Organic compounds -- part of the class 532-570 series – Organic compounds – Halogen containing
Reexamination Certificate
1999-08-23
2001-05-29
Richter, Johann (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Halogen containing
Reexamination Certificate
active
06239319
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for the preparation of perfluoroalkanes, which have many applications in various fields of industries and are represented by a general formula Rf-F (wherein Rf- is a perfluoroalkyl group represented by F(CF
2
)
n
— and n is an integer of 2 to 10) and which are exemplified by perfluoroethane (C
2
F
6
) for use as a dry etching gas, a process gas in semiconductor production, and the like, perfluorohexane (C
6
F
14
) for use as a cleaning agent, a heat medium, and the like from the standpoint of very high stability in chemical and thermal terms, and also for the preparation of iodine pentafluoride (IF
5
) useful as a reactive fluorinating agent or a material for intermediate products in the production of fluorine-containing compounds.
2. Description of the Prior Art
It is known to produce C
6
F
14
by effecting a coupling reaction of C
3
F
7
I as a feed material with a metal such as zinc. Disadvantages of this process are, for example, that C
3
F
7
I for use as a feed material is difficult to obtain and that metal iodides are produced as by-products.
In general, methods known as those for producing a perfluoro-compound are as follows:
(a) electrolytic fluorination of a hydrocarbon or a halogenated hydrocarbon;
(b) fluorination of a hydrocarbon with a metal fluoride;
(c) thermal decomposition of a highly fluorinated perfluoro-compound; and
(d) direct fluorination of carbon or a hydrocarbon with gaseous fluorine.
However, the above-mentioned methods are associated with, for example, the following problems.
In the method (a), since various side reactions take place and many by-products other than a target product are produced, separation/purification to obtain the target product is so difficult that the yield of the target product is remarkably reduced.
In the method (b), since many partially fluorinated products are produced, the yield of a perfluoro-compound cannot be increased.
In the method (c), a high temperature is needed for the reaction and the yield of a target product is not good.
In the method (d), there is an advantage that partially fluorinated products are hardly produced. However, gaseous fluorine is so reactive that control of reaction temperature is not easy because of vigorous heat generation involved in the reaction. As a result, C—C bonds are severed and therefore the yield of the target product decreases. In addition, since a risk of explosion and equipment corrosion accompanies the reaction, this method cannot be industrially advantageous.
Alternatively, a method in which a perfluoroalkyl iodide (Rf-I) is reacted with fluorine to obtain a perfluoroalkane and IF
5
is known. According to this method, however, on the one hand, the energy produced at the time of reaction is too large to amounts to about 300 kcal/mol, and on the other hand, the amount of heat being removed is too small when an ordinary heat removing means, for example, an indirect heat exchanger (such as a spiral tube, an outer jacket, and the like) which relies on the removal of sensible heat is used. Accordingly, unless the extent of the reaction itself is controlled, there is a risk that the reaction might become out of control and cause an explosion.
For example, the reaction itself between pentafluoroethyl iodide and gaseous fluorine has been reported by D. E. Johnson et al. (see International Journal of Chemical Kinetics, Vol. 28, 43-55, 1996). In order to utilize this method as an industrial method for producing pentafluoroethane and to obtain the target product in a good yield, the heat of reaction needs to be efficiently removed. However, a concrete technical means to solve the above-mentioned problem has not yet been known.
SUMMARY OF THE INVENTION
As seen from the foregoing description, the methods hitherto known for producing perfluoroalkanes are not necessarily satisfactory from the viewpoint of industrial practicality. Accordingly, it is an object of the present invention to overcome the above described disadvantages in the prior art and to provide a new method for producing perfluoroalkanes which can be industrially practical and replace the methods of prior art.
As a result of intensive studies about industrial methods for producing perfluoroalkanes such as perfluoroethane (hexafluoroethane), perfluorohexane (tetradecafluorohexane), and the like, the inventors have found that, when the above-mentioned reaction, in which a perfluoroalkyl iodide and gaseous fluorine are used to produce a perfluoroalkane and IF
5
, is effected in the presence of the liquid which is at least one liquid which is inert to the perfluoroalkyl iodide and gaseous fluorine and has a boiling, point lower than that of IF
5
and which can therefore be present at least partially in a liquid phase under the reaction condition and can easily be evaporated by the heat generated by the reaction and which is selected from a perfluoro-compound, a chlorofluoro-compound, and hydrogen fluoride, the huge amount of heat generated by the reaction may be absorbed/removed as latent heat required for the evaporation of the above-mentioned at least one liquid, which is selected from a perfluoro-compound, a chlorofluoro-compound, and hydrogen fluoride, so that the reaction temperature may be easily and efficiently controlled.
Consequently, since the reaction temperature can be prevented from being excessively high, that is, the reaction temperature can be controlled as desired, side reactions can be inhibited. In addition, since conventionally employed equipment for indirectly cooling the reaction liquid to remove the heat of reaction may be omitted, the reaction equipment as a whole becomes simple and economically advantageous.
Moreover, there is an advantage that IF
5
, which is produced simultaneously from the reaction, can be used as a starting material for the production of, for example, a perfluoroalkyl iodide.
Accordingly, the present invention provides a process for producing a perfluoroalkane corresponding to a general formula Rf-F (wherein Rf- is a perfluoroalkyl group represented by F(CF
2
)
n
— and n is an integer of 2 to 10) by contacting a perfluoroalkyl iodide with gaseous fluorine so as to react them, characterized in that the contact is made in the presence of at least one liquid compound selected from a perfluoro-compound, a chlorofluoro-compound, and hydrogen fluoride which liquid compound is substantially inert to the perfluoroalkyl iodide and gaseous fluorine under conditions of the process.
The term “substantially inert” as used herein means that a compound is inert such that it does not exert an adverse influence which offsets the advantages obtainable by performing the process of the present invention. In other word, it means that a compound is substantially inert vie to a reaction in which a perfluoroalkane and IF
5
are produced and therefore the compound does not exert on the reaction an adverse influence that overrides the advantage obtainable by the present invention.
REFERENCES:
patent: 5482682 (1996-01-01), Tarancon
patent: 5734073 (1998-03-01), Chambers et al.
patent: 0200908 A1 (1986-12-01), None
patent: 62-005929 (1987-01-01), None
patent: 09241186 (1997-09-01), None
Johnson, D. E. et al.International Journal of Chemical Kinetics, vol. 28, pp. 43-55 (1996).
Aoyama Hirokazu
Hirata Tatsuya
Kan Kyohiro
Otsuka Tatsuya
Birch & Stewart Kolasch & Birch, LLP
Daikin Industries Ltd.
Parsa J.
Richter Johann
LandOfFree
Processes for the preparation of perfluoroalkanes and iodine... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Processes for the preparation of perfluoroalkanes and iodine..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Processes for the preparation of perfluoroalkanes and iodine... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2519221