Role of palladium additives in CO oxidation over a complex vanadium catalyst

At small concentrations of CO, palladium initiates a radical-chain process. At high CO concentrations CO oxidation occurs only on the surface of the heterogeneous catalyst and the effect of palladium is mainly due to the specific activation of carbon monoxide on the palladium surface.

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CO . CO .

     

Oxidation of n-propanol over vanadium oxide catalysts

The kinetics of catalytic oxidation of n-propanol on V₂O₅ and V₂O₅ modified with BeO, MgO, CaO and SrO has been investigated. A high selectivity of the oxidation to propionaldehyde was observed. The activation energies of the reaction and of the exchange of oxygen in these catalysts with molecular oxygen and CO₂ were found to change in parallel.

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- V₂O₅ V₂O₅ BeO, CaO, MgO SrO. . .

     

Kinetics of the vapor-phase oxidation of o-xylene over a vanadium oxide catalyst

(Pt–Sn)/Al₂O₃. , , , , .

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The catalytic and adsorption properties of the (Pt–Sn)/Al₂O₃ system have been studied. The results of benzene hydrogenation, cyclohexane dehydrogenation and temperature-programmed hydrogen desorption show that the introduction of tin into the Pt/Al₂O₃ catalyst significantly changes the dispersity and electronic state of supported platinum.

     

Relaxation kinetic studies of sulfur dioxide oxidation over vanadium catalyst

Relaxation processes of approaching a steady state of the catalytic system in sulfurous anhydride oxidation over a vanadium catalyst have been studied by a transient response method. It is shown that the experimental results can be interpreted in terms of a two-route mechanism.

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- . , - .

     

Oxidation of carbon monoxide over a copper(II) oxide catalyst

Transient FTIR observations in conjuction with gas phase CO conversion measurements indicate an adsorbed CO species which seems not to participate directly in the oxidation reaction over a silica supported copper(II) oxide catalyst. This observation together with order of reaction determinations suggest that oxidation occurs via an Eley-Rideal mechanism.

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CO CO, (II), . , , , -.

     

Oxidation of benzene to phenol by dioxygen over vanadium oxide nano-plate

Direct oxidation of benzene to phenol with dioxygen is an attractive and challenging subject. V⁴⁺ vanadium species play an important role in the reaction. Nano vanadium oxide which consists mainly of the quadrivalence vanadium species was synthesized via hydrothermal method and used to catalyze the reaction without addition of reducing reagent. Investigations about performances of catalysts show that 3.7% conversion of benzene and nearly 100% selectivity of phenol are given over the fresh catalyst VO-N-A. Morphology observations display that the VO-N-A is made of nano-plate. Thermogravimetric curve illuminates that the catalyst is stable under the reaction temperature.     

Selective hydrogenation of styrene/1-octene mixtures over a monolithic Pd catalyst

Mixtures of styrene and 1-octene in toluene were hydrogenated over a monolithic Pd catalyst in the three-phase regime. Styrene was preferably hydrogenated to ethylbenzene, while a major part of the initial quantity of 1-octene was isomerized to internal olefins. Formation of alkylcyclohexanes was negligible. Observed rates of styrene hydrogenation were high compared to the values listed in literature.     

On-line analysis of complex hydrocarbon mixtures using comprehensive two-dimensional gas chromatography

This paper discusses the first setup for on-line qualitative and quantitative comprehensive two-dimensional gas chromatography (GC × GC) of complex hydrocarbon mixtures. A built-in 4-port 2-way valve allows switching between flame ionization detection (FID) and time-of-flight mass spectrometry (TOF-MS) between runs, without the need to cool down and vent the MS. Proper selection of GC carrier gas flow rates enables maximal agreement between the obtained chromatograms in both configurations. For on-line analysis of reactor effluents, a dedicated sampling system allows automatic sampling of the hot reactor effluent gases and immediate injection of the sample on the GC × GC. To determine a complete effluent composition in a single run of the GC × GC, a subzero oven starting temperature was employed. Modulation is started when the oven temperature reaches 40 °C, thus dividing the chromatogram in a conventional 1D and a comprehensive 2D part. This work illustrates the mature and robust character of GC × GC, extending its capabilities from mere laboratory use to on-line routine analysis for industrial processes in the (petro-)chemical industry.     

Selective oxidation of anthracene to 9,10-anthraquinone over silica supported vanadium catalyst

The inner-ring oxidation of anthracene over V₂O₅/SiO₂ catalyst was investigated at various oxygen concentrations, contact times of the reactants and reaction temperatures. Up to 90 % yield to 9,10-anthraquinone is obtained at 218-220^oC.     

A new vanadium Schiff base complex as catalyst for oxidation of alcohols

The monoanionic bidentate Schiff base, N-(phenolyl)-benzaldimine (HL), has been employed to synthesize a new vanadium(IV) complex of general composition [VO(L)₂] (where L?=?O,?N donor of Schiff base). The ligand and complex have been fully characterized by elemental analyses, molar conductance data, FT-IR, ¹H- and ¹³C-NMR, and UV-Vis spectroscopies. Oxidation of alcohols to their corresponding aldehydes and ketones was conducted by this complex catalyst using Oxone as oxidant under biphasic reaction conditions (CH₂Cl₂/H₂O) and tetra-n-butylammonium bromide as phase transfer agent under air at room temperature.     

Pd-Co/C催化剂上葡萄糖的催化氧化反应

Pd-Co/C催化剂上葡萄糖的催化氧化反应     

Formation of the active component of a vanadium complex catalyst for the oxidation of anthracene to anthraquinone

The phase composition in various stages of preparation of the active material coating the catalyst for the partial oxidation of anthracene to anthraquinone was studied. The presence of an active phase was evidenced in the final active material as well in a precursor.

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, . , .

     

Oxidation of CO and hydrocarbons over perovskite-type complex oxides

The catalytic activity of perovskites M^IM^IIO₃ (M^I=La; M^II=Co, Mn, Cr, Al, Ni, and V) and M^ICoO₃ (M=Y, Nd, Sm, and Er) in the oxidation of CO, propylene, and ethylbenzene was investigated. The highest activity was observed for the M^ICoO₃ catalysts with perfect perovskite structure. The nature of the rare-earth element has no influence on the catalytic activity. Deformation of the octahedral coordination of the metal was found for the less active catalysts. The interaction of gases (CO, CO+air) with the catalyst surface was investigated. The more active catalysts adsorb a greater amount of O₂, and the adsorption occurs in the temperature region of the oxidation reaction. The activities of the perovskite- and spinel-type catalysts were compared under similar conditions. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 698–701, April, 1999.     

Kinetic conversion of complex hydrocarbon mixtures in reforming on platinum/alumina catalysts

General forms of the kinetic equations for the conversion of various hydrocarbons in reforming of multicomponent gasoline fractions on platinum/alumina catalysts have been confirmed experimentally by using a gradientless method.

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.

     

Reduction of nitrogen oxides with ammonia over complex vanadium and chromium oxides

Catalytic properties of -Al₂O₃ -supported complex vanadium and chromium oxides V_2–x Cr _x O_5– (0 < × s 1.3), amorphous to X-rays, in the reduction of nitrogen oxides with ammonia were studied. Vanadium exists in these catalysts mostly in a pentavalent state and chromium exists as Cr³⁺ and Cr⁶⁺. As the content of chromium in the catalysts increases, the optimal temperature of the process decreases, and the degree of conversion of nitrogen oxides increases.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 339–342, February, 1996.     

Nanoparticle supported,magnetically separable vanadium complex as catalyst for selective oxidation of sulfides

A magnetically recyclable vanadium(V) catalyst was synthesized by covalent anchoring of VO(salen)Cl on silica-coated Fe₃O₄ nanoparticles. This straightforward preparation yields magnetically separable Fe₃O₄@SiO₂@VO(salen) nanoparticles with high vanadium loading. These nanoparticles were efficient catalysts for selective oxidation of sulfides to corresponding sulfoxides with urea hydrogen peroxide in excellent yields. Leaching and recycling experiments revealed that the nanocatalyst can be applied for nearly complete oxidation of sulfides for at least five successive cycles.     

Effect of vanadium over NiMo/sepiolite hydrotreating catalyst

Summary Hydrotreating (HDT) and hydrodesulfuration (HDS) using an FCC feed were carried out at 673-748 K and 50 MPa total pressure. The effect of vanadium impregnated on a NiMo catalyst supported on sepiolite for HDT and HDS reactions was studied. A commercial NiMo/Al₂O₃ catalyst was used as reference. The hydrotreating conversions (wt.% HDT) is defined here as the net hydrotreating conversion into products boiling below 653 K. The results were compared with an accelerated ageing test using the catalysts on a FCC feed, with vanadium in the form of naphthenate (2000 ppm of V) added to rapidly deactivate catalysts via metal deposition. The results indicate that vanadium affects more the catalyst supported on sepiolite that the commercial catalyst. Also, at our reaction conditions, the effect of vanadium on sepiolite catalyst is similar, to those used with vanadium impregnated on the catalyst or on the catalyst where the vanadium in naphthenate form was added to FCC feed.     

Prediction of viscosities of hydrocarbon mixtures

A new model for prediction of the viscosities of hydrocarbons including oil and gas mixtures is presented. The model is based on the principle of corresponding states with methane and decane as reference components. The viscosity of a given component or mixture is determined from the reduced viscosities of the reference components using the molecular weight as an interpolation parameter.

The model has been used for prediction of viscosities of both pure components and mixtures over large pressure ranges and for reduced temperatures above 0.476. The results are in good agreement with the experimental data. The new model compares favorably with earlier published methods, which use only one reference component.

Finally, the model has been tested on data for 6 oil mixtures from the North Sea. The mean deviation based on 34 experimental points was 6.4 %.     

Oxidation of ammonia on a bismuth-manganese oxide catalyst

The doping of MnO₂ with small quantities of Bi₂O₃ results in an increase of the surface oxygen bond energy. Accordingly, the values of the specific catalytic activity and selectivity to nitrous oxide are lower for the doped catalyst than for pure MnO₂. The mechanism of low temperature ammonia oxidation is the same on both catalysts.

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Bi₂O₃ MnO₂ . , , MnO₂. .