Note: Descriptions are shown in the official language in which they were submitted.
2192843
W O 96101797 PCT/US95I08404
PROCESS FOR THE MANUFACTURE OF
1,1.1.3,3-PENTAFLUOROPROPANE
BACKGROUND OF THE INVENTION
' S
This invention relates to a novel method of manufacturing 1,1,1,3,3-
pentafluoropropane, CF3CH2CF2H, which is referred to in the art as HFC-245fa.
Specifically, the invention relates to the fluorination with hydrogen fluoride
of a
compound ofthe formula:
CFYCI3_yCH2CHFw,Cl2-w
wherein w = 0 or 1, and y = 0 - 3, in the presence of a fluorination catalyst
to produce
HFC-245fa.
HFC-245fa has physical properties, including a boiling point of about 14
°C ,
which make it particularly attractive as a blowing agent. (See Ger. Offen, DE
3,903,336, 1990 (EP 381,986 A)). It also has the ability to function as an
aerosol
propellant (U.S. Patent 2,942,036 to Smith and Woolf) in a manner similar to
trichlorofluowomethane, which is referred to in the art as CFC-11, and as a
heat
transfer agent. (Jpn. Kokai Tokyo Koho JP 02,272,086 in 114 Chemical Abstracts
125031q (1991)).
Traditionally, chlorofluorocarbons (CFCs) like CFC-l l and
dichlorodifluoromethane (CFC-12) have been used as refrigerants, blowing
agents and
propellants. These materials, however, are believed to contribute to
stratospheric
ozone depletion. The fluorocarbon industry therefore has focused its attention
on
developing stratospherically safer alternatives to these materials. HFC-245fa
is a
candidate replacement material since it functions in substantially the same
way as the
CFCs but is zero ozone depleting. Because the demand for these and other low
or
zero ozone depleting materials will increase dramatically in the future,
commercially
viable processes for their preparation are needed.
Only two methods for manufacturing HFC-245fa (which are not
hydrofluorination reactions) are reported in the art. However, these methods
are not
without their shortcomings. Knunyants, et al., Catalytic Hydrogenation of
Perfluoro
Olefins, 55 Chemical Abstracts 349f(1961), discloses the reduction of
1,1,1,3,3-
pentafluoropropene to HFC-245fa. Because this process includes multiple steps,
it is
inefficient and uneconomical. Burdon, et al., Pnrtial Flrrorination of
Tetrahydrofurau
with Cobalt Tr~voride, J. Chem. Soc. (C), 1739 (1969), discloses the elemental
WO 96101797 219 2 8 4 3 2 PC1YIJS95108404
fluorination of tetrahydrofuran to produce HFC-245fa. This process suffers the
disadvantage that it produces a host of other by-products, thus reducing the
yield of
the desired product.
S As far as hydrofluorination reactions are concerned, there are no such
methods
for the production ofHFC-245fa reported in the art, let alone fluorination
reactions
which use 1,1,1,3,3-pentachloropropane (CCI3CH2CHCl2) as the starting material
to '
produce HFC-245fa. Although the conversion of-CCI3 groups to -CF3 groups is
well-known in the art, attempts to fluorinate terminal -CHC12 or -CHC1F groups
to
CHF2 groups in compounds having more than two carbons, (in particular
compounds
of the formula RCH2CHCl2 and RCH2CHFX wherein X is Cl or Br and R is an alkyl
group having at least one carbon atom), have not been successful. See Henne,
et al.,
Flrroroethanes and Flrroroelhylene.s, 58 J. Am. Chem. Soc. 889 (1936).
Tarrant, et al., Free Radical Additions Irmolairtg Fluorine Compounds. IV.
The Addition ofDibromodiflnoromethane to Some Flnoroolefins, 77 J. Am. Chem.
Soc. 2783 (1955) report the fluorination of compounds of the type
CF2BrCH2CHFBr
with hydrogen fluoride (HF) in the presence of a Sb(V) salt catalyst, such as
SbClS
and TaFS. However, this method produced only a 14% yield of CF3CH2CHFBr at
125°C, and only a modest improvement in yield at 170°C. Even
a~elevated
temperatures, no HFC-245fa was produced.
DESCRIPTION OF THE INVENTION
We have discovered that the drawbacks associated with the prior art processes
for manufacturing 1,1,1,3,3-pentafluoropropane or HFC-245fa can be eliminated
by
the process of our invention. That is, we have discovered an efficient and
economical
means of manufacturing HFC-245fa on a commercial scale, which uses readily
available raw materials and which produces HFC-245fa in high yield.
The invention relates to a process for manufacturing 1,1,1,3,3-
pentafluoropropane comprising:
1) reacting a compound ofthe formula:
CFyCl3_yCH2CHFr,,Cl3-w
wherein w = 0 or I, and y = 0 - 3, with hydrogen fluoride in the presence of a
fluorination catalyst under conditions sufficient to produce a compound of the
formula
CF3CH2CF2H; and __
2192843
W 0 96I0 1797 PCT/US95/08404
3
2) optionally recovering a compound of the formula CF3CH2CF2H.
The organic starting materials corresponding to the formula CFYCI3_
yCH2CHFN,Cl2_w , wherein w = 0 or l, and y = 0 - 3, include CCI3CH2CHC12,
CF3CH2CHC12, CFCI2CH2CHC12, CF2CICH2CHCI2, CFCI2CH2CHC1F,
CF2CICH2CHFC1, and CF3CH2CHFCI. The preferred starting material is
CCI3CH2CHCI2.
These materials are not commercially available. However, they may be
prepared by any means well-known in the art. See, for example, B. Boutevin, et
al.,
Monofzrnctional Yinyl Chloride Telnmers. 1. Syrrlhesi.s and Characterization
of Vinyl
Chloride Telomer Standards, 18 Eur. Polym. J. 675 (1982) in 97 Chemical
Abstracts
182966c (1982); and Kotora, et al., Selectiae Acfdiliorzs of Polyhalogenated
Compounds 1o Chloro Substinrted ~therres Catalyzed by a Copper Complex, 44(2)
React. Kinet. Catal. Lett. 415 ( I 991 ). See also the method disclosed in
Examples 1
and 2 below. When CCI3CH2CHC12 is the starting material, it is preferably
prepared
according to the method provided in Example 1 below. Alternatively,
CC13CH2CHCI2 may be prepared by the reduction of CC13CH2CCI3 (see Example 2)
as well as by photochlorination of CCI3CH2CH2Cl.
Any water in the HF will react with and deactivate the fluorination catalyst.
Therefore, substantially anhydrous HF is preferred. By "substantially
anhydrous" we
mean that the HF contains less than about 0.05 weight % water and preferably
contains less than about 0.02 weight % water. However, one of ordinary skill
in the
art will appreciate that the presence of water in the catalyst can be
compensated for by
increasing the amount of catalyst used. HF suitable for use in the reaction
may be
purchased from AlliedSignal lnc. of Morristown, New Jersey.
Based on reaction stoichiometry, the required mole ratio of HF to organics
(i.e., CFyCl3_yCH2Fv,C12_~,) is 5-y-w (or the number of chlorine atoms in the
organic
starting material) to 1Ø HF is preferably used in an amount from about 1 to
about IS
times the stoichiometric amount of HF to organics, and more preferably from
about 6
to about IS times the stoichiometric amount ofHF to organics.
Fluorination catalysts useful in the process of the invention include: (L)
pentavalent antimony, niobium, arsenic and tantalum halides; (IL) pentavalent
antimony, niobium, arsenic and tantalum mixed halides; and (IIL) mixtures of
WO 96101797 219 2 8 4 3 PCTlUS95/08404
4
pentavalent antimony, niobium, arsenic and tantalum halide catalysts. Examples
of
catalysts of group (L) include antimony pentachloride and antimony
pentafluoride.
Examples of catalysts of group (IL) include SbC12F3 and SbBr2F3. Examples of
catalysts of group (IIL) include a mixture of antimony pentachloride and
antimony
S pentafluoride.
Pentavalent antimony, niobium, arsenic and tantalum halides are commercially
available, and mixed halides thereof are created in sinr upon reaction with
HF.
Antimony pentachloride is preferred because of its low cost and availability.
Pentavalent antimony mixed halides of the formula SbCInFS_n where n is 0 to 5
are
more preferred. The fluorination catalysts used in this invention preferably
have a
purity of at least about 97%. Although the amount of fluorination catalyst
used may
vary widely, we recommend using from about 5 to about 50%, or preferably from
about 10 to about 25% by weight catalyst relative to the organics.
It may be advantageous to periodically regenerate the catalyst due to the
dissociation of the pentavalent catalyst over time. This may be accomplished
by any
means well known in the art. The catalyst may be regenerated, for example, by
adding
chlorine (in an amount of from about 1 to about 10 mole percent relative to
the
amount of pentavalent catalyst initially present in the reactor) to the
combination
stream comprised of organics of the formula CFyCl3_yCH2CHFN,Cl2_~,, and the
recycled stream comprised of under-fluorinated materials and HF. The chlorine,
which
is continuously added to the process of this invention when operating in a
continuous
mode (and periodically added when operating in a batch mode), oxidizes the
catalyst
from the trivalent to the pentavalent state. One of ordinary skill in the art
can readily
determine without undue experimentation the amount of chlorine to be added in
order
to optimize the use of the catalyst.
The temperature at which the fluorination reaction is conducted and the period
of reaction will depend on the starting material and catalyst used. One of
ordinary skill
in the art can readily optimize the conditions of the reaction without undue
experimentation to get the claimed results, but the temperature will generally
be in the
range of from about 50 to about 175 °C, and preferably from about 115
to about 155
°C, for a period of, for example, from about I to about 25 hours, and
preferably from
about 2 to about 8 hours.
Pressure is not critical. Convenient operating pressures range from about 1500
to about 5000 KPa, and preferably from about 1500 to about 2500 KPa.
W O 96101797 2 7 9 2 8 4 3 PCT/U595I08404
tJ
The equipment in which the fluorination reaction is conducted is preferably
made of corrosion resistant material such as Inconel or Monel.
' S HFC-245fa may be recovered from the mixture of unreacted starting
materials,
by-products, and catalyst by any means known in the art, such as distillation
and
extraction. As illustrated in Example 3, at the end of the heating period,
i.e. the
amount of time for complete reaction in batch mode operations, the
fluorination
reaction product and remaining HF may be vented through a valve on the
autoclave
head, which in turn is connected to an acid scrubber and cold traps to collect
the
product. Alternatively, unreacted HF and organics may be vented and condensed,
and
the HF layer recycled to the reactor. The organic layer can then be treated,
i.e. washed
with an aqueous base, to remove dissolved HF and distilled. This isolation
procedure
is particularly useful for a continuous fluorination process. Under-
fluorinated
materials, such as CF3CH2CHFC1, may be recycled in subsequent runs.
In another embodiment, the invention relates to a process for the manufacture
of 1,1,1,3,3-pentafluoropropane which comprises:
1. reacting CCI4 and vinyl chloride in the presence of a telomerization
catalyst
under conditions sufFcient to produce a compound of the formula
CC13CH2CHCI2;
2. reacting a compound of the formula CC13CH2CHCI2 with hydrogen
fluoride in the presence of a fluorination catalyst under conditions
sufficient to
produce a compound of the formula CF3 CH2CF2H; and
3. optionally recovering a compound ofthe formula CF3CH2CF2H.
The telomerization of vinyl chloride by reaction with carbon tetrachloride to
produce CCI3CH2CHC12 is known in the art. See, for example, B. Boutevin, et
al.,
Monofinrctional Yirryl Chloride Telomers. !. Syrrthesi.s acrd Characterization
of Vinyl
Chloride Telomer Standards, 18 Eur. Polym. J. 675 (1982) in 97 Chemical
Abstracts
182966c (I982); and Kotora, et al., Selectioe Additions of Polyhalogenated
Compormds to Chloro Snbstinned Ethenes Catalyzed by a Copper Complex, 44(2)
React. Kinet. Catal. Lett. 415 ( 1991 ).
WO 96101797 ~ ~ PCBYUS95I08404
6
The starting materials for the telomerization reaction, i.e. carbon
tetrachloride
and vinyl chloride, are available from commercial sources. The molar ratio of
CCI4 to
vinyl chloride is about 0.5:10, preferably about 1:8 ( in order to minimize
the
formation of higher telomers), and most preferably about 1:5.
The telomerization of vinyl chloride can be initiated by any commercially
available catalyst known in the art to be useful in initiating and catalyzing
the
telomerization of carbon tetrachloride and vinyl chloride. Suitable catalysts
include,
but are not limited to, organic peroxides, metallic salts, and metal
carbonyls. Copper
and iron salt catalysts, such as cuprous chloride (CuCI), cuprous iodide
(CuI), and iron
chloride (FeCl2), are preferred. The amount of catalyst used in the
telomerization
reaction is at least about 0.1 to about 50 mmol, and preferably about 1 to
about 20
mmol per mole of organics (i.e., CC13CHZCHC12).
An amine co-catalyst, such as an alkanol amine, alkyl amine, and aromatic -
amine, may optionally be used in order to allow for the use of milder
conditions in the
telomerization process. Examples of suitable amine co-catalysts include
ethanol
amine, butyl amine, propyl amine, benzylamine, and pyridine. 2-propylamine is
the
most preferred co-catalyst. Such co-catalysts are commercially available. When
a co-
catalyst is used, it should be used in an amount from about I to about 10
moles per
mole of catalyst, i.e., e.g. copper salt.
In order to dissolve the catalyst, a solvent, which is inert to the reactants
and
the desired product, may be used in the telomerization reaction. Suitable
solvents
include, but are not limited to, commercially available acetonitrile,
dimethylsulfoxide,
dimethylformamide, tetrahydrofuran, isopropanol, and tertiary butanol.
Acetonitrile is
preferred because of ease of handling and stability. The amount of solvent
used ranges
from about 5 times the amount of catalyst used on a mole basis to about 80
percent of
xhe total volume of the total telomerization reaction mixture (i.e., solvent,
catalyst, co-
catalyst, carbon tetrachloride, vinyl chloride), and more preferably between
about 10
to 50 times the amount of catalyst used on a mole basis.
The temperature at which the telomerization reaction is conducted and the
period of reaction will depend on the catalyst selected, the presence of a co-
catalyst,
and the solubility of the catalyst system in the solvent. One of ordinary
skill in the art ,
can readily optimize the conditions of the reaction without undue
experimentation to
get the claimed results but the temperature will generally be in the range of
from about
25 to about 225 °C, preferably from about 50 to about 150 °C.
The period of reaction
WO 96!01797 219 2 8 4 3 PCT/US95108404
will generally range from about 3 to about, 72 hours, preferably from about 10
to about
24 hours.
Pressure is not critical.
n
Preferably the telomerization reaction is conducted in a conventional
apparatus,
such as an autoclave made of corrosion resistant materials such as Teflon and
glass.
Preferably, the telomerization product is recovered from by-products, solvent,
catalyst and co-catalyst prior to the fluorination reaction to substantially
eliminate the
production ofby-products in the fluorination step. The telomerization product
may be
recovered by any means well known in the art such as distillation and
extraction.
Optionally, the telomerization product may be further purified by additional
distillation.
Due to the toxicity of vinyl chloride, other procedures for preparing
CC13CH2CHC12 may be employed. See Example 2 (reduction ofCC13CH2CC13).
Alternatively, CCI3CH2CC13 may be prepared according to the well-known
telomerization reaction of vinylidene chloride with carbon tetrachloride.
Exflmnle 1. Preparation of CCI3CH C2 HC~, from CCI4 and CH2=CHCI
A 600-mL mope! autoclave equipped with mechanical stirrer was charged with
1 g CuCI, 156.6 g CCl4 and 75 mL acetonitrile. The contents were cooled in an
ice
bath, and the autoclave was closed and evacuated briefly. 36.7 g of vinyl
chloride was
then added, and the contents stirred and heated to 135 °C for 16 hours.
The volatile
materials were removed by distillation at atmospheric pressure. Distillation
at 23 mm
Hg resulted in 90.0 g (7l% yield based on vinyl chloride added) of a colorless
liquid.
The identity of this liquid was confirmed via proton nuclear magnetic
resonance
("NMR") to be CCI3CH2CHC12 (boiling point 72-74 °C. 1H NNiIt (CDCl3): b
6.15
(t, 1 H), 3.7 (d, 2 H)).
Example 2. Preparation of CCI ~CH7CHC12 by reduction of CC13CH2CCIz
A 600-mL mope! autoclave equipped with mechanical stirrer was charged with
199.9 g CCI3CH2CCI3, 199.5 g isopropanol, and 4 g CuI. The autoclave was
closed
and evacuated briefly. The contents were heated to 120 - 125 °C for 16
hours. The
volatile materials, including by-product isopropyl chloride, were removed by
rotary
evaporation, leaving 200 g of residue . Analysis on a Varian gas chromatograph
having a packed column ("GC Analysis") indicated CC13CH2CHCI2 and
CCI3CH2CCI3 in a ratio of about 1:2, respectively. Distillation at 29 mmHg
resulted
WO 96101797 219 2 8 4 3 PCT/US95108404
in 107.9 g of starting material (boiling point from about 105 to 107
°C), and 36.9 g
(46% yield) of CCI3CH2CHCI2 (boiling point from about 85 to 90 °C).
Example 3. Flnorieration of CC13CH C? HC! with AF/SbClc
. A 600-mL mooel autoclave equipped with mechanical stirrer was charged with
8.7 g SbClS and cooled to -27 ° C. The autoclave was then evacuated and
charged
with 49.8 g ofanhydrous HF. The contents were cooled to -40 ° C, and 44
g
CCI3CH2CHCI2 was added. The reactor was then connected to a packed
column/condenser assembly. The condenser was maintained at -20 °C. The
reaction
mixture was heated to 135 ° C over 2.25 hours and maintained at that
temperature for
an additional 2 hours. During this heating period, the pressure in the
autoclave was
maintained from about 1965 to 2655 KPa (300 - 400 psig) by periodically
venting
pressure (HCl by-product) in excess of 2655 KPa (400 psig). Venting was done
from
the top of the condenser to a cold aqueous KOH scrubber which was connected to
-78
°C cold trap. The reactor was then completely vented to the cold trap.
18.5 g of a
colorless liquid were collected. The identity of this liquid was determined by
GC
analysis to be 84% CF3CH2CHF2 (corresponding to a yield of 57%) and 11%
CF3CH2CHCIF.
Example 4. Flnorination of CF;CHZCHC12 with AF/SbFs
The experiment described in Example 3 was repeated except that
CF3CH2CHCI2 was used as the starting material. To the apparatus described in
Example 3 was charged 8.2 g SbFS, 41 g HF, and 37 g CF;CH2CHCI2._ (The
CF3CH2CHC12 was obtained via the room temperature photochlorination of
commercially available CF3CH2CH2CL) This mixture was heated with stirring to
about 130 - 135 °C for 4.5 hours at a maximum operating pressure of
3450 KPa. 18.1
g (corresponding to a yield of 57%) of a colorless liquid were recovered. GC
analysis
identified the material as 94% pure HFC-245fa .
Example S. Flnorination of CF3CH~CHCIZ with
HF/Sb I at 150 - 160 °C :rnd Low Oneratine Pressure
The experiment described in Example 3 was repeated except that
CF3CH2CHCI2 was used as the starting material. To the apparatus described in.
,
Example 3 was charged 9.5 g SbClS, 47.9 g HF, and 34.6 g CF3CH2CHCl2. This
mixture was heated with stirring to about 150 - 160 °C for 3.5 hours
and maintained at
that temperature for an additional 2 hours. The maximum operating pressure,
controlled by periodic venting of by-product HCI, was 1280 KPa. GC analysis
ofthe
crude reaction product indicated that it contained 71% HFC-245fa.
WO 96f01797 219 2 8 4 3 pCT~595108404
9
As illustrated by the above-described Examples, HFC-245fa is produced in
high yield without the use of high temperatures or pressures and without using
large
quantities of expensive catalysts.
