Catalytic oxidation of chlorophenol over V2O5/TiO2 catalysts

Catalytic and in situ Fourier Transform Infrared (FTIR) spectroscopic studies were conducted to investigate the adsorption and oxidation of o- and p-chlorophenol over a 3.6 wt.% V2O5/TiO2 catalyst. At a space velocity of approximately 53,000 cm3 g−1 h−1, this catalyst was found to be active for the oxidation of o- and p-chlorophenol at temperatures as low as 200 °C, yielding CO2 and HCl as the main products. Trace amounts of higher molecular weight products were also detected at the reactor outlet indicating the operation of additional condensation, coupling and chlorination/dechlorination side reactions in parallel to the main complete oxidation scheme. The in situ FTIR studies revealed that different phenols adsorb on the V2O5/TiO2 catalyst through their hydroxyl group. Furthermore, the formation of similar surface species (i.e., maleates, acetates, formates and an aldehyde-type species) was observed. The results were compared with those of previous studies on the oxidation of m-dichlorobenzene (m-DCB) and benzene and suggest that a similar reaction mechanism is operating in all cases, although the relative kinetic significance of the different steps varies with the presence and the position of the hydroxyl and chlorine groups on the aromatic ring.