Selective Catalytic Reduction of NO_x over Perovskite-Based Catalysts Using C_xH_y(O_z), H₂ and CO as Reducing Agents—A Review of the Latest Developments

Abstract

Selective catalytic reduction (SCR) is probably the most widespread process for limiting NOx emissions under lean conditions (O2 excess) and, in addition to the currently used NH3 or urea as a reducing agent, many other alternative reductants could be more promising, such as CxHy/CxHyOz, H2 and CO. Different catalysts have been used thus far for NOx abatement from mobile (automotive) and stationary (fossil fuel combustion plants) sources, however, perovskites demand considerable attention, partly due to their versatility to combine and incorporate various chemical elements in their lattice that favor deNOx catalysis. In this work, the CxHy/CxHyOz−, H2−, and CO-SCR of NOx on perovskite-based catalysts is reviewed, with particular emphasis on the role of the reducing agent nature and perovskite composition. An effort has also been made to further discuss the correlation between the physicochemical properties of the perovskite-based catalysts and their deNOx activity. Proposed kinetic models are presented as well, that delve deeper into deNOx mechanisms over perovskite-based catalysts and potentially pave the way for further improving their deNOx efficiency.

Keywords

• NO_x
• perovskites
• CO-SCR
• H₂-SCR
• hydrocarbon-SCR