Catalytic oxidation of chlorinated benzenes over V 2O 5/TiO 2 catalysts

Abstract

Kinetic and in situ infrared spectroscopic studies were conducted to investigate the oxidation of different chlorinated benzenes (i.e., chlorobenzene, 1,2- 1,3-, and 1,4-dichlorobenzene) over V 2O 5/TiO 2 catalysts. The oxidation of cyclohexyl chloride and that of benzene were also examined for comparison. Observed differences in the reaction rates and activation energies can be correlated to the structural differences of these compounds, in light of a common reaction mechanism. This mechanism is supported by the results of in situ FTIR studies, which indicate the presence of similar surface intermediates on the catalyst surface under reaction conditions for all the aromatic compounds examined. The results further suggest that the following two are the important mechanistic steps in the oxidation of chlorinated benzenes: (1) the adsorption of the aromatic compound on the catalyst via a nucleophilic attack on the chlorine position in the aromatic ring and (2) the subsequent oxidation of the remaining aromatic ring.