MECHANISM OF THE SELECTIVE CATALYTIC REDUCTION OF NITRIC-OXIDE BY AMMONIA ELUCIDATED BY IN-SITU ONLINE FOURIER-TRANSFORM INFRARED-SPECTROSCOPY

The selective catalytic reduction reaction of nitric oxide by ammonia over vanadia-titania catalysts is one of the methods of removing NOx pollution. In the present study, it has been possible to identify the reaction mechanism and the nature of the active sites in these catalysts by combining transient or steady-state in situ (Fourier transform infrared spectroscopy) experiments directly with on-line activity studies. The results suggest a catalytic cycle that consists of both acid and redox reactions and involves both surface V-OH (Bronsted acid sites) and V=O species. A fundamental microkinetic model is proposed, which accounts for the observed industrial kinetics performance.