Process for producing fluoroolefins

Details Process for producing fluoroolefins Process for producing fluoroolefins

2001-09-25

2003-04-15

Siegel, Alan (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Halogen containing

Reexamination Certificate

active

06548719

ABSTRACT:

BACKGROUND OF THE INVENTION
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”).
The production of fluoroolefins such as CF
3
CH═CH
2
by catalytic vapor phase fluorination of various saturated and unsaturated halogen-containing C
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 fluorinated olefins using a chloro- or bromo-halofluorocarbon and HF.
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)
2
or Mg(OH)
2
or by contact of the HFC-245fa in the vapor phase with a chromium based catalyst at elevated temperature.
A. L. Henne et al., J.Am.Chem.Soc. (1946) 68, 496-497, describe the synthesis of various fluoroolefins from CF
3
CH
2
CF
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.
P. Tarrant et al., J.Am.Chem.Soc. (1955), 77, 2783-2786, describe the synthesis of CF
3
CH═CF
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-tetrafluoropropene and reacting it with HF at 150° C. and neutralizing the reaction products with a potassium hydroxide solution.
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
8
and C
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.
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.
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
Process for the preparation of a fluoroolefin of the formula CF
3
CY═CX
n
H
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
3
C (R
1
a
R
2
b
)C(R
3
c
R
4
d
) wherein R
1
, R
2
, R
3
, and R
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
1
, R
2
, R
3
, and R
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
3
CH
2
CF
2
H (a commercially available compound also known as HFC-245fa) or CF
3
CH
2
CF
2
Cl, a by-product from the manufacture of HFC-245fa.
DETAILED DESCRIPTION
The present invention can be generally described as a process for the preparation of fluoroolefins of the formula CF
3
CY═CX
n
H
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
3
C (R
1
a
R
2
b
)C(R
3
c
R
4
d
) wherein R
1
, R
2
, R
3
, and R
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
1
, R
2
, R
3
, and R
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.
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:
CF
3
C(R
1
a
R
2
b
)C(R
3
c
R
4
d
)  (I)
wherein R
1
, R
2
, R
3
, and R
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
1
, R
2
, R
3
, and R
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. Included among the compounds of formula (I) that can be used in the present invention is 1,1,1,3,3-pentafluoropropane or HFC-245fa. 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. No. 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
3
CH
2
CCl
3
by the reaction of CCl
4
with vinylidene chloride; 2) conversion of CCl
3
CH
2
CCl
3
to CF
3
CH
2
CF
2
Cl by reaction with HF in the presence of a fluorination catalyst, selected from TiCl
4
, SnCl
4
or mixtures thereof; and 3) reduction of CF
3
CH
2
CF
2
Cl to CF
3
CH
2
CF
2
H. Since both CF
3
CH
2
CF
2
H and CF
3
CH
2
CF
2
Cl 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
3
CH
2
CF
2
H, 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
3
CH═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
3
CH
2
CF
2
Br; CF
3
CH
2
CF
2
I; CF
3
CHFCF
2
Br; CF
3
CH
2
CH
2
Cl; CF
3
CH
2
CH
2
Br; CF
3
CH
2
CH
2
I; CF
3
CHBrCF
2
Br; CF
3
CHClCF
2
Cl; CF
3
CH
2
CFHCl; CF
3
CH
2
CFHBr; CF
3
CHClCF
2
H; CF
3
CH
2
CCl
3
; CF
3
CH
2
CF
3
; and the like.
In order to carry out the dehydrohalogenatio

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