Review on the selective catalytic reduction of NO with H2 by using novel catalysts

Selective catalytic reduction is a common technology to control nitrogen oxides (NOx) in coal-fired industries, diesel engines, etc., among which, selective catalytic reduction of NOx by NH3 (NH3-SCR) has been commercially applied. However, its drawbacks such as the ammonia slipping, air heater fouling, catalyst poisoning, high investment and cost of operating have stimulated the development of new-type DeNOx technology. Nowadays, selective catalytic reduction with H2 (H2-SCR) has been regarded as a promising DeNOx technology. This review begins with the reaction mechanism of H2-SCR and then the noble metal SCR catalysts (Pt-based and Pd-based ones) and the non-noble metal catalysts for NOx removal are reviewed. Then, the effects of different preparation methods and different supports for H2-SCR performance are discussed. What follows is the homogeneous reactions of H2-SCR catalysts with O2, H2, H2O, SO2, CO, CO2, etc. And the recent progress of SCR mechanism by DFT calculations is summarized. Finally, the challenges and prospects for H2-SCR catalysts with the corresponding effective strategies are proposed. Hopefully, this article may provide insights into the gap between the newly developed H2-SCR catalysts and the practical demand in NOx removal, thus promoting their future commercial application.