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MnO 2 -Fe 2 O 3 catalysts were successfully deposited on the surface of polyphenylene sulfide (PPS) filter felt by a redox method, and the as-obtained catalytic filter material was tested in the low-temperature NH 3 -SCR. NO conversions in the 79.8–99.2% range at 140–180 °C and a gas hourly space velocity (GHSV) of 120,000 cm 3 g − 1 h − 1 were obtained, result which is attributed to the presence of amorphous MnO 2 and Fe 2 O 3 catalytic phases. The formation mechanism of the MnO 2 -Fe 2 O 3 catalyst decorated on the polyphenylene sulfide filter felt is discussed. [ABSTRACT FROM AUTHOR]

The four manganese oxides with different oxidation states (MnO, MnO 2 , Mn 2 O 3 , Mn 3 O 4) was synthesized using the hydrothermal method through adjusting process parameters and feedstock ratio, and their catalytic performances for the carbonylation of n-butylamine by CO 2 were also investigated. The results showed that the catalytic activities of manganese oxides with different oxidation states in the catalytic carbonylation of n-butylamine by CO 2 follow the order of MnO 2 > Mn 3 O 4 > Mn 2 O 3 > MnO, in which MnO 2 with the Mn4+ ion exhibited as high as 91.60% yield of N,N'-dibutylurea using polyethylene glycol 400 (PEG 400) as solvent under the reaction conditions of 160 ℃, 4 h, and 5.0 MPa. And then a series of characterization including XRD, XPS, H 2 -TPR, and CO 2 /NH 3 -TPD were performed on the as-synthesized manganese oxides with different oxidation states, indicating that the content of oxygen vacancy on the surface of the manganese oxides with different oxidation states plays a key role in catalytic performances of the carbonylation of n-butylamine with CO 2. [Display omitted] • N,N′-dibutylurea was synthesized by carbonylation of 1-butanamine by CO 2 over the manganese catalysts. • The four manganese oxides with different oxidation states (MnO, MnO 2 , Mn 2 O 3 , Mn 3 O 4) were synthesized by hydrothermal method. • The MnO 2 with the Mn4+ ion exhibited highly active, non-toxic, and easily recycled. • Its high activity is attributed to high concentration of surface oxygen vacancy. [ABSTRACT FROM AUTHOR]

In this article, a facile one-step strategy for the synthesis of ternary MnO 2 –Fe 2 O 3 –CeO 2 –Ce 2 O 3 /carbon nanotubes (CNT) catalysts was discussed. The as-prepared catalysts exhibited 73.6–99.4% NO conversion at 120–180 °C at a weight hourly space velocity (WHSV) of 210 000 ml·g cat − 1 ·h − 1 , which benefited from the formation of amorphous MnO 2 , Fe 2 O 3 , CeO 2 , and Ce 2 O 3 , as well as high Ce 3 + and surface oxygen (O ε ) contents. The mechanism of formation of MnO 2 –Fe 2 O 3 –CeO 2 –Ce 2 O 3 /CNT catalysts was also proposed. [ABSTRACT FROM AUTHOR]

Carbon nanotubes (CNTs) supported manganese oxide catalysts were prepared through different thermal treatment routes and used for low-temperature selective catalytic reduction of NO with NH3. The MnOx/CNTs catalyst prepared by calcined the precursor in air at 300°C showed lower NO conversions than that treated at 250°C, while it showed higher NO conversions than the one calcined in nitrogen. BET, TGA, XRD and H2-TPR results indicated that CNTs may impose effects on the oxidation state and redox ability of the manganese oxide and hence on the catalytic activity during the calcination process at given temperatures. [ABSTRACT FROM AUTHOR]

A ternary nanostructure, composed of graphite oxide (GO), MnO2 and poly[(2,5-di-phenyl-1,3,4-oxadiazole)-4-diylvinylene-alt-3,6-(N-butyl-carbazolenevinylene)] (POXA-CAR), is fabricated via a simple two-step method. The as-prepared composite is characterised by X-ray diffraction, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy and cyclic voltammetry. The specific capacitance of the composite electrode reached 310 F/g at a charging current of 2.5 mA, which is attributed to the synergistic effects from each component. GO has a large surface area and great mechanical properties. The conducting polymer provides electron transport path and partakes of the charge storage process. This Letter suggests that the ternary composite is a promising candidate for high-performance energy storage devices. [ABSTRACT FROM AUTHOR]

Manganese oxide octahedral molecular sieves (OMS-2) is a kind of excellent redox catalysts, a key challenge still remains to further increase their catalytic performance. Herein, we report a facile reduction method to enhance the catalytic activity of OMS-2 by producing more oxygen vacancy and creating an active interface between the main phase MnO 2 and the minor phase Mn 3 O 4 . Compared to the pristine OMS-2, the OMS-2 catalyst reduced in a relatively short time exhibits superior performance for dimethyl ether combustion with a starting-off temperature of 163 °C and a complete combustion temperature of 230 °C. Such enhanced activity can be ascribed to the higher reducibility, the more oxygen vacancy, and the active heterogeneous interface. These findings open up a new way to design highly efficient catalysts, especially the metal oxides-based catalysts, for redox reactions. [ABSTRACT FROM AUTHOR]

Abstract: The catalysts of transition metals (Fe, Co, Ni, Cu, Cr) doped cryptomelane-type manganese oxide (M-OMS-2) were prepared and investigated for the catalytic combustion of dimethyl ether (DME). The catalysts were characterized by XRD, FT-IR, BET, TEM, ICP-AES, XPS and H2-TPR techniques. The effects of surface area, the average oxidation state, and the redox properties on catalytic activities were studied. The results showed that 100% CO2 selectivity can be realized over the doped OMS-2 catalysts. The M-OMS-2 catalysts displayed the nanorod morphology with a 13nm diameter and the length ranging from 50 to 220nm. The Cu doped OMS-2 catalyst exhibited the best activity, achieving the light-off temperature (the temperature acquired for 10% DME conversion, T 10) and full-conversion temperature (the temperature acquired for 90% DME conversion, T 90) of 171 and 180°C, respectively. DME catalytic combustion over M- OMS-2 catalysts was found to follow a Mars–van-Krevelen mechanism with the presence of redox between Mn4+/Mn3+ and M m +/M( m −1)+ (M=Fe, Co, Ni, Cu, Cr). [Copyright &y& Elsevier]

Abstract: Manganese oxides with different crystalline structures, namely α-, β-, and γ-, were synthesized by a facile hydrothermal method and characterized by X-ray powder diffraction (XRD), surface area analyzer, scanning electron microscopy (SEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS) and hydrogen temperature-programmed reduction (H2-TPR) techniques. The dimethyl ether combustion was used as a probe reaction to explore the crystalline phase effect of the manganese oxides. The results revealed that α-MnO2 with nanorod shape possesses higher catalytic activity compared to the other two manganese oxides. Their different catalytic activities for dimethyl ether combustion have also been discussed in terms of surface areas, crystalline structures and oxygen mobilities. [Copyright &y& Elsevier]

Abstract: Cryptomelane-type manganese oxide (OMS-2) was rapidly prepared under ultrasonic irradiation in short time. Characterization results using X-ray powder diffraction (XRD), surface area analyzer, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), oxygen temperature-programmed desorption (O2-TPD) revealed that ultrasonic irradiation has tremendous effect on the surface area, morphology, surface defects, and redox properties of the OMS-2 materials. The OMS-2 prepared via ultrasonic irradiation shows nanoneedle morphology with smaller crystallite size, larger surface area (120.4m2/g), more surface defects, and higher oxygen mobility, thus it demonstrates excellent activity in the catalytic combustion of dimethyl ether with a start-off temperature of 160°C and a complete combustion temperature of 172°C. [Copyright &y& Elsevier]