- Non-isothermal studies for the decomposition course of CdC 2O4-ZnC2O4 mixture in air
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The thermal decomposition of cadmium-zinc oxalate (1:1mol ratios) mixture in air was investigated by non-isothermal thermogravimetric analysis. Intermediates and the final products were characterized by X-ray diffraction and scanning electron microscopy techniques. TG showed that the mixture dehydrated in two steps and decomposed exothermically to CdO-ZnO mixture at 390°C in a further two steps. The observed increase in the intensity of the X-ray diffraction lines by raising the calcination temperature from 400 to 800°C is attributed to the grain growth of CdO-ZnO mixture as revealed from SEM experiments. The kinetics of the oxalate decomposition steps was performed using the various reaction interface models and differential techniques of computational analysis of non-isothermal data. The activation parameters, calculated using the integral composite method, showed that the reactions were best described by the random nucleation model characteristic of solid state nucleation growth mechanism. The results of activation parameters for the different decomposition steps are compared and discussed.
- Gabal
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- A simple and novel route for the preparation of ZnO nanorods
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Synthesis of zinc oxide (ZnO) nanorods was achieved by thermal decomposition of the precursor of ZnC2O4 obtained via chemical reaction between Zn(CH3COO)2·2H2O and H2C2O4·2H2O in the presence of surfactant nonyl phenyl ether (9)/(5) and NaCl flux. Transmission electron microscopy, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, selected area electron diffraction, and high-resolution transmission electron microscopy were used to characterize the structure features and chemical compositions of the as-made nanorods. The results showed that the as-prepared nanorods are composed of ZnO with diameter of 10-60 nm, and lengths ranging from 1 to 3 μm. The mechanism of formation of ZnO nanorods is also discussed.
- Xu, Congkang,Xu, Guoding,Liu, Yingkai,Wang, Guanghou
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- Synthesis, crystal structure, and properties of two zinc(II) complexes with 2-propyl-4,5-imidazoledicarboxylic acid
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A tetradentate 2-propyl-4,5-imidazoledicarboxylic acid [H3pimdc] reacts with zinc sulfate in the ethanol aqueous solution and zinc acetate in the N,N-dimethylformamide (DMF) aqueous solution to give two complexes [Zn(H 2pimdc)2(H2O)2]·4H 2O and [Zn(H2pimdc)2(H2O) 2]·2DMF. The complexes were characterized by X-ray single crystal analysis, thermal analysis, and IR spectrum. Because of the different coordination of water, complex 1 forms a fishing net-like latticed topology geometry via hydrogen bonds and π-π stacking interaction, but complex 2 forms a layer-like topology geometry via hydrogen bonds and π-π stacking interaction. Copyright Taylor & Francis Group, LLC.
- Luo, Zhirong,Zhuang, Jichang,Wu, Qiaolan,Yin, Xianhong,Zheng, Xiaoxia,Wei, Huan
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- Synthesis and thermal decomposition of new complexes of bipyridine isomers with zinc(II) and cadmium(II) oxalates
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The new mixed ligand complexes with the formulae Zn(2-bipy)(ox), Zn(4-bipy)1.5(ox)·H2O, Zn(2,4′-bipy)2(ox)·2H2O, Cd(2-bipy)(ox)·2H2O, Cd(4-bipy)2(ox) and Cd(2,4′-bipy)(ox)·2H2O (2-bipy, 4-b
- Czakis-Sulikowska,Malinowska,Markiewicz
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- Solar photocatalytic and self-cleaning performances of HoVO4 doped ZnO
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In this article we report preparation of 5 wt% HoVO4 doped ZnO via template-free hydrothermal process and investigated its photocatalytic activity against azo dyes Rhodamine-B (Rh-B), Trypan Blue (TB) and Acid Black 1 (AB 1) in solar light irradiation. Th
- Thirumalai, Kuppulingam,Shanthi, Manohar,Swaminathan, Meenakshisundaram
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- Easy and Green Route towards Nanostructured ZnO as an Active Sensing Material with Unexpected H2S Dosimeter-Type Behaviour
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Nanostructured ZnO particles were prepared through a straightforward, quick and low-temperature synthesis route involving coprecipitation of the metal precursor salts with oxalic acid, followed by hydrothermal treatment at 135 or 160 °C. The synthesised nanostructured powders were thoroughly characterised by a wide array of analytical techniques from the morphological (Scanning Electron Microscopy -SEM-, Transmission Electron Microscopy -TEM-, Energy-dispersive X-ray Spectroscopy -EDXS-), structural (Powder X-ray Diffraction -PXRD-, Selected Area Electron Diffraction -SAED-), compositional (X-ray Photoelectron Spectroscopy -XPS-) and physical (thermal stability) point of view. As far as functional applications are concerned, the powders were tested as gas sensor materials for H2S detection. Thereby these ZnO particles showed unexpected gas dosimeter behaviour at 150 °C. Based on these observations and on a comparison with literature a new model for the interaction of ZnO nanostructures with H2S is proposed.
- Diodati, Stefano,Hennemann, J?rg,Fresno, Fernando,Gialanella, Stefano,Dolcet, Paolo,Lavren?i? ?tangar, Ur?ka,Smarsly, Bernd M.,Gross, Silvia
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- Synthesis of ZnO nanoparticles for varistor application using Zn-substituted aerosol OT microemulsion
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This paper describes a new method for the synthesis of zinc oxide nanoparticles using ethanol-in-oil microemulsions with Zn-DEHSS (diethylhexyl sulfosuccinate) as surfactant. The zinc oxide nanoparticles find application in varistors and other functional devices. These particles have been characterized by X-ray diffraction, TEM, and BET surface area. Microemulsion droplets were characterized by quasi elastic light scattering (QELS). Varistors formed from doped zinc oxide nanoparticles finds application as low voltage surge devices with low leakage current and high coefficient of nonlinearity (α). In this paper, we have shown that the critical voltage of the varistor is related to the grain size which is related to size of ZnO particles. The smaller ZnO particles lead to larger grain size, thereby lowering the critical voltage.
- Singhal,Chhabra,Kang,Shah
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- Synthesis of zinc glycerolate microstacks from a ZnO nanorod sacrificial template
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We synthesized zinc glycerolate (ZnGly) microstacks by treating ZnO with glycerol at 100°C under reflux. We observed that the morphology of the ZnO source has a pronounced effect on the appearance of the ZnGly product. In the absence of structure-directin
- Remias, Robert,Kukovecz, Akos,Daranyi, Maria,Kozma, Gabor,Varga, Szilvia,Konya, Zoltan,Kiricsi, Imre
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- Photocatalytic degradation of methyl orange using ZnO nanopowders synthesized via thermal decomposition of oxalate precursor method
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ZnO nanoparticles were synthesized by thermal decomposition of oxalate precursor method. The nanopowders were characterized using powder X-ray diffraction technique and scanning electron microscopy and sample was found to have hexagonal wurtzite structure of ZnO. Average crystallite size of ZnO was found to be ~27 nm. The photocatalytic activity of ZnO was evaluated by using methyl orange (MO) as probe molecule. It was inferred from control experiments that presence of both ZnO and UV light is necessary for photodegradation. From photocatalytic experiment it was observed that MO is completely degraded in 80 min when the amount of catalyst is 1 g/L and initial concentration of MO is 0.03 mM. The effect of dye concentration, catalyst loading and solution pH on photodegradation rate was also investigated. It was found that optimal conditions for photodegradation of MO are 1 g/L catalyst at a solution pH 9. Photodegradation of MO was found to follow pseudo-first order kinetics. Langmuir-Hinshelwood model was also used to describe the photodegradation process.
- Kaur, Japinder,Bansal,Singhal, Sonal
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- Defect-enhanced photocatalytic activity of ZnO micro/nanostructures
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ZnO micro/nanocrystals with controlled oxygen defects are successfully prepared through annealing precursors obtained via a simple solvothermal method. The size and surface defects of the as-synthesized ZnO micro/nanocrystals increase with the solvent volume ratio of water/ethanol increasing; the BET surface areas of the corresponding samples decrease during these processes; photoluminescence reveals that the type and concentration of surface defects (oxygen vacancy and interstitial oxygen) are quite different for the samples prepared via different solvent volume ratio of water/ethanol. In addition, it is found that the photocatalytic activity of the synthesized ZnO nanocrystals is mainly dependent on the concentration of surface defects. The sample with more surface defects exhibits higher photocatalytic activity toward the degradation of methylene blue (MB). The possible photocatalytic mechanism is discussed in detail. Copyright
- Wang, Yu,Yan, Mei,Chen, Qinguo,Peng, Yin
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- Superficial sonication synthesis of a highly sunshine active metal modified ZnO photocatalyst and its multiple applications
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Hexagonal and spherical-like SrO/Ag/ZnO nanostructures have been successfully synthesized by a simple sonication method. The structure and composition of the samples were analyzed by XRD, FE-SEM, EDX, TEM, DRS, PL, XPS and BET surface area measurements. In this present work, the photocatalytic degradation of Trypan blue dye with prepared heterogeneous photocatalyst for SrO/Ag/ZnO under the natural sun light. The behavior of operational parameters such as pH, catalyst dosage, dye concentration and stability of the catalyst on photo mineralization of TB dye has been investigated. The Sr/Ag/ZnO stability was studied by its antiphotocorrosion property. The result shows that antiphotocorrosive property of SrO/Ag/ZnO is better than bare ZnO because of their reusability and photostability behavior. The antibacterial activity was also tested by SrO/Ag/ZnO, pure ZnO, and commercial ZnO. The mineralization of Trypan Blue dye has been confirmed by COD measurements.
- Dhatshanamurthi, P.,Jayamoorthy, K.,Sasikala, R.,Shanthi, M.,Subash, B.,Vijaya, P.
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- Photocatalytic oxidation of methane over CuO-decorated ZnO nanocatalysts
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Catalytic oxidation of methane under mild conditions remains a challenge in the industrial catalytic processes. Herein, we report a highly efficient CuO/ZnO nanocomposite photocatalyst for methane oxidation under ambient conditions. It was found that both the CH4 photooxidative activity and stability over ZnO are considerably improved by loading a tiny amount of CuO, though CuO itself exhibits no activity on methane oxidation. On the basis of the experimental results in conjunction with in situ electron paramagnetic resonance (EPR) and Fourier transform infrared spectroscopy (FTIR) studies, the photocatalytic reaction process of CH4 over CuO/ZnO composite microstructures is comprehensively discussed.
- Li, Zhonghua,Pan, Xiaoyang,Yi, Zhiguo
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p. 469 - 475
(2019/01/09)
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- Preparation method and application of zinc carbodiimide material
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The invention provides a preparation method of a zinc carbodiimide material. The method comprises the following steps: 1) uniformly mixing octan zinecnaty and oxalic acid, grinding, and drying to obtain a zinc oxalate precursor; 2) uniformly mixing the zinc oxalate precursor and melamine, grinding, calcining and cooling, and grinding again, thereby obtaining the needed zinc carbodiimide material.The invention further provides application of the zinc carbodiimide material serving as a photocatalyst in degradation of environmental pollutants and a method for degrading the environmental pollutants. According to the preparation method and application of the zinc carbodiimide material provided by the invention, the reactive raw materials are simple and readily available, the reaction conditions are mild and easy to control, the preparation yield is high, the preparation steps are simple and feasible, the production cost is low, and environmental pollution is avoided. The prepared zinc carbodiimide material is stable in structure, has high photocatalytic activity, is capable of effectively degrading or discoloring the environmental pollutants and has excellent popularization and application value.
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Paragraph 0040; 0041; 0046; 0047; 0051; 0052; 0056; 0057
(2018/11/22)
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- Very fast crystallisation of MFe2O4 spinel ferrites (M = Co, Mn, Ni, Zn) under low temperature hydrothermal conditions: A time-resolved structural investigation
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MFe2O4 spinel ferrites (M = Co, Mn, Ni, Zn) were synthesised through a low-temperature aqueous route combining co-precipitation of oxalates and hydrothermal treatment at 135 °C. With the objective of gaining a deeper understanding of the structural evolution of the compounds to crystalline materials during the synthetic process, samples were prepared within different reaction times, showing in most cases a fully crystalline habit already after short treatment times. The resulting solids were characterised through several state-of-the-art analytical techniques, both on the atomic (XAS) and mesoscopic (XRPD, SAXS) scales. In parallel, temperature-programmed characterisation was carried out to investigate the evolution of the compounds during the heating process.
- Dolcet, Paolo,Diodati, Stefano,Zorzi, Federico,Voepel, Pascal,Seitz, Christoph,Smarsly, Bernd M.,Mascotto, Simone,Nestola, Fabrizio,Gross, Silvia
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p. 2257 - 2268
(2018/05/29)
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- Graphene based nanoassembly for simultaneous detection and degradation of harmful organic contaminants from aqueous solution
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Graphene based nanoassemblies that can simultaneously detect and degrade harmful organic contaminants from water are important for conquering the risk of hazardous chemicals. A unique semiconductor-metal-graphene nanosheet assembly design has been successfully fabricated by a wet chemical method. Such a nanoassembly arrangement is made up of ZnO-Ag core-shell nanostructures and integrates on graphene nanosheets (GNSs). High-resolution scanning transmission electron microscopy reveals that ZnO-Ag core-shell nanostructures consist of a core ZnO nanosphere covered by a Ag shell and are chemically decorated on the GNS surface. This ZnO-Ag-GNS nanoassembly is SERS active and hence able to sense organic contaminants such as acridine orange dye. The sunlight-driven photocatalytic activity of the ZnO-Ag-GNS nanoassembly design demonstrates the tremendous enhancement in the detection and degradation of organic contaminants. The results in the present study show that the enhancement in the photocatalytic activity is attributed to the interfacial charge transfer effect in ZnO-Ag-GNS interfaces. This new design exhibits an efficient photocatalytic degradation of organic dye under sunlight irradiation. This could have great potential for a high sensing, stable and reusable material for energy and environmental cleaning applications.
- Rakkesh, R. Ajay,Durgalakshmi,Balakumar
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p. 34342 - 34349
(2016/05/09)
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- Preparation and thermal behaviour of divalent transition metal complexes of pyromellitic acid with hydrazine
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Hydrazine forms two different types of complexes with divalent metal ions and pyromellitic acid (H4pml) in aqueous medium: (i) hydrazinium complexes of formulae, (N2H5)2M(pml) ?xH2O, where x = 3 for M=Ni and x = 4 for M=Co or Zn, and (N2H5)2Mn(H2pml)2, at pH 4.5, (ii) neutral hydrazine complexes with formulae, M2(pml)(N 2H4) n ?xH2O where M=Co or Ni when n = 4 and x = 5 or 4 and M=Zn or Cd when n = 2, and x = 4 or 3 at pH 7, and M(H2pml)(N2H4)?xH2O where x = 4; M=Cu and x = 0; M=Hg, at pH 3, 7.5, respectively. All the complexes are insoluble in water, alcohol and ether. The N-N stretching frequency (990-1,007 cm-1 for coordinated hydrazinium ion and 956-985 cm-1 for bridged neutral hydrazine) indicates the nature of hydrazine present in the complexes. Simultaneously TG-DTA analysis indicates that hydrazinium complexes undergo dehydration and dehydrazination in a single step endothermally in the range of 289-300 °C whereas neutral hydrazine complexes undergo endothermic dehydration (~100 °C) followed by exothermic dehydrazination in the temperature range, 253-332 °C. The anhydrous metal carboxylates further decompose exothermally to leave the respective metal oxides or metal carbonates except zinc, which gives its oxalate as the end product. X-ray powder patterns indicate that even the complexes with the same formulation possess no isomorphism.
- Vairam,Premkumar,Govindarajan
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p. 979 - 985
(2011/01/10)
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- Subtle balance of steric and electronic effects for the synthesis of atactic polyketones catalyzed by Pd complexes with meta-substituted Aryl-BIAN ligands
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Both symmetric and nonsymmetric bis(aryl)acenaphthenequinonediimine ligands, featured by substituents in meta-positions of the aryl rings, have been applied for the first time as ancillary ligands for the palladium-catalyzed CO/vinyl arene copolymerizatio
- Scarel, Alessandro,Axet, M. Rosa,Amoroso, Francesco,Ragaini, Fabio,Elsevier, Cornelis J.,Holuigue, Alexandre,Carfagna, Carla,Mosca, Luca,Milani, Barbara
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p. 1486 - 1494
(2009/02/01)
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- Interaction of zinc, cadmium, and manganese oxalates with ammonia sulfur
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Interaction of zinc, cadmium, and manganese oxalates with molten sulfur has been investigated by a nonisothermal method. This interaction has been shown to be accompanied by the formation of zinc, cadmium, and manganese sulfide oxalates, which are mixed-anion compounds. The compositions of the sulfide oxalates have been determined. The activation energies have been determined for the reactions that lead to the formation of sulfide oxalates. Copyright
- Odin,Grin'ko,Safronov
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p. 990 - 991
(2008/10/09)
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- A comparative study of the thermal reactivities of some transition metal oxalates in selected atmospheres
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The nonisothermal, solid-state thermal decompositions of the oxalates of six divalent transition metals, were investigated in alternative flowing atmospheres. Derivative thermogravimetry and differential scanning calorimetry response peak maxima, provided a measure of reaction temperatures. It was found that in inert and reducing atmospheres, the decomposition temperature increased with rise in enthalpy of formation of the divalent transition metal oxide. The results show that the trends of reactivity changes with salt compositions, offer a complementary approach to that provided by the study of single salts.
- Mohamed, Mohamed A.,Galwey, Andrew K.,Halawy, Samih A.
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- Synthesis of Ar-BIAN ligands (Ar-BIAN = bis(aryl)acenaphthenequinonediimine) having strong electron-withdrawing substituents on the aryl rings and their relative coordination strength toward palladium(0) and-(II) complexes
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The synthesis of Ar-BIAN ligands (Ar-BIAN = bis(aryl)acenaphthenequinonediimine) having strong electron-withdrawing substituents on the aryl ring is reported. Most of these derivatives had escaped isolation in a pure form up to now. A quantitative scale of coordination strength of the newly synthesized ligands in the complexes Pd0(L)(DMFU) (DMFU = dimethylfumarate) and PdII(L)(OAc)2 has been measured. The series also includes some previously known Ar-BIAN ligands, phenanthroline, bipyridine, and Ph-DAB (Ph-DAB = diphenyldiazabutadiene). A good correlation is observed for the Ar-BIAN ligands between the Hammet σ constants of the substituents of the aryl group and the relative binding constant with respect to Ph-BIAN. The values for the p constant for the Pd(L)(DMFU) and Pd(L)(OAc)2 series are respectively -1.57 and -3.44, indicating that electron-rich ligands bind more strongly in both series, but the effect is much stronger in the Pd(II) series. The observed effect is relevant to the question of the effective oxidation state of palladium in the Pd(L)(DMFU) complex. Phenanthroline and bipyridine are stronger ligands than any Ar-BIAN compound, whereas Ph-DAB is the weakest ligand of all. The sterically hindered 2,6-Pr2iC6H6-BIAN binds less strongly than its basicity would suggest.
- Gasperini, Michela,Ragaini, Fabio,Cenini, Sergio
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p. 2950 - 2957
(2008/10/08)
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- Selective Production of Hydrogen by Partial Oxidation of Methanol over ZnO-Supported Palladium Catalysts
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Hydrogen production by partial oxidation of methanol (CH3OH + 1/2 O2 ? 2 H2 + CO2) was studied over zinc oxide-supported Pd catalysts. Catalyst performance was investigated as a function of the Pd loading and pretreatment in hydrogen environment under feed ratios O2/CH3OH (molar) of 0.3 and 0.5 at 503-543 K. High yields of hydrogen were obtained under integral operation regime. The hydrogen selectivity showed a strong dependence on the methanol conversion, which suggests that oxidation and reforming steps take place consecutively. Catalyst characterization by temperature-programmed reduction, X-ray diffraction, and X-ray photoelectron spectroscopy revealed that PdZn alloys can be formed upon reduction at moderate temperatures. A shift of +0.7 eV has been observed in the binding energy of Pd 3d5/2 core level spectrum of catalyst 1% Pd/ZnO prereduced at temperatures as low as 373 K and catalyst 5% Pd/ZnO reduced at 573 K and above. The relative ease with which PdZn alloy is formed in 1% Pd/ZnO catalyst is explained in terms of a stronger metal-metal oxide interactions of the smaller Pd particles. PdZn alloys were also detected by X-ray diffraction on the 2% Pd/ZnO catalyst after on-stream operation. Pretreatments of the catalysts in hydrogen at high temperatures led to sintering of metallic particles with the subsequent drop in methanol conversion.
- Cubeiro,Fierro
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p. 150 - 162
(2008/10/09)
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- CRYSTAL STRUCTURE OF THE ORDERED PHASE OF ZINC OXALATE AND THE STRUCTURE OF ANHYDROUS Fe2+, Co2+, Ni2+, Cu2+, AND Zn2+ OXALATES
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Conditions were found for the preparation of ordered phases of Fe2+, Co2+, Ni2+, and Zn2+ oxalates.The powder pattern was used to determine the structure of the ZnC2O4 phase using 62 reflections obtained with λCu Kα radiation and refinement by the full-matrix method of least squares to R = 0.12 (space group P21/n, Z = 2).This structure consist of cation-anion chains connected by Zn-O bonds in a three-dimensional framework.The zinc ion has octahedral coordination and the oxygen atoms differ in the number of their bonds with the cation, leading to inequality in the C-O bond lengths in the C2O42- anion (1.40 and 1.15 Angstroem).The unit cell parameters were found and refined for all the ordered phases.Indexing was carried out for the powder patterns of the disordered isostructural CuC2O4 phases with superpositional structure.
- Kondrashev, Yu. D.,Bogdanov, V. S.,Golubev, S. N.,Pron', G. F.
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