Process for the preparation of fluoroolefins

Details Process for the preparation of fluoroolefins Process for the preparation of fluoroolefins

1997-12-29

1999-07-27

Siegel, Alan

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

Organic compounds

Halogen containing

C07C 1702

Patent

active

059292938

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

This invention concerns processes for the preparation of fluoroolefins.


TECHNICAL BACKGROUND

U.S. Pat. No. 3,377,390 discloses compounds of the formula R.sub.f IF.sub.x where x is an integer of two or four. This patent discloses that a compound of the formula R.sub.f IF.sub.x will initiate telomerization of perfluoroalkyl iodides with certain olefins.
U.S. Pat. No. 3,557,224 discloses a process for the manufacture of perfluoroalkyl iodide telomers from the corresponding monomers by telomerizing a perfluoroalkyl iodide with a perfluoroethylene or a perfluoropropylene containing at least one Cl atom in the presence of a catalyst.
U.K. Patent No. 1,443,444 discloses a process for preparing bromine containing telomers.


SUMMARY OF THE INVENTION

This invention provides a process for the preparation of perfluorinated olefins of the structure R.sub.f CF.dbd.CFCF.sub.3 by the reaction of perfluoroalkyliodides of the structure R.sub.f CF.sub.2 I, wherein R.sub.f is C.sub.n F.sub.2n F, wherein n is 1 to 12, with perfluoroolefins in the presence of an aluminum chlorofluoride catalyst.
Included herein is a process for the preparation of perfluorobutene-2 by the dimerization of tetrafluoroethylene, in the presence of an aluminum chlorofluoride/perfluoroalkyl iodide catalyst system.
This invention also provides a process for the deiodofluorination of an iodine containing fluorocarbon comprising contacting said iodine containing fluorocarbon with a fluoroolefin capable of picking up the elements of iodine monofluoride in the presence of an aluminum chlorofluoride catalyst (ACF).


DETAILED DESCRIPTION OF THE INVENTION

The processes of the present invention are illustrated by the following equations. ##STR1## wherein R.sub.f in Equations 1 and 2 is C.sub.n F.sub.2n F where n is 1-12, R.sub.f, is selected from F and C.sub.n F.sub.2n F and R.sub.f" is selected from F and CF.sub.3.
The iodine-containing starting compound is believed to add across the double bond of tetrafluoroethylene (TFE). The secondary perfluoroalkyl iodide formed in Equation 1 reacts, as shown in Equation 2, with a second molecule of TFE or with hexafluoropropene to generate the product olefin and a molecule of short-chain perfluoroalkyl iodide, R.sub.f" CFICF.sub.3 (R.sub.f" =CF.sub.3 or F). Perfluoroalkyl iodide generated in this reaction of perfluoroalkyl iodide with TFE (Eq 2, R.sub.f' =F) competes with starting iodide R.sub.f CF.sub.2 I in the reaction with TFE.
The special case of equation 1 and 2 is the case where R.sub.f CF.sub.2 I is perfluoroethyl iodide. This reaction generates perfluoroethyl iodide (see Eq 3) and the process becomes catalytic in perfluoroethyl iodide. ##STR2##
The process of Eq. 2, which involves the transfer of iodine monofluoride from a perfluoroalkyl iodide, can be carried out independently of Eq. 1 with primary or secondary perfluoroalkyl iodides using TFE or hexafluoropropylene (HFP) as perfluoroolefin (Eq. 2 and 4). .fwdarw.R.sub.f CF.dbd.CF.sub.2 CF.sub.3 +R.sub.f "CFICF.sub.3Equation 4 R.sub.f " is F or CF.sub.3.
The discussion below summarizes the embodiments exemplified in certain examples; however, the invention is not meant to be limited to these examples as equivalents are also intended to be included.
In Example 1, illustrating equations 1 and 2, R.sub.f is CF.sub.3 ; and thus R.sub.f CF.sub.2 I is perfluoroethyl iodide. This is the special case cited above.
In Example 2, illustrating equations 1 and 2, R.sub.f is n-C.sub.3 F.sub.7, R.sub.f ' is F and thus R.sub.f 'CF.dbd.CF.sub.2 is TFE. Because only 0.06 mole of perfluoro-n-butyl iodide is present versus 0.5 mole of TFE, and because perfluoroethyl iodide reacts faster than perfluoro-n-butyl iodide, the predominant products arise from the generated perfluoroethyl iodide competing successfully with perfluoro-n-butyl iodide. The major product is perfluorobutene-2.
In Example 3, as compared to Example 2, the molar ratio of perfluoro-n-butyl iodide to TFE is increased 2.1 times. Here, the products reflect less successful competition be

REFERENCES:
patent: 3192274 (1965-06-01), Baranauckas et al.
patent: 3377390 (1968-04-01), Rondestvedt, Jr. et al.
patent: 3557224 (1971-01-01), Jaeger
patent: 4073817 (1978-02-01), Jager
patent: 4587366 (1986-05-01), Werner

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