Synthesis characterization and catalytic evaluation of Ni/ZrO<Subscript>2</Subscript>/SiO<Subscript>2</Subscript> aerogels catalysts

The Ni/ZrO₂/SiO₂ aerogels catalysts were synthesized via three different routes: (i) impregnation ZrO₂–SiO₂ composite aerogels with a aqueous solution of Ni(NO₃)₂, (ii) impregnation SiO₂ aerogels with a mixed aqueous solution of Ni(NO₃)₂ and ZrO(NO₃)₂ · 2H₂O, (iii) one-pot sol–gel procedure from precursors Ni(NO₃)₂/ZrO(NO₃)₂ · 2H₂O/Si(OC₂H₅)₄. These catalysts were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), ammonia temperature-programmed desorption (NH₃-TPD), N₂ adsorption–desorption isotherms and Fourier transform infrared (FT-IR). The Liquid-phase hydrogenation of maleic anhydride (MA) was performed over these catalysts. The results revealed that the different preparation routes result in a difference between the obtained samples, concerning the crystal structure and composition, surface acidity, mixed level of each component, texture, and catalytic selectivity.     

Binary ZrO<Subscript>2</Subscript>-SiO<Subscript>2</Subscript> xerogels: Synthesis and properties

Binary systems of silica and zirconia xerogels have been prepared by hydrolysis of zirconium(IV) oxychloride in the silica gel matrix. Systems of various composition have been studied by ¹H NMR, IR spectroscopy, and thermogravimetry and have been tested in a model process of hydrogen peroxide decomposition. It has been shown that the physicochemical properties of binary oxide systems can be tailored by varying the component ratio.     

Synthesis and characterization of ZrO<Subscript>2</Subscript> thin films

Physicochemical processes involved in the preparation of zirconia thin films by sol-gel technology from film-forming solutions (FFSs) on the basis of zirconium oxochloride and ethanol were studied. The phase composition, structure, and properties of the films were determined.     

Synthesis and characterization of ZrO<Subscript>2</Subscript>-Y<Subscript>2</Subscript>O<Subscript>3</Subscript> nanofilms

Processes involved in the preparation of zirconia and yttria thin films by sol-gel technology from film-forming solutions (FFSs) were studied over the entire range of concentrations. The physicochemical properties, composition, and structure of the films were studied.     

Influence of ZrO<Subscript>2</Subscript> on the physicochemical properties of the ZrO<Subscript>2</Subscript>-TiO<Subscript>2</Subscript> binary system

A series of ZrO₂-TiO₂ mixed oxides with different weight ratios (5, 20, and 30% ZrO₂) were prepared by wet impregnation of TiO₂-P25 Degussa with certain amounts of ZrO(NO₃)₂·6H₂O (Fluka) dissolved in deionised water. The samples were characterized by the XRD, , , , and BET methods. An increase in ZrO₂ content shifted the phase transition temperature (anatase into rutile) toward higher temperatures. X-ray diffraction using an Anton Paar XRK900 reactor chamber indicated that, in the case of samples containing ZrO₂, an additional diffraction peak appeared after cooling down to 25°C. This peak could be attributed to a polymorph of TiO₂ such as in the single crystal of anatase or hexagonal form of TiO₂ which appears in the presence of ZrO₂. Generally, the preparation of dioxide systems can modify the properties of pure compounds or generate new catalytic sites as a result of strong interaction between ZrO₂ and TiO₂ oxides. The binary systems exhibit advantages like strong acidity, extended specific surface area, and high thermal stability in comparison with TiO₂. The article is published in the original.     

Thermal stability and catalytic properties of the composite amorphous Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-nanocrystals ZrO<Subscript>2</Subscript>

Catalytic properties in relation to the hydrogen oxidation reaction and thermal stability of materials based on the nanocomposite amorphous Al₂O₃-nanocrystalline ZrO₂ were studied.     

Oxygen redistribution in ZrO<Subscript>2</Subscript>-Y<Subscript>2</Subscript>O<Subscript>3</Subscript> system

This work represents the results of oxygen redistribution studies at quantitative and isotopic levels in synthesis and thermal treatment of ZrO - (0 to 35 mol %) Y₂O₃ solid solution crystals. The crystals were grown by directed melt crystallization method in a cold container using direct high-frequency heating. The crystal oxygen content and isotopic composition data was collected with respect to stabilizer concentration and technological conditions of synthesis. The temperature and frequency relationships of crystal electroconductivity were also studied. Some strength and tribological characteristics of the given materials were represented. The solid state formation by directional melt crystallization was shown to involve oxygen isotopic exchange interaction between the melt, growing crystal, and gas phase.     

A kinetic analysis of thermal decomposition of polyaniline/ZrO<Subscript>2</Subscript> composite

Synthesis, characterization and thermal analysis of polyaniline (PANI)/ZrO₂ composite and PANI was reported in our early work. In this present, the kinetic analysis of decomposition process for these two materials was performed under non-isothermal conditions. The activation energies were calculated through Friedman and Ozawa-Flynn-Wall methods, and the possible kinetic model functions have been estimated through the multiple linear regression method. The results show that the kinetic models for the decomposition process of PANI/ZrO₂ composite and PANI are all D₃, and the corresponding function is ƒ(α)=1.5(1−α)^2/3[1−(1-α)^1/3]−1. The correlated kinetic parameters are E _a=112.7±9.2 kJ mol⁻¹, lnA=13.9 and E _a=81.8±5.6 kJ mol⁻¹, lnA=8.8 for PANI/ZrO₂ composite and PANI, respectively.     

Mechanism of methanol conversion on ZrO<Subscript>2</Subscript> and 5% Cu/ZrO<Subscript>2</Subscript> according to in situ IR spectroscopic data

It is demonstrated by in situ IR spectroscopy that, in methanol conversion on ZrO₂ and 5% Cu/ZrO₂ catalysts, methoxy groups are present on the catalyst surface, which result from O-H or C-O bond breaking in the methanol molecule. Two types of formate complexes, localized on ZrO₂ and CuO, are also observed. The formate complexes form via the oxidative conversion of the methoxy groups. There are two types of linear methoxy groups. First-type linear methoxy groups condense with the formate complex located on CuO to yield methyl formate and then CO and H₂. Second-type methoxy groups appear as intermediate products in the formation of dimethyl ether. The main hydrogen formation reactions are the recombination of hydrogen atoms (which result from the interconversion of surface complexes) on copper clusters and the decomposition of methyl formate. The source of CO₂ in the gas phase is the formate complex, and the source of CO is methyl formate. The effect of water vapor and oxygen the surface reactions and product formation is discussed.     

Yttria stabilized zirconia solid electrolyte surface modification with ZrO<Subscript>2</Subscript>, Y<Subscript>2</Subscript>O<Subscript>3</Subscript>, and ZrO<Subscript>2</Subscript> + 9 mol % Y<Subscript>2</Subscript>O<Subscript>3</Subscript> films

The surface of ceramic electrolyte ZrO₂ + 9 mol % Y₂O₃, hereinafter referred to as YSZ (abbreviated yttria stabilized zirconia), was modified with 0.1 to 0.2 μm oxide films of ZrO₂, Y₂O₃, and YSZ (same composition as substrate) by dip coating in alcohol solutions of the relevant salts and further annealing. The results of scanning electronic microscopy and X-ray diffraction evidence epitaxial film growth. By means of impedance spectroscopy at the temperatures of 500 to 600°C, the effect of YZS electrolyte surface modification with ZrO₂, Y₂O₃, and YSZ films to the polarization resistance of silver electrode was studied.     

Study and Thermodynamic Analysis of the ZrO<Subscript>2</Subscript>-SiO<Subscript>2</Subscript> System

The system ZrO₂-SiO₂ was additionally studied by means of differential thermal analysis. The temperatures of the solid-state decomposition of zircon and the coordinates of the eutectic point were refined. A thermodynamic calculation of the system in terms of the theory of subregular ionic solutions was carried out on the basis of the experimental data obtained.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 2, 2005, pp. 207–210.Original Russian Text Copyright © 2005 by Kamaev, Archugov, Mikhailov.     

Photocatalytic properties of mesoporous TiO<Subscript>2</Subscript>/ZrO<Subscript>2</Subscript> films in gas-phase oxidation of alcohols

We have used the sol-gel template synthesis method to obtain mesoporous zirconium-containing titanium dioxide films and have studied their structural and sorption characteristics, surface acid function, and photocatalytic activity during gas-phase oxidation of aliphatic alcohols. We have shown that the zirconium content changes the acidity and specific surface area of the films, determining the rate at which the studied processes occur and the relative yield of reaction products. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 41, No. 6, pp. 354–359, November–December, 2005.     

Synthesis,structure, and electric properties of oxygen-deficient perovskites Ba<Subscript>3</Subscript>In<Subscript>2</Subscript>ZrO<Subscript>8</Subscript> and Ba<Subscript>4</Subscript>In<Subscript>2</Subscript>Zr<Subscript>2</Subscript>O<Subscript>11</Subscript>

Perovskite phases Ba₃In₂ZrO₈ and Ba₄In₂Zr₂O₁₁ with the nominal concentration of structural oxygen vacancies 1/9 and 1/12, respectively, were synthesized by solid-phase and solution methods. X-ray diffraction showed cubic symmetry of both phases with the unit cell parameter a = 0.4193(2) and 0.4204(3) nm, respectively. The absence of superstructural lines resulted in the conclusion on statistical arrangement of oxygen vacancies. Thermogravimetry and mass spectrometry proved that both phases can reversibly absorb water from gas phase (pH₂O = 2 × 10⁻² atm) with observed correlation between the concentration of oxygen vacancies and amount of absorbed water. The total water amount was up to 0.9 mol per formula unit or, if recalculated for perovskite unit ABO₃, 0.3 and 0.23 mol H₂O, respectively. The temperature curves of coductivity in the atmosphere with various partial water vapor pressures (pH₂O = 3 × 10⁻⁵ and 2 × 10⁻² atm) showed significantly higher conductivity and lower activation energy (0.52 eV) in humid atmosphere due to proton transfer. The proton conductivity is up to 5 × 10⁻⁴ Ohm⁻¹ cm⁻¹ at 300°C for Ba₃In₂ZrO₈ specimen. IR spectrometry showed that protons in the structure exist primarily in OH-groups.     

ZrO<Subscript>2</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> binary oxides as promising supports for palladium catalysts of hydrodechlorination

Deposited palladium catalysts of the hydrodechlorination of 1,3,5-trichlorobenzene were studied. Pure zirconium and aluminum oxides and ZrO₂-Al₂O₃ mixtures with 1, 5, and 10 mol % Al₂O₃ prepared by coprecipitation were used as supports. Palladium was deposited by the precipitation of its hydroxide on supports. Catalysts on binary supports (ZrO₂ + 1% Al₂O₃ and ZrO₂ + 5% Al₂O₃) exhibited higher activity and stability in hydrodechlorination compared with catalysts on pure supports. The suggestion was made that the high activity and stability of these systems in hydrodechlorination was related to the formation of binary oxide in the interaction of ZrO₂ with palladium oxide at the stage of annealing of the catalyst precursor. Binary oxide, which was a center of the activation of the C-Cl bond, was simultaneously a source of active hydrogen. The presence of various palladium states in catalysts was substantiated by the temperature programmed reduction method.     

Oxygen redistribution during crystal growth of ZrO<Subscript>2</Subscript>-R<Subscript>2</Subscript>O<Subscript>3</Subscript> solid solutions

This paper presents the results of our experimental studies of quantitative redistribution and isotope fractionation of oxygen during the crystal growth of cubic solid solutions based on ZrO₂. The single crystals were grown by directional crystallization of a melt in a cold container. As stabilizing oxides, we used Y₂O₃, Gd₂O₃, and Yb₂O₃ in concentrations of 8–40 mol %. The results showed that the oxygen isotopic growth effects changed depending on the type and content of the stabilizer in the crystals of ZrO₂-R₂O₃ solid solutions.     

Thermal Decomposition of the System CO(NH<Subscript>2</Subscript>)<Subscript>2</Subscript>-H<Subscript>3</Subscript>PO<Subscript>4</Subscript> in the Presence of Nitrate Compounds

Chemical, derivatographic, IR spectral, and X-ray diffraction analyses were used to study thermal transformations in the system CO(NH₂)₂-H₃PO₄ and in the same system with addition of KNO₃, CsNO₃, LiNO₃ · 3H₂O, and NH₄NO₃ salts in the temperature range 20–600°C. The influence of the chosen nitrate compounds on the process of reorganization of the constituent ingredients, evolution of nitrogen into the gas phase, yield of the solid residue, and preservation of nitrogen and phosphorus was revealed.     

Sol-gel synthesis of mesoporous mixed oxides in the ZrO<Subscript>2</Subscript>-SiO<Subscript>2</Subscript> system

Simple and convenient method was proposed for synthesis of mixed oxides in the system ZrO₂-SiO₂ (10–60 mol% zirconium dioxide). Starting substances were tetraethylorthosilicate and zirconium chloride octahydrate. The surface properties of the synthesized samples were studied and the degree of their homogeneity and the strength of acid centers were determined.