Deactivation and regeneration of a commercial SCR catalyst: Comparison with alkali metals and arsenic

Deactivation of alkali metals and arsenic and regeneration methods are studied on commercial V 2 O 5 –WO 3 /TiO 2 for the SCR reaction using experiments and DFT calculations. The poisoning of alkali metals is found to decrease the amount of Bronsted acid sites and the reducibility of active V 5+ sites. Arsenic decreases the amount of Lewis acid sites and the stability of Bronsted acid sites and increases N 2 O formation. After the catalysts are poisoned by both alkali metals and arsenic, the activity and N 2 selectivity are significantly suppressed. Diluted H 2 SO 4 effectively removes alkali metals from the poisoned catalysts. Half of the amount of arsenic can be removed using a 4% H 2 O 2 solution; however, some V 2 O 5 and surface sulfates are also eliminated from the catalysts. The activity of the regenerated catalysts is almost recovered at high temperatures. From the DFT results on the V 2 O 5 /TiO 2 (0 0 1) plane, potassium and arsenic significantly alter the electronic structures of the V orbitals and broaden the band gap of the models. Interactions between potassium and arsenic are also found. Potassium covers the active sites of the models that are constructed by V 2 O 5 and As 2 O 5 , which further decreases the number of acid sites. Potassium causes V and As orbitals to move to lower energies and inhibits the reactivity of the model.