U.S. patent application number 11/757782 was filed with the patent office on 2007-10-11 for process for producing fluoropropenes.
This patent application is currently assigned to HONEYWELL INTERNATIONAL INC.. Invention is credited to Daniel C. Merkel, Rajiv R. Singh, Hsueh Sung Tung.
Application Number | 20070238908 11/757782 |
Document ID | / |
Family ID | 34522570 |
Filed Date | 2007-10-11 |
United States Patent
Application |
20070238908 |
Kind Code |
A1 |
Merkel; Daniel C. ; et
al. |
October 11, 2007 |
PROCESS FOR PRODUCING FLUOROPROPENES
Abstract
Dehydrohalogenation processes for the preparation of
fluoropropenes from corresponding halopropanes, in which the
fluoropropenes have the formula CF.sub.3CY.dbd.CX.sub.NH.sub.P,
wherein X and Y are independently hydrogen or a halogen selected
from fluorine, chlorine, bromine and iodine; and N and P are
independently integers equal to 0, 1 or 2, provided that
(N+P)=2.
Inventors: |
Merkel; Daniel C.; (West
Seneca, NY) ; Singh; Rajiv R.; (Getzville, NY)
; Tung; Hsueh Sung; (Getzville, NY) |
Correspondence
Address: |
HONEYWELL INTERNATIONAL INC.
101 COLUMBIA ROAD
P O BOX 2245
MORRISTOWN
NJ
07962-2245
US
|
Assignee: |
HONEYWELL INTERNATIONAL
INC.
Morristown
NJ
|
Family ID: |
34522570 |
Appl. No.: |
11/757782 |
Filed: |
June 4, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10694272 |
Oct 27, 2003 |
7230146 |
|
|
11757782 |
Jun 4, 2007 |
|
|
|
Current U.S.
Class: |
570/136 |
Current CPC
Class: |
C07C 17/206 20130101;
C07C 17/25 20130101; C07C 17/25 20130101; C07C 21/18 20130101; C07C
19/08 20130101; C07C 19/10 20130101; C07C 21/18 20130101; C07C
17/206 20130101; C07C 17/206 20130101 |
Class at
Publication: |
570/136 |
International
Class: |
C07C 21/18 20060101
C07C021/18 |
Claims
1. A process for the manufacture of 1,3,3,3-tetrafluoropropene
comprising decomposing, in the presence of a fluorinated catalyst,
a reactant comprising at least one of
1-chloro-1,3,3,3-tetrafluoropropane and
1,1,3,3,3-pentafluoropropane, under conditions sufficient to
dehydrochlorinate 1-chloro-1,3,3,3-tetrafluoropropane and/or to
dehydrofluorinate 1,1,1,3,3-pentafluoropropane, to form a reaction
product which comprises 1,3,3,3-tetrafluoropropene.
2. The process of claim 1 wherein
1-chloro-1,3,3,3-tetrafluoropropane is dehydrochlorinated to form a
reaction product which comprises 1,3,3,3-tetrafluoropropene.
3. The process of claim 1 wherein 1,1,3,3,3-pentafluoropropane is
dehydrofluorinated to form a reaction product which comprises
1,3,3,3-tetrafluoropropene.
4. The process of claim 1 wherein said dehydrochlorination of
1-chloro-1,3,3,3-tetrafluoropropane and said dehydrofluorination of
1,1,1,3,3-pentafluoropropane are conducted substantially
simultaneously in the same reactor.
5. The process of claim 1 which is conducted at a temperature of
from about 30.degree. C. to about 400.degree. C.
6. The process of claim 1 which is conducted at a temperature of
from about 50.degree. C. to about 350.degree. C.
7. The process of claim 1 which is conducted at a temperature of
from about 75.degree. C. to about 300.degree. C.
8. The process of claim 1 which is conducted at atmospheric
pressure or under vacuum.
9. The process of claim 1 which is conducted a superatmospheric
pressure.
10. The process of claim 1, wherein said fluorinated catalyst is a
fluorinated transition metal oxide.
11. The process of claim 10 wherein said fluorinated transition
metal oxide is fluorinated chromium (III) oxide.
12. The process of claim 11 wherein said fluorinated chromium (III)
oxide is formed by fluorinating chromium (III) oxide with H F.
13. The process of claim 1 wherein the
1-chloro-1,3,3,3-tetrafluoropropane and/or
1,1,1,3,3-pentafluoropropane are previously prepared by
fluorinating 1,1,1,3,3-pentachloropropane with hydrogen fluoride in
the vapor phase in the presence of a fluorination catalyst.
14. The process of claim 13 wherein said fluorination catalyst is
selected from the group consisting of transition metal halides,
Group IVb metal halides, Group Vb metal halides and combinations
thereof on activated carbon or fluorinated alumina.
15. The process of claim 13 wherein said fluorination catalyst is
selected from the group consisting of SbCl.sub.5, SbCl.sub.3,
SbF.sub.5, TaCl.sub.5, SnCl.sub.4, NbCl.sub.5, TiCl.sub.4,
MoCl.sub.5, Cr.sub.2O.sub.3, Cr.sub.2O.sub.3/Al.sub.2O.sub.3,
Cr.sub.2O.sub.3/AlF.sub.3, Cr.sub.2O.sub.3/carbon,
CoCl.sub.2/Cr.sub.2O.sub.3/Al.sub.2O.sub.3,
NiCl.sub.2/Cr.sub.2O.sub.3/Al.sub.2O.sub.3, CoCl.sub.2/AlF.sub.3,
NiCl.sub.2/AlF.sub.3 and combinations thereof.
16. The process of claim 13 wherein said fluorination catalyst is
selected from the group consisting of Cr.sub.2O.sub.3,
Cr.sub.2O.sub.3/carbon, Cr.sub.2O.sub.3/AlF.sub.3,
CoCl.sub.2/AlF.sub.3, NiCl.sub.2/AlF.sub.3 and combinations
thereof.
17. The process of claim 13 wherein said fluorination catalyst
comprises SbCl.sub.3 or SbCl.sub.5 supported on activated
carbon.
18. The process of claim 13 wherein the fluorinating is conducted
at a temperature of from about 100.degree. C. to about 350.degree.
C.
19. The process of claim 13 wherein the fluorinating is conducted
at atmospheric pressure or under vacuum.
20. The process of claim 13 wherein the fluorinating is conducted
at superatmospheric pressure.
21. The process of claim 13 wherein the mole ratio of hydrogen
fluoride to 1,1,1,3,3-pentachloropropane is from about 2:1 to about
100:1.
22. The process of claim 13 further comprising feeding chlorine to
the fluorinating reaction to keep the fluorination catalyst
active.
23. The process of claim 1 wherein the
1-chloro-1,3,3,3-tetrafluoropropane and/or
1,1,1,3,3-pentafluoropropane are previously prepared by
fluorinating 1,1,1,3,3-pentachloropropane with hydrogen fluoride in
a liquid phase in the presence of a fluorination catalyst.
24. The process of claim 23 wherein said fluorination catalyst is
selected from the group consisting of transition metal halides,
Group IVb metal halides, Group Vb metal halides and combinations
thereof.
25. The process of claim 24 wherein said fluorination catalyst is
selected from the group consisting of SbCl.sub.5, SbCl.sub.3,
SbF.sub.5, TaCl.sub.5, SnCl.sub.4, NbCl.sub.5, TiCl.sub.4,
MoCl.sub.5, and combinations thereof.
26. The process of claim 25 wherein said fluorination catalyst is
selected from the group consisting of SbCl.sub.5, SbCl.sub.3 and
combinations thereof.
27. The process of claim 23 wherein the fluorinating is conducted
at a temperature of from about 60.degree. C. to about 180.degree.
C.
28. The process of claim 23 wherein the fluorinating is conducted
at a pressure of from about 50 psig and 400 psig.
29. The process of claim 23 wherein the mole ratio of hydrogen
fluoride to 1,1,1,3,3-pentachloropropane is from about 2:1 to about
100:1.
30. The process of claim 23 further comprising feeding chlorine to
the fluorinating reaction to keep the fluorination catalyst active.
Description
RELATED APPLICATIONS
[0001] The present application is a continuation of U.S.
application Ser. No. 10/694,272, filed Oct. 27, 2003, which is
incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to a process for producing
fluoropropenes in good yield on an industrial scale using
commercially and readily available starting materials. More
particularly, the present invention relates to a process for
producing fluoropropenes by the dehydrohalogenation of
halo-propanes, either by reaction with an essentially miscible
alkali or alkaline earth metal hydroxide solution in a non-alcohol
solvent, or by thermal decomposition.
[0003] The production of fluoropropenes such as
CF.sub.3CH.dbd.CH.sub.2 by catalytic vapor phase fluorination of
various saturated and unsaturated halogen-containing C.sub.3
compounds is described in U.S. Pat. Nos. 2,889,379; 4,798,818 and
4,465,786. U.S. Pat. No. 5,532,419 discloses a vapor phase
catalytic process for the preparation of fluoroalkene using a
chloro- or bromo-halofluorocarbon and HF. EP 974,571 discloses the
preparation of 1,1,1,3-tetrafluoropropene by contacting
1,1,1,3,3-pentafluoropropane (HFC-245fa) in the vapor phase with a
chromium-based catalyst at elevated temperature, or in the liquid
phase with an alcoholic solution of KOH, NaOH, Ca(OH).sub.2 or
Mg(OH).sub.2.
[0004] A fluoropropene of particular interest is
1,3,3,3-tetrafluoropropene (HFC-1234ze), which has potential use as
a low global warming potential refrigerant. However, this material
is presently not available in commercial quantity. The existing
technology to make HFC-1234ze is a fluorination process using
1,1,1,3,3-pentachloropropane (HCC-240fa) and HF in the presence of
a vapor phase catalyst. HFC-1234ze is a by-product of the reaction
that is made in relatively small quantity, i.e., less than about 8
area % in a gas chromatograph (GC) of the organic reaction
product.
[0005] The process is very expensive because of the low selectivity
for the desired product, HFC-1234ze. The reaction is actually
intended for the manufacture of HFC-245fa, in which small
quantities of HFC-1234ze is produced as a by-product. Complicating
matters, the process involves handling large quantities of
hazardous materials such as HF and HCl.
[0006] Henne et al., J. Am. Chem. Soc. 68 496-497 (1946) described
the synthesis of various fluoropropenes from
CF.sub.3CH.sub.2CF.sub.3 using, e.g., alcoholic KOH, with varying
degrees of success. For example, it is stated that in some
instances dehydrohalogenation was unsuccessful. In another
instance, a protracted reaction time (3 days) was required, or
relatively low product yield (40%, 65%) was obtained.
[0007] Tarrant, et al., J. Am. Chem. Soc. 77 2783-2786 (1955)
described the synthesis of CF.sub.3CH.dbd.CF.sub.2 starting with:
(1) 3-bromo-1,1,3,3-pentafluoropropane and reacting it with a hot
solution of KOH in water; and (2)
3-bromo-1,1,3,3-tetrafluoropropene, reacting it with HF at
150.quadrature.C and neutralizing the reaction products with a KOH
solution.
[0008] Kimura, et al., J. Org. Chem. 48, 195-198 (1983) described
multi-phase dehydrohalogenation of brominated compounds using
aqueous KOH and a phase transfer catalyst based on polyethylene
glycols and polyethylene glycol-grafted copolymers. The preparation
of fluoropropenes by the dehydrohalogenation of fluoropropane using
aqueous KOH and a phase transfer catalyst, but with improved yields
and selectivity is disclosed by U.S. Pat. No. 6,548,719.
[0009] There is a continuing need for means by which fluoropropenes
can be produced commercially with high yield and selectivity,
either catalytically or non-catalytically.
SUMMARY OF THE INVENTION
[0010] The present invention provides two new dehydrohalogenation
methods by which fluoropropenes may be commercially produced with
high yield and selectivity. According to one aspect of the present
invention, a dehydrohalogenation process is provided for the
preparation of fluoropropenes of the formula
CF.sub.3CY.dbd.CX.sub.NH.sub.P wherein X and Y are independently
hydrogen or a halogen selected from the fluorine, chlorine, bromine
and iodine, and N and P are independently integers equal to 0, 1 or
2, provided that (N+P)=2, in which there is reacted, without a
catalyst, a halopropane of the formula:
CF.sub.3C(YR.sup.1)C(X.sub.NH.sub.PR.sub.2) wherein R.sub.1,
R.sub.2, X and Y are independently hydrogen or a halogen selected
from fluorine, chlorine, bromine and iodine, provided that at least
one of R.sub.1, R.sub.2, X and Y is a halogen and there is at least
one hydrogen and one halogen on adjacent carbon atoms; with a
solution of at least one alkali or alkaline earth metal hydroxide
in a non-aqueous, non-alcohol solvent therefor that is at least
essentially miscible with the halopropane, wherein the reaction is
performed at a temperature at which dehydrohalogenation will
occur.
[0011] Reactions performed without a catalyst produce cleaner
reaction products, thereby simplifying product work-up and
isolation. The halopropane can be CF.sub.3CH.sub.2CF.sub.2H (a
commercially available compound also known as HFC-245fa) or
CF.sub.3CH.sub.2CHClF (HCFC-244fa) a by-product of the manufacture
of HFC-245fa. Both halopropanes will dehydrohalogenate to form
HFC-1234ze.
[0012] According to another aspect of the present invention, a
dehydrohalogenation process is provided for the preparation of
fluoropropenes of the formula CF.sub.3CY.dbd.CX.sub.NH.sub.P,
wherein X and Y are independently hydrogen or a halogen selected
from fluorine, chlorine, bromine and iodine, and N and P are
independently integers equal to 0, 1 or 2 provided that (N+P)=2,
comprising heating to a temperature at which dehydrohalogenation by
thermal decomposition occurs a halopropane of the formula:
CF.sub.3C(YR.sub.1)C(X.sub.NH.sub.PR.sub.2) wherein R.sub.1,
R.sub.2, X and Y are independently hydrogen or a halogen selected
from fluorine, chlorine, bromine and iodine, provided that at least
one of R.sub.1, R.sub.2, X and Y is a halogen and there is at least
one hydrogen and one halogen on adjacent carbon atoms. The thermal
decomposition reaction can be performed either with or without a
catalyst for hydrogen halide removal, such as transition metal
halides and oxides and combination thereof, preferably iron
halides, nickel halides, cobalt halides and combinations thereof.
HFC-245fa and CF.sub.3CH.sub.2CHClF (HCFC-244fa) can also be
reacted by the thermal decomposition reaction of the present
invention to form HFC-1234ze.
DETAILED DESCRIPTION OF THE INVENTION
[0013] The present invention can be generally described as a
process for the preparation of fluoropropenes of the formula
CF.sub.3CY.dbd.CX.sub.NH.sub.P wherein X and Y are independently a
hydrogen or a halogen selected from fluorine, chlorine, bromine and
iodine; and N and P are integers independently equal to 0, 1 or 2,
provided that (N+P)=2.
[0014] Two dehydrohalogenation methods by which the fluoropropenes
may be prepared are disclosed. Both methods dehydrohalogenate a
halopropane having the formula:
CF.sub.3C(YR.sub.1)C(X.sub.NH.sub.PR.sub.2) wherein R.sub.1,
R.sub.2, X and Y are independently hydrogen or a halogen selected
from fluorine, chlorine, bromine and iodine, provided that at least
one of R.sub.1, R.sub.2, X and Y is a halogen and there is at least
one hydrogen and one halogen on adjacent carbon atoms.
[0015] Included among the halopropanes that can be included in the
present invention is 1,1,1,3,3-pentafluoropropane or HFC-245fa and
1-chloro-1,3,3,3-tetrafluoropropane or HCFC-244fa. Various methods
for producing these materials are described in U.S. Pat. Nos.
5,710,352; 5,969,198; 5,728,904; and 6,023,004. Another method
described in U.S. Pat. No. 5,574,192 is said to be economical,
amenable to large-scale application and uses readily available raw
materials. The process of that patent uses two steps as follows:
(1) formation of CCl.sub.3CH.sub.2CHCl.sub.2 by the reaction of
CCl.sub.4 with vinyl chloride; and (2) conversion of
CCl.sub.3CH.sub.2CHCl.sub.2 to CF.sub.3CH.sub.2CHF.sub.2 and
CF.sub.3CH.sub.2CHFCl by reaction with HF in the presence of a
fluorination catalyst selected from antimony halides, niobium
halides, arsenic halides, tantalum halides; tin halides; titanium
halides; antimony mixed halides; niobium mixed halides, arsenic
mixed halides, tantalum mixed halides, mixed tin halides; mixed
titanium halides and mixtures thereof. Under-fluorinated materials,
such as CF.sub.3CH.sub.2CHCl.sub.2, may be recycled in subsequent
runs. The under-fluorinated material CF.sub.3CH.sub.2CHClF, or
HFC-244fa, can also be used as a starting material in the present
invention for producing a fluoropropene. Thus, the above-described
process can be utilized to obtain two different starting materials
for the process of the present invention.
[0016] Furthermore, commercial quantities of
CF.sub.3CH.sub.2CF.sub.2H are available from Honeywell
International, Inc., Morristown, N.J., for use as the starting
material of the present process for direct conversion to the
fluoroalkene CF.sub.3CH.dbd.CFH by dehydrofluorination according to
either process disclosed herein. Other useful starting materials
for the production of fluoropropenes and/or fluorohalopropenes
include the following: CF.sub.3CH.sub.2CF.sub.2Br;
CF.sub.3CH.sub.2CF.sub.21; CF.sub.3CHFCF.sub.2Br;
CF.sub.3CH.sub.2CH.sub.2Cl; CF.sub.3CH.sub.2CH.sub.2Br;
CF.sub.3CH.sub.2CH.sub.21; CF.sub.3CHBrCF.sub.2Br;
CF.sub.3CHClCF.sub.2Cl; CF.sub.3CH.sub.2CFHCl;
CF.sub.3CH.sub.2CFHBr; CF.sub.3CHClCF.sub.2H;
CF.sub.3CH.sub.2CCl.sub.3; CF.sub.3CH.sub.2CF.sub.3; and the
like.
[0017] In another embodiment of the invention, HCFC-244fa and/or
HFC-245fa can be prepared by fluorinating
1,1,1,3,3-pentachloropropane(HCC-240fa). In this embodiment, in a
preliminary step, the process of the invention involves the
formation of HCFC-244fa and/or HFC-245fa by reacting
1,1,1,3,3-pentachloropropane (HCC-240fa) with hydrogen fluoride
(HF) in the vapor phase, or the liquid phase, preferably in the
presence of a fluorination catalyst as is well known in the
art.
[0018] The result is a reaction product of one or both of the two
products, HCFC-244fa and/or HFC-245fa. In the preferred embodiment
of the invention, the HF to HCC-240fa mole ratio preferably ranges
from about 2:1 to about 100:1; more preferably from about 4:1 to
about 50:1 and most preferably from about 5:1 to about 20:1.
[0019] Useful fluorination catalysts include, but are not limited
to, transition metal halides, Group IVb and Vb metal halides, and
combinations thereof, preferably supported on activated carbon or
fluorinated alumina. More specifically, preferred vapor phase
fluorination catalysts non-exclusively include SbCl.sub.5,
SbCl.sub.3, SbF.sub.5, TaCl.sub.5, SnCl.sub.4, NbCl.sub.5,
TiCl.sub.4, MoCl.sub.5, Cr.sub.2O.sub.3,
Cr.sub.2O.sub.3/Al.sub.2O.sub.3, Cr.sub.2O.sub.3/AlF.sub.3,
Cr.sub.2O.sub.3/carbon, CoCl.sub.2/Cr.sub.2O.sub.3/Al.sub.2O.sub.3,
NiCl.sub.2/Cr.sub.2O.sub.3/Al.sub.2O.sub.3, CoCl.sub.2/AlF.sub.3,
NiCl.sub.2/AlF.sub.3 and mixtures thereof. Preferred liquid phase
fluorination catalysts non-exclusively include SbCl.sub.5,
SbCl.sub.3, SbF.sub.5, TaCl.sub.5, SnCl.sub.4, NbCl.sub.5,
TiCl.sub.4, and MoCl.sub.5. It is understood that after
pre-treatment with HF or during reaction in the presence of HF the
above mentioned catalyst will be partially fluorinated Chromium
oxide/aluminum oxide catalysts are described in U.S. Pat. No.
5,155,082 which is incorporated herein by reference. Chromium (III)
oxides such as crystalline chromium oxide or amorphous chromium
oxide are preferred vapor phase fluorination catalysts with
amorphous chromium oxide being the most preferred vapor phase
catalyst. Chromium oxide (Cr.sub.2O.sub.3) is a commercially
available material which may be purchased in a variety of particle
sizes. Unsupported SbCl.sub.5 and SbCl.sub.3 halides are preferred
liquid phase catalysts. Both of these liquid phase catalysts are
commercially available and well known in the art. Fluorination
catalysts having a purity of at least 98% are preferred. The
fluorination catalyst is present in an amount sufficient to drive
the reaction. The fluorination reaction may be conducted in any
suitable fluorination reaction vessel or reactor but it should
preferably be constructed from materials which are resistant to the
corrosive effects of hydrogen fluoride such as nickel and its
alloys, including Hastelloy, Inconel, Incoloy, and Monel or vessels
lined with fluoropolymers.
[0020] Any water in the hydrogen fluoride (HF) will react with and
deactivate the fluorination catalyst. Therefore substantially
anhydrous hydrogen fluoride is preferred. By "substantially
anhydrous" it is meant 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 HF can be compensated for by
increasing the amount of catalyst used.
[0021] The liquid phase fluorination of HCC-240fa is preferably
conducted at a temperature of from about 50.degree. C. to about and
450.degree. C., more preferably from about 60.degree. C. to about
180.degree. C. and most preferably from about 65.degree. C. and
150.degree. C. Fluorination is preferably conducted at a pressure
of from about 50 psig to about 400 psig. The reactor is preferably
preheated to the desired fluorination reaction temperature while
anhydrous HF is fed to the reactor. The HCC-240fa and HF may be fed
to the reactor at the desired temperatures and pressures that are
described herein. In a preferred embodiment of the invention,
either or both of the HCC-240fa and HF are pre-vaporized or
preheated prior to entering the reactor.
[0022] When HCC-240fa and HF are reacted in a vapor phase with the
fluorination catalyst the HCC-240fa and HF may be fed to the
reactor at the desired temperatures and pressures that are
described herein. The reactor is preheated to the fluorination
reaction temperature while anhydrous HF is fed to the reactor. The
HCC-240fa and HF may be fed to the reactor at any convenient
temperature and pressure. In a preferred embodiment either or both
of the HCC-240fa and HF are pre-vaporized or preheated to a
temperature of from about 30.degree. C. to about 300.degree. C.
prior to entering the reactor. In another embodiment, the HCC-240fa
and HF are vaporized in the reactor.
[0023] The HF and HCC-240fa feeds are then adjusted to the desired
mole ratio. The HF to HCC-240fa mole ratio preferably ranges from
about 2:1 to about 100:1; more preferably from about 4:1 to about
50:1 and most preferably from about 5:1 to about 20:1.
[0024] The fluorination reaction is conducted at a preferred
temperature ranging from about 80.degree. C. to about 400.degree.
C.; more preferably from about 100.degree. C. to about 350.degree.
C. and most preferably from about 200.degree. C. to about
330.degree. C. Reactor pressure is not critical and can be
superatmospheric, atmospheric or under vacuum. The vacuum pressure
can be from about 5 torr to about 760 torr. The reactant vapor is
allowed to contact the fluorination catalyst for from about 0.01 to
about 240 seconds, more preferably from about 0.1 to about 60
seconds and most preferably from about 0.5 to about 20 seconds.
[0025] Usually the process flow of the HCC-240fa and HF is in the
down direction through a bed of the catalyst. Before each use, the
catalyst is preferably dried, pre-treated and activated. It may
also be advantageous to periodically regenerate the catalyst after
prolonged use while in place in the reactor. For Cr.sub.2O.sub.3,
Cr.sub.2O.sub.3/Al.sub.2O.sub.3, Cr.sub.2O.sub.3/AlF.sub.3,
Cr.sub.2O.sub.3/carbon, CoCl.sub.2/Cr.sub.2O.sub.3/Al.sub.2O.sub.3,
NiCl.sub.2/Cr.sub.2O.sub.3/Al.sub.2O.sub.3, CoCl.sub.2/AlF.sub.3,
NiCl.sub.2/AlF.sub.3 catalysts, pre-treatment can be done by
heating the catalyst to about 250.degree. C. to about 430.degree.
C. in a stream of nitrogen or other inert gas. The catalyst may
then be activated by treating it with a stream of HF diluted with a
large excess of nitrogen gas in order to obtain high catalyst
activity. Regeneration of the catalyst may be accomplished by any
means known in the art such as, for example, by passing air or air
diluted with nitrogen over the catalyst at temperatures of from
about 100.degree. C. to about 400.degree. C., preferably from about
200.degree. C. to about 375.degree. C., for from about 1 hour to
about 3 days, depending on the size of the reactor. For SbCl.sub.5,
SbCl.sub.3, TaCl.sub.5, SnCl.sub.4, NbCl.sub.5, TlCl.sub.4,
MoCl.sub.5 catalysts, supported on an solid support such as
activated carbon, pre-treatment or activation can be done by first
heating the catalyst to about 30.degree. C. to 250.degree. C. in a
stream of nitrogen or other inert gas. It is then treated with a
stream of HF in the absence or presence of an oxidizing agent such
as chlorine gas in order to obtain high catalyst activity. In
addition, the catalyst may optionally be kept active by co-feeding
chlorine to the reactor during reaction.
[0026] HCFC-244fa and HFC-245fa may be recovered from the
fluorination reaction product mixture comprised of unreacted
starting materials and by-products, including HCl, by any means
known in the art, such as by scrubbing, extraction, and preferably
distillation. For example, the distillation may be preferably
conducted in a standard distillation column at a pressure, which is
less than about 300 psig, preferably less than about 150 psig and
most preferably less than 100 psig. The pressure of the
distillation column inherently determines the distillation
operating temperature. HCl may be recovered by operating the
distillation column at from about -40.degree. C. to about
25.degree. C., preferably from about -40.degree. C. to about
-20.degree. C. Single or multiple distillation columns may be used.
The distillate portion includes substantially all the HCFC-244fa,
HFC-245fa, unreacted HF and HCl produced in the reaction as well as
any other impurities. In the preferred embodiment, HCFC-244fa and
the HFC-245fa are separated from all other reaction by-products and
unreacted HF for further reaction in step (b) described herein. In
the preferred embodiment, any HF present may also be recovered and
recycled back for subsequent fluorination reactions. 1234ze is
formed by the dehydrochlorination of
1-chloro-1,3,3,3-tetrafluoropropane (HCFC-244fa) or the
dehydrofluorination of 1,1,1,3,3-pentafluoropropane
(HFC-245fa).
[0027] According to one method of the present invention, the
halopropane is dehydrohalogenated with an alkali metal or alkaline
earth metal hydroxide in a non-aqueous, non-alcohol solvent for the
alkali metal or alkaline earth metal hydroxide that is at least
partially miscible with the halopropane. Alkali metal and alkaline
earth metal hydroxides suitable for use in the present invention
include, but are not limited to LiOH, KOH, NaOH, CaO, Ca(OH).sub.2,
CaCO.sub.3, and/or lime stone, and the like. By either method, the
dehydrochlorination of HCFC-244fa proceeds as follows:
[0028] The dehydrohalogenation is performed within a temperature
range at which the halopropane will dehydrohalogenate. According to
one aspect of this method, alkali metal or alkalin earth metal
hydroxide pellets are dissolved in the solvent with agitation under
otherwise ambient conditions. The halopropane is then bubbled
through the alkali metal or alkaline earth metal hydroxide solution
as the temperature of the solution is gradually increased by
heating. Gradual heating is continued until initiation of
dehydrohalogenation is observed, after which the temperature at
which dehydrohalogenation initiation occurred is maintained until
completion of the process.
[0029] In carrying out the process, the molar ratio of alkali metal
or alkaline earth metal hydroxide relative to the amount of
halopropane is from about 1:1 to about 20:1, preferably from about
1:1 to about 15:1; and more preferably from about 1:1 to about
12:1; for example, from 1:1 to about 10:1. In the preferred
embodiment of the invention, the caustic strength of the caustic
solution is from about 2 wt % to about 100 wt %, more preferably
from about 5 wt % to about 90 wt % and most preferably from about
10 wt % to about 80 wt %. The reaction is preferably conducted at a
temperature of from about 20.degree. C. to about 15.degree. C.,
more preferably from about 30.degree. C. to about 110.degree. C.
and most preferably from about 40.degree. C. to about 90.degree. C.
The reaction pressure is not critical. The reaction can be
conducted at atmospheric pressure, super-atmospheric pressure or
under vacuum. The vacuum pressure can be from about 5 torr to about
760 torr. Preferably, the reaction is conducted at atmospheric or
super-atmospheric pressure.
[0030] The dehydrohalogenation reaction can be accomplished using a
solution of at least one alkali metal or alkaline earth metal
hydroxide in a non, aqueous, non-alcohol solvent for the alkali
metal or alkaline earth metal hydroxide that is essentially
miscible with the halopropane. For purposes of the present
invention, "essentially miscible" means that an agitated mixture
containing 50 wt. % halpropane and 50 wt. % solvent does not
separate to form more than one liquid phase over the temperature
range at which the dehydrohalogenation will occur, or, if such
separation does occur, one of the liquid phases is very small, less
than 10 wt. % of the total weight of the blend.
[0031] Examples of non-alcohol solvents suitable for use with the
present invention include, but not limited to, nitriles such as
acetonitrile, ethers such as diethyl ether, tetrahydrofuran and
perfluoro-tetrahydrofuran, esters such as methyl acetate and ethyl
acetate, amides, ketones, sulfoxides, phosphates, carboxylates, and
the like.
[0032] The alkali metal or alkaline earth metal hydroxide need not
be highly soluble in the solvent. An amount of water, alcohol, or
mixture thereof may be added to the solvent for the alkali metal or
alkaline earth metal hydroxide in quantities that improve the
solubility of the alkali metal or alkaline earth metal hydroxide
therein. Embodiments according to this aspect of the present
invention will blend a solution of the alkali metal or alkaline
earth metal hydroxide in water, alcohol or a mixture of water and
alcohol, with the solvent. Typically, the amount of water, alcohol,
or water-alcohol blend will not exceed about 50 wt. % of the total
quantity of solvent for the alkali metal or alkaline earth metal
hydroxide, and preferably will not exceed about 20 wt. %. Alcohols
that may be used contain from 1 to 5 carbon atoms, and preferably
from 1 to 3 carbon atoms.
[0033] Solvents are selected that are at least partially miscible
with the alkali metal or alkaline earth metal hydroxide solution,
which may be in water, alcohol or a mixture thereof. For purposes
of the present invention "partially miscible" means a level of
miscibility that permits the solvent to dissolve in the alkali
metal or alkaline earth metal hydroxide solution to the extent that
the dehydrohalogenation reaction will occur upon contact of the
halopropane therewith the blend. A high degree is miscibility is
not required in order for the reaction to proceed at the interface
of the solvent and alkali metal or alkaline earth metal hydroxide
solution. More caustic will dissolve as the amount in solution is
depleted by the dehydrohalogenation reaction. The solvent need only
be at least about 1%, preferably at least about 5%, and more
preferably at least 10% soluble, the alkali metal or alkaline earth
metal hydroxide solution on a weight basis.
[0034] In an alternate embodiment of the invention, the
dehydrochlorination of HCFC-244fa and dehydro-fluorination of
HFC-245fa may be done by thermal decomposition in the presence or
in the absence of a catalyst. Suitable catalysts include transition
metal halides and oxides, supported or bulk. Preferred catalysts
include, but not limited to, FeCl.sub.2, FeCl.sub.3, NiCl.sub.2,
CoCl.sub.2, supported or in bulk. The preferred temperatures for
the thermal decomposition are from about 30.degree. C. to about
400.degree. C., more preferably from about 50.degree. C. to about
350.degree. C. and most preferably from about 75.degree. C. to
about 300.degree. C. As above, the reaction is preferably conducted
at atmospheric pressure, super-atmospheric pressure. Reaction under
vacuum is also acceptable. The vacuum pressure can be from about 5
torr to about 760 torr.
[0035] The reactions may be conducted in any suitable reactor.
Further, the dehydrochlorination of HCFC-244fa and the
dehydrofluorination of HFC-245fa may either be conducted
simultaneously in the same reactor, or they may first be separated
followed by separately dehydrochlorinating HCFC-244fa with the
caustic solution or by thermal decomposition and separately
dehydrofluorinating HFC-245fa with the caustic solution or by
thermal decomposition. The result of this two step process is a
high yield of HFC-1234ze.
[0036] Therefore, according to preferred embodiments of the
invention, the dehydrochlorination of HCFC-244fa and
dehydrofluorination of HFC-245fa are accomplished either by thermal
decomposition or by reacting these with a strong caustic solution
at an elevated temperature. By either method, the
dehydrochlorination of HCFC-244fa proceeds as follows:
CF.sub.3--CH.sub.2--CHClF.fwdarw.CF.sub.3--CH.dbd.CHF+HCl [0037]
(HCFC-244fa) (HFC-1234ze)
[0038] Furthermore, by either method, the dehydrofluorination of
HFC-245fa proceeds as follows:
CF.sub.3--CH.sub.2--CHF.sub.2.fwdarw.CF.sub.3--CH.dbd.CHF+HF [0039]
(HFC-245fa) (HFC-1234ze)
[0040] Both the dehydrochlorination of HCFC-244fa and
dehydrofluorination of HFC-245fa are achieved according to the
present invention by using caustic for hydrogen halide removal or
by thermal decomposition in the absence of a catalyst or with a
catalyst selected from transition metal halides and oxides and
combinations thereof, preferably iron halides, nickel halides,
cobalt halides and combinations thereof.
[0041] Both processes described herein are useful for the
preparation of fluoropropenes and/or fluorohalopropenes having the
following formula: CF.sub.3CY.dbd.CX.sub.NH.sub.P wherein X and Y
and independently hydrogen or a halogen selected from fluorine,
chlorine, bromine and iodine; and N and P are integers
independently equal to 0, 1 or 2, provided that (N+P)=2. Such
compounds include CF.sub.3CH.dbd.CF.sub.2, CF.sub.3CH.dbd.CFH,
CF.sub.3CBr.dbd.CF.sub.2, CF.sub.3CH.dbd.CH.sub.2,
CF.sub.3CF.dbd.CF.sub.2, CF.sub.3CCl.dbd.CF.sub.2,
CF.sub.3CF.dbd.CClF, CF.sub.3CCl.dbd.CHF, CF.sub.3CH.dbd.CHCl,
CF.sub.3CCl.dbd.CClF, CF.sub.3CH.dbd.CCl.sub.2,
CF.sub.3CF.dbd.CCl.sub.2, and the like. The fluoropropenes prepared
by both methods of this invention are readily recovered by any
means known in the art, such as by scrubbing, extraction, and
preferably distillation. Depending on extent of conversion of the
starting material, the product can be used directly or further
purified by standard distillation techniques. Unreacted halopropane
and certain reaction by-products can be recycled back to the
reaction vessel to provide a continuous process. Alternatively,
fresh halopropane may be supplied to the reaction mixture in order
to run the process continuously.
[0042] The fluoropropenes obtained by the inventive processes are
useful as monomers for producing fluorine-containing oligomers,
homopolymers and copolymers, as well as intermediates for other
fluorine-containing industrial chemicals.
[0043] The following examples are given as specific illustrations
of the invention. It should be understood, however, that the
invention is not limited to these specific details set forth in the
examples. All parts and percentages in the examples, as well as in
the remainder of the specification, are by weight unless otherwise
specified.
[0044] Further, any range of numbers recited in this specification
or paragraphs hereinafter describing or claiming various aspects of
the invention, such as that representing a particular set of
properties, units of measure, conditions, physical states or
percentages, is intended to literally incorporate expressly herein
by reference or otherwise, any number falling within such range,
including any subset of numbers or ranges subsumed within any range
so recited. The term "about" when used as a modifier for, or in
conjunction with, a variable, is intended to convey that the
numbers and ranges disclosed herein are flexible and that practice
of the present invention by those skilled in the art using
temperatures, concentrations, amounts, contents, carbon numbers,
and properties that are outside of the range or different from a
single value, will achieve the desired result, namely, processes
for the preparation of fluoropropenes and reactants used in such
processes.
EXAMPLES
Example 1
[0045] To a reaction setup consisting of a 3-neck round bottom
flask (5 L), mechanical agitator, reflux condenser, and low
temperature cold trap was added to 3000 ml acetonitrile and 9.9
moles (504 g) of KOH pellets. After mixing, 5.1 moles (684 g) of
HFC-245fa were added through a dip tube. The reagents were heated
slowly with vigorous agitation. Reaction was observed at about
60.degree. C. The crude product was collected in the cold finger.
The crude material was analyzed by GC and consisted of a good yield
of HFC-1234ze.
Example 2
[0046] Example 1 is repeated except 5 moles (752 grams) of HCFC
244fa is added to the acetonitrile/caustic solution through the dip
tube. The reagents were heated slowly with vigorous agitation.
Reaction is observed at slightly lower temperatures than in Example
1. The crude product is collected in the cold finger. The crude
material collected consisted of a good yield of HFC-1234ze.
Example 3
[0047] A 50 gal. Fluoropolymer lined reactor was charged with 75
lbs of liquid SbCl.sub.5 fluorination catalyst. The reactor was
equipped with a 6''D.times.8'L catalyst stripper containing
structured packing and reflux condenser. The catalyst was first
fluorinated by adding a sufficient amount of Hydrogen Fluoride
(HF). The reactor was heated to 80-95.degree. C. and brought to a
pressure of 150-180 psig. Gaseous HF was fed to the reactor
continuously at a rate of 23-28 lb/hr through a sparger and liquid
1,1,1,3,3-pentachloropropane (HCC-240fa) was fed continuously at a
rate of 40-50 lb/hr. Cl.sub.2 was continuously added to the
reaction mixture to keep the catalyst active at 1.5-2.0 lb/hr. The
gas exiting the reflux condenser was passed through a scrubber that
contained KOH solution to remove excess HF and the HCl that was
generated during the reaction. Several thousand lbs of the crude
product was collected after the scrubber and was analyzed by GC.
The following is the analysis of the major component of the crude
product in GC area %. Note the presence of the HFC1234ze after the
material was passed through the scrubber containing KOH solution.
TABLE-US-00001 Component GC area % G1234 0.1157 245fa 92.7560
1233zd 0.1269 244fa 3.3879 243fa 1.6298 Others 1.9837
Example 4
[0048] About 132 g (about 1.33 g/cc bulk density) of a chromium
(III) oxide catalyst was charged to a reactor of 1'' diameter Monel
pipe. The catalyst was dried and pretreated with HF before use. The
reactor was preheated to the reaction temperature of about
300.degree. C. while anhydrous HF was fed to the reactor. An
organic feed (HCC-240) was started when the reactor reached the
desired temperature and pressure. The HF and organic feeds were
then adjusted to the desired rates. HCFC-244fa and HFC-245fa were
found in the reactor effluent product stream, along with other
partially fluorinated species such as 1233zd, 1234ze and 243fa.
Example 5
[0049] In a typical experiment, a 2.54 cm.times.81 cm Monel.RTM.
reactor is used. About 500 ml of FeCl.sub.3 catalyst supported on
activated carbon was packed into the reactor. The reactor was
heated to 150.degree. C. under 1 liter/hr of nitrogen flow to dry
the catalyst for 4 hours. Then, the reactor temperature is brought
to 250.degree. C. under the same nitrogen flow and 244fa is fed to
the reactor at 1 g/min, and in the mean time the nitrogen flow is
stopped. HFC-1234ze was found by using the in-line GC at the outlet
of the reactor at 98% selectivity and 95% single pass
conversion.
Example 6
[0050] The same experiment described in Example 5 is repeated,
except that 245fa is used as feed. At the outlet of the reactor,
1234ze is found at 95% selectivity and 85% single pass
conversion.
[0051] The principles, preferred embodiments, and modes of
operation of the present invention have been described in the
foregoing specification. The invention which is intended to be
protected herein, however, is not to be construed as limited to the
particular forms disclosed, since these are to be regarded as
illustrative rather than restrictive. Variations and changes may be
made by those skilled in the art, without departing from the spirit
of the invention.
* * * * *