Formation of a nickel catalyst on the surface of aluminosilicate supports for the synthesis of catalytic fibrous carbon

Conditions for the homogeneous precipitation of nickel hydroxide in the presence of urea onto the surface of aluminosilicate honeycomb monoliths, which were prepared based on clay, talc, and amorphous aluminum hydroxide, were examined. Factors affecting the concentration of supported nickel (synthesis time, starting solution concentrations, loaded amount of the support, and support calcination temperature) were studied. The possibility of supporting nickel hydroxide onto the surface of cellular ceramic foam, glass foam, and haydite was demonstrated. The morphology of nickel hydroxide particles, nickel metal particles on support surfaces, and carbon coatings synthesized in the course of the catalytic pyrolysis of a propane-butane mixture was studied by scanning electron microscopy.     

Relationship between sulfur dioxide oxidation and selective catalytic NO reduction by ammonia on V2O5?TiO2 catalysts doped with WO3 and Nb2O5

The performance of V₂O₅–TiO₂ catalysts doped by WO₃ and Nb₂O₅ in sulfur dioxide oxidation, and in selective catalytic reduction (SCR) of NO by ammonia has been studied. Addition of tungsten and niobium oxides was found to suppresses sulfur dioxide oxidation thus increasing the catalysts resistance to SO₂ poisoning and their activity in SCR.     

Study of vanadium distribution in supported V?Mg catalysts by XPS and SIMS

The catalyst surface is occupied predominantly by mono- and bilayer vanadium oxide species, vanadium being mainly in the form of polylayer species that occupy a small part of the surface.

---

- , , .

     

Changes in the catalytic properties of a multicomponent molybdenum catalyst under vibro-fluidized catalyst bed conditions

Activation effect of oxidative dehydrogenation of butene-l on a multicomponent molybdenum catalyst at various temperatures has been studied by pulse and flow techniques. It is shown that under vibrofluidization not only reactive but also adsorption properties of the catalyst surface change. Oxygen consumption in the reaction process has been examined.

---

-1 . , , . .

     

Solid-state ionics in energy converters

Solid-state ionics, based on fast ionic transport in solids and characterized by anomalously large diffusion coefficients of ions at room temperature and unipolar conductivity (0.05–0.1 S cm^?1), assumed in the last few years great importance in the context of creation and subsequent explanation of mechanisms and kinetics of electrode processes during the work of chemical power sources (CPS). It is demonstrated that products of cathodic reactions possess ionic conduction in a solid phase.     

Surface Stabilization of Nano-sized Titanium Dioxide: Improving the Colloidal Stability and the Sintering Morphology

We have developed a simple surface modification technique to avoid irreversible agglomeration of titanium dioxide nanoparticles. The technique is based on hydrolysis-precipitation procedure, using TiOSO₄ as a precursor and water as a hydrolyser and a preparation medium. Diethylene glycol monomethyl ether is used as a surface modifier. Using a variety of characterization techniques, including XRD, SEM, TEM, TGA, DTA, AES, XPS, ELS and DLS, the resulting powders and the mechanism of surface stabilization were investigated. According to the proposed mechanism, hydroxyl-terminated ether molecules react with the surface of nanoparticles and then chemically adsorbed there. The layer of adsorbed molecules prevents the strong irreversible agglomeration during precipitation from the sol. The obtained anatase powder remains within the nanometric scale under heat-treatment up to 760 °C. The powders can be re-dispersed in water by ultrasound treatment, resulting in relatively stable aqueous dispersions. In addition, the morphology of sintered bodies made of these powders is significantly improved as compared to non-stabilized powders, due to less agglomeration in the initial sintering stage.     

Intrinsic ambipolarity and rotation in stellarators

It is shown that collisional plasma transport is intrinsically ambipolar only in quasiaxisymmetric or quasihelically symmetric magnetic configurations. Only in such fields can the plasma rotate freely, and then only in the direction of quasisymmetry. In a non-quasi-symmetric magnetic field, the average radial electric field is determined by parallel viscosity, which in turn is usually governed by collisional processes. Locally, the radial electric field may be affected by turbulent Reynolds stress producing zonal flows, but on a radial average taken over several ion gyroradii, it is determined by parallel viscosity, at least if the turbulence is electrostatic and obeys the conventional gyrokinetic orderings. This differs from the situation in a tokamak, where there is no flow damping by parallel viscosity in the symmetry direction and the turbulent Reynolds stress may affect the global radial electric field.     

Shock-wave compression of hydrogen isotopes condensed under megabar pressures

Experiments on shock wave compression of solid hydrogen (protium) up to 66 GPa and deuterium (in the initially liquid or solid phase) up to 123 GPa using spherical devices where a steel ball (impactor) is explosion-accelerated to 23 km/s are described. The experimental data are compared with those obtained by American researchers for liquid deuterium and protium, who used conventional explosives and light-gas guns as energy sources in the experiments carried out on the Z machine at Sandia National Labs, where an impactor was accelerated by an ultrahigh magnetic field, or on the NOVA laser at the Livermore National laboratory. Our data agree well with those derived by Sandia Labs.     

Selective Catalytic Oxidation of Methane to Syngas over Supported Mixed Oxides Containing Ni and Pt

The activity of Ni, Pt, and LaNiO₃ supported on -Al₂O₃ is studied in the selective catalytic oxidation of methane to syngas at 900°C and a contact time of 0.002 s using dilute mixtures (1000 ppm CH₄ + 500 ppm O₂ in He). The grain size was 100 m. The method of X-ray phase analysis shows that supported LaNiO₃, both pure and containing Pt, has a perovskite hexagonal structure with altered lattice parameters. Using temperature-programmed reduction by hydrogen, it was found that the reduction of supported LaNiO₃ is simplified in the presence of Pt and/or Ce_0.2Zr_0.8O₂. The activity and selectivity of the catalysts in the reaction of selective catalytic oxidation of methane depends on their composition and oxidative-reductive treatment. It was found that, in the presence of catalysts based on LaNiO₃ and containing Pt and/or Ce_0.2Zr_0.8O₂, the reaction occurs with an induction period. It was assumed that the value of the induction period depends both on the dynamics of phase LaNiO₃ reduction to Ni, which is associated with the accumulation of carbonate complexes and surface hydroxylation, and on slow changes in the defect structure of Ce_0.2Zr_0.8O₂, which are associated with oxidation-reduction.     

Influence of atomic vacancy ordering in the nonmetallic sublattice on the electronic structure of titanium hydride

We present a calculation of the electronic density of states in TiH_x alloys (x=2.0, 1.7, and 1.5) with various degrees of long-range atomic order, η, in the subsystem of hydrogen and vacancies in the nonstoichiometric hydrides. In comparing the calculated results with the features of the photoelectron spectrum of TiH_1.5 we find agreement for η=0.5. We determine the temperature range for the establishment of atomic vacancy order. Siberian V. D. Kuznetsov Physicotechnical Institute, Tomsk University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 7–14, October, 1998.