High Performance of Mn-Doped MgAlOx Mixed Oxides for Low Temperature NOx Storage and Release

Abstract

NOx storage-reduction (NSR) is a potential approach for the effective removal of NOx under the lean conditions in lean-burn engines. Herein, manganese-doped mixed oxides (Mn/MgAlOx) with high performance for low temperature NOx storage and release were derived from hydrotalcites precursors prepared by a facile coprecipitation method. The catalysts were characterized by X-ray diffraction (XRD), SEM, N2 adsorption-desorption, H2-TPR, FT-IR, and X-ray photoelectron spectroscopy (XPS) techniques. The Mn-doped MgAlOx catalysts exhibited high NOx storage capacity (NSC) at low temperature range (150–300 °C), which was related to their increased surface area, improved reducibility and higher surface Mn3+ content. The largest NSC measured, 426 μmol/g, was observed for NOx adsorption at 200 °C on Mn15 catalyst (the sample containing 15 wt% of Mn). The in situ DRIFTS spectra of NOx adsorption proved that the Mn-doped hydrotalcite catalysts are preferred for low temperature NOx storage and release due to their ability to store NOx mainly in the form of thermally labile nitrites. NSR cycling tests revealed the NOx removal rate of Mn15 sample can reach above 70% within the wide temperature range of 150–250 °C. Besides, the influence of CO2, soot, H2O and SO2 on NOx storage performance of Mn15 catalyst was also studied. In all, owning to their excellent NOx storage capacity, NSR cycling performance, and resistance to CO2, soot, SO2 and H2O, the Mn-doped MgAlOx NSR catalysts have broad application prospects in NOx control at low temperatures.

Exceptionally high and reversible NOx uptake by hollow Mn–Fe composite nanocubes derived from Prussian blue analogues

“…The Mn 1 Fe 2 -450 sample exhibited the best adsorption performance, in which Mn 3+ could contribute to NO x adsorption by oxidizing NO into NO 2 which is more easily to be adsorbed. 38–40…”

“…The Mn 1 Fe 2 -450 sample exhibited the best adsorption performance, in which Mn 3+ could contribute to NO x adsorption by oxidizing NO into NO 2 which is more easily to be adsorbed. [38][39][40] Two prominent peaks of Fe 2p 1/2 and Fe 2p 3/2 can be observed at 724.8 eV and 711.1 eV. The Fe 2p 3/2 spectrum was fitted to two characteristic peaks (Fig.…”

An Overview on the Catalytic Materials Proposed for the Simultaneous Removal of NOx and Soot

“…A series of Mn-doped MgAlO x was also prepared by Cui et al [30]. The catalysts exhibited high NO x storage capacity at low temperatures (150-300 • C), due to its greater surface area, improved reducibility and higher surface Mn 3+ content.…”

“…Additionally, the results suggested that the addition of Cu significantly increased the activity of catalysts; among the tested catalysts, Cu(3)MgAlO x sample calcined at 800 • C shows the best activity with T i = 260 • C and total amount of N 2 formed during the TPR run near 6.0 × 10 −5 mol, as evident in Figure 2. A series of Mn-doped MgAlOx was also prepared by Cui et al [30]. The catalysts exhibited high NOx storage capacity at low temperatures (150-300 °C), due to its greater surface area, improved reducibility and higher surface Mn 3+ content.…”

Editorial Catalysts: Catalysis for the Removal of Gas-Phase Pollutants

“…This system is based on the storage of the NO x as nitrates during the lean period and on the desorption and reduction in the NO x stored during the rich period. Cui et al [23] studied the performance of Mn-doped MgAlO x -mixed oxides for low-temperature NO x storage and release. The Mn-doped MgAlO x catalysts exhibited a high NO x storage capacity (NSC) at a low temperature range (150-300 • C), which was related to an increased surface area, an improved reducibility, and to the presence of surface Mn 3+ .…”