Organic compounds -- part of the class 532-570 series – Organic compounds – Halogen containing
Patent
1997-06-03
1999-05-11
Siegel, Alan
Organic compounds -- part of the class 532-570 series
Organic compounds
Halogen containing
203 50, 203 67, C07C19/08
Patent
active
059029110
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to the production of hydrohalofluorocarbons and their azeotropes with HF, and more particularly to the hydrogenolysis reactions of 2,2-dichlorohexafluoropropane using palladium-containing catalysts and products which can be produced thereby.
BACKGROUND
Various processes for the catalytic hydrogenolysis of chlorofluorocarbons and hydrochlorofluorocarbons are known. For example, U.S. Pat. No. 2,942,036 discloses the reaction of 1,2,2-trichloropentafluoropropane with hydrogen in the presence of palladium on activated carbon catalyst to produce 1,2,2-trihydropentafluoropropane. The examples show that under the conditions of the experiments one of the products from this reaction is CF.sub.3 CH.dbd.CF.sub.2. Japanese Patent Application Publication Hei 1(1989)-319441 discloses a process where one chlorine atom is selectively replaced by hydrogen in 1,1,1-trichlorotrifluoroethane using a platinum catalyst. For comparison, a palladium on carbon catalyst is disclosed to produce 1,1,1-trifluoroethane as the major product under the conditions of the experiment.
It is well known that the hydrogenolysis of compounds such as chlorofluorocarbons to replace chlorine by hydrogen produces hydrogen chloride as a co-product. Loss of fluorine when it occurs (e.g., to produce overhydrogenated products) can produce HF as a by-product.
SUMMARY OF THE INVENTION
The present invention provides a process for the monohydrogenolysis of 2,2-dichlorohexafluoropropane (i.e., CF.sub.3 CCl.sub.2 CF.sub.3, or CFC-216aa) to 2-chloro-2-hydrohexafluoropropane (i.e., CF.sub.3 CHClCF.sub.3, or HCFC-226da). The process comprises reacting said 2,2-dichlorohexafluoropropane with hydrogen at an elevated temperature of about 150.degree. C. or less in the presence of a catalyst containing a catalytically effective amount of palladium supported on trivalent chromium oxide in the presence of an acid of the formula HZ, where Z is selected from the group consisting of Cl, F and mixtures thereof, to produce 2-chloro-2-hydrohexafluoropropane with a selectivity of over 70% based upon the 2,2-dichlorohexafluoropropane converted.
Azeotropic compositions (e.g., an azeotropic composition comprising from about 80 to 47 mole percent HF and from about 20 to 53 mole percent CF.sub.3 CHClCF.sub.3) are also provided; as is a process for producing an azeotropic composition of HF and 2-chloro-2-hydrohexafluoropropane as a product of the monohydrogenolysis of 2,2-dichlorohexafluoropropane where HF is present.
DETAILED DESCRIPTION
The catalysts suitable for the process of this invention comprise palladium and may optionally contain other components such as other Group VIII metals. The palladium is supported on chromium oxide. Any source of chromium oxide is suitable, but chromium oxide prepared by the thermal decomposition of (NH.sub.4).sub.2 Cr.sub.2 O.sub.7 is especially preferred. A procedure for the preparation of Cr.sub.2 O.sub.3 by the thermal decomposition of (NH.sub.4).sub.2 Cr.sub.2 O.sub.7 is disclosed in U.S. Pat. No. 5,036,036, the entire contents of which are incorporated herein by reference.
The acid HZ is at least partially produced during the reaction as the halogen Cl is removed from the starting material as a result of the hydrogenolysis. Accordingly, Z is ordinarily at least in part Cl. Also of note are embodiments where Z is partially F (i.e., the acid is a mixture of HCl and HF). HF can be present for example, as a result of overhydrogenolysis, wherein fluorine substituents of the starting material are partially replaced by hydrogen. HF can also be present in the reaction feed. For example, residual HF can be present from processes used to make the 2,2-dichlorohexafluoropropane. Of note in this regard are embodiments where said starting material is a component of an azeotrope of HF and said starting material, and starting material from said azeotrope is reacted with hydrogen in the presence of HF from said azeotrope.
Unlike alumina supports which are readily fluorinated, chromia fluorinates much mo
REFERENCES:
patent: 2942036 (1960-06-01), Smith et al.
patent: 4319060 (1982-03-01), Cunningham et al.
patent: 4873381 (1989-10-01), Kellner et al.
patent: 5036036 (1991-07-01), Lerou
patent: 5091600 (1992-02-01), Moore et al.
patent: 5146018 (1992-09-01), Kellner et al.
patent: 5171901 (1992-12-01), Gassen et al.
patent: 5463152 (1995-10-01), Rao
patent: 5481051 (1996-01-01), Rao
Bitner, J.L. et al., Thermochemical and Photochemical stuides on organic fluorine compounds, Chemical Abstract, 54:22311, 1959.
Zubovich, I.A., Oxidation--Reduction Catalysis by Palladium--Gold and Palladium-Silber Systems on Different Types of Carrier, Russian Journal of Phys. Chem., 56(5), 798-799, 1982.
Sokolskii, D.V. et al., Liquid-phase Hydrogenation of B-Ionone on a Stationary NiCr203 Catalyst in a Flow Apparatus under Hydrogeen Pressure, Russian Journal of Phys. Chem., 56(7), 1075-1076, 1982.
Rao Velliyur Nott Mallikarjuna
Warwas Edwin James
E. I. Du Pont de Nemours and Company
Siegel Alan
LandOfFree
Production of 2-chloro-2-hydrohexafluoropropane and azeotropes t does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Production of 2-chloro-2-hydrohexafluoropropane and azeotropes t, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Production of 2-chloro-2-hydrohexafluoropropane and azeotropes t will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-246284