V. A. Ushakov

Metal foam supported perovskite catalysts

The impregnation technique and the polymer coating method were applied to synthesize a LaCoO3 perovskite catalyst on a metal foam support. The synthesized catalysts were examined by X-ray diffraction analysis, BET method, scanning electron microscopy. The perovskite phase was characterized by temperature-programmed reduction and diffused reflectance electron spectroscopy. The activity of the catalysts was tested in the methane oxidation reaction.

Application of plasma spraying in the preparation of metal-supported catalysts

Abstract Catalysts supported on metals are widely used today, but room still remains for further improvement of catalyst characteristics. The subject of this paper is the application of a plasma spray for the deposition of alumina coatings on metal substrates of different geometry (plates, foams) for subsequent synthesis of catalysts. The alumina layer sprayed successfully solves two different problems: (i) it serves as a washcoat on which a catalyst is synthesized, and (ii) it protects the metal surface from oxidation at high temperatures.

Supported honeycomb monolith catalysts for high-temperature ammonia decomposition and H2S removal

Abstract Catalysts that have potential in simultaneous removal of H 2 S and NH 3 decomposition were developed. The monolith supports of high surface area and acceptable mechanical strength based on titania and silica–alumina precursors were prepared and tested. Preparation routine and composition of Mn, Fe and Cu oxides supported honeycomb catalysts have been optimized. Impregnated and washcoated monolith catalysts were tested in ammonia high-temperature decomposition.

Laser-induced luminescence of model Fe/Al2O3 and Cr/Al2O3 catalysts

The laser-induced luminescence of Cr3+ impurity ions in model Fe/Al2O3 and Cr/Al2O3 catalysts with different calcination temperatures was studied. It was found that an additional luminescence band at 770 nm appeared in the luminescence spectra of low-temperature samples as a result of the interaction of octahedrally coordinated Cr3+ ions with Fe3+ impurity ions. In the θ-Al2O3 phase with a concentration of Cr3+ ions higher than 0.1 wt %, the interaction of the Cr3+-Cr3+ ion pairs in the immediate surroundings resulted in the appearance of Nθ lines due to the splitting of Rθ lines. The differences of these lines from the Nα lines of α-Al2O3 were related to the individuality of the crystal lattice of the θ phase and the coordination of Cr3+ impurity ions in the immediate surroundings, which is different from that in the α phase. Based on the laser-induced luminescence spectroscopic data, it was found that regions with a local Cr3+ concentration higher than the average Cr3+ concentration in the bulk of a catalyst by one order of magnitude were formed in the α-Al2O3-Fe2O3 system with the bulk Fe and Cr concentrations of 2.5 and 0.04 wt %, respectively, which was calcined at 1220°C, as a result of the diffusion of chromium and iron ions.

Study of Catalysts for Catalytic Burners for Fuel Cell Power Plant Reformers

Catalytic burners for fuel cell power plant reformers are alternatives to conventional flame burners. Their application is expected to provide uniform temperatures in the reformer, efficient use of low-calorific gaseous by products and reduction of pollutant emissions. For testing in the burners, a series of spherical Pd/CeO2/Al2O3 catalysts were prepared. An optimum concentration of ceria providing the highest thermal stability of catalysts was determined. An effect of catalyst activation in the reaction mixture-1% methane in air was observed. A series of Mn containing oxide catalysts on spherical γ-Al2O3 or (γ+Χ)-Al2O3, both pure and doped with La, Ce and Mg oxides were prepared. The catalysts were characterized by chemical analysis, X-ray phase analysis, BET surface area and activity measurements in methane oxidation. A batch of Mn-Mg-La-Al-O catalyst was prepared for further long-term testing in a model reformer with a catalytic burner. A model reformer with a catalytic burner was designed and fabricated for testing in the composition of the bench-scale Fuel Cell Power Plant. Preliminary testing of this catalyst showed that it provided complete methane combustion at the specified operational temperatures over 900 °C.

Synthesis of a mechanically strong and thermally stable alumina support for catalysts used in combustion processes

Abstract It is shown that simultaneous modification of spherical alumina by bi- and three-valence cations (that are strengthening and thermally stabilizing additives, respectively) by a special method leads to the formation of supports with unique properties. These results are due to the specific interaction between the additives and alumina.

Effect of Modifying Alumina Desiccants with Sulfuric Acid on Their Physicochemical Properties

In the production of alumina desiccants by extrusion, the introduction of sulfuric acid at the stage of preparing a mouldable paste based on hydroxides containing bayerite or pseudoboehmite increases the sorption capacity of the product. This effect is most pronounced for the pseudoboehmite-based materials. The dynamic capacity of these desiccants increases to the level characteristic of the bayerite-containing hydroxide (>5 g H2O/100 cm3) for a dew point of −40°C and a contact time of 1.5 s), and their static capacity exceeds this value (increasing from 21.13 to 23.1 g H2O/100 cm3). This procedure changes the phase composition and textural characteristics of the pseudoboehmite-based desiccants and increases Brønsted acidity and generates strong Lewis acid sites on the surface of all oxides. The dynamic capacity of desiccants with similar textural characteristics depends on the acid-base properties of their surface.

Characterization of new catalysts based on uranium oxides

Catalysts based on uranium oxides were systematically studied for the first time. Catalysts containing various amounts of uranium oxides (5 and 15%) supported on alumina and mixed Ni-U/Al2O3 catalysts were synthesized. The uranium oxide catalysts were characterized using the thermal desorption of argon, the low-temperature adsorption of nitrogen, X-ray diffraction analysis, and temperature-programmed reduction with hydrogen and CO. The effects of composition, preparation conditions, and thermal treatment on physicochemical properties and catalytic activity in the reactions of methane and butane oxidation, the steam and carbon dioxide reforming of methane, and the partial oxidation of methane were studied. It was found that a catalyst containing 5% U on alumina calcined at 1000°C was most active in the reaction of high-temperature methane oxidation. For the Ni-U/Al2O3 catalysts containing various uranium amounts (from 0 to 30%), the introduction of uranium as a catalyst constituent considerably increased the catalytic activity in methane steam reforming and partial oxidation.

Characteristics optimization of activated alumina desiccants based on product of a centrifugal thermal activation of gibbsite

Activated alumina desiccants modified with NaOH and KOH were synthesized from the product of a centrifugal thermal activation of gibbsite, with the subsequent hydration in an acid or alkaline medium, and their properties were studied. It was shown that the modification makes it possible to raise the dynamic capacity of desiccants produced from pseudoboehmite by up to a factor of 2 via formation of new super-strong basic centers the concentration of which grows with increasing content of an alkaline oxide. A correlation was found between the total concentration of basic centers on the surface of the desiccants and their dynamic capacity in drying of both dry and humid air. Use of the modified desiccants with high static and dynamic capacity will make it possible to improve the drying efficiency.

Fuel combustion reactions and catalysts. XXI: Synthesis and characterization of modified Mn-Al-O catalysts for high-temperature oxidation

The phase composition of supported Mn–Al–O catalysts and their activity in the reaction of methane oxidation were studied depending on the composition of aluminum oxide supports (γ-Al2O3 with different χ-Al2O3 contents modified with individual Mg, La, and Ce oxides or Mg + La and Mg + Ce oxide mixtures) and calcination temperatures (500, 900, and 1300°C). It was found that the Mn–Al–O catalysts based on γ-alumina containing χ-Al2O3 and modified with Mg, La, or Ce additives are more active and thermally stable (up to 1300°C) than the samples based on pure γ-Al2O3. A conclusion was drawn that a higher degree of disorder of the structure of χ-Al2O3, compared to that of γ-Al2O3, is favorable for a deeper interaction of manganese and modifying additives with the support at the early stages of the synthesis and for the formation of Mn–Al compounds with complex composition (solid solutions and/or hexaaluminates) at 1300°C. These compounds are responsible for the stability and high activity of the catalysts in methane oxidation.