Liquid-phase hydrogenation on new AlPO4?SiO2 supported rhodium catalysts

The liquid-phase catalytic hydrogenation of various organic compounds was carried out using new rhodium catalysts supported on AlPO₄–SiO₂ (2080 wt. %) system, in methanol as solvent, under low hydrogen pressure (0.55 MPa) and at 293 K. Neither alkene isomerization nor hydrogenolysis products were detected in any of the cases.

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AlPO₄–SiO₂ (2080 . %), , , (0,55 MPa) 293 . , .

     

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.

     

Investigation of the acid distribution near the reactant-product interface during the thermal decomposition of copper hypophosphite thin layers

During the decomposition of thin layers of copper hypophosphite on a plate, an increased concentration of the active product of the reaction (acid) may be observed near the reactantproduct interface, The acid profile near the interface widens on increase of the decomposition temperature. The profile can also be widened by reducing the efficiency of acid removal to the plate by its preliminary acid saturation. In both cases the rate of interface propagation is increased. The increased reactivity of copper hypophosphite near the interface, and the technological character of the decomposition reaction, are caused by acid diffusion from the reaction product into non-reacted parts of the substance.

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Zusammenfassung Während der Zersetzung dünner Schichten Kupferhypophosphit kann in der Umgebung der Reaktand-Reaktionsprodukt Grenzfläche eine erhöhte Konzentration des aktiven Produktes der Reaktion (Säure) beobachtet werden. Die Säurezone in der Umgebung der Grenzfläche wird mit zunehmender Temperatur breiter. Diese Zone kann auch durch Verringern der Wirksamkeit der Säureentfernung in Richtung Träger durch dessen vorangehende Säuresättigung verbreitert werden. In beiden Fallen ist die Geschwindigkeit des Grenzflächenzuwachses erhöht. Die erhöhte Reaktivität von Kupferhypophosphit in der Umgebung der Grenzfläche sowie der technologische Charakter der Zersetzurrgsreaktion wird durch Säurediffusion von den Reaktionsprodukten in noch unreagierte Zonen der Substanzen verursacht.

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— , . . , . . .

     

Kinetics of Co?Mo/Al2O3 catalyst reduction

According to kinetic studies on the reduction of commercial Co–Mo/Al₂O₃ and model catalysts in H₂ at 523–773 K, the kinetic curves for the reduction process have been determined. The reduction rate is shown to be higher for the commercial catalyst. Activation energies E_act for the reduction of several forms of Mo and Co in Co–Mo/Al₂O₃ catalysts are presented.

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H₂ 523–773 . , : Mo Co .

     

State of components in supported catalysts prepared via interaction of platinum-tin complexes with Al2O3 surface

The interaction of platinum-tin complexes with the OH groups of Al₂O₃ is shown to lead to the formation of surface complexes in which tin ions bonded to the support are not reduced to metal and inhibit platinum agglomeration.

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OH- Al₂O₃ , .

     

Lattice oxygen removal from nearly stoichiometric V2O5

The activation energy of the removal of lattice oxygen connected with slight thermal dissociation of V₂O₅ was measured by the TPD method. The small value (24.7 kcal/mol O₂) of this energy is discussed as the result of bivariant equilibria V₂O_5–x–O₂ within the range x<0.01.

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, V₂O₅, . V₂O_5–x–O₂ x<0,01.

     

Unsteady-state performance of NOx catalytic reduction by NH3

Experimental results of studying NO_x catalytic reduction by NH₃ under periodic reversals in the direction of filtration of the mixture purified in a catalyst bed are discussed.

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NO_x .

     

Reduction kinetics of NiO-MoO3 catalysts

Reduction kinetics of NiO–MoO₃ catalysts in H₂ at 573–723 K has been studied. Reduction activation energies E_a have been determined. The degree of NiO–MoO₃ reduction is shown to increase with increasing NiO content.

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NiO–MoO₃ H₂ 573–723 . E NiO–MoO₃ . , NiO–MoO₃ NiO .

     

Stopped-flow study of the oxidation of ascorbic acid by the oxo-bridged trinuclear ruthenium complex [(NH3)5RuORu(NH3)4 ORu(NH3)5]7+

The kinetics of the oxidation of ascorbic acid by [(NH₃)₅RuORu(NH₃)₄ORu(NH₃)₅]⁷⁺ has been studied by the stopped-flow method. The activation parameters have been calculated and a possible mechanism is suggested.

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[(NH₃)₅RuORu(NH₃)₄ORu·(NH₃)₅]⁷⁺ . .

     

Nature of the activity and the kinetics of cyclohexene hydrogenation by the catalytic system (C5H5)2 TiCl2?LiC4H9

The reaction of tributylphosphine with the catalytic system (C₅H₅)₂ TiCl₂–LiC₄H₉ prepared in an atmosphere of H₂ has been investigated in toluene solution. By using the ESR technique, a hydride complex Cp₂Ti(H) (PBu₃) has been detected. The proportionality between the rate of cyclohexene hydrogenation and the complex concentration has been established. The kinetics of cyclohexene hydrogenation has been investigated and a reaction mechanism is proposed.

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Cp₂TiCl₂–LiC₄H₉ (Cp–C₅H₅), H₂, Cp₂Ti(H) (PBu₃). Ti (III). .

     

Influence of added copper on the activity of Ni/Al2O3 catalysts in the hydrogenolysis of n-butane

The influence of small Cu admixture to the Ni/Al₂O₃ system on its activity in the hydrogenolysis of n-butane was studied in the temperature range of 723–573 K. The activity was measured in a gradientless reactor. Cu added to Ni/Al₂O₃ was found to have a strong influence on the overall activity, selectivity and ratio for n-butane hydrogenolysis. A mechanism of hydrogenolysis of n-butane on the Ni–Cu/Al₂O₃ system is proposed.

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Cu Ni/Al₂O₃ - 723–573°. . Cu Bi/Al₂O₃ -. - Ni–Cu/Al₂O₃.

     

Electroconductivity changes of Na-modified TiO2 and Pt/TiO2 films

Electrolytic supporting of metallic sodium on the surface of TiO₂ and Pt/TiO₂ films is shown to change significantly the Fermi level of the semiconductor substrate already at small concentrations of sodium. The steady-state catalytic activity changes only at high concentrations of supported sodium, varying the chemical composition of the active phase. The contact process does not play any significant role in the catalytic process.

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, TiO₂ Pt/TiO₂ . , . .

     

V2O5/TiO2 oxidation catalysts, III. Oxidation of CO on pure and sodium-doped systems

The activity of vanadia/titania catalysts in CO oxidation has been tested and found to be of the same order as that observed for unsupported vanadia; the simultaneous presence of vanadium-sodium compounds cancels the activity, probably because of the elimination of labile V=0 species at surface defects.

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V₂O₅/TiO₂ CO, V₂O₅; - , , V=0 .

     

Rate constant of unimolecular decomposition of the radical (CH3)2juvyCCH(CH3)2

The energy of activation of CH ₃ ^. radical rupture from the radical (CH₃)₂juvyCCH(CH₃)₂ is 142.2 kJ mol^–1; the selfcombination rate constant is k_c {(CH₃)₂juvyCCH(CH₃)₂}=10^7.3 dm³ mol^–1 s^–1.

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CH ₃ ^. (CH₃)₂juvyCCH(CH₃)₂ 142,2 /, k_c {(CH₃)₂juvyCCH(CH₃)₂}=10^{7,3 3–1 –1}.

     

Role of the V=O double bond in the selective oxidation of benzene on V2O5 and V2O5?MoO3 catalysts

Infrared spectra of both fresh and reductively activated V₂O₅ and V₂O₅–MoO₃ catalysts were recorded and compared with the results of catalytic measurements. The results indicate that the presence of V=O double bonds in the catalytically active mass is not essential for the selective oxidation of benzene to maleic anhydride.

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, V₂O₅ V₂O₅–MoO₃. . , V=O .

     

n-Hexane cracking over heteropoly acids, 2. Catalytic activity and thermal stability of H4SiW12O40, H6P2W18O62 and H6P2W21O71(H2O)3

The catalytic activity of three heteropoly acids has been studied in n-hexane cracking. Only H₄SiW₁₂O₄₀ does not decompose into oxides at the reaction temperature. Its acidic form is active in cracking but its dehydration leads to an inactive compound.

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-. H₄SiW₁₂O₄₀ . , .

     

Kinetic studies of Pt/Al2O3 catalyst pellets with nonuniform activity

Catalysts with nonuniform distribution of the catalytically active component (Pt) over their porous support (Al₂O₃) have been studied. A nonuniform activity distribution changes not only the reaction rate but also the kinetics can be different on these catalysts.

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(Pt) (Al₂O₃). , , .

     

Catalysts for metathesis of olefins, prepared by anchoring of MoO2(acac)2 to Al2O3

New highly active catalysts for metathesis of olefins were obtained through the interaction of bis(acetylacetonato)dioxymolybdenum(VI) with surface OH groups of -Al₂O₃ and subsequent reduction in H₂ or CO.

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()(VI) OH -Al₂O₃ H₂ CO .

     

Calculation of the rate of SO2 oxidation to SO3

Approximate equation to calculate the effectiveness factor of catalyst for SO₂ oxidation to SO₃ has been derived. Calculated data agree well with those predicted by a quasi-homogeneous model.

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. .

     

Effect of mechanical treatment on some properties of Fe2O3?MoO3 catalysts

Methanol oxidation on mechanically treated amorphous catalysts has been shown to lead to their crystallization and the restoration of their primary properties except for the surface area, which remains decreased. It is suggested that the amorphous state is not responsible for the catalytic properties.

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, . , , , . , .