Low-temperature selective catalytic reduction of NO with NH3 using perovskite-type oxides as the novel catalysts

In order to investigate the activities of perovskite-type mixed oxides for selective catalytic reduction (SCR) of NO with NH3, a series of LaBO3 or La2BO4 perovskite-based catalysts with different B-site ions (B = Cu, Co, Mn, and Fe) was prepared by citrate complexation procedure and characterized by XRD, BET, TPD of NO + O2 and NH3. It was found that Mn-based perovskite exhibited the best catalytic activity, yielding 78% NO conversion at 250 °C. The NH3 adsorption ability of the perovskites is the key factor for the SCR performance. In situ DRIFTS investigation was further carried out over LaMnO3 to explore the reaction mechanism. It is revealed that the SCR reaction starts with NH3 chemical adsorption, being thought as the rate-determining step. The mechanism essentially involves a Langmuir–Hinshelwood mechanism mainly depending on an interaction between NH4+ ionic species and nitrite species in the low-temperature range.

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► LaMnO3 achieved an ideal performance for low-temperature NO-SCR by NH3.
► The ability of perovskites for NH3 adsorption plays a ruling role on NO reduction.
► The SCR reaction follows L–H mechanism involving nitrite and NH4+ species.