Organic compounds -- part of the class 532-570 series – Organic compounds – Halogen containing
Patent
1994-11-04
1996-07-16
Evans, Joseph E.
Organic compounds -- part of the class 532-570 series
Organic compounds
Halogen containing
570153, 570171, C07C 1726, C07C 17354, C07C 1909
Patent
active
055368905
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/EP93/01073 May 03, 1993.
The present invention relates to an improved process for preparing 1,1,1,4,4,4-hexafluorobutane, i,e, a saturated, fluorine-containing and chlorine-free hydrocarbon such as has recently been of interest as a blowing gas for polyurethane foams (as a substitute for CFCs). It is known, from Chem. Lett. 1990, 870-880, that in the case of the compound CCl.sub.2 F--CClF.sub.2 in the presence of hydrogen on a nickel catalyst, an intramolecular elimination of hydrogen chloride takes place with the formation of the unsaturated, chlorine-containing compound CClF.dbd.CF.sub.2. Dimerisation to give butane or butene derivatives does not occur.
It is known, from Chem. Lett. 1991, 1825-1826, that chlorine-containing butenes are formed from the compound CF.sub.3 --CCl.sub.3 in the presence of hydrogen, with argon as a diluent, on a nickel catalyst, due to dimerisation. Under these conditions, CF.sub.3--CHC 1F and small proportions of a perhalogenated butane derivative are formed from the compound CF.sub.3 --CFCl.sub.2.
A process for preparing 1,1,1,4,4,4-hexafluorobutane has now been found which is characterised in that a trifluorethane compound of the formula (I) and and without a diluent, on a palladium- and/or nickel-containing supported catalyst, and the reaction product, optionally after separation of 1,1,1,4,4,4-hexafluorobutane, is subsequently hydrogenated.
The trifluoroethane compounds of the formula (I) required as starting compounds for the process according to the invention are easily accessible and commercially available products.
CF.sub.3 --CCl.sub.3, CF.sub.3 --CHCl.sub.2 or CF.sub.3 --CH.sub.2 Br are preferably used in the process according to the invention.
Reaction of the trifluoroethane compounds of the formula (I) with hydrogen may take place, for example, in such a way that the compound of the formula (I) is evaporated and passed in gaseous form together with hydrogen over the palladium- and/or nickel-containing supported catalyst. 5 to 200 N1 of hydrogen can be used, for example, for every 100 g of compound of the formula (I). This amount is preferably 10 to 30 N1 of hydrogen.
Reaction of compounds of the formula (I) with hydrogen is performed in the absence of diluents (e.g. argon or nitrogen).
Suitable catalysts for this reaction are, for instance, those which contain 0.5 to 20 g of palladium and/or 100 to 1000 g of nickel per litre. The catalysts preferably contain 1 to 10 g of palladium and/or 300 to 800 g of nickel per litre. The palladium and/or nickel is preferably present completely, or at least partly, in elemental form. Suitable support materials for these catalysts are, for instance, silicon dioxide, silicates, aluminium dioxide, spinels, barium sulphate, titanium dioxide, magnesium oxide and carbon. Silicon dioxide and activated carbon, in particular silicon dioxide for nickel and activated carbon for palladium, are preferred.
The catalysts may optionally contain other metals as promoters. Promoters may be present, for instance, in amounts of 0 to 5 wt % with reference to palladium or nickel. Examples of promoters are zirconium, titanium, vanadium, niobium, tantalum, thallium, tin and/or copper.
Reaction of compounds of the formula (I) with hydrogen may be performed at atmospheric pressure or at an elevated pressure, up to 20 bar for example. The process is preferably performed at atmospheric pressure. The temperature for this reaction may be in the range 20.degree. to 550.degree. C. for example Temperatures between 120.degree. and 480.degree. C. in particular those of 250.degree. to 450.degree. C., are preferred.
The gas mixture present after this reaction can be worked up, for example, by condensing the organic components and then performing a hydrogenation reaction. It is preferable to separate out the 1,1,1,4,4,4,-hexafluorobutane already contained in the condensed organic material, by distillation for example, before subsequent hydrogenation.
Subsequent hydrogenation of the organic condensate, which preferably no longer contai
REFERENCES:
patent: 4902839 (1990-02-01), Bielefeldt et al.
patent: 5382720 (1995-01-01), Ikawa et al.
Chemistry Letters (1990)--Mar. 5, pp. 879-880.
Chemistry Letters (1991)--Jul. 9, pp. 1825-1826.
Bielefeldt Dietmar
Marhold Albrecht
Bayer Aktiengesellschaft
Evans Joseph E.
Gil Joseph C.
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