detector temperature, 1008C; H2 ¯ow rate,
50 ml/min.
3. Experimental
3.1. Chemicals
3.3. Preparation of catalyst and reaction procedure
CoCl2Á6H20 +99.0% purity), Mg+CH3COO)2Á4H2O +99.0%
purity), CrCl3Á6H2O +99.5% purity), were purchased from
The catalyst is prepared by following procedure. PAF,
the support catalyst, is prepared by packing 30 ml g-Al2O3
into the reactor, ¯ushing with N2 +200 ml/min) at 2008C for
4 h, activating with a mixture stream of AHF +100 ml/min)
and N2 +300 ml/min) at 3008C for 16 h. Then the pure AHF
passes through the reactor for 2 h. The prepared PAF was
impregnated into a suf®cient amount of metal chloride
solution +about 20 wt.%) overnight. The amount of metal
chloride in the solution was adjusted to give a ®nal metal
loading 3 wt.%. The saturated support was dried at 1208C
for 2 h and 2008C for 2 h. The dried pellets were packed into
the nickel alloy reactor and ¯uorinated by N2/AHF ˆ 1:1
Á
Xõan Regent Factory, China. AHF +99.0% purity), 42% HF
aqueous solution were obtained from Shan Dong Chemicals
Co., China. g-Al2O3 +surface area 315.8 m2/g, average pore
volume 0.43 cc/g) were produced by the Research Institute
of Shan Xi Aluminum Works, China.
3.2. Instrument
Apparatus for investigating the reaction consist of an N2
mass ¯ow controller, an AHF ¯ow rate meter, an electrically

H.-D. Quan et al. / Journal of Fluorine Chemistry 111 12001) 193±199
199
[5] Chemical Week 15 +1992) 151.
+100 ml:100 ml) at 2008C for 2 h, then pure AHF passed
through the reactor at 2008C for 2 h and 3008C for 2 h.
The ¯uorination procedure is as follows. A certain amount
of AHF and HCFC-133a was passed through the reactor. The
mixture of products was washed by a dilute solution of
Ê
NaOH and H2O, then dried by molecular sieve +4 A) and
passed to the GC for analysis.
[6] D.H. Cho, Y.G. Kim, J.S. Chung, Catal. Today 53 +1998) 199±203.
[7] S. Brunet, B. Requieme, E. Colnay, J. Barrault, M. Blanchard, Appl.
Catal. B 5 +1995) 305±317.
[8] A. Kohne, E. Kemnitz, J. Fluor. Chem. 75 +1995) 103±110.
[9] S. Brunet, B. Requieme, E. Matouba, J. Barrault, M. Blanchard, J.
Catal. 152 +1995) 70±74.
[10] H. Quan, Z. Li, H. Yang, J. Lu, J. Ren, H. Li, Appl. Catal. B 8 +1996)
209±215.
[11] J. Lu, H. Yang, S.K. Chen, L. Shi, J.G. Ren, H.L. Li, S.Y. Peng, Catal.
Lett. 41 +1996) 221±224.
Acknowledgements
[12] H. Lee, H.D. Jeong, Y.S. Chung, H.G. Lee, M.J. Chung, S. Kim, H.S.
Kim, J. Catal. 169 +1997) 307±316.
[13] H. Lee, H.S. Kim, H. Kim, W.S. Jeong, I. Seo, J. Mol. Catal. A:
Chem. 136 +1998) 85±89.
We gratefully acknowledge the ®nancial support of this
investigation by National Planning Committee +CNPC) of
China. Thanks are also given to Xiao-yu Li for his help in
measuring XRD.
[14] H. Lee, Y.G. Kim, M.J. Chung, J.S. Chung, Appl. Catal. B 18 +1998)
251±261.
[15] K.G. Carl, M.E. Leo, US Patent 493,558 +1990).
[16] O. Hiromoto, N. Hidetoshi, JP Patent 02,273,634 +1989).
[17] G. Paolo, M. Antonio, EP 0,408,005A +1990).
[18] B.S. Ahn, Y.S. Kwon, K.Y. Park, M.J. Chung, US Patent 5,841,007
+1998).
References
[19] H.D. Quan, M. Tamura, T. Takagi, A. Sekiya, J. Fluor. Chem. 99
+1999) 167±170.
[1] L.E. Manzer, Catal. Today 13 +1992) 13±22.
[2] R. Firth, G. Foll, US Patent 3,755,477 +1973).
[3] M. Vecchio, G. Groppelli, J.C. Tatlow, J. Fluor. Chem. 4 +1974)
117±139.
[20] H.D. Quan, M. Tamura, J. Murata, R.X. Gao, A. Sekiya, J. Fluor.
Chem. 106 +2000) 121±125.
[21] H.D. Quan, M. Tamura, R.X. Gao, A. Sekiya, Tetrahedron 57 +2001)
4111±4114.
[4] C. Gervasutti, L. Marangoni, W. Marra, J. Fluor. Chem. 19 +1981) 1±20.