D'elf Atochem S.a.

Elf Atochem S.a.

Societe Atochem

Jean-Michel Galland

Dominique Rouzies

Jean-Pierre Schirmann

Sylvain Perdrieux

Emmanuel Guiraud

Michel Bergougnan

Rene Perdriau

A process for the separation of hydrogen fluoride (HF) and of difluoromethane (F32) by fractional distillation and/or condensation, in at least one stage, including in at least one stage obtaining a stream whose HF and F32 contents correspond.

Process for the separation of hydrogen fluoride and of difluoromethane

The subject of the invention is a continuous process for the preparation of 1,1,1,2-tetrafluoroethane (134a) from 2-chloro-1,1,1-trifluoroethane (133a) and hydrofluoric acid in the gaseous phase in the presence of a chromium-based catalysts. According to the invention, the flow of gas leaving the reactor is subjected to a distillation in order to separate at the top a flow containing almost all the HC1 and at least 90% of the 134a produced by the reaction and at the bottom a flow containing at least 90% of the unconverted reactants (133a and HF), and the latter flow is recycled directly to the reactor, without any purifying operation.

Process for the preparation of 1,1,1,2-tetrafluoroethane

The invention relates to continuous production of 1,1,1-chlorodifluoroethane from 1,1,1-trichloroethane and hydrofluoric acid by reaction in liquid phase in the presence of at least one fluorination catalyst. According to the invention, the process is carried out under an absolute pressure of between 6 and 30 bars and at a temperature of between 50.degree. and 120.degree. C., the content of catalyst(s) in the reaction mixture, expressed as a percentage by weight of metal, being between 0.05 and 10% and the content of organohalogenated by-products not belonging to series 140 in the reaction mixture being controlled at a value below 40% by weight. This process makes it possible, at the same time, to obtain a high degree of conversion of hydrofluoric acid, to minimize the coproduction of 1,1,1-trifluoroethane and organohalogenated by-products and to facilitate the recovery of the hydrochloric acid formed.

Process for the production of 1,1,1-chlorodifluoroethane

The invention relates to the separation of hydrogen fluoride (HF) from its mixtures with 1,1,1-trifluoro-2-chloroethane (F133a). By settling of the mixture of HF and F133a in the presence of trichloroethylene at a temperature below 0.degree. C., a lower organic phase which is poor in HF and an upper phase which is rich in HF are obtained. The latter can be directly recycled to the fluorination reactor or subjected to a distillation in order to separate, at the head, the HF/F133a azeotrope which is returned to the settler, and to recover, at the foot, practically pure HF. By distillation of the lower phase, the HF/F133a azeotrope which is returned to the settler is separated at the head and a mixture of F133a and trichloroethylene is recovered at the foot. The latter mixture is subjected to a distillation which makes it possible to separate, at the head, pure F133a from trichloroethylene at the foot.

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Vernaison, France

Jean-Michel Galland