Copper-Containing Mixed Metal Oxides (Al, Fe, Mn) for Application in Three-Way Catalysis

Abstract

Mixed oxides were synthesized by co-precipitation of a Cu source in combination with Al, Fe or Mn corresponding salts as precursors. The materials were calcined at 600 and 1000 °C in order to crystallize the phases and to mimic the reaction conditions of the catalytic application. At 600 °C a mixed spinel structure was only formed for the combination of Cu and Mn, while at 1000 °C all the materials showed mixed spinel formation. The catalysts were applied in three-way catalysis using a reactor with a gas mixture containing CO, NO and O2. All the materials calcined at 600 °C displayed the remarkable ability to oxidize CO with O2 but also to reduce NO with CO, while the pure oxides such as CuO and MnO2 were not able to. The high catalytic activity at 600 °C was attributed to small supported CuO particles present and imperfections in the spinel structure. Calcination at 1000 °C crystallized the structure further which led to a dramatic loss in catalytic activity, although CuAl2O4 and CuFe2O4 still converted some NO. The materials were characterized by X-ray diffraction (XRD), Raman spectroscopy, H2-Temperatrue Programmed Reduction (H2-TPR), N2-sorption and scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX).

Enabling Efficient Aerobic 5‐Hydroxymethylfurfural Oxidation to 2,5‐Furandicarboxylic Acid in Water by Interfacial Engineering Reinforced Cu−Mn Oxides Hollow Nanofiber

“…According to the reported reference, the vibration at 309 and 640 cm À 1 can be classified as Mn 2 O 3 , and the vibration at 430 and 580 cm À 1 is ascribed to the Cu 1.4 Mn 1.6 O 4 spinel phase. [13] The proportion of vibration peaks intensity in the Raman test is consistent with corresponding XRD results, that is, the higher calcination temperature easier causes the generation of Mn 2 O 3 phase in the composited catalyst. FTIR results (Figure S4) of CMO-500 reveal the lowfrequency region of 400-800 cm À 1 is mainly the lattice vibration of metal-oxygen (MÀ O).…”

One-Step Enameling and Sintering of Low-Carbon Steels

“…In the case of steel, spinels are formed on the interface. These spinels are typically formed at 1000 • C [65,66], but the presence of fluxes can reduce this temperature. Those spinels form in the interface, and the roughness of the substrate provided good enamel adhesion, as shown in Figures 13 and 14.…”

Solution Synthesis of Cubic Spinel Mn–Ni–Cu–O Thermistor Powder

“…In general, electrical conduction in spinel manganites occur through hopping mechanism between the Mn 3+ and Mn 4+ states at the B sites. In the case of Cu-doped nickel manganite, a solid-state charge transfer redox system exists that oxidizes Mn 3+ to Mn 4+ and reduces Cu 2+ to Cu + [39][40][41]. Further, the monovalent copper occupies the A sites, while bivalent copper occupies both A and B sites of the spinel [8,9].…”