Positive effect of NOx on the performances of VOx/TiO2-based catalysts in the total oxidation abatement of chlorobenzene

The influence of NO on the performances of VOx/TiO2, VOx-WOx/TiO2, and VOx-MoOx/TiO2 catalysts is investigated in the combustion of chlorobenzene. NO proves to induce an increase in the chlorobenzene conversion. However, this happens only if O2 is present and is maximized when the catalyst contains W or Mo. The suggested mechanism for the effect is: 1) NO is oxidized to NO2 mainly on WOx and MoOx; 2) afterward, NO2 assists O2 in the reoxidation step (as described by Mars-van Krevelen) of the VOx phase, thus speeding up the oxidation cycle, which macroscopically corresponds to the increase in chlorobenzene conversion.