Organic compounds -- part of the class 532-570 series – Organic compounds
Patent
1992-12-23
1994-08-02
Evans, Joseph E.
Organic compounds -- part of the class 532-570 series
Organic compounds
570257, C07C 1724, C07C 1902, C07C 1904
Patent
active
053347820
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The present invention relates to a method wherein a polychloromethane, particularly carbon tetrachloride, which is regulated from the standpoint of global environmental protection, is used as a starting material, and this starting material is converted to a hydrogen-containing chloromethane such as chloroform which is useful as a starting material for various fluorine-containing compounds.
2. Background Technique
Heretofore, carbon tetrachloride has been used primarily as a starting material for various chlorofluorocarbons. However, these chlorofluorocarbons as well as carbon tetrachloride as the starting material have been restricted in their production, and a technique to decompose these materials or to convert them to useful materials, has been desired widely throughout the world.
On the other hand, a hydrogen-containing chloromethane such as chloroform obtainable by substituting hydrogen atoms for the chlorine atoms in carbon tetrachloride, is useful as a starting material for various chemical products. Accordingly, it is urgently desired to develop a technique for introducing hydrogen effectively to a polychloromethane such as carbon tetrachloride to convert it to a hydrogen-containing chloromethane.
Various methods have been known to introduce hydrogen to carbon tetrachloride. A method for the electrolytic reduction in the presence of a protic solvent has a drawback such that the reaction is slow, and can hardly be adopted on an industrial basis. On the other hand, a method for the hydrogenation reduction by means of a reduction catalyst as shown, for example, in Japanese Unexamined Patent Publication No. 133939/1991 is believed to be advantageous for development on an industrial basis, since the reaction rate is high, and hydrogen chloride as a by-product can also be utilized. However, the method disclosed in Japanese Unexamined Patent Publication No. 133939/1991 is a gas phase hydrogenation reduction method employing a widely used catalyst such as iron or platinum, whereby it has been found that the catalytic activities decrease in a short period of time. Further, a method of gas phase hydrogenation reduction of carbon tetrachloride has had a problem that the yield of the desired product is not high enough, since a dimmer such as hexachloroethane or a polymer having from 5 to 7 carbon atoms, particularly at a high temperature, tends to form as a by-product.
The present inventors have conducted various studies with respect to the above gas phase hydrogenation reduction method. Firstly, as a result of an analysis of the organic components deposited on a deactivated catalyst, many of them were found to be polymers. Further, from the inspection by a transmission electron microscope and the analysis by the X-ray diffraction, the particle size of the catalyst was found to be substantially the same as the size before use. Therefore, deposition of the polymers is considered to be the primary cause for the deactivation.
DISCLOSURE OF THE INVENTION
The present inventors have conducted an extensive study with respect to a reaction method for controlling the rapid deactivation of the catalyst. As a result, it has been found that the rapid deterioration of the catalyst can be eliminated, and a hydrogen-containing chloromethane can be obtained in good yield by adopting a method which comprises reducing a polychloromethane by hydrogen in a liquid phase state in the presence of a reduction catalyst. The present invention has been accomplished on the basis of this discovery and presents a method for producing a hydrogen-containing chloromethane, which comprises reducing a polychloromethane by hydrogen in a liquid phase in the presence of a reduction catalyst. The present invention will be described in detail hereinafter together with Examples.
The polychloromethane may be carbon tetrachloride, chloroform or methylene chloride. According to the method of the present invention, chloroform, methylene chloride or methyl chloride can be obtained by the reduction of carbon tetrachloride
REFERENCES:
patent: 3579596 (1971-05-01), Mullin et al.
patent: 5097081 (1992-03-01), Correia et al.
patent: 5105032 (1992-04-01), Holbrook et al.
patent: 5146013 (1992-09-01), Dogimont et al.
patent: 5208393 (1993-05-01), Miguel et al.
Morikawa Shinsuke
Tatematsu Shin
Yoshitake Masaru
AG Technology Co., Ltd.
Evans Joseph E.
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