Mixed-Phase Oxide Catalyst Based on Mn-Mullite (Sm, Gd)Mn ₂ O ₅ for NO Oxidation in Diesel Exhaust

Abstract

Oxidation of nitric oxide (NO) for subsequent efficient reduction in selective catalytic reduction or lean NO(x) trap devices continues to be a challenge in diesel engines because of the low efficiency and high cost of the currently used platinum (Pt)-based catalysts. We show that mixed-phase oxide materials based on Mn-mullite (Sm, Gd)Mn(2)O(5) are an efficient substitute for the current commercial Pt-based catalysts. Under laboratory-simulated diesel exhaust conditions, this mixed-phase oxide material was superior to Pt in terms of cost, thermal durability, and catalytic activity for NO oxidation. This oxide material is active at temperatures as low as 120°C with conversion maxima of ~45% higher than that achieved with Pt. Density functional theory and diffuse reflectance infrared Fourier transform spectroscopy provide insights into the NO-to-NO(2) reaction mechanism on catalytically active Mn-Mn sites via the intermediate nitrate species.

K-supported catalysts for diesel soot combustion: Making a balance between activity and stability

“…On the other hand, the interaction of free active K + with K 2 Al 2 O 4 and Al 2 O 3 ( Table 1) was weaker than that with pure electro-negative oxides (MgO, CeO 2 or ZrO 2 ), which leads to a stronger bond of K + with O* and thus the mobility or reactivity of the O* species was reduced relative to that for K/MgO, K/CeO 2 and K/ZrO 2 [40]. The existence of active oxygen in K/Al 2 O 3 can also be confirmed by in situ IR of NO adsorption, in which NO is used as a probe molecule because NO can be efficiently stored on K + cation sites only after NO has been oxidized to NO 2 [46,47]. As shown in Fig.…”

Molten salt synthesis of mullite nanowhiskers using different silica sources

“…A study published recently [1] indicates that a synthetic analogue of mullite is an efficient substitute for commercial Pt-based catalysts used to reduce the amount of pollution generated by diesel engines. This finding will undoubtedly accelerate the development of the market for mullite compounds.…”

Highly dispersed Pd on macroporous SmMn2O5 mullite for low temperature oxidation of CO and C3H8

“…[20][21][22] In 2012, Wang et al proposed a new type of mixed-phase oxide catalyst for NO oxidation based on Mn mullite ((Sm, Gd)Mn 2 O 5 ), which has exhibited favorable thermal and structural stability. 23 Compared with the representative LaCoO 3 perovskite catalyst, the SmMn 2 O 5 mullite catalyst has higher TWC reactivity, anti-poisoning ability and OSC. 24 Hence, it is probable that mullite-supported Pd catalysts should display improved performance and serve as potential candidate as low precious metal loading catalysts.…”