Mechanism-dependent on the different CeO2 supports of phosphotungstic acid modification CeO2 catalysts for the selective catalytic reduction of NO with NH3

The mechanism of phosphotungstic acid modification CeO2 catalysts (P-WiCeO(2)) with different CeO2 supports were investigated by in situ diffuse reflectance infrared transform spectroscopy for the selective catalytic reduction of NO by NH3. The results indicated that the NH3-SCR reaction over P-WiCeO(2) followed both the Langmuir-Hinshelwood mechanism and the Eley-Rideal mechanism. The reaction between NH4+ and bidentate nitrate (NO3-) took place, and then the H2O, N-2 and adsorbed NO2 were formed. The coordinated NH3 species reacted with adsorbed NO2 and gaseous NO to generate N-2 and H2O The interaction between CeO2 and phosphotungstic acid contributed to the favored surface acidity (Lewis and Bronsted acid sites) and excellent redox property. The Bronsted acid sites facilitated the generation of NO2-adsorbed and Lewis acid sites accelerated the Eley-Rideal mechanism, while the NO oxidation to bidentate nitrate or NO2-adsorbed species was an important step in the reaction mechanism of P-WiCeO(2). (C) 2016 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.