Fluorination of chlorofluoroether using catalysts supported by porous aluminum fluoride

Article abstract of DOI:10.1016/S0022-1139(01)00483-3

Reaction of 1,2-dichloro-1,1,2-trifluoro-2-methoxyethane with anhydrous hydrogen fluoride (AHF) was investigated in the presence of metal fluorides supported on porous aluminum fluoride (PAF). 2-Chloro-1,1,2,2-tetrafluoro-2-methoxyethane, a new compound,

Full text of DOI:10.1016/S0022-1139(01)00483-3

Journal of Fluorine Chemistry 112 )2001ꢀ 145±148
Fluorination of chloro¯uoroether using catalysts supported by
porous aluminum ¯uoride
a,*
Akira Sekiya , Heng-dao Quan , Masanori Tamura , Ren-Xiao Gao , Junji Murata
b
a
b
b
a
National Institute of Advanced Industrial Science and Technology ꢀAIST), Formerly National Institute of Materials and
Chemical Research, 1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan
b
Research Institute of Innovative Technology for the Earth ꢀRITE), c/o AIST, 1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan
Abstract
Reaction of 1,2-dichloro-1,1,2-tri¯uoro-2-methoxyethane with anhydrous hydrogen ¯uoride )AHFꢀ was investigated in the presence of
metal ¯uorides supported on porous aluminum ¯uoride )PAFꢀ. 2-Chloro-1,1,2,2-tetra¯uoro-2-methoxyethane, a new compound, was
prepared in 85% yield in the presence of CoF
#
2
/PAF. Methyl chlorodi¯uoroacetate was also obtained and its formation was discussed.
2001 Elsevier Science B.V. All rights reserved.
Keywords: Porous aluminum ¯uoride; 1,2-Dichloro-1,1,2-tri¯uoro-2-methoxyethane; 2-Chloro-1,1,2,2-tetra¯uoro-2-methoxyethane; Methyl chlorodi¯uor-
oacetate
1
. Introduction
tri¯uoro-2-methoxyethane )1ꢀ with anhydrous hydrogen
uoride )AHFꢀ in the presence of metal ¯uorides supported
on PAF was investigated for the ®rst time. In the reaction, 2-
¯
Partially ¯uorinated ethers have been proposed as possi-
ble third generation alternatives to replace CFCs, HCFCs,
and PFCs as refrigerants, form blowing agent, and cleaning
solvents because of their low environmental effect, in¯am-
mability, low toxicity, and similar physical properties to
CFCs [1].
chloro-1,1,2,2-tetra¯uoro-2-methoxyethane )2ꢀ, a new com-
pound, was obtained in 85% yield when CoF /PAF was used
2
as a catalyst. Compound 2 will be a possible intermediate of
)HFE-245mcꢀ,
1,1,1,2,2-penta¯uoro-2-methoxyethane
which is expected as a prime candidate of CFCs alternatives
[10]. On the other hand, methyl chlorodi¯uoroacetate )3ꢀ
was obtained around 50% yield in the presence of PAF or
As we know, the replacement of chlorine atoms by
uorine atoms occupies a practically important position
¯
in the preparation of partially ¯uorinated ethers. In the
literatures, the replacement of chlorines in chlorinated ether
by ¯uorine was studied by ¯uorination with metal ¯uorides
CrF /PAF in the reaction.
3
[
2,3], liquid-phase ¯uorination by Swart's reaction [4,5],
2. Results and discussion
direct ¯uorination with gaseous ¯uorine [6], and electro-
chemical ¯uorination [7].
In our previous work, partially halogen-ethers were
The reaction of 1 with PAF or with AHF in the presence of
metal ¯uorides supported on PAF was attempted and the
results were listed in Table 1. The reaction proceeded as
shown in Scheme 1.
From the results, 2 and 3 were formed as main products in
the reaction of PAF alone with 1 at 2008C. The results
indicated that PAF has not only activity of ¯uorination, but
also activity of esteri®cation )Table 1, No. 1ꢀ. In order to
observe the effect of AHF, we tried to put AHF to reaction.
Then the yield of 2 increased to 27%, and 3 increased to 54%
at 2008C )Table 1, No. 2ꢀ. The results indicated the yields of
products 2 and 3 were improved and the decomposition
¯
uorinated by gaseous ¯uorine when substrates were
absorbed on porous aluminum ¯uoride )PAFꢀ [8]. The
PAF was also used as a catalyst support to prepare
1,2,2,2-tetra¯uoroethane )HFC-134aꢀ by vapor-phase cat-
alytic ¯uorination [9].
Here, we investigated the preparation of partially ¯uori-
nated ethers via exchange of halogens by vapor-phase
catalytic ¯uorination. The reaction of 1,2-dichloro-1,1,2-
*
Corresponding author. Tel.: ‡81-298-61-4570; fax: ‡81-298-61-4570.
products, such as CH Cl and CF ClCOF, were reduced in
3
E-mail addresses: akira-sekiya@aist.go.jp, sekiya@nimc.go.jp
2
)A. Sekiyaꢀ.
the presence of AHF.
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 8 3 - 3

146
A. Sekiya et al. / Journal of Fluorine Chemistry 112 ꢀ2001) 145±148
Table 1
a
Catalyst effect for reaction of 1
No.
Catalyst
1 )mmolꢀ
AHF )mmolꢀ
Products )yield %ꢀ
Recovery of 1 )%ꢀ
2
3
1
2
3
4
PAF
PAF
2.9
2.6
1.0
1.0
±
12
27
46
85
33
54
42
9
0
4
4
2
6.7
5.9
6.0
b
3
CrF /PAF
c
CoF /PAF
2
a
b
c
Reaction temperature, 2008C; reaction time, 1 h; catalyst, 2 g, for each reaction.
Cr, 5 wt.%.
Co, 5 wt.%.
recovered when reaction temperature is <2008C, and char-
ring occurred at 3008C.
From these results, the reaction mechanism may be
inferred as follows: MF )M ˆ Al, Co, Crꢀ acts as a Lewis
n
acid to activate chlorine reactivity. The ¯uorine atom of MF
attacks the a-carbon to replace chlorine atom to form 2 and
n
Scheme 1.
MF Cl
m
)Scheme 2, route 1ꢀ. The MF was regenerated
n
nÀm
by the reaction of MF Cl
Catalysts supported on PAF, CoF /PAF and CrF /PAF,
2
with AHF. AlF )OHꢀ
m
3
m
nÀm
3Àm
were studied. Ether 2 was formed in 85% yield when CoF2/
PAF was used in the reaction at 2008C )Table 1, No. 4ꢀ. On
the other hand, ether 2 and ester 3 were obtained in 46 and
exists on the surface of aluminum ¯uoride after it was dried
at about 3508C [11,12]. The OH group should be on the
surface of PAF and catalysts because their treating tempera-
4
2% yield, respectively, when CrF /PAF was used at 2008C
ture was about 3008C. The OH group of AlF )OHꢀ
3Àm
could
3
m
)
Table 1, No. 3ꢀ. The results indicate the ef®cacy of the
attack the a-carbon of 1 to give ester 3 and AlClF
-
)OHꢀ3 )Scheme 1, route 2ꢀ. The esteri®cation competes
mÀ1
catalysts with respect to the ¯uorination falls in the
sequence: CoF2=PAF > CrF3=PAF > PAF.
The effect of temperature for the reaction of 1 using CoF2/
Àm
with ¯uorination, so both 2 and 3 were obtained. In the case
of CoF /PAF, ether 2 was predominately obtained, which
2
PAF and CrF /PAF were investigated and the results were
3
shows that the ¯uorination with CoF overcome esteri®ca-
2
listed in Tables 2 and 3, respectively. In each case, the
reaction at 2008C gave best results. Starting material was
tion by AlF )OHꢀ . As the ¯uorination ability of CrF3
m
3Àm
would be weaker than that of CoF , so that the yield of 2 was
2
almost same as that of 3 in the presence of the existing of
CrF /PAF. In the case of PAF, the ¯uorination ability would
much weaker, so the ester formation was predominant.
3
Table 2
a
Effect of temperature for reaction of 1 using catalyst CoF /PAF
2
On the other hand, after AlF )OHꢀ
m
3Àm
reacted with 1, it
, and this would catalyze
would generate AlClF )OHꢀ
m
2Àm
the decomposition of 1 to form CF ClCOF and CH Cl
No.
AHF
mmolꢀ
Reaction
Products GC area )%ꢀ
)
temperature )8Cꢀ
2
3
2
3
1
)
)
Scheme 1, route 3ꢀ. In the presence of AHF, AlClF
OHꢀ
-
, so that the
mÀ1
would be converted into AlF )OHꢀ
m
1
2
3
4
4.3
5.2
6.0
4.6
100
150
200
300
1
40
4
83
33
2
3Àm
3Àm
18
9
addition of AHF to the reaction can reduce the decomposi-
tion of 1 and increase the yield of 2 and 3.
Further ¯uorination studies of 2 to HFE-245mc are cur-
rently being investigated.
85
Decomposition
a
Starting material 1 is 1 mmol for each reaction; reaction time, 1 h;
catalyst amount, 2 g; Co, 5 wt.%.
3. Experimental
Table 3
a
3
Effect of temperature for reaction of 1 using catalyst CrF /PAF
3
.1. Chemicals
No.
AHF
mmolꢀ
Reaction
Products GC area )%ꢀ
)
temperature )8Cꢀ
2
Surfaceareaandporevolume)V ꢀ ofPAFwere75 m /gand
3
.3 cm /g, respectively [8]. 1,1,2-Tri¯uoro-2-methoxyethene
2
3
1
s
0
1
2
3
7.0
5.9
4.0
150
200
300
23
20
42
55
4
46
Decomposition
)4ꢀ was from Daikin ¯uorochemical Co. The AHF was
obtained from Morita Chem. Ind. Co. Ltd. 1,2-Dichloro-
1,1,2-tri¯uoro-2-methoxyethane )1ꢀ was prepared by the
reaction of 4 with equimolar amount of gaseous chlorine [13].
a
Starting materials 1 is 1 mmol for each reaction; reaction time, 1 h;
catalyst amount, 2 g; Cr, 5 wt.%.

A. Sekiya et al. / Journal of Fluorine Chemistry 112 ꢀ2001) 145±148
147
Scheme 2.
3
.2. Instrument
Catalysts were prepared by following way. First, the PAF
was dehydrated by heating at 3008C for 10 h and then
impregnated to a suf®cient amount of salt solution overnight.
The amount of salt in the solution was adjusted to give ®nal
metalloadingfrom1±5 wt.%.Thesaturatedsupportwasdried
at 1208C for 2 h and 2008C for 2 h. The dried pellets were
packed on Monel alloy reactor and ¯uorinated by
1H NMRand 19F NMRwere recorded on JNM-EX270
)JEOL, 270 MH ꢀ at 258C with Me Si and CFCl , respec-
tively, as internal reference in CDCl as a solvent.
The FT-IRspectrometer )FT-IR620, Japan Spectroscopic
Co. Ltd.ꢀ was used for measuring.
Z
4
3
3
The GC±MS was a Hewlett-packard 5790 series system
equipped with a Jet Separator for the 5890A GC. The
capillary column was Pora plot Q with 0.32 mm i.d. and
N :AHF ˆ 1:1 )100:100 mlꢀ at 2008C for 2 h, then pure
2
AHF passes through the reactor at 2008C for 2 h and 3008C
for2 h. Finally, remainingAHFon the catalyst was washed by
2
5 m length from J & W Scienti®c Inc. The operation
N . The prepared catalyst is used to ¯uorination procedure.
2
condition of GC is as follows: column temperature 808C
for 2 min and heated for 20 min at a rate of 108C/min;
detector temperature, 2008C; carrier gas, 1 cc He/min; split
ratio, 45:1; sample size, 1.2 ml; pressure, 50 kPa.
Products were handled in glass and metal vacuum line
system. Amounts and molecular weight of products were
determined by measuring the sample pressure under a
certain volume in the vacuum line.
3.4. Reaction of 1 with AHF in the presence of catalyst
About 2 g of catalyst was placed in a stainless steel reactor
3
with 80 cm volume. The reactor was cooled to À1968C, and
1 mmol of 1 and 3 mmol AHF were introduced into the
reactor. The reactor was heated to 2008C and kept at this
temperature for 1 h. Remaining AHF was adsorbed by NaF.
The products were analyzed by FT-IR, GC±MS, and NMR.
The results were listed in Table 1. Compounds 2 and 3 were
formed as main products.
3
.3. Preparation of catalyst
Apparatus for preparing catalyst consists of two mass ¯ow
controllers )one is for N and another for AHFꢀ and an
Compound 2 is a new compound. The boiling point is 41±
428C at 760 mmHg. The spectra data were listed as follows;
IR: 2974 )wꢀ, 1460 )wꢀ, 1351 )mꢀ, 1251 )sꢀ, 1181 )vsꢀ, 1129
)vsꢀ, 1050 )wꢀ, 1015 )sꢀ, 947 )sꢀ.
2
electrically heated tubular Monel reactor 14 cm in diameter
and 30 cm in length equipped with an inside Monel tube for
inserting type-K thermocouples with a 1 mm diameter. A
thermocouple enters the reactor through a type-Monel
‡
‡
MS peaks m/e: 15 CH ; 81 CH OCF ; 131 CH OCF -
2
3
3
2
2
‡
‡
‡
CF H ; 147 CH OCF CFCl ; 165 CH OCF CF Cl .
2
2
3
2
2
2
1
CAJON ®tting and penetrates to the whole of the catalyst
bed to measure the temperature change of different position
of the reactor.
NMRchemical shifts:
CH ÀOÀCF ÀCF Cl
3
2
2
3
1
2

148
A. Sekiya et al. / Journal of Fluorine Chemistry 112 ꢀ2001) 145±148
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