U.S. patent application number 09/962974 was filed with the patent office on 2003-03-27 for process for producing fluoroolefins.
Invention is credited to Bradley, David E., Demmin, Timothy R., Nair, Haridasan K., Nalewajek, David, Poss, Andrew J., Puy, Michael Van Der, Shankland, Ian R..
Application Number | 20030060670 09/962974 |
Document ID | / |
Family ID | 25506573 |
Filed Date | 2003-03-27 |
United States Patent
Application |
20030060670 |
Kind Code |
A1 |
Nair, Haridasan K. ; et
al. |
March 27, 2003 |
PROCESS FOR PRODUCING FLUOROOLEFINS
Abstract
A process for producing a fluoroolefin of the formula:
CF.sub.3CY.dbd.CX.sub.nH.sub.p wherein Y is a hydrogen atom or a
halogen atom (i.e., fluorine, chlorine, bromine or iodine); X is a
hydrogen atom or a halogen atom (i.e., fluorine, chlorine, bromine
or iodine); n and p are integers independently equal to 0, 1 or 2,
provided that (n+p)=2; comprising contacting, in the presence of a
phase transfer catalyst, a compound of the formula:
CF.sub.3C(R.sup.1.sub.aR.sup.2.sub.b)
C(R.sup.3.sub.cR.sup.4.sub.d), wherein R.sup.1, R.sup.2, R.sup.3,
and R.sup.4 are independently a hydrogen atom or a halogen selected
from the group consisting of fluorine, chlorine, bromine and
iodine, provided that at least one of R.sup.1, R.sup.2, R.sup.3,
and R.sup.4 is halogen and there is at least one hydrogen and one
halogen on adjacent carbon atoms; a and b are independently=0, 1 or
2 and (a+b)=2; and c and d are independently=0, 1, 2 or 3 and
(c+d)=3; and at least one alkali metal hydroxide. The alkali metal
hydroxide can be, for example, potassium or sodium hydroxide and
the phase transfer catalyst can be, for example, at least one:
crown ether such as 18-crown-6 and 15-crown-5; or onium salt such
as, quaternary phosphonium salt and quaternary ammonium salt. The
olefin is useful, for example, as an intermediate for producing
other industrial chemicals and as a monomer for producing oligomers
and polymers.
Inventors: |
Nair, Haridasan K.;
(Williamsville, NY) ; Puy, Michael Van Der;
(Amherst, NY) ; Nalewajek, David; (West Seneca,
NY) ; Demmin, Timothy R.; (Grand Island, NY) ;
Poss, Andrew J.; (Kenmore, NY) ; Bradley, David
E.; (Buffalo, NY) ; Shankland, Ian R.;
(Randolph, NJ) |
Correspondence
Address: |
HONEYWELL INTERNATIONAL
Colleen D. Szuch
101 Columbia Road
Morristown
NJ
07962-1057
US
|
Family ID: |
25506573 |
Appl. No.: |
09/962974 |
Filed: |
September 25, 2001 |
Current U.S.
Class: |
570/155 |
Current CPC
Class: |
C07C 17/25 20130101;
C07C 17/04 20130101; C07C 17/04 20130101; C07C 19/14 20130101; C07C
17/25 20130101; C07C 21/18 20130101 |
Class at
Publication: |
570/155 |
International
Class: |
C07C 017/25 |
Claims
We claim:
4. Process for the preparation of fluorine-containing olefins of
the formula CF.sub.3CY.dbd.CX.sub.nH.sub.p wherein Y is a hydrogen
atom or a halogen atom selected from the group consisting of
fluorine, chlorine, bromine or iodine; X is a hydrogen atom or a
halogen atom selected from the group consisting of fluorine,
chlorine, bromine or iodine; n and p are integers independently
equal to 0, 1 or 2, provided that (n+p)=2 comprising contacting, in
the presence of a phase transfer catalyst: (A) a compound of the
formula CF.sub.3C(R.sup.1.sub.aR.sup.2.sub.b)C(R.sup.3.-
sub.cR.sup.4.sub.d), wherein R.sup.1, R.sup.2, R.sup.3, and R.sup.4
are independently a hydrogen atom or a halogen selected from the
group consisting of fluorine, chlorine, bromine and iodine,
provided that at least one of R.sup.1, R.sup.2, R.sup.3, and
R.sup.4 is halogen and there is at least one hydrogen and one
halogen on adjacent carbon atoms; a and b are independently=0, 1 or
2 and (a+b)=2; and c and d are independently=0, 1, 2 or 3 and
(c+d)=3; and (B) at least one alkali metal hydroxide.
5. Process of claim 1 wherein R.sup.1 and R.sup.2 are hydrogen,
R.sup.3 is F and c is 2, and R.sup.4 is hydrogen or chlorine.
6. Process of claim 2 wherein said phase transfer catalyst is
selected from: crown ethers; cryptates; polyalkylene glycols or
derivatives thereof; and onium salts.
7. Process of claim 3 wherein said crown ether is selected from
18-crown-6 and 15-crown-5.
8. Process of claim 3 wherein said polyalkylene glycol is selected
from polyethylene glycol and polypropylene glycol.
9. Process of claim 3 wherein said onium salt is selected from
ammonium and phosphonium salts.
10. Process of claim 6 wherein said onium salt is selected from the
group consisting of benzyltriethylammonium chloride,
methyltrioctylammonium chloride, tetra-n-butylammonium chloride,
tetra-n-butylammonium bromide, tetra-n-butylphosphonium chloride,
bis[tris(dimethylamino)phosphine]imini- um chloride and
tetratris[tris(dimethylamino)phosphinimino] phosphonium
chloride.
11. Process of claim 1 conducted in the presence of at least one
diluent selected from the group consisting of water, alcohols,
ethers, esters, alkanes and fluorinated diluents and
chlorofluorocarbons.
12. Process of claim 3 wherein said alkali metal is selected from
Group 1 of the Periodic Table of the Elements.
13. Process of claim 9 wherein said alkali metal is selected from
lithium, sodium and potassium.
14. Process of claim 10 wherein said alkali metal is sodium and
said phase transfer catalyst is 15-crown-5 ether.
15. Process of claim 10 wherein said alkali metal is potassium and
said phase transfer catalyst is 18-crown-6 ether.
16. Process of claim 10 wherein said phase transfer catalyst is
benzyltriethylammonium chloride.
17. Process of claim 1 wherein said process is conducted at from
about -50.degree. C. to about 100.degree. C.
18. Process of claim 2 wherein the molar ratio of alkali metal
hydroxide to
CF.sub.3C(R.sup.1.sub.aR.sup.2.sub.b)C(R.sup.3.sub.cR.sup.4.sub.d)
is from about 1 to about 10.
19. Process of claim 2 wherein the molar ratio of phase transfer
catalyst to
CF.sub.3C(R.sup.1.sub.aR.sup.2.sub.b)C(R.sup.3.sub.cR.sup.4.sub.d)
is from about 0.001 mol % to about 10 mol %.
20. Process of claim 2 wherein R.sup.4 is hydrogen.
21. Process of claim 1 wherein R.sup.1 is hydrogen and R.sup.2 is
bromine, R.sup.3 is F and c is 2, and R.sup.4 is bromine.
22. Process of claim 1 conducted in a continuous manner.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a process for producing
fluoroolefins or fluorohaloolefins or fluorine-containing olefins,
sometimes referred to hereinafter for convenience as fluoroolefins
or fluorine-containing olefins, useful as intermediates for making
industrial chemicals, in good yield, on an industrial scale and
using commercially and readily available starting materials. More
particularly, the present invention relates to a process for
producing fluoroolefins, for example, 1,1,1,3,3-pentafluoropropene
(also designated as "HFC-1225zc"), by the dehydrohalogenation of a
halofluorocarbon, for example,
1-chloro-1,1,3,3,3-pentafluoropropane (also designated as
"HCFC-235fa"). which halofluorocarbon can be produced by
photochlorinating 1,1,3,3,3-pentafluoropropane (also designated as
"HFC-245fa").
[0002] The production of fluoroolefins 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.
[0003] U.S. Pat. No. 5,532,419 discloses a vapor phase catalytic
process for the preparation of fluorinated olefins using a chloro-
or bromo-halofluorocarbon and HF.
[0004] EP 974571 discloses the preparation of
1,1,1,3-tetrafluoropropene by contacting
1,1,1,3,3-pentafluoropropane (HFC-245fa) with either an aqueous or
alcoholic solution of KOH, NaOH, Ca(OH).sub.2 or Mg(OH).sub.2 or by
contact of the HFC-245fa in the vapor phase with a chromium based
catalyst at elevated temperature.
[0005] A. L. Henne et al., J.Am.Chem.Soc. (1946) 68, 496-497,
describe the synthesis of various fluoroolefins 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 dehydrochlorination was unsuccessful, in another instance
a protracted reaction time (three days) was required, or relatively
low product yield (40%, 65%) was obtained.
[0006] P. Tarrant et al., J.Am.Chem.Soc. (1955), 77, 2783-2786,
describe the synthesis of CF.sub.3CH.dbd.CF.sub.2 starting with:
(1) 3-bromo-1,1,1,3,3-pentafluoropropane and reacting it with a hot
solution of potassium hydroxide in water; and (2)
3-bromo-1,1,3,3-tetrafluoroprope- ne and reacting it with HF at
150.degree. C. and neutralizing the reaction products with a
potassium hydroxide solution.
[0007] Y. Kimura et al., J.Org.Chem. (1983), 48, 195-198, describe
multiphase dehydrohalogenation of brominated compounds using
aqueous potassium hydroxide and a phase transfer catalyst based on
polyethylene glycols and polyethylene glycol-grafted copolymers.
The authors note that poor results were obtained in the case of
dehydrochlorination (page 197) and that C.sub.8 and C.sub.10
polyglycols having terminal hydroxyl groups were particularly
effective compared to other phase transfer catalysts such as
tetraalkylammonium salts, benzyltriethylammonium chloride and crown
ethers. The authors also describe the selective activity for
various phase transfer catalysts in particular reactions.
[0008] M. Halpern et al., J.Org.Chem. (1985), 50, 5088-5092,
describe hydroxide ion (aqueous sodium hydroxide) initiated
elimination of HCl and HBr from haloaromatic compounds using a
quaternary ammonium salt phase transfer catalyst.
[0009] In view of the limited technology available to do so, it was
desirable to develop an efficient, industrially acceptable method
for producing fluoroolefins.
SUMMARY OF THE INVENTION
[0010] Process for the preparation of a fluoroolefin of the formula
CF.sub.3CY.dbd.CX.sub.nH.sub.p wherein Y is a hydrogen atom or a
halogen atom selected from the group consisting of fluorine,
chlorine, bromine or iodine; X is a hydrogen atom or a halogen atom
selected from the group consisting of fluorine, chlorine, bromine
or iodine; n and p are integers independently equal to 0, 1 or 2,
provided that (n+p)=2 comprising contacting, in the presence of a
phase transfer catalyst: (A) a compound of the formula CF.sub.3C
(R.sup.1.sub.aR.sup.2.sub.b)C(R.sup.3.sub.cR.sup- .4.sub.d),
wherein R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are independently a
hydrogen atom or a halogen selected from the group consisting of
fluorine, chlorine, bromine and iodine, provided that at least one
of R.sup.1, R.sup.2, R.sup.3, and R.sup.4 is halogen and there is
at least one hydrogen and one halogen on adjacent carbon atoms; a
and b are independently=0, 1 or 2 and (a+b)=2; and c and d are
independently=0, 1, 2 or 3 and (c+d)=3; and (B) at least one alkali
metal hydroxide. The compound of step (A) can be
CF.sub.3CH.sub.2CF.sub.2H (a commercially available compound also
known as HFC-245fa) or CF.sub.3CH.sub.2CF.sub.2Cl, a by-product
from the manufacture of HFC-245fa.
DETAILED DESCRIPTION
[0011] The present invention can be generally described as a
process for the preparation of fluoroolefins of the formula
CF.sub.3CY.dbd.CX.sub.nH.- sub.p wherein Y is a hydrogen atom or a
halogen atom selected from the group consisting of fluorine,
chlorine, bromine or iodine; X is a hydrogen atom or a halogen atom
selected from the group consisting of fluorine, chlorine, bromine
or iodine; n and p are integers independently equal to 0, 1 or 2,
provided that (n+p)=2, comprising contacting, in the presence of a
phase transfer catalyst: (A) a compound of the formula CF.sub.3C
(R.sup.1.sub.aR.sup.2.sub.b) C (R.sup.3.sub.cR.sup.4.sub.d),
wherein R.sup.1, R.sup.2, R.sup.3and R.sup.4 are independently a
hydrogen atom or a halogen selected from the group consisting of
fluorine, chlorine, bromine and iodine, provided that at least one
of R.sup.1, R.sup.2, R.sup.3, and R.sup.4 is halogen; a and b are
independently=0, 1 or 2 and (a+b)=2; and c and d are
independently=0, 1, 2 or 3 and (c+d)=3; and (B) at least one alkali
metal hydroxide.
[0012] Fluoroolefins are produced by the process of the present
invention by dehydrohalogenating, in the presence of a phase
transfer catalyst, a compound of formula (I) comprising contacting
the compound of formula (I) with at least one alkali metal
hydroxide:
1.
CF.sub.3C(R.sup.1.sub.aR.sup.2.sub.b)C(R.sup.3.sub.cR.sup.4.sub.d)
(I)
[0013] wherein R.sup.1, R.sup.2, R.sup.3, and R.sup.4 are
independently a hydrogen atom or a halogen selected from the group
consisting of fluorine, chlorine, bromine and iodine, provided that
at least one of R.sup.1, R.sup.2, R.sup.3, and R.sup.4 is halogen
and there is at least one hydrogen and one halogen on adjacent
carbon atoms; a and b are independently=0, 1 or 2and (a+b)=2; and c
and d are independently=0, 1, 2 or 3and (c+d)=3. Included among the
compounds of formula (I) that can be used in the present invention
is 1,1,1,3,3-pentafluoropropane or HFC-245 fa. Various methods for
producing this material are described in U.S. Pat. Nos. 5,710,352;
5,969,198; and 6,023,004. Another method described in U.S. Pat.
Nos. 5,728,904 is said to be economical, amenable to large scale
application and uses readily available raw materials. The process
of that patent uses three steps, as follows: 1) formation of
CCl.sub.3CH.sub.2CCl.sub.3 by the reaction of CCl.sub.4 with
vinylidene chloride; 2) conversion of CCl.sub.3CH.sub.2CCl.sub.3 to
CF.sub.3CH.sub.2CF.sub.2Cl by reaction with HF in the presence of a
fluorination catalyst, selected from TiCl.sub.4, SnCl.sub.4 or
mixtures thereof; and 3) reduction of CF.sub.3CH.sub.2CF.sub.2Cl to
CF.sub.3CH.sub.2CF.sub.2H. Since both CF.sub.3CH.sub.2CF.sub.2H and
CF.sub.3CH.sub.2CF.sub.2Cl are useful in the present invention for
producing a fluoroolefin, the described process can be utilized to
obtain alternative starting materials. Furthermore, commercial
quantities of CF.sub.3CH.sub.2CF.sub.2H, also known as HFC-245fa,
are available from Honeywell International Inc., Morristown, N.J.
for use as the starting material of the present process for direct
conversion to the olefin CF.sub.3CH.dbd.CFH by dehydrofluorination
according to the process disclosed herein. Other useful starting
materials for the production of fluoroolefins and/or
fluorohaloolefins include the following:
CF.sub.3CH.sub.2CF.sub.2Br; CF.sub.3CH.sub.2CF.sub.2I;
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.2I;
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.
[0014] In order to carry out the dehydrohalogenation process step
of the present invention there is employed at least one alkali
metal hydroxide. The alkali metal is selected from the group
consisting of the metals of Group 1 of the Periodic Table of the
Elements as shown in Hawley's Condensed Chemical Dictionary,
13.sup.th Edition, 1997. Reference to "groups" in this table is
made according to the "New Notation". Preferably the alkali metal
is selected from the group consisting of lithium, sodium and
potassium; more preferably, sodium and potassium; most preferably,
potassium. Useful concentrations of the hydroxide are from about 1
to about 50 wt. %; preferably from about 5 to about 30 wt. %; most
preferably from about 10 to about 30 wt. %. While it is possible to
use hydroxides other than alkali metal hydroxides, they tend to be
less soluble, particular in aqueous systems and are therefore less
desirable. For example, hydroxides of the Group 2 metals (e.g., Ca,
Mg, and Ba) are of this type; such as magnesium hydroxide. In
carrying out the process, the molar ratio of hydroxide, preferably
alkali metal hydroxide, relative to the amount of
CF.sub.3C(R.sup.1.sub.aR.sup.2.sub.b-
)C(R.sup.3.sub.cR.sup.4.sub.d) is from about 1 to about 20;
preferably from about 1 to about 15; more preferably from about 1
to about 12; for example, from about 1 to about 10.
[0015] The dehydrohalogenation reaction can be accomplished using
an aqueous solution of at least one alkali metal hydroxide, without
the need for additional solvent or diluent, other than the water
present as a consequence of using aqueous base or alkali metal
hydroxide. However, a solvent or diluent can be used if desired for
convenience in carrying out the process, e.g., to modify the system
viscosity, to act as a preferred phase for reaction by-products, or
to increase thermal mass, etc. Useful solvents or diluents include
those that are not reactive with or negatively impact the
equilibrium or kinetics of the process and include alcohols such as
methanol and ethanol; ethers such as diethyl ether, dibutyl ether;
esters such as methyl acetate, ethyl acetate and the like; linear,
branched and cyclic alkanes such as cyclohexane, methylcyclohexane;
fluorinated diluents such as perfluoroisopropanol,
perfluorotetrahydrofuran; chlorofluorocarbons such as
CFCl.sub.2CF.sub.2Cl, etc.
[0016] The dehydrohalogenation reaction is conveniently and
preferably conducted in the presence of a phase transfer catalyst.
For purposes of the present invention, a phase transfer catalyst is
a substance that facilitates the transfer of ionic compounds (e.g.,
reactants or components) into an organic phase from, e.g., a water
phase. In the present invention, an aqueous or inorganic phase is
present as a consequence of the alkali metal hydroxide and an
organic phase is present as a result of the fluorocarbon. The phase
transfer catalyst facilitates the reaction of these dissimilar and
incompatible components. While various phase transfer catalysts may
function in different ways, their mechanism of action is not
determinative of their utility in the present invention provided
that the phase transfer catalyst facilitates the
dehydrohalogenation reaction based on the identified reactants. The
phase transfer catalyst can be ionic or neutral and is selected
from the group consisting of crown ethers, onium salts, cryptates
and polyalkylene glycols and derivatives thereof. An effective
amount of the phase transfer catalyst should be used in order to
effect the desired reaction; such an amount can be determined by
limited experimentation once the reactants, process conditions and
phase transfer catalyst are selected. Typically, the amount of
catalyst used relative to the amount of
CF.sub.3C(R.sup.1.sub.aR.sup.2.sub.b)C(R.sup.3.sub.cR.sup.4.sub.d)
present is from about 0.01 to about 10 mol %; for example from
about 0.01 to about 5 mol %; alternatively, for example from about
0.05 to about 5 mol %.
[0017] Crown ethers are cyclic molecules in which ether groups are
connected by dimethylene linkages; the compounds form a molecular
structure that is believed to be capable of "receiving" or holding
the alkali metal ion of the hydroxide and to thereby facilitate the
reaction. Particularly useful crown ethers include 18-crown-6,
especially in combination with potassium hydroxide; 15-crown-5,
especially in combination with sodium hydroxide; 12-crown-4,
especially in combination with lithium hydroxide. Derivatives of
the above crown ethers are also useful, e.g., dibenzo-18-crown-6,
dicyclohexano-18-crown-6, and dibenzo-24-crown-8 as well as
12-crown-4. Other polyethers particularly useful for alkali metal
compounds, and especially for lithium, are described in U.S. Pat.
No. 4,560,759 which is incorporated herein by reference to the
extent permitted. Other compounds analogous to the crown ethers and
useful for the same purpose are compounds which differ by the
replacement of one or more of the oxygen atoms by other kinds of
donor atoms, particularly N or S, such as
hexamethyl-[14]-4,11-dieneN.sub.4.
[0018] Onium salts include quaternary phosphonium salts and
quaternary ammonium salts that may be used as the phase transfer
catalyst in the process of the present invention; such compounds
can be represented by the following formulas II and III:
1. R.sup.1R.sup.2R.sup.3R.sup.4p.sup.(+)X'.sup.(-) (II)
2. R.sup.1R.sup.2R.sup.3R.sup.4N.sup.(+)X'.sup.(-) (III)
[0019] wherein each of R.sup.1, R.sup.2, R.sup.3, R.sup.4and
R.sup.4, which may be the same or different, is an alkyl group, an
aryl group or an aralkyl group, and X' is a halogen atom. Specific
examples of these compounds include tetramethylammonium chloride,
tetramethylammonium bromide, benzyltriethylammonium chloride,
methyltrioctylammonium chloride (available commercially under the
brands Aliquat 336 and Adogen 464), tetra-n-butylammonium chloride,
tetra-n-butylammonium bromide, tetra-n-butylammonium hydrogen
sulfate, tetra-n-butylphosphonium chloride, tetraphenylphosphonium
bromide, tetraphenylphosphonium chloride,
triphenylmethylphosphonium bromide and triphenylmethylphosphoni- um
chloride. Among them, benzyltriethylammonium chloride is preferred
for use under strongly basic conditions. Other useful compounds
within this class of compounds include those exhibiting high
temperature stabilities (e.g., up to about 200.degree.0 C.) and
including 4-dialkylaminopyridiniu- m salts such as
tetraphenylarsonium chloride, bis[tris(dimethylamino)phosp- hine]
iminium chloride and tetratris[tris(dimethylamino)phosphinimino]
phosphonium chloride; the latter two compounds are also reported to
be stable in the presence of hot, concentrated sodium hydroxide
and, therefore, can be particularly useful.
[0020] Polyalkylene glycol compounds useful as phase transfer
catalysts can be represented by the formula:
2. R.sup.6O(R.sup.5O).sub.tR.sup.7 (IV)
[0021] wherein R.sup.5 is an alkylene group, each of R.sup.6 and
R.sup.7, which may be the same or different, is a hydrogen atom, an
alkyl group, an aryl group or an aralkyl group, and t is an integer
of at least 2. Such compounds include, for example glycols such as
diethylene glycol, triethylene glycol, tetraethylene glycol,
pentaethylene glycol, hexaethylene glycol, diisopropylene glycol,
dipropylene glycol, tripropylene glycol, tetrapropylene glycol and
tetramethylene glycol, and monoalkyl ethers such as monomethyl,
monoethyl, monopropyl and monobutyl ethers of such glycols, dialkyl
ethers such as tetraethylene glycol dimethyl ether and
pentaethylene glycol dimethyl ether, phenyl ethers, benzyl ethers,
and polyalkylene glycols such as polyethylene glycol (average
molecular weight about 300) dimethyl ether, polyethylene glycol
(average molecular weight about 300) dibutyl ether, and
polyethylene glycol (average molecular weight about 400) dimethyl
ether. Among them, compounds wherein both R.sup.6 and R.sup.7 are
alkyl groups, aryl groups or aralkyl groups are preferred.
[0022] Cryptates are another class of compounds useful in the
present as phase transfer catalysts. These are three-dimensional
polymacrocyclic chelating agents that are formed by joining
bridgehead structures with chains that contain properly spaced
donor atoms. For example, bicyclic molecules that result from
joining nitrogen bridgeheads with chains of (--OCH2CH2--) groups as
in 2.2.2-cryptate (4,7,13,16,21,24-hexaoxa-1,10-d-
iasabicyclo-(8.8.8)hexacosane; available under the brand names
ryptand 222 and Kryptofix 222). The donor atoms of the bridges may
all be O, N, or S, or the compounds may be mixed donor macrocycles
in which the bridge strands contain combinations of such donor
atoms.
[0023] Combinations of phase transfer catalysts from within one of
the groups described above may also be useful as well as
combinations or mixtures from more than one group, for example,
crown ethers and oniums, or from more than two of the groups, e.g.,
quaternary phosphonium salts and quaternary ammonium salts, and
crown ethers and polyalkylene glycols.
[0024] The reaction is conducted usually at a temperature within
the range of from about 0.degree. C. or slightly above to about
80.degree. C., preferably from about 0.degree. C. or slightly above
to about 60.degree. C., more preferably from about 0.degree. C. or
slightly above to about 40.degree. C.; for example from about
0.degree. C. to about 25.degree. C. Reference to "slightly" above
is intended to mean in the range of from about 1 to about 5.degree.
C. and temperatures therein between. Under process conditions where
freezing of the diluent, solvent or reactants is not a factor,
temperatures below 0.degree. C. can be used, for example from about
-20.degree. C. to about 80.degree. C.; preferably from about
-10.degree. C. to about 6020 C.; more preferably from about
-5.degree. C. to about 40.degree. C.
[0025] While there is no particular restriction as to the reaction
pressure, in other words the reaction may be conducted under
atmospheric pressure or under an elevated pressure, it may be
necessary to operate at elevated pressure if it is desired to
maintain the fluorocarbon starting material and the fluoroolefin in
the liquid state, at least during the reaction. When the reaction
is conducted under elevated pressure, useful pressures are from
about 1 to about 5 atmospheres (about 100 kPa to about 500 kpa).
The reaction time can vary in accordance with the starting compound
CF.sub.3C(R.sup.1.sub.aR.sup.2.sub.b)C(R.sup.3.sub.cR.sup.4.sub.-
d), as well as the reaction temperature selected and the yield or
conversion desired. For example, typically reaction times for
reactions conducted at from about 0.degree. C. to about 65.degree.
C., preferably from about 0 to about 25.degree. C., can vary from
about 0.1 to about 20 hours; preferably from about 0.1 to about 2.0
hours.
[0026] The process described herein is useful for the preparation
of fluoroolefins and/or fluorohaloolefins having the following
formula:
3. CF.sub.3CY.dbd.CX.sub.nH.sub.p (V)
[0027] wherein Y is a hydrogen atom or a halogen atom selected from
the group consisting of fluorine, chlorine, bromine or iodine; X is
a hydrogen atom or a halogen atom selected from the group
consisting of fluorine, chlorine, bromine or iodine; 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.3CH.dbd.CHCl, CF.sub.3CCl.dbd.CHF, CF.sub.3CH.dbd.CCl.sub.2,
CF.sub.3CF.dbd.CCl.sub.2, and the like. The fluorine-containing
olefins prepared by the method of this invention are readily
removed from the reaction mixture and/or solvent or diluent by
phase separation. Depending on the extent of conversion of the
starting material, the product can be used directly or further
purified by standard distillation techniques.
[0028] The fluoroolefins obtained by the process of the present
invention are useful as monomers for producing fluorine-containing
oligomers, homopolymers and copolymers as well as intermediates for
other fluorine-containing industrial chemicals.
[0029] All references herein to elements or metals belonging to a
certain Group refer to the Periodic Table of the Elements as it
appears in Hawley's Condensed Chemical Dictionary, 13.sup.th
Edition. Also, any references to the Group or Groups shall be to
the Group or Groups as reflected in this Periodic Table of Elements
using the"New Notation" system for numbering groups.
[0030] The following examples are given as specific illustrations
of the invention. It should be understood, however, that the
invention is not limited to the 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.
[0031] Further, any range of numbers recited in the 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 fluoroolefins and reactants used in such
processes.
EXAMPLES
Example 1
Dehydrofluorination of CF.sub.3CH.sub.2CF.sub.2H (HFC-245fa)
[0032] To 100 mL aqueous solution of KOH (20 wt. %) containing the
crown ether, 18-crown-6 (0.050 g, 0.2 mmol), at about 0.degree. C.
in an autoclave/pressure bottle was added CF.sub.3CH.sub.2CF.sub.2H
(5.93 g, 44 mmol). The stirred reaction mixture was brought to room
temperature (about 20-25.degree. C.) gradually and stirred for an
additional time period of about 2 hours. The volatile product,
CF.sub.3CH.dbd.CFH, (3.76 g, 33 mmol, 75% yield) formed by the
reaction was collected in a cold trap at about -78.degree. C.
Example 2
Dehydrofluorination of CF.sub.3CH.sub.2CF.sub.2H (HFC-245fa)
[0033] (A) In the Absence of Crown Ether
[0034] To 20 mL aqueous solution of KOH (50 wt. %) at about
0.degree. C. in an autoclave/pressure bottle was added
CF.sub.3CH.sub.2CF.sub.2H (5.93 g, 44 mmol). The stirred reaction
mixture in the sealed reaction vessel/pressure bottle was brought
to room temperature and stirred for 24 hours. Gas chromatographic
analysis of the volatile material from the reaction vessel
indicated only the unreacted starting material.
[0035] (B) In the Presence of Crown Ether
[0036] The reaction in (A) was repeated as above except that the
crown ether, 18-crown-6, (0.025 g, 0.1 mmol) was added to the
reaction mixture. Under these conditions, CF.sub.3CH.dbd.CFH (67%
yield) (85% conversion) was obtained.
Example 3
Dehydrochlorination of CF.sub.3CH.sub.2CF.sub.2Cl (HCFC-235fa)
[0037] To 100 mL aqueous solution of KOH (20 wt. %) containing the
crown ether, 18-crown-6, (0.084 g, 0.31 mmol), at about 0.degree.
C. in an autoclave/pressure bottle was added
CF.sub.3CH.sub.2CF.sub.2Cl (6.4 g, 38.7 mmol). The stirred reaction
mixture in the sealed autoclave/pressure bottle was brought to room
temperature gradually and stirred additionally for about 1 hour.
Gas chromatographic analysis (retention time 1.9 min for
CF.sub.3CH.dbd.CF.sub.2) indicated 93% conversion. The volatile
material, CF.sub.3CH.dbd.CF.sub.2, (3.47 g, 26 mmol, 67% yield)
formed during the reaction was collected in a cold trap at about
-78.degree. C.
Example 4
Dehydrochlorination of CF.sub.3CH.sub.2CF.sub.2Cl (HCFC-235fa) in
the Absence of Crown Ether
[0038] The reaction of Example 3 was repeated except that the crown
ether, 18-crown-6, was not included. Under these conditions, gas
chromatographic analysis indicated only the unreacted starting
material (CF.sub.3CH.sub.2CF.sub.2Cl).
[0039] In an effort to drive the dehydrochlorination reaction, more
severe conditions were employed. To 100 mL aqueous solution of KOH
(20 wt. %) at about 0.degree. C. in an autoclave/pressure bottle
was added CF.sub.3CH.sub.2CF.sub.2Cl (8.37 g, 50 mmol). The stirred
reaction mixture was heated to and maintained at 65.degree. C. for
2.5 hours. Gas chromatographic analysis indicated 52% conversion to
the product. Additional heating for 8 h at 60-65.degree. C.
resulted in 93% conversion to product. This indicates that, when
the reaction is conducted outside the scope of the present
invention, even if dehydrohalogenation occurs, compared with the
inventive process, it may require substantially elevated
temperature and extended reaction time in order to obtain the
product.
Example 5
[0040] (A) Preparation of CF.sub.3CHBrCF.sub.2Br
[0041] Under nitrogen, in to a cooled (-78.degree. C.) 3-necked
round bottom flask, equipped with dry ice condenser and stirrer,
was added 109 g (0.83 mol) CF.sub.3CH.dbd.CF.sub.2. Bromine 132 g
(0.83 mol) was added drop-wise with stirring over a period of about
4 hours. The temperature during bromine addition ranged from -66 to
-46.degree. C. After complete addition, the reaction mixture was
stirred for an additional 20 minutes, washed with aqueous sodium
bisulfite (10 wt. %) until the organic layer became colorless. The
colorless organic layer was separated, dried over MgSO.sub.4 and
filtered to afford 199 g (82% yield) CF.sub.3CHBrCF.sub.2Br as a
colorless liquid. The structure was confirmed by nuclear magnetic
resonance (NMR) spectroscopy.
[0042] (B) Dehydrobromination of CF.sub.3CHBrCF.sub.2Br
[0043] To a 250 mL 3-necked round bottom flask operating under
nitrogen purge, equipped with a water condenser (at about 1520 C.),
stirrer, and fitted with a dry ice trap (at about -78.degree. C.),
was added 100 mL aqueous potassium hydroxide (23 wt. %) solution
and the crown ether, 18-crown-6, (0.1 g, 0.37 mmol). To this
solution at about 20.degree. C., was added CF.sub.3CHBrCF.sub.2Br
(24.6 g, 84 mmol) drop-wise via an addition funnel over a period of
about 35 minutes. The dehydrobrominated product,
CF.sub.3CBr.dbd.CF.sub.2 (gas chromatograph retention time, 2.0
min), as formed, was continuously collected in the dry ice trap.
After complete addition of CF.sub.3CHBrCF.sub.2Br, the reaction
mixture was stirred for an additional 60 minutes. A total of 17.1 g
(81 mmol) of CF.sub.3CBr.dbd.CF.sub.2 (96% yield), was collected in
the dry ice trap. The structure was confirmed by NMR
spectroscopy.
[0044] 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.
* * * * *