Mechanism of the Selective Catalytic Reduction of Nitric Oxide by Ammonia Elucidated by in Situ On-Line 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 NO x 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 (Brønsted acid sites) and V=O species. A fundamental microkinetic model is proposed, which accounts for the observed industrial kinetics performance.