Catalytic Activity Of MnO Research Articles

Removal efficiency and mechanism of bio-treated coking wastewater by catalytic ozonation using MnO<sub>2</sub> modified with anionic precursors

In this paper, MnO<sub>2</sub> catalyst were firstly prepared and modified by four kinds of anionic precursors (i.e., NO<sub>3</sub><sup>-</sup>, AC<sup>-</sup>, SO<sub>4</sub><sup>2-</sup> and Cl<sup>-</sup>) through redox precipitation method. After that, bio-treated coking wastewater (BTCW) was prepared and employed as targeted pollutants to investigate the catalytic ozonation performance of prepared-MnO<sub>2</sub> catalyst was investigated and characterized by the removal efficiencies and mechanism of the prepared bio-treated coking wastewater (BTCW), which was employed as the targeted pollutants. Specifically, the effects of specific surface area, crystal structure, valence state of Mn element and lattice oxygen content on catalytic activity of MnO<sub>2</sub> materials were characterized by BET, XRD and XPS, respectively. Results showed that COD of BTCW could be removed 47.39% under MnO<sub>2</sub>-NO<sub>3</sub><sup>-</sup> catalyst with 2 h reaction time, which was much higher than that of MnO<sub>2</sub>-AC<sup>-</sup> (3.94%), MnO<sub>2</sub>-SO<sub>4</sub><sup>2-</sup> (12.42%), MnO<sub>2</sub>-Cl<sup>-</sup> (12.94%) and pure O<sub>3</sub> without catalyst (21.51%), respectively. So, MnO<sub>2</sub>-NO<sub>3</sub><sup>-</sup> presented the highest catalytic performance among these catalysts. The reason may be attributed to a series of better physiochemical properties including the smaller average grain, the larger specific surface area and active groups, more crystal defect and oxygen vacancy, higher relative content of Mn<sup>3+</sup> and adsorbed oxygen (O<sub>ads</sub>) than that of another three catalysts.

Synthesis, Characterization and Catalytic Activity of Cu/Cu2O Nanoparticles Prepared in Aqueous Medium

Copper/Copper oxide (Cu/Cu2O) nanoparticles were synthesized by modified chemical reduction method in an aqueous medium using hydrazine as reducing agent and copper sulfate pentahydrate as precursor. The Cu/Cu2O nanoparticles were characterized by X-ray Diffraction (XRD), Energy Dispersive X-ray Fluorescence (EDXRF), Scanning Electron Microscope (SEM), and Transmission Electron Microscope (TEM). The analysis revealed the pattern of face-centered cubic (fcc) crystal structure of copper Cu metal and cubic cuprites structure for Cu2O. The SEM result showed monodispersed and agglomerated particles with two micron sizes of about 180 nm and 800 nm, respectively. The TEM result showed few single crystal particles of face-centered cubic structures with average particle size about 11-14 nm. The catalytic activity of Cu/Cu2O nanoparticles for the decomposition of hydrogen peroxide was investigated and compared with manganese oxide MnO2. The results showed that the second-order equation provides the best correlation for the catalytic decomposition of H2O2 on Cu/Cu2O. The catalytic activity of hydrogen peroxide by Cu/Cu2O is less than the catalytic activity of MnO2 due to the presence of copper metal Cu with cuprous oxide Cu2O. © 2015 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0)

Effect of the mechanical activation of a mixture of MnCO3 · mMn(OH)2 · nH2O and AlOOH as a stage of the preparation of a MnO x -Al2O3 catalyst on its phase composition and catalytic activity in CO oxidation

The effect of the mechanical activation of a mixture of MnCO3 · mMn(OH)2 · nH2O and AlOOH as a stage in the preparation of a MnO x -Al2O3 catalyst on the characteristics of the resulting samples was studied. It was found that the catalytic activity of MnO x -Al2O3 increased even after mechanical activation for 5 min. It was established that a decrease in the concentration of manganese hydroxocarbonate within the limits of the tested ratios between the components exerted the greatest positive effect of mechanical activation on catalytic activity. This was likely because the dispersion of this compound increased and interactions between the components strengthened in the course of mechanical activation. This was evidenced by a considerable increase in the amount of the α-Al2O3 phase relative to δ-Al2O3 in the catalyst calcined at 950°C. According to the results of temperature-programmed reduction with hydrogen, the formation of a larger number of catalytically active, fine MnO x particles after high-temperature heat treatment was responsible for the strengthening of interactions between the initial components upon mechanical activation. Transmission electron-microscopic data also indicated an increase in the dispersity of manganese oxide particles with the use of mechanical activation as a stage of the preparation of the MnO x -Al2O3 catalyst.

Catalytic activity of MnOx/WO3 nanoparticles: synthesis, structure characterization and oxidative degradation of methylene blue

MnOx/WO3 nanoparticles were found to be an effective catalyst for the degradation of methylene blue, an important industrial dye and a problematic pollutant.

Enhancing Electrocatalytic Oxygen Reduction on MnO2 with Vacancies

Oxygen-vacant nanocrystalline MnO(2) has been prepared by the simple process of annealing pristine oxide in Ar or O(2) . Both experimental and computational studies indicate that the catalytic activity of MnO(2) towards oxygen reduction is enhanced by introducing a modest concentration of oxygen vacancies.

MnO x/Al 2O 3/Ce 0.45Zr 0.45M 0.10O y (M = Mn, Y, La) catalysts used for ethanol catalytic combustion

MnO x /Al 2O 3/Ce 0.45Zr 0.45M 0.10O y (M = Mn, Y, La) catalysts were prepared by impregnation method and characterized by BET, TPR and XRD analyses. The catalytic activities toward ethanol combustion were investigated in a microreactor. The results demonstrated that the catalytic activity of MnO x /Al 2O 3/Ce 0.50Zr 0.50O 2 monolithic catalyst could be improved by doping Mn, Y and La into Ce 0.50Zr 0.50O 2. When doping Y into Ce 0.50Zr 0.50O 2, the catalyst MnO x /Al 2O 3/Ce 0.45Zr 0.45Y 0.10O 1.95 showed the highest activity. The 100% conversion temperature of ethanol was 230 °C. Furthermore, once the conversion of ethanol started, the complete conversion was quickly achieved. The doping of Mn, Y and La led to better activity for ethanol combustion and lower temperature reduction peaks in TPR profiles. The doping of Mn resulted in enhanced oxygen storage capacity (OSC), larger area of the reduction peaks, and excellent reactivity, and the doping of Y resulted in the lowest reduction temperature and the best activity.

Effect of metal doping into Ce 0.5Zr 0.5O 2 on catalytic activity of MnO x/Ce 0.5– xZr 0.5– xM 0.2 xO y/Al 2O 3 for benzene combustion

The research investigated the effect of doping two metals separately or together into Ce 0.5Zr 0.5O 2 on the catalytic activity of MnO x /Ce 0.5– x Zr 0.5– x M 0.2 x O y /Al 2O 3 (M=Y, Mn, Y and Mn) for catalytic combustion of benzene. The prepared catalysts were characterized by X-ray diffraction (XRD), surface area analysis, oxygen storage capacity (OSC), and H 2-temperature programmed reduction (H 2-TPR). Catalytic test was performed on a conventional fixed bed flow reactor. The characterization results revealed that Y and Mn ions entered into the ceria-zirconia mixed oxides framework, which improved the textural properties and greatly promoted the MnO x dispersion on the support surface. The complete conversion temperature of benzene on MnO x /Ce 0.4Zr 0.4Y 0.1Mn 0.1O y /Al 2O 3 was 563 K, and the selectivity of carbon dioxides was 99%. This catalyst could be applied in a wide range of GHSV and wide concentration condition, showing great potential for application.

Promoting effect of copper on the catalytic activity of MnOx–CeO2 mixed oxide for complete oxidation of benzene

Abstract The promoting effect of copper on the catalytic activity of MnO x –CeO 2 for complete oxidation of benzene was investigated. The results showed that the addition of copper could significantly improve the catalytic activity of the mixed oxide and the complete conversion of benzene was achieved at 523 K. Structural analysis by X-ray powder diffraction (XRD) and H 2 -temperature-programmed reduction (H 2 -TPR) measurements indicated that the copper species was highly dispersed on the surface of the mixed oxide, which greatly promoted the redox properties of the catalyst leading to the at low temperatures. X-ray photoelectron spectra (XPS) and FTIR characterizations of the Cu/MnO x –CeO 2 catalyst further revealed that the addition of copper significantly increased the generation of surface O β species and also created more active sites for benzene adsorption.

Effect of Metal Oxide Doping into Ce 0.5Zr 0.5O 2 on Catalytic Activity of MnO x/γ-Al 2O 3/Ce 0.45Zr 0.45M 0.1O x (M = Y, La, Mn) Honeycomb Catalysts

This article showed that the catalytic activity of MnO x /γ-Al 2O 3/Ce 0.5Zr 0.5O 2 monolithic catalyst toward the catalytic combustion of ethanol in a fixed bed reactor could be greatly improved by doping three metal oxides into Ce 0.5Zr 0.5O 2. The catalytic activity of MnO x /γ-Al 2O 3/Ce 0.45Zr 0.45M 0.1O x (M = Y, La, Mn) is better than that of Mn O x /γ-Al 2O 2/Ce 0.5Zr 0.5O 2. The order of activity of the catalysts is as follows: MnO x /γ-Al 2O 3/Ce 0.45Zr 0.45Y 0.1O x > MnO x /γ-Al 2O 3/Ce 0.45Zr 0.45La 0.1O x > MnO x /γ-Al 2O 3/Ce 0.45Zr 0.45Mn 0.1O x > MnO x /γ-Al 2O 3/Ce 0.5Zr 0.5O 2. The influence of the loading amount of manganese oxide in enhancing the catalytic activity of MnO x /γ-Al 2O 3/Ce 0.45Y 0.1O x was investigated. The results showed that when MnO 2 loading amount was 10% (mass fraction), the MnO x /Al 2O 3/Ce 0.45Zr 0.45Y 0.1O x catalyst recorded the highest activity.

Inorganic models of photosystem II of plant photosynthesis. Catalytic and photocatalytic oxidation of water with participation of manganese compounds

Manganese dioxide is shown to be the catalyst of oxygen evolution at the oxidation of water by the one-electron oxidant Ru(bpy) 3 3+ in neutral and slightly acidic media. Catalytic activity of MnO 2 depends on the method of preparation, the most active samples being those consisting of the smallest particles, i.e., having the largest surface-to-volume ratio. Ru(bpy) 3 3+ was found to be formed at the irradiation of Ru(bpy) 3 2+ solutions by visible light (λ = 436 nm) in the presence of such acceptors as Ce(IV), Hg(II), and Mn(IV) pyrophosphate. Continuous O 2 evolution from water is observed when the system Mn(IV) pyrophosphate plus Ru(bpy) 3 2+ plus MnO 2 is irradiated by visible light. The system is discussed in connection with the active center of photosystem II of plant photosynthesis.

Physicochemical properties of MnO 2 and MnO 2CuO and their relationship with the catalytic activity for H 2O 2 decomposition and CO oxidation

The catalytic activity of MnO 2 prepared by different methods has been determined from the initial rate of decomposition of H 2O 2 and the conversion of CO to CO 2. The activity is correlated with various physicochemical properties such as active oxygen, surface excess oxygen, surface OH groups, crystalline modifications, lattice parameters, and thermal decomposition data. Some of the above properties are interrelated. Experimental evidence shows that the presence of Mn 3+ as MnOOH in the MnO 2 lattice is mainly responsible for the origin of catalytic activity in nonstoichiometric manganese dioxide where electron transfer between Mn 4+ and Mn 3+ ions can take place. The loss of strongly bound compositional water creates lattice defects which are also responsible for the increase in the catalytic activity. The reason for the promoting effect of CuO in MnO 2-CuO catalysts has been discussed in the light of the formation of “surface CuMn 2O 4” through the exchange of Cu 2+ on the hydrated manganese oxide surface.