Characterization of perovskite-type oxide catalysts RECoO3 by TPR

Reducibility of a series of RECoO₃ (RE=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy) perovskite-type oxides were measured by temperature programmed reduction (TPR) technique. Catalytic activity for CO oxidation of them were investigated. The relation among T_max in TPR, catalytic activity and surface oxygen binding energy is discussed.

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RECoO₃ (RE=La, Pr, Nd, Sm, Eu, Gd, Tb, Dy) . CO. T_max , .

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Project Supported by the Science Fund of the Chinese Academy of Sciences     

CO hydration over catalysts prepared via supporting Fe3(CO)12 and (NEt4)2[Fe2Mn(CO)12] on oxide supports

A comparison of the properties of iron-containing catalysts prepared through carbonyl clusters Fe₃(CO)₁₂ and (NEt₄)₂[Fe₂Mn(CO)₁₂] and iron and manganese nitrates in CO hydration indicates that the addition of Mn incorporated in (NEt₄)₂[Fe₂Mn(CO)₁₂] decreases the methane yield and increases the portion of higher hydrocarbons.

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, Fe(CO)₁₂ (NEt₄)₂[Fe₂Mn(CO)₁₂] , CO. Mn (NEt₄)₂[Fe₂Mn(CO)₁₂] .

     

Influence of chemical non-steady-state on SO2 conversion in fluidized catalyst bed

The effect of the influence of catalyst non-steady-state on SO₂ conversion ion a fluidized catalyst bed has been studied depending on the ratio of relaxation time for the catalytic reaction step to the characteristic time of particles diffusion.

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Some spectroscopic and freezing point depression measurements on the homogeneous hydrogenation catalyst CoH3(PPh3)3

NMR, EPR and freezing point depression (FPD) experiments were performed on solutions of the homogeneous hydrogenation catalyst CoH₃(PPh₃)₃. The results of these measurements show that the compound has a dynamic structure on the NMR time scale at room temperature and that it is slightly dissociated into bisphosphine species and free phosphine. FPD and¹H-NMR measurements indicate that one Et₂O molecule is present per catalyst molecule.

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, () CoH₃(PPh₃)₃. , , . H¹- , Et₂O.

     

Kinetics and mechanism of OsO4 catalyzed oxidation of maleic, fumaric, cinnamic and acrylic acids by acid bromate

The title reactions are zero order in bromate, first order in both substrate and catalyst. The order of reactivity is cinnamic acid>acrylic acid>fumaric acid>maleic acid. A plausible mechanism is discussed.

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, . : > > > . .

     

V2O5/TiO2 oxidation catalysts. I. Preparation and characterization by XRD and IR spectroscopy

V₂O₅/TiO₂ systems have been prepared by reacting VO-(acetylacetonate)₂ with differently hydroxylated TiO₂ supports. When the OH population is increased, a larger vanadia content, but well dispersed, is achieved. The presence of sodium ions leads to the formation of Na–V bronze crystallites, decreasing the dispersity of the supported phase.

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V₂O₅/TiO₂ VO()₂ TiO₂, . OH V₂O₅, , , . Na–V, .

     

Inhomogeneity of strong Lewis acid centers on Al2O3 surface

Specificity of the bands at 1630–1620 cm^–1 in IR spectra of coordinatively bonded pyridine has been studied. Three strong Lewis-type acid centers have been revealed on Al₂O₃ surface.

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- 1630–1620 ^–1.

     

Structure of surface species in Mo/Al2O3 catalysts prepared through Mo(V) oxalate

EXAFS and RED structural studies of surface species of Mo/Al₂O₃ catalysts prepared through the anchoring of [Mo₂O₄(C₂O₄)₂(H₂O)]^2– anion to -Al₂O₃ have shown that these surface metal complexes preserve a binuclear structure of the Mo(V) oxalate framework fragment.

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EXAFS Mo/Al₂O₃, [Mo₂O₄(C₂O₄)₂(H₂O)₂]^2– -Al₂O₃. , (V).

     

Cyclohexane photooxygenation by air oxygen in CH2Cl2 in the presence of chromium oxocomplex-iodosylbenzene system

Cyclohexane is oxidized by air oxygen in CH₂Cl₂ solution to yield cyclohexanol, cyclohexanone and cyclohexyl chloride when irradiated by light (>310 nm) in the presence of (Bu₄N)₂CrO₄ or (Bu₃SnO)₂CrO₂. The addition of PhIO greatly accelerates the reaction and increases the yield of products. The reaction mixture contains neither cyclohexanol nor cyclohexanone when the photoreaction in the presence of the Cr(VI)–PhIO system is carried out in argon atmosphere. Hence neither iodosylbenzene nor oxochromium compounds can be oxygen atom donors in alkane oxygenation. The accelerating effect of iodosylbenzene may be due to the enhanced oxidizing power of photo-excited oxochromium species when coordinated to iodosylbenzene.

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CH₂Cl₂ , , (>310 ) (Bu₄N)₂CrO₄ (Bu₃SnO)₂CrO₂. PhIO . Cr(VI)–PhIO , , . , ( ) . .

     

Ligand exchange between bis-acetylacetonato cobalt (II) and organotin compounds SnR2Cl2 (R=Ph, Et), I. NMR identification of exchange products in the Co(AA)2?SnPh2Cl2 system

NMR studies of the interaction between bis-acetylacetonato Co(II) and organotin compound SnPh₂Cl₂ (Ph=C₆H₅ ^–) in chloroform solutions with pyridine additive have revealed ligand exchange between the initial components to form Co(II) and Sn(IV) complexes with different numbers of ligands.

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Co(II) SnPh₂Cl₂ (Ph=C₆H₅ ^–). , Co(II) Sn(IV) .

     

Role of strongly bound vanadia in V2O5/Al2O3 catalysts for selective catalytic reduction of nitric oxide by ammonia

V₂O₅/Al₂O₃ catalysts prepared by impregnation and by ammonia treatment of impregnated samples were tested for activity in the NO–NH₃ reaction. The ammonia treated samples, with higher proportions of strongly bound vanadia, were found to be comparable in activity to the impregnated catalysts and equally sensitive to the presence of oxygen.

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V₂O₅/Al₂O₃, , NO–NH₃. .

     

X-ray photoelectron (ESCA) spectra of some fluorine containing aluminas

The binding energies of the F(1s) and Al(2p) electrons in fluorine containing alumina catalysts are reported. The X-ray photoelectron peaks confirm the formation of a bulk phase of AlF₃ at higher fluorine contents, whereas the fluorine signals at lower percentages originate from surface groups which are substituted by fluorine. By comparing X-ray photoelectron spectroscopy with X-ray diffraction we conclude that the combination of these techniques is a potential tool in detecting crystals on a catalyst surface which have a size under the detection limit of X-ray diffraction.

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F(1s) Al(2p) , . AlF₃ , , . , , , .

     

Nature of ethylene complexes on the surface of Ag/SiO2 as evidenced by13C NMR data

The formation of -complexes of C₂H₄ with Ag⁺ on oxidized Ag/SiO₂ catalysts is shown by¹³C NMR. These complexes are similar in nature to those of olefins with silver in solution.

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¹³C , Ag/SiO₂ - C₂H₄ Ag⁺, - .

     

Calorimetric studies of the properties of Pd/Al2O3 with different metal contents

Hydrogen on Pd/Al₂O₃ catalysts (1,2,4% Pd) is sorbed in three forms with a heat of 152.6–2.1 kJ/mol. Metallic surface of the catalysts has been measured by the amount of adsorbed oxygen, whose adsorption heat varies in the range of 313.7–3.4 kJ/mol. Catalytic activity and selectivity of Pd/Al₂O₃ was studied in isoprene hydrogenation.

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Pd/Al₂O₃- 152,6–2,1 /. , 313,7–3,4 /. Pd/Al₂O₃ .

     

Active site for hydrogenation on reduced V2O5/Al2O3 catalyst

Active sites for C₂H₄ hydrogenation produced by reduction of V₂O₅/Al₂O₃ catalyst pretreated at 450°C were found to be composed of both strong Lewis acid sites associated with V⁴⁺ and basic sites of Al₂O₃. C₂H₄ polymerization concurrent with hydrogenation was assumed to occur on Lewis acid sites with higher acid strengths than those of the hydrogenation sites.

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C₂H₄, V₂O₅/Al₂O₃, 450°C, , Al₂O₃. , , , C₂H₄.

     

1H,13C and17O NMR studies of cumene hydroperoxide coordination to Cr(AA)3

It has been established that the outer sphere coordination of cumene hydroperoxide to Cr(AA)₃ is due to both the formation of hydrogen bonds between hydroxyl proton and chelate oxygen atoms and the --interactions between the aromatic ring and chelate -system.

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, - Cr(III) , --- - .

     

Ausbrennen von Kohlenstoffhaltigen,in den Ziegelrohstoff Eingepressten Stoffen

Zusammenfassung Die Kinetik der Ausbrennung organischer Stoffe im Ziegelscherben wird verfolgt und erläutert. Die Möglichkeiten der Beeinflussung des energetischen Aufwandes unter Nutzung moderner analytischer Methoden sind festzustellen. Bei einem diffusen Ausbrennen ist die Dichte und Durchlässigkeit des Scherbens massgebend. Praktische Anwendungsmöglichkeiten verschiedener auszubrennender Stoffe in unterschiedlichen Rohstoffen der Ziegelindustrie.

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The kinetics of burn-out of organic materials in bricks has been followed and explained. It is to establish that using new analytical methods the energy consumption can be influenced. The diffuse burn-out is determined by the density and permeability of bricks. There is a possibility for practical use of the results in the brick-industry with the different compounds to be burnt out from various raw materials.

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$ . , . . .

     

Influence of Pr ions on the properties of Pd/SiO2 and Pt/SiO2 catalysts in oxidation of n-butane

It has been established that (M_VIII+Pr)/SiO₂ catalysts (M_VIII=Pd or Pt) obtained from organometallic precursors, have increased the dispersity of Pt, but their TN in deep oxidation of n-butane is by 3–6 times lower than that of unmodified M_VIII/SiO₂.

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(M_VIII+Pr)/SiO₂ ( M_VIII=Pd, Pt), , Pt, 3–6 - M_VIII/SiO₂.

     

Oxidation with MnO2 supported on Y,FAU zeolite

MnO₂ supported on Na-Y,FAU prepared as described in a previous paper has been tested for selective oxidation of benzyl alcohol to benzaldehyde. Experimental results have shown that oxidation is selective and stoichiometric under the conditions used, but the adsorption of the substrate and/or the product on the zeolite support decreases the yield of benzaldehyde.

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MnO₂, Na–Y,FAU, , . . , , , / .

     

51V NMR studies of systems V2O5-KHSO4 and V2O5?K2SO4

Systems V₂O₅–KHSO₄ and V₂O₅–K₂SO₄ have been studied by the⁵¹V NMR method. The first system demonstrates the same states of vanadium as the previously studied V₂O₅–K₂S₂O₇, in this system a compound with an equimolar ratio of components has been found. In V₂O₅–K₂SO₄ the state of vanadium differs from the above systems and the formation of a compound with V/K=4 is observed.

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⁵¹V KHSO₄–V₂O₅ K₂SO₄–V₂O₅. , K₂S₂O₇–V₂O₅, . K₂SO₄–V₂O₅ V/K4.