Research progress on the performance and mechanism of H2-assisted HC-SCR denitration
Diesel engine exhaust is one of the sources of nitrogen oxides(NOx).Hydrocarbon(HC)selective catalytic reduction(HC-SCR)of nitrogen oxides is a common technique for NOx reduction.However,the NOx reduction activity of Ag-based oxide catalysts is not sufficiently high in low temperature region and the active temperature window is narrow.The addition of small amounts of hydrogen(H2)in HC-SCR reaction atmosphere can significantly increase the low-temperature denitrification activity and broaden the active temperature window of catalysts such as Ag/γ-Al2O3.Based on the background of lean-burn diesel engine exhaust denitration,the aim of this review is to summarize the effects of H2 on the types of active Ag species,the activation of hydrocarbons and oxygen,and the conversion of active nitrogen-containing intermediates.The role of H2 in improving the sulfur and water resistance of HC-SCR catalysts is summarized,and the application of new catalysts in H2-assisted HC-SCR(H2-HC-SCR)reaction in recent years is introduced as well.Relevant studies have shown that H2 promotes the formation of the active Ag species in HC-SCR and the activation of O2 into reactive oxygen species.H2 also accelerates the conversion of hydrocarbons into key intermediates such as isocyanate and enolic surface species and reduces the content of nitrate species which would poison the catalytic active sites.Blending H2 into the feed of the HC-SCR eventually improves the denitrification activity of HC-SCR.H2-assisted HC-SCR denitration technology is expected to play an important role in the denitration of motor vehicle exhaust,and to promote the development of HC-SCR of nitrogen oxides technology.
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维普
