High-Selective Catalyst Based on Intermetallic Rh1In1 Particles for Nitrobenzene Hydrogenation

Kinetics and Catalysis - The catalytic performance of a bimetallic RhIn/SiO2 catalyst was studied in the liquid-phase hydrogenation of nitrobenzene. The formation of intermetallic Rh1In1...     

Manganese Catalysts for the Ozone-Assisted Oxidation of Volatile Organic Compounds: Effect of the Mn3+/Mn4+ Active Site Ratio on Catalytic Properties

Kinetics and Catalysis - The catalytic properties of supported Mn/carrier catalysts (carriers: Al2O3, SiO2, SiO2–Al2O3) in the ozone-assisted oxidation of volatile organic compounds (using...     

Photocatalytic removal of nitrogen oxides from air on TiO<Subscript>2</Subscript> modified with bases and platinum

The efficiency of TiO₂ (Degussa P-25) modified with an alkaline admixture (urea, BaO), sulfuric acid, or platinum in the photocatalytic oxidation of NO (50 ppm) with a flowing 7% O₂ + N₂ mixture under UV irradiation in a flow reactor at room temperature and atmospheric pressure is reported. Because of the progressive blocking of active sites of the photocatalyst by the reaction products (NO₂, NO₃⁻), it is impossible to realize prolonged continuous removal of NO _x (NO + NO₂) from air without catalyst regeneration at elevated temperatures. The efficiency of the photocatalysts is characterized by specific photoadsorption capacity (SPC) calculated from the total amount of NO _x adsorbed during 2-h-long irradiation. Modification of TiO₂ with 5% BaO or 5% urea raises the SPC of the catalyst by a factor of 2–3. Presumably, this promoting effect is due to the basic properties of these dopants, which readily sorb NO₂ and NO₃⁻. A considerable favorable effect on SPC is also attained by adding 0.5% Pt to (5% BaO)/TiO₂. The SPC of the (0.5% Pt)/TiO₂ catalyst depends on the state of the platinum. The samples calcined in air at 500°C, which contain Pt⁺ and Pt²⁺, have an approximately 2 times higher SPC than unpromoted TiO₂ and ensure a much larger NO₂/NO ratio at the reactor outlet. Conversely, the samples reduced in an H₂ atmosphere at 200°C, whose platinum is in the Pt0 state, show a lower SPC than the initial TiO₂ and cause no significant change in the NO₂/NO ratio.     

Condensation of 3,5-Dialkyltetrahydro-4H-thiopyran-4-ones with Formaldehyde

Russian Journal of General Chemistry - The reaction of 3,5-dimethyl- and 5-methyl-3-(2-propyl)tetrahydro-4H-thiopyran-4-ones with formaldehyde without or in the presence of 0.1–0.5 equiv....     

Palladium(II) Extraction from Hydrochloric Acid Solutions with 4-[(Hexylsulfanyl)methyl]-3,5-Dimethyl-1H-Pyrazole

Palladium(II) extraction from hydrochloric acid solutions with a novel weakly basic complexing reagent, 4-[(hexylsulfanyl)methyl]-3,5-dimethyl-1H-pyrazole, dissolved in chloroform was studied. Palladium(II) was found to be highly efficiently extracted from 0.1–3 mol/L HCl solutions. A coordination mechanism of palladium(II) extraction with a protonated form of the reagent via fast interphase transfer of ion associates was proposed. The composition of the extracted compound, [PdCl₂μ-L]_n (n > 2), was found, and the way of coordination of the reagent to metal ions through N(2) nitrogen atom and thioether sulfur atom was determined. The reagent can be recommended for concentrating palladium(II) and selectively separating it from platinum(IV), copper(II), nickel(II), and iron(III).     

Thermal and Chemical Nonequilibrium Effects in Free-Burning Arcs

Effects caused by thermal and chemical nonequilibrium in free-burning arcs in argon are presented and discussed. The results cover a range of arc currents between 100 and 200 A, interelectrode distance of 5–10 mm, and a variation of the electrode material and the shape of the cathode tip. The results obtained show that nonequilibrium in the near-electrode regions has a strong impact on the distributions of temperatures, electric conductivity and current density, and the arc voltage. Departure from chemical nonequilibrium in the vicinity of the cathode as a result of transport processes is indicated. Moreover, overpopulation of the atomic ground state close to the arc axis, under population of the excited states in the arc periphery with respect to the equilibrium values, axial dependence of the off-axis maximum of the radial emission coefficient of Ar I at 696.5 nm, and enhanced population of the Ar (1s₄) resonance level due to trapping of resonance radiation in the arc periphery are considered.     

Influence of SF6 on HF laser plasma parameters

Summary This paper presents the results of calculations of electron drift velocity, mean energy and ionization, and attachment coefficients in SF₆: C₃H₈: He mixtures performed according to the multiterm Boltzmann-equation analysis. The parameters for wide variation of gas mixture composition andE/N values are obtained. The results presented may be useful in studying the HF laser action, analysis of the gas discharge, and research, development and modelling of this type of lasers. The authors of this paper have agreed to not receive the proofs for correction.     

Coherent focusing of high harmonics: a new way towards the extreme intensities

We demonstrate analytically and numerically that focusing of high harmonics produced by the reflection of a few-femtosecond laser pulse from a concave plasma surface opens a new way to unprecedentally high intensities. The key features allowing the boosting of the focal intensity are the harmonics coherency and the small exponent of the power-law decay of the harmonics spectrum. Using similarity theory and direct particle-in-cell simulations, we find that the intensity at the focus scales as I(CHF) alpha a(3)(0)I(0), where a(0) and I(0) alpha a(2)(0) are the dimensionless relativistic amplitude and the intensity of the incident laser pulse. The scaling suggests that due to the coherent harmonic focusing (CHF), the Schwinger intensity limit can be reached using lasers with I(0) approximately 10(22) W/cm(2). The pulse duration at the focus scales as tau(CHF) alpha 1/a(2)(0) and reaches the subattosecond range.