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 p ollution. In the present study, it has been possible to identify the r eaction mechanism and the nature of the active sites in these catalyst s by combining transient or steady-state in situ (Fourier transform in frared spectroscopy) experiments directly with on-line activity studie s. The results suggest a catalytic cycle that consists of both acid an d 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.