Palladium‐Assisted Electrodehalogenation of 1,1,2‐Trichloro‐1,2,2‐trifluoroethane on Lead Cathodes Combined with Hydrogen Diffusion Anodes

Abstract

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, and energy dispersive x‐ray. While chlorotrifluoroethene was the main product obtained from CFC 113 in MeOH‐water solutions containing , different and suitable conditions which lead to its complete dechlorination are described in this paper. In the presence of small amounts of 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 in solution, even in the presence of Pd black electrodeposited on the cathode. In the presence of , the main products in the gas phase were difluoroethene and trifluoroethene. Small amounts of 1,2‐dichloro‐1,1,2‐trifluoroethane, chlorotrifluoroethene, difluoroethane, 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 . Because of this reaction, contamination of the working‐electrolyte by other oxidation products such as or MeOH derivatives were avoided. This system allows new electrosynthetic processes along with CFC electrodegradation.