Process for the separation of a mixture comprising at least one hydrofluoroalkane and hydrogen fluoride, processes for the preparation of a hydrofluoroalkane and azeotropic compositions

DETAILED DESCRIPTION The invention claimed is: 1.
An azeotropic or pseudoazeotropic composition which comprises 1.
5 mol % to 27.
5 mol % of 1,1,1,3,3-pentafluorobutane and of 72.
5 mol % to 98.
5 mol % of hydrogen fluoride.
2.
The composition as claimed in claim 1, which consists essentially of 1.
5 mol % to 27.
5 mol % of 1,1,1,3,3-pentafluorobutane and of 72.
5 mol % to 98.
5 mol % of hydrogen fluoride.
3.
The composition according to claim 1, comprising hydrogen fluoride and 1,1,1,3,3-pentafluorobutane in a hydrogen fluoride/1,1,1,3,3-pentafluorobutane molar ratio of approximately 11 mol/mol at a pressure of 3 bar.




Description:
The present invention relates to a process for the separation of a mixture comprising a hydrofluoroalkane and hydrogen fluoride, as well as to processes for the preparation of a hydrofluoroalkane and to azeotropic compositions.
Hydrofluoroalkanes can be prepared by reaction of an appropriate chlorinated precursor with hydrogen fluoride, as disclosed, for example, in Patent Applications EP-A1-0,699,649 and WO-A1-97/15540 (on behalf of Solvay) and in Patent Application WO-A1-97/05089.
In such a process, at the outlet of the reactor, the mixture of reaction products comprises, in addition to the desired hydrofluoroalkane, hydrogen chloride originating from the removal of the chlorine atom or atoms from the starting chlorinated precursor, hydrogen fluoride, chlorofluorinated intermediates, generally unconverted chlorinated precursor, possibly inert diluents, and various byproducts in small amounts.
Given that the operation is usually carried out with an excess of hydrogen fluoride with respect to the chlorinated precursor, unconverted hydrogen fluoride is generally present in the mixture of reaction products.
Whereas the majority of the constituents of the mixture of reaction products can be easily and completely separated by distillation, complete separation between the hydrofluoroalkane and the hydrogen fluoride is generally very difficult to achieve by distillation, this being because these compounds often form azeotropic mixtures