Comparison of MoO3 and WO3 on arsenic poisoning V2O5/TiO2 catalyst: DRIFTS and DFT study

The mechanisms of arsenic poisoning on MoO3- and WO3-doped V2O5/TiO2 catalysts are studied and the poisoning resistance effect of MoO3 are revealed. The arsenic at certain amount (above 10% of arsenic from XPS) decreases the surface area and the number of active sites where reduction takes place. From the results of DRIFTS and DFT, arsenic lowers the surface acidity by decreasing the quantity of Lewis acid sites and the stability of Bronsted acid sites. We also found newly formed As-OH groups of poisoned catalysts (at 1440 cm(-1)) have quite low activity at high temperature. MoO3 provides better activity on poisoned catalysts than WO3 does on V2O5/TiO2 catalysts. This may be due to the good dispersion of MoO3 on the support. The reactivity of surface W-O-W and W = O groups is considerably lower than the corresponding Mo-O-Mo and Mo = O groups from the OFT calculations models. This could be one of the explanations on the decrease of surface acidity of poisoned catalysts. (C) 2015 Elsevier B.V. All rights reserved.