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

NO x storage-reduction (NSR) is a potential approach for the effective removal of NO x under the lean conditions in lean-burn engines. Herein, manganese-doped mixed oxides (Mn/MgAlO x) with high performance for low temperature NO x storage and release were derived from hydrotalcites precursors prepared by a facile coprecipitation method. The catalysts were characterized by X-ray diffraction (XRD), SEM, N 2 adsorption-desorption, H 2-TPR, FT-IR, and X-ray photoelectron spectroscopy (XPS) techniques. The Mn-doped MgAlO x catalysts exhibited high NO x storage capacity (NSC) at low temperature range (150–300 °C), which was related to their increased surface area, improved reducibility and higher surface Mn 3+ content. The largest NSC measured, 426 μmol/g, was observed for NO x adsorption at 200 °C on Mn15 catalyst (the sample containing 15 wt% of Mn). The in situ DRIFTS spectra of NO x adsorption proved that the Mn-doped hydrotalcite catalysts are preferred for low temperature NO x storage and release due to their ability to store NO x mainly in the form of thermally labile nitrites. NSR cycling tests revealed the NO x removal rate of Mn15 sample can reach above 70% within the wide temperature range of 150–250 °C. Besides, the influence of CO 2, soot, H 2O and SO 2 on NO x storage performance of Mn15 catalyst was also studied. In all, owning to their excellent NO x storage capacity, NSR cycling performance, and resistance to CO 2, soot, SO 2 and H 2O, the Mn-doped MgAlO x NSR catalysts have broad application prospects in NO x control at low temperatures. View Full-Tex