Effect of Preparation Conditions of Zeolites Cu/ZSM-5 and Cu/Erionite on Their Catalytic Activity in Co Oxidation

The catalytic properties of Cu/ZSM-5 and Cu/erionite in the oxidation of carbon monoxide were studied. After treatment in a hydrogen stream, these copper zeolite catalysts displayed higher catalytic activity than prior to treatment. Variation of the catalytic properties of the systems obtained was attributed to differences in the state of the copper ions.     

Investigation by experiment and calculation of a supersonic stream adjacent to a wall in an accompanying supersonic flow

In well-known papers devoted to the investigation of supersonic streams adjacent to a wall, the authors, as a rule, restrict themselves to the case of a subsonic blast. In the present paper we determine the velocity field and the concentration field of an admixture of helium in a plane supersonic stream of air (M₁=2.18), propagating along a surface in an accompanying supersonic flow of air (M₂=2.7 and 3.8). In the boundary layer approximation a numerical calculation is made of the non-self-similar isobaric flow, using the equation for the turbulent viscosity [1] as the closing relationship. Results of the calculation are compared with experimental data.Moscow. Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 4, pp. 25–32, July–August, 1972.     

Estimation of the specific content and nature of sorption sites of iron(<Emphasis Type="SmallCaps">III</Emphasis>) and zirconium(<Emphasis Type="SmallCaps">IV</Emphasis>) oxyhydroxides

The sorption of anions H₂PO₄ ⁻, HPO₄ ²⁻, PO₄ ³⁻, [Fe(CN)₆]³⁻, and [Fe(CN)₆]⁴⁻ from aqueous solutions on the surface of Fe^III and Zr^IV oxyhydroxide hydrogels freshly precipitated at pH 4–13 was studied. The region of sorbate concentrations was from 0.00025 to 0.06 mol L⁻¹. The plots of the anion uptakes vs. their equilibrium concentrations are represented by isotherms of the first type, which are well described by the Langmuir equation if the quantity of the amount adsorbed is expressed as mol-site g⁻¹. The maximum uptakes and constants of the Langmuir equation were calculated. The phosphate anions occupy the same number of sorption sites on the sorbents precipitated at different pH. The average specific content of sorption sites for the ferro- and zirconogels in the metastability period is independent of the pH of their precipitation, being 3.1·10⁻³ and 3.2·10⁻³ mol-site g⁻¹, respectively. The [Fe(CN)₆]³⁻ and [Fe(CN)₆]⁴⁻ anions are sorbed only on the positively charged sites of the hydrogels and occupy not more than 2·10 mol-site g⁻¹ in the studied interval of pH of precipitation. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1736—1741, August, 2005.     

Comparison of the sorption properties of crystalline and amorphous samarium(III) oxohydroxides

The influence of the pH of precipitation (pH₁) and the ionic medium on the sorption properties of as-precipitated samarium(III) oxohydroxides,i.e., the pH of zero charge point and the rate of heterogeneous hydrolysis of the IrCl₆ ²⁻, RhCl₆ ³⁻, and PtCl₄ ²⁻ complexes, was studied. The composition of precipitates was studied by the drop titration of solutions of samarium nitrate and thermography. It was found that as-predipitated samarium oxohydroxides are amorphous and the substitution of NO₃ ⁻ ions by OH⁻ is not complete even at pH₁ 11. Heterogeneous hydrolysis occurs on the surface of samarium oxohydroxide, and its rate increases with increasing pH₁. The as-precipitated samarium oxohydroxides have much higher sorption activities than crystalline Sm₂O₃, and their activities are similar to those of ferrogels. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 583–588, April, 1998.     

Magnetic Susceptibility of Dilute La0.67Sr0.33MnO3-LaAlO3 Solid Solutions

Russian Journal of General Chemistry -     

Investigation of a compressible turbulent boundary layer in the presence of tangential blowing and a positive pressure gradient

The present study is devoted to the computational investigation of the compressible turbulent boundary layer and flow that are formed during tangential blowing of various gases in a thick boundary layer for large positive pressure gradients. Such flows occur in elements of the gas-dynamic channel of turbojet engines and liquid-fuel rocket engines, ejector pumps, and other technical devices. Using a numerical method we investigate the effect of various factors (the Mach number of blowing, the type of blown gas, and the intensity of variation of the pressure gradient) on the stability of the boundary layer up to its separation.     

Convergence near a point and the Arzela-Ascoli-type theorems

Theorems are proved giving necessary and sufficient conditions for the convergence of a sequence of continuous (differentiable) functions to a continuous (differentiable) function. The concepts of convergence near a point and equipotential convergence near a point are introduced. These concepts are introduced locally; on a segment, they are equivalent to the quasiuniform convergence and to the uniform convergence of a sequence of functions, respectively.Translated from Ukrainskii Matemahcheskii Zhurnal, Vol. 45, No. 8, pp. 1090–1095, August, 1993.