Low-Temperature Selective Catalytic Reduction of NO_x with NH₃ over Novel Mn–Zr Mixed Oxide Catalysts

Abstract

Novel Mn−Zr mixed oxide catalysts have been prepared by the citric acid method for the low-temperature selective catalytic reduction (SCR) of NO x with ammonia in the presence of excess oxygen. They have been characterized by a series of techniques, specifically N 2 adsorption−desorption, X-ray diffraction (XRD), temperature programmed reduction (TPR), temperature programmed desorption (TPD), and X-ray photoelectron spectroscopy (XPS). It was found that an Mn(0.5)− ZrO x -450 (Mn/(Mn + Zr) mole ratio of 0.5) catalyst showed the highest activity, giving 100% NO x conversion at 100 °C with a space velocity of 30 000 h −1 . XRD results suggested that an Mn−Zr solid solution was formed in the Mn(0.5)−ZrO x -450 catalyst, with highly dispersed MnO x . TPR data indicated a strong interaction between the zirconium oxide and manganese oxide, which improved the reduction ability of the MnO x . The TPD results indicated that an appropriate NH 3 adsorption ability was beneficial for the low-temperature SCR. The catalyst showed a certain level of sulfur tolerance and water resistance. The effect of H 2 O could be quickly eliminated after its removal, whereas deactivation by SO 2 proved to be irreversible.

Hydrogenation of biomass-derived compounds containing a carbonyl group over a copper-based nanocatalyst: Insight into the origin and influence of surface oxygen vacancies

“…S9 in Supporting Information shows the spin-orbit splitting of Mn2p 1/2 and Mn2p 3/2 signals for calcined samples. The asymmetric and broad Mn2p 3/2 peak may be deconvoluted into two symmetry peaks centered at about 640.5 and 642.4 eV, which are assigned to Mn 2+ and Mn 3+ species, respectively [63]. Most of the Mn is present in the form of Mn 3+ species, and only a small amount of Mn 2+ species can be found in calcined samples.…”

ZrMn Oxides for Aqueous‐Phase Ketonization of Acetic Acid: Effect of Crystal and Porosity

“…Sharp peaks are observed for ZrMn-COM-750-4, andanew phase of hausmannite Mn 3 O 4 (ICDD PDF No. [10] It is interesting that the crystallite sizes of ZrMn-COMc atalysts increase with temperature when oxidized fort he same time, but decreasew ith oxidation time at the same temperature,a s shown in Ta ble 1. Peak positions of different catalysts have no significant differences with each other,b ut are larger than that of Zr-COM-350-4 ( Figure S1 and Ta bleS1i nt he Supporting Information).…”

Enhanced Oxygen Vacancies in a Two-Dimensional MnAl-Layered Double Oxide Prepared via Flash Nanoprecipitation Offers High Selective Catalytic Reduction of NOx with NH3

“…There are many choices of supports for Mn-based catalysts at low temperature, including Mn/zeolite [5]. Mn/activated carbon [6,7], Mn/TiO 2 [8,9], Mn/Al 2 O 3 [10], Mn/ZrO 2 [11], and Mn/Vermiculite (VMT) [12]. In general, a suitable catalyst carrier should have unique properties, including strong surface acids, a high specific surface area, high thermal stability, and strong mechanical strength [13].…”