A. N. Kharlanov

Structure and Lewis acid properties of gallia–alumina catalysts

Abstract The surface structure of Ga 2 O 3 –Al 2 O 3 catalysts was investigated by IR and ESR spectroscopy. As a result of modification by gallia, alumina hydroxyl cover changes significantly. The new band 3680–3688 cm −1 ascribed to bridging structure GaOHAl has been observed. By means of IR spectroscopy, adsorbed CO and ESR with anthraquinone as a probe molecule, two types of Lewis acid sites and their concentration were defined. These sites are coordinately unsaturated aluminium cation Al cus 3+ and coordinately unsaturated gallium cation Ga cus 3+ . In the case of Ga 2 O 3 –Al 2 O 3 catalysts with a gallia content of 1–10 mol%, surface Lewis acid properties are in accordance with the assumption of solid solution formation. Only under significantly non-equilibrium conditions (large excess of dopant — 20 mol% Ga 2 O 3 –Al 2 O 3 , relatively low temperature of calcination −720 K, short time of interaction — 4 h) it becomes possible to stabilize highly dispersed state of gallium oxide, for which the characteristic feature is high concentration and local regulation of Ga cus 3+ on the surface. It was shown that on the alumina surface there are favourable (more than in the case of pure gallia) conditions for the Ga cus 3+ formation.

Ultradispersed diamond as a new carbon support for hydrodechlorination catalysts

The properties of palladium and nickel catalysts supported on ultradispersed diamond (UDD) were studied in the vapor-phase hydrodechlorination (HDC) reaction of chlorobenzene and the multiphase HDC of polychlorobenzenes. The catalysts on UDD exhibited a number of advantages: the vapor-phase HDC of chlorobenzene on Ni/UDD occurred at lower temperatures, and the multiphase HDC of chlorobenzene, 1,3,5-trichlorobenzene, and 2,4,8-trichlorodibenzofuran on Pd/UDD occurred more rapidly than that on catalysts supported on activated carbon. The structure of the catalysts and the electronic states of the active components were studied using IR spectroscopy, temperature-programmed reduction, and adsorption techniques. It was found that the properties of the catalysts depend on the electronic state of palladium, which depends on its concentration in the sample; the structural properties, which are responsible for the accessibility of the active surface to adsorption; and the presence of other metal impurities.

Effect of the Detonation Nanodiamond Surface on the Catalytic Activity of Deposited Nickel Catalysts in the Hydrogenation of Acetylene

A comparative study is performed of the catalytic activity of nanosized nickel deposited on detonation synthesis nanodiamond (DND) and coal (CSUG) produced by burning sugar and crystalline quartz in the hydrogenation of acetylene. Nanosized nickel is obtained through the thermal decomposition of nickel formate under a dynamic vacuum. The catalysts are studied by means of scanning electron and transmission electron microscopy, X-ray fluorescence, IR-spectroscopy, X-ray diffraction, and pulse microcatalytic method. It is shown that Ni/DND is an active catalyst of acetylene hydrogenation, considerably surpassing Ni/quartz and Ni/CSUG. The apparent activation energy of the hydrogenation of acetylene is calculated, and the region of the reaction are determined for all catalysts. It is found that the influence of the structure and nature of a functional coating of nanodiamond on the catalytic activity of Ni/DND deposited catalyst in the hydrogenation of acetylene. The ability of Ni/DND to hold active hydrogen is detected.

Effect of cobalt weight content on the structure and catalytic properties of Co/CNT catalysts in the fischer–tropsch synthesis

Cobalt-based Fischer–Tropsch synthesis (FTS) catalysts containing 1 to 40 wt % cobalt supported on multi-walled carbon nanotubes (CNTs) have been investigated. The CNTs have been characterized by low-temperature nitrogen adsorption, scanning electron microscopy, and X-ray photoelectron spectroscopy. All catalysts have been prepared by impregnating, with an ethanolic solution of cobalt nitrate, the CNTs preoxidized with concentrated nitric acid and have been tested in the FTS at 220°C and atmospheric pressure. Correlations have been established between the cobalt weight content of the catalyst and the Co particle size determined by transmission electron microscopy and X-ray diffraction. The Co content and particle size have an effect on the activity and selectivity of the catalyst and on the target fraction (C5+) yield in the FTS. The highest CO conversion is observed for the catalyst containing 20 wt % Co; the highest selectivity and activity, for the catalyst containing 5 wt % Co; the highest C5+ yield, for the catalyst containing 10 wt % Co.

Transformation of wood during ozonization in the presence of hydrogen peroxide

Samples of ozonized aspen wood pretreated with hydrogen peroxide solutions of various concentrations are investigated by UV diffuse reflectance spectroscopy, IR spectroscopy, and X-ray structural analysis. The general course of wood transformation under the action of the O3/H2O2 system is associated with the destruction of lignin and oxidation of carbohydrates, raising the fraction of the crystalline phase in a lignocarbohydrate material. The possibility of varying the depth of the chemical and structural transformation of the substrate upon changing the hydrogen peroxide concentration in the O3/H2O2 system is demonstrated.

Delignification of deciduous wood under the action of hydrogen peroxide and ozone

AbstractKinetic curves of the dependence of ozone specific absorption (Qr, sp) upon the ozonation of aspen wood pretreated with solutions of hydrogen peroxide of various concentrations (from 5 × 10−4 to 2 × 10−1 mol/L) are obtained. The water content in the samples being 56 ± 3%. The initial rate of ozone absorption and total ozone consumption (Qinlet) are determined. Wood samples are investigated by IR and UV diffuse reflection spectroscopy. Based on the kinetics and spectral data, it is concluded that pretreating wood with a H2O2 solution allows the degree of delignification (DD) to be increased at a constant Qinlet value. The DD is maximal at

IR Absorption Spectra of Cellulose Obtained from Ozonated Wood

C_{H_2 O_2 } = 5 \times 10^{ - 3}

The Electron Acceptor and Catalytic Properties of Zirconium Dioxide Modified with Aluminum and Gallium Oxides

mol/L and is 88% in contrast to a sample ozonated without H2O2 (DD = 85%). The role of pretreatment with hydrogen peroxide and the subsequent action of the O3/H2O2 system in the process of delignification of wood is analyzed.