Papers by Keyword: Catalysis

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Authors: Wan Li Yang, Zhong Qi Shi, Zhi Hao Jin, Guan Jun Qiao
Abstract: The three kind of oxides such as 3Y-ZrO2, Fe2O3 and MgO were used as catalyst in reaction bonded silicon nitride (RBSN) with low-purity silicon powder as raw materials. The oxides can strongly promoted the nitridation ratio of RBSN, and the catalysis effects of these oxides for RBSN were investigated. After 4h nitridation, the degree of nitridation increased from 43% to 96% by adding 10wt% of 3Y-ZrO2 additive comparing with the sample without additive, and the catalystic effects of Fe2O3 and MgO were slightly less than 3Y-ZrO2 additive. XRD patterns revealed that the main phases of the reaction products were α-Si3N4, β-Si3N4 and Si-N-O intermediation. SEM micrographs show that the hexagonal columnar β-Si3N4 separated from acicular α-Si3N4.
409
Authors: Wei Wang, Bo Yan, Jun Jiang, Guan Yu Yang
Abstract: p-Nitrobenzoic acid could be efficiently prepared from aerobic oxidation of p-nitrotoluene using manganese dioxide (MnO2) and N-hydroxyphthalimide (NHPI) as catalysts. The conditions of oxidation were also optimaized: 97 % conversion of p-nitrotoluene and 89 % isolated yield of p-nitrobenzoic acid could be obtained at 110 °C under 0.4 MPa for 4 h in presence of 10 mol% NHPI and 10 mol% MnO2.
317
Authors: Hua Nan Guan, Jia Ying Xin, Dan Dan Chen, Chao Ze Yan, Ying Xin Zhang, Chun Gu Xia
Abstract: The electrochemical behavior of catechol oxidation by H2O2 which catalyzed by the copper binding methanobactin in aqueous solutions had been studied using cyclic voltammetry with a glassy carbon electrode. The contribution described the production and purification of a novel copper-binding peptide, methanobactin from Methylosinus trichosporium 3011, among which the copper binding methanobactin exhibited efficient horseradish peroxidase-like catalytic activity. The determinations of mimetic peroxidase activity in human/rat blood, garlic, onion and scallion serve as models for the proposed method. A comparison of the results with established classical analysis is satisfactory.
462
Authors: Xiao Ya Jia, Jian Wei Zhao, Li Rong Qin, Cai Feng Yang
Abstract: We report a facile synthesis of PtNi nanosheets on the flexible ITO/PET substrate by electrochemical deposition method. The morphology and composition of the PtNi nanosheets were characterized and it was revealed that the PtNi nanosheets were polycrystalline with a thickness of about 4 nm. The average Ni content in the nanosheets was about 10 at%. The results of the electrochemical measurements showed that the PtNi nanosheets have excellent catalytic activity and stability toward the electro-oxidation of methanol in alkaline medium, which making it more attractive for fuel cell applications.
150
Authors: A. De Stefanis, Sabrina Foglia, A.A.G. Tomlinson
103
Authors: Zhong Xu Dai, Chang Liu, Xin Zhang, Jun Quan Jiang
Abstract: To promote the alcohol catalytic oxidation of Pd/C catalysts, it was implemented that the lanthanide Yb was introduced to the catalyst via the precipitation thermal decomposition and chemical reduction methods. The structure analysis and surface morphology of Pd-Yb/C catalysts were investigated by XRD and SEM. The ethanol electrocatalytic oxidation activity of in alkaline media was studied by cyclic voltammetry. The results show that the performance of ethanol catalytic oxidation on Pd-Yb/C electrode is better than that on the Pd/C electrode. The introduction of Yb can promote Pd/C catalytic oxidation alcohol and its poisoning tolerance ability.
583
Authors: M.A. Ribeiro, Laédna Souto Neiva, Ruth Herta Goldsmith Aliaga Kiminami, J.B.L. de Oliveira, L. Gama
Abstract: Because of the unique properties that the system TiO2-ZrO2 has, this system has attracted great interest in catalytic circles. In general, the TiO2-ZrO2 oxides composites have a greater surface area and a stronger acidity when compared to the single oxide and they are used as catalysts supports for many catalytic reactions. This work is to evaluate the effect of calcined temperature in structural and morphological characteristics of Ti1-xZrxO2 nanopowders obtained by Pechini method. For this study, the doping value was 0.25 moles of Zr. The powders were calcined at temperature of 500 to 900°C for one hour. The powders were characterized by XRD, SEM and BET. The X-ray diffraction showed that the powders present a TiO2 anatase phase and another of ZrO2 tetragonal. The crystallite size ranged from 4.8 to 14.6 nm for the temperature of 500 to 900°C, respectively. The analysis of scanning electron microscopy showed soft homogeneous agglomerates with particles around 100 nm. The main particles sizes by BET were ranged from 10 to 20 nm, showing that the synthesis is effective to obtain nanometric powders.
1393
Authors: Maroš Soldán, Karol Balog, Hana Kobetičová
Abstract: Many industries, such as paper, plastics, food, cosmetics, textile, etc., use dyes in order to colour their products. The presence of these dyes in water, even at very low concentrations, is highly visible and undesirable. Since some of these dyes are toxic in nature, their removal from the industrial effluents is a major environmental problem. The objective of this work is to verify the catalytic activity of waste from metal production namely waste from aluminium production red mud for removal of methylene blue. This waste is still dumped on dumping ground and may be a potential environmental problem.
99
Authors: Elvia Leal, Laédna Souto Neiva, Jean Pierre La Martini Lima Sousa, Fábio Argolo, Heloysa Martins Carvalho Andrade, Ana Cristina Figueiredo de Melo Costa, Lucianna Gama
Abstract: The aim of this work is to evaluate the catalytic activity of NiAl2O4 powders, prepared by combustion reaction with different glycine contents, for the steam reforming of methane. The NiAl2O4 powders were prepared according to the theory of propellants and explosives, using glycine reductant in stoichiometric ratio (Φe = 1) and in excess of 10% and 20% (Φe < 1). During the synthesis, parameters such as flame combustion temperature and time were measured. The samples were characterized by XRD, textural analysis by nitrogen adsorption (BET/BJH), TPR and evaluated as catalysts for the steam reforming of methane. The XRD results showed the presence of NiAl2O4 as major phase and traces of NiO and Ni in all the samples. The glycine content increase caused a decrease of crystallite size and an increase of surface area, from 29 to 39 m2/g. The TPR profiles showed reduction peaks of NiO species in weak interaction with the support, and reduction of nickel present in the NiAl2O4. It was observed that higher methane conversions were obtained in the presence of NiAl2O4 samples prepared using glycine excess. However, it was also observed a rapid deactivation of these catalysts due to high coke deposition onto the active surface phases.
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