Palladium-assisted electrodehalogenation of 1,1,2-trichloro-1,2,2-trifluoroethane on lead cathodes combined with hydrogen diffusion anodes

In this work, the efficiency and product formation in the electroreduction of 1,1,2-trichloro-1,2,2-trifluoroethane (CFC 113) to obtain completely dechlorinated products has been studied using constant-current electrolysis at different current densities, gas chromatography, scanning electron microscopy, arid energy dispersive x-ray. While chlorotrifluoroethene was the main product obtained from CFC 113 in MeOH-water solutions containing NH4Cl, different and suitable conditions which lead to its complete dechlorination are described in this paper. In the presence of Small amounts of Pd2+ in solution, a very thin film of Pd black was electrodeposited on the Pb cathode and the efficiency of the CFC 113 electroreduction was about 98%. The efficiency was much smaller and the product composition very different in the absence of Pd2+ in solution, even in the presence of Pd black electrodeposited on the cathode. In the presence of Pd2+, the main products in the gas phase were difluoroethene and trifluoroethene. Small amounts of 1,2-dichloro-1,1,2-trifluoroethane, chlorotrifluoroethene, difluoro ethane, and fluroethane were also present in the gas phase. The liquid composition was enriched in the less volatile compounds. A possible reaction pathway involving the removal of halides by successive reactions is discussed. The anode employed in these experiments was a thin Pd foil with electrodeposited Pd black, which permitted hydrogen diffusion and its further oxidation to H+. Because of this reaction, contamination of the working electrolyte by other oxidation products such as Cl-2, or MeOH derivatives were avoided. This system allows new electrosynthetic processes along with CFC electrodegradation.