Ausimont S.p.a.

Ausimont S.r.l.

Antonio Masiero

Paolo Cuzzato

Letanzio Bragante

Francesco Rinaldi

Process for preparing pentafluoroethane (HFC-125) wherein 1,1,1-trifluorodichloroethane (HFC-123) is reacted with HF at a temperature from 310&deg; to 380&deg; C., in the presence of a catalyst comprising Cr,O,supported on preformed AlF,. HFC-125 is obtained with high yields (up to 60-70% and over), high conversions (over 80%) and high selectivity, i.e. formation of by-product in very low amounts (5% by moles at most) Moreover, the catalyst maintains a high activity for a long time also with high organic charges.

Process for preparing pentafluoroethane

1,1,1,2-tetrafluoroethane (134a) is prepared by reacting, in the gas phase, trichloroethylene with 1,1,1-trifluorochloroethane (133a) and hydrofluoric acid with trichloroethylene/133a molar ratios ranging from 5/95 to 50/50, in the presence of a catalyst consisting of Cr.sub.2 O.sub.3 carried on AlF.sub.3. The process provides 134a yields higher than 90% and permits an exceptionally long life of the catalyst. In this way it is possible to realize a continuous process by recycling the unreacted trichloroethylene and 133a, thereby making up for the relatively low global conversion of the reagents.

Process for preparing 1,1,1,2-tetrafluoroethane

1,1,2-trifluoro-1,2-dichloroethane (Al23a) is isomerized to 1,1,1-tri-fluoro-2,2-dichloroethane (Al23) by contacting it with AlF.sub.3 at temperatures ranging from 180.degree. to 400.degree. C. Advantageously, it is operated with mixtures of Al23a with Al23 and/or other chlorofluorocarbons coming from the preparation of Al23 by hydrofluorination of perchloroethylene.

Process for isomerizing 1,1,2-trifluoro-1,2-dichloroethane to

1,1,1-trifluoro-2-fluoroethane (CFC 134a) is purified from 1,1-difluoro-2-chloroethylene (CFC 1122) by reacting a mixture comprising said compounds with hydrofluoric acid, at temperatures from 200.degree. C. to 450.degree. C., in one presence of chrome oxide (Cr.sub.2 O.sub.3) in substantially crystalline form.

Process for purifying 1,1,1-trifluoro-2-fluoroethane

1,1,1-trifluoro-2-fluoroethane (CFC 134a) is purified from 1,1-difluoro-2-chloroethylene (CFC 1122) by reacting a mixture comprising said compounds with hydrofluoric acid, at temperatures from 200.degree. C. to 450.degree. C., in the presence of chrome oxide (Cr.sub.2 O.sub.3) in substantially crystalline form.

The 1,1,2-trifluoro-1,2-dichloroethane content is reduced or removed from 1,1,1-trifluoro-2,2-dichloroethane by contacting a gaseous mixture comprising said compounds with chrome oxide (Cr.sub.2 O.sub.3) either as such or supported, at temperatures from 180.degree. to 400.degree. C.

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Padua, Italy

Antonio Masiero