L. M. Plyasova

STATE OF COPPER-CONTAINING CATALYST FOR METHANOL SYNTHESIS IN THE REACTION MEDIUM

Hydrogen interaction with solid solutions of the composition Cu0.08Zn0.02O* and Cu0.15Al0.10Zn0.75O* has been studied. It is shown that at catalytic temperatures the surface of anion-modified zinc oxide contains epitaxially bonded metallic copper particles. Reversibility of this phenomenon upon removing hydrogen indicates that in hydrogen medium a complex system consisting of the oxide stabilized by protons and epitaxially bonded with oxide metal copper particles formed.

Catalytic properties of V−Mo−O systems in acrolein oxidation

Catalytic properties of V−Mo−O systems have been studied in acrolein oxidation. When catalysts are activated in reaction mixtures at 673 K, then a solid solution of molybdenum oxides in reduced vanadium oxides is formed, which is responsible for deep oxidation. Also, several compounds are produced, which by their activity and selectivity to acrylic acid formation are arranged in the sequences VMo3O11≅VMo2O8+x>V6Mo4O25, and VMo3O11>VMo2O8+x≫V6Mo4O25, respectively.AbstractВ реакции окисления акролеина исследована V−Mo−O система. При формировании катализаторов при 673 K в реакционной смеси в системе образуются твердый раствор оксидов молибдена в восстановленных оксидах ванадия, который катализирует в основном глубокое окисление, и ряд химических соединений, которые по активности располагаются в ряд: VMo3O11≈VMo2O8+x>V6Mo4O25, а по селективности в реакции образования акриловой кислоты: VMo3O11>VMo2O8+x≫V6Mo4O25.

Formation of active component of MoVTeNb oxide catalyst for selective oxidation and ammoxidation of propane and ethane

Abstract The effect of slurry pH on the formation of active component of MoVTeNbO catalyst for selective (amm)oxidation of ethane and propane has been studied. pH affects the nature and composition of the crude and dry precursors as well as chemical and phase composition of the final catalyst. The most effective catalyst is prepared at pH = 3.0, which is characterized by a maximum content of M1 phase.

Copper-cobalt catalysts for higher alcohols synthesis from syngas

Publisher Summary This chapter describes the synthesis of higher alcohols from syngas with the help of copper-cobalt (Cu–Co) catalysts and the active state of Cu–Co based catalysts with the help of in situ high temperature x-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. The catalyst is prepared by coprecipitation of metal nitrates with sodium carbonate at pH 7. A dried sample is calcined at 4900C for 10 hours in flowing helium. XRD studies are carried out using a diffractometer D-500 (Siemens) with CuKα radiation (a graphite monochromator with a reflected beam). Electron microscopic studies, including TEM and selected area diffraction (SAD), are carried out using an electron microscope JEM-100 CX. Cu–Co based catalysts are known as selective toward alcohols in CO hydrogenation. Cu–Co surface alloy is also an active state for higher alcohol formation. Higher alcohols, along with hydrocarbons, are seen to be synthesized within the temperature range of 300–370° C.

Preparation, active component and catalytic properties of supported vanadium catalysts in the reaction of formaldehyde oxidation to formic acid

Abstract The influence of the support nature was investigated with supported vanadium catalysts prepared by a wet impregnation method. SiO 2 , γ-Al 2 O 3 , ZrO 2 and TiO 2 (anatase) were used as supports. Two series of catalysts were prepared, the first one consisting of catalysts of composition ca. 20% wt. V 2 O 5 /80% wt. support (series 1) and the second one prepared by washing the series 1 samples with nitric acid (series 2). In the catalysts of series 1 (except 20% V 2 O 5 /80% SiO 2 ), vanadium is represented by both monolayer species (monomeric and polymeric VO x ) and crystalline V 2 O 5 phase. When vanadium is supported on SiO 2 , only the crystalline V 2 O 5 is formed. Washing the samples of series 1 with nitric acid removes crystalline V 2 O 5 phase. Monomeric and polymeric vanadia species are more active in the reaction of formaldehyde oxidation to formic acid as compared to V 2 O 5 .

Structure transformations of copper chromite under reduction-reoxidation conditions

Abstract Structure transformations accompanying reoxidation preliminary reduced at 270°C copper chromite were studied using X-ray powder diffraction method, and comparison of the structures of the initial and reoxidized copper chromite was carried out. Conditions under which cation-deficient spinel, stabilized with hydrogen and epitaxially bonded with its surface Cu0 particles (derived from reduction of copper chromite by hydrogen) forms copper chromite with the tetragonal spinel structure are revealed. It is shown that the reoxidized spinel is non-stoichiometric and possibly contains some amount of hydrogen in the form of protons bonded to the lattice oxygen. Differences of reversible phase transformation of copper chromite under reduction–reoxidation conditions from reversible polymorphism of copper chromite with temperature variations are analyzed.

Physico-chemical studies of the temperature range for the formation of anion-modified oxides

The effect of metal ions on the temperature range for the exstence of anion-modified oxides formed during the formation of Mg and Zn oxides and solid solutions of Cu, Al, Cr and Ni ions in these oxides through thermal decomposition of the respective hydroxo compounds, has been established.AbstractОбнаружено влияние ионов металла на температурную область существовния анионно-модифицированных оксидов, образующихся при формировании оксидов Mg и Zn, твердых растворов Cu, Al, Cr, и Ni в них путем терморазложения соответствующих гидроксосоединений.

Structural features of copper ferrite-chromites

The structural features and the distribution of cations over crystallographic sites of copperchromite, copper ferrite, and mixed chromite-ferrites with the spinel structure obtained by thermal decomposition at 600°C and 900°C of mixed hydroxy compounds of copper, iron, and chromium with the composition Cu2+/(Fe3++Cr3+) = 1/2 and different Fe3+/Cr3+ ratios are studied using a set of physicochemical methods. It is shown that the spinel-structure phases formed exist in two modifications: cubic and tetragonal, depending on the Fe3+/Cr3 ratio. The crystallographic relationship between the cubic and tetragonally distorted phases of spinel is analyzed. The distribution of cations over crystallographic sites, the character and degree of tetragonal distortion of Cu–Fe–Cr spinel depend on the Fe3+/Cr3+ ratio: when Fe3+/Cr3+ > 1, the ratio of unit cell parameters c*/а* > 1; when Fe3+/Cr3+ < 1, the ratio c*/а* < 1; when Fe3+/Cr3+ = 1, the spinel is cubic irrespective of the temperature of thermal treatment. The oxygen coordination of copper ions in the spinel structure has a significant effect on the catalytic properties of the samples in the low-temperature water gas shift reaction.

Effect of preparation conditions on the phase composition of the MoVTe(Nb) oxide catalyst for the oxidative conversions of propane

The replacement of expensive propylene by propane, which requires the development of catalysts for the direct oxidation of propane into acrylonitrile, is an important and insufficiently studied problem. Multicomponent MomVnTekNbx oxide systems are promising in one-stage ammoxidation of propane to acrylonitrile. Despite considerable attention of various authors to the preparation methods for these catalysts, the reproducibility of their physicochemical and catalytic properties is low. To optimize the technology of catalyst synthesis, we studied the effect of drying method (evaporation or spray drying) for the aqueous suspension of the initial compounds on the formation of the Mo1V0.3Te0.23(Nb0.12) oxide catalyst. It is shown that the method of drying determines the chemical and phase composition of solid catalyst precursors and the phase composition of the final catalyst in high-temperature treatment. The use of spray drying provides the required physicochemical characteristics of the catalyst (the specific surface area and the phase composition) that determine the high activity and selectivity in the selective conversion of propane. These catalysts contain two crystalline phases: orthorhombic M1 and hexagonal M2 in an optimal ratio of 3: 1.

New Compounds Of The Vanadium-Molybdenum Oxide System. In Situ Investigation Of The Mechanism Of Acrolein Oxidation To Acrylic Acid. The Role Of The Structure And Bond Energy Of The Intermediate Compounds

Abstract In V-Mo oxide system the composition range of 3-30 mol.% V 2 0 4 .- 97- 70 mol.% Mo0 3 is active and selective in the reaction of acrolein oxidat ion to acrylic acid. This range corresponds to a number of phases with variable composition, where VMo 3 0 11 has the best catalytic properties. The surface complexes formed at the adsorption of acrolein on VMo 3 0 11 have been identified by IR spectroscopy, and the kinetics of their transformation to acrylic acid have been in situ established. The bond energy of the lattice oxygen has been determined by calorimetry in situ. The quantitative dependence of the rate of the acrylic acid formation on the bond energy of oxygen, acrylate and the quantity of V 4+ ions has been shown.