Dehalogenation of 1,1,2-Trichloro-1-fluoroethane over α-Cr2O3 (101̄2)

The reaction of CFCl2CH2Cl over the stoichiometric Cr2O3 (101̄2) surface yields CFClCH2, HC⋮CH, and surface halogen. The 1,2-dihalo-elimination reaction to CFClCH2 is initiated via C−Cl bond cleavage at the CFCl2-end of the molecule to give a −CFClCH2Cl haloalkyl surface intermediate. A rate-limiting β-chlorine elimination from the surface alkyl gives rise to the CFClCH2 product. Acetylene is formed by the subsequent reaction of CFClCH2 in series. The chlorine liberated from CFCl2CH2Cl binds at the five-coordinate surface Cr3+ sites on the stoichiometric surface and shuts down the dehalogenation chemistry by site blocking. No carbon buildup is observed on deactivated surfaces, and no evidence is seen for the replacement of surface lattice oxygen by halogen under the conditions of this study. At elevated temperatures, the thermal removal of surface chlorine is observed, and it is attributed to migration into the sample bulk.