Effect of H2 on deNOx performance of HC-SCR over Ag/Al2O3: Morphological, chemical, and kinetic changes

The enhanced deNOx performance of the Ag/Al2O3 catalyst by addition of H2 was investigated for HC-SCR using a mixture of simulated diesel and ethanol as the reductant. As H2 concentration increased in the feed-gas stream, the low-temperature NOx reduction activity was remarkably enhanced. Addition of H2 promoted the oxidation of both NO and hydrocarbons, resulting in an increased formation of nitrates, enolic, and isocyanate species regarded as reaction intermediates. Results of the UV–vis indicated that H2 promoted the transformation of Ag+ to image and Ag0 on the surface of Ag/Al2O3 catalyst, while those of H2-TPR, O2-TPD, in situ FTIR, and TGA revealed the formation of highly mobile and reactive oxygen species under the (O2 + H2) flow. A reaction mechanism is proposed to elucidate the role of H2 in the enhancement of deNOx performance of HC-SCR in view of morphological, chemical, and kinetic changes of the Ag/Al2O3 catalytic system.