The role of acidity in the decomposition of 1,2-dichlorobenzene over TiO2-based V2O5/WO3 catalysts

The influence of Lewis and Brønsted acid sites on the performance of V2O5/TiO2 and V2O5–WO3/TiO2 catalysts in the total oxidation of o-dichlorobenzene was investigated. Catalytic activity of these materials resulted strongly affected by their acidic properties. The presence of Brønsted acid sites significantly increases the o-DCB conversion but also leads to the uncompleted degradation of chlorinated compounds, promoting the formation of partial oxidation products, as dichloromaleic anhydride. On the contrary, Lewis acid sites, acting as absorbing sites, promote the further oxidation of intermediates to CO and CO2, without any by-products desorption.Furthermore, the presence of water in the feed-stream was proven to decrease o-DCB conversion but also to play a positive role on process selectivity, increasing COx production. Plausible reasons for this effect are the reduction of Brønsted acid sites and the hydrolysis of anhydride during wet tests.

This study demonstrated that V2O5/TiO2 and V2O5–WO3/TiO2 catalysts are active for the total oxidation of o-dichlorobenzene and that the activity behaviour resembles the trend of Brønsted acidity, indicating that these sites are beneficial for o-DCB conversion. Nevertheless these materials lead, in some case, to the formation of partially oxidized compounds, in particular to o-dichloromaleic anhydride (DCMA). The production of this molecule resulted strongly affected by the acidic properties of the catalysts.Figure optionsDownload as PowerPoint slide