BigPatents India

This invention provides an improved process for the preparation of 2,2-dichloro-1,1,1-trifluoroethane by catalytic hydrogenolysis of chlorofluorocarbons (CFC-113a) using a catalyst containing Pd/Pt and of at least one or more metals selected consisting of Cobalt, Copper, Iron, Ruthenium, Rhodium supported on carbon typically constitutes between 0.1 and 5 percent by wt. of the catalyst. Suitable hydrogenolysis catalyst may be prepared by treating carbon support with hydrochloric acid or nitric acid and then washed thoroughly with demineralised water to bring down the ash content. The present invention comprises I) preparation and activation of the catalyst II) hydro dehalogenation of chlorofluoro carbon (CFC-113a) to the formation of hydro chlorofluorocarbon (HCFC-123). The process is a continuous vapor phase reaction and typically achieved at atmospheric or super-atmospheric pressures. Generally, in order to provide substantial hydrodehalogenation to promote high product yields, the amount of hydrogen used is at least about one mole per mole of CFC-113a. The reaction is suitably carried out at a temperature, which depends to some extent on the formation of by-products. The desired temperatures are in the range 120 degree-160 degree C where by-products formation is minimum and higher selectivity towards HCFC-123 is achieved. The contact time of raw materials on the surface of the catalyst plays an important role in conversions and selectivity and is preferably between 30-70 sec. The exit product stream of the reactor is bubbled in demineralised water, dried over molecular sieves and cooled in condenser collected in receivers at-20 to 25 degree C