Physico-chemical properties of silica-supported vanadium oxide catalysts

- . TiO₂ ZnO. - CO₂ H₂O. — .

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The effect of visible light on propane and n-butane oxidation has been sutied on a seires of metal oxides. TiO₂ and ZnO have been found to exert a photocatalytic effect. On TiO₂, propane and n-butane are oxidized to CO₂ and H₂O. On ZnO as catalyst, partial oxidation products, aldehydes and ketones, are formed.

     

Resistive properties of La2 ? x Sr x CuO4 low-dopped cuprates in the antiferromagnetic state at low temperatures

The nonlinear dependence of conductivity and negative differential resistance of ceramic samples of La_{2 ? x} Sr _x CuO₄ in the antiferromagnetic state is revealed. The possible influence of a spatially inhomoge-neous distribution of strontium impurities on the low-temperature behavior of conductivity is discussed.     

Aggregation properties of copper dibenzo-barrelenophthalocyanine

Depending on the solvent in which they are placed or from which they have been obtained, sterically hindered copper octa-tert-butyltetra-4,5-dibenzobarrelenophthalocyanines in solution and as a powder can take a monomeric form or dimer or trimer aggregate forms. In the aggregates, the molecules are disposed opposite one another around a high-order axis at an angle of 45° from equatorial displacement.Institute for the Chemistry of Natural Organic Materials, Russian Academy of Sciences, Krasnoyarsk 660000. Scientific-Research Institute for Organic Itermediates and Dyes, Moscow 103787. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 171–175, February, 1995. Original article submitted December 22, 1994.     

The role of local environment in charge ordering of perovskite-like oxides

The properties of magnetically diluted perovskite-like complex oxides La_{2 ? x} A _x MO₄ (M is Fe or Mn and A is Sr or Ba) have been studied. Charge and spin ordering is suggested to be interrelated with the local structural characteristics and the electronic structure of nanoclusters of transition elements found in the ceramics studied.     

The spin state of manganese atoms in Sr2MnSbO6 complex oxides

The magnetic susceptibility of Sr₂MnSbO₆ solid solutions in a Sr₂AlSbO₆ diamagnetic diluent is investigated. Variation in the magnetic characteristics with temperature and the solution concentration indicates the coexistence of two spin states of manganese atoms: low-spin and high-spin. The possibility of spin transitions is due to temperature-dependent local distortions in the crystal structure of the solutions.     

Effect of an oxidant on the nature of bulk defects in Li/CaO and its catalytic activity in the oxidative dimerization of methane

The nature of bulk defects formed in Li/CaO during the oxidative dimerization of methane with O₂ and N₂O as oxidants is studied with the use of ESR. Changing the oxidant from oxygen to nitrogen oxide results in changes in the nature of the bulk defects and the catalytic behavior of Li/CaO.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 599–601, March, 1993.     

New Mechanism for the Catalytic Oxidation of Lignin to Vanillin

The previously proposed mechanism for lignin oxidation to vanillin was supported experimentally. This process begins with the formation of a phenoxyl radical and ends with the step of retroaldol cleavage of substituted coniferaldehyde to vanillin. The oxidation of model compounds was studied, and experimental evidence for the proposed mechanism was obtained. The postulated intermediate coniferyl alcohol was detected in the oxidation of eugenol. The proposed mechanism was supported by kinetic data and the composition of the oxidation products of vanillideneacetone, lignosulfonates, eugenol, isoeugenol, guaiacylethanol, and guaiacylpropanol.     

State of atoms of the transition group elements in dilute solid solutions based on LiMO2 (M = Sc, Ga, Al): IV. Magnetic susceptibility of the LiMxGa1?xO2 solid solutions (M = Cr, Cu)

Magnetic dilution of LiMO₂ complex oxides (M = Cu, Cr) was studied. The results obtained were correlated to the physical and chemical properties of two-dimensional perovskite-like oxides containing copper and lithium. Various valence and spin states of copper and chromium were found, which are associated with essential anisotropy of the local surrounding of a transition element and with the influence of lithium atoms on the electron state of nanoclusters containing these elements. Original Russian Text ? N.P. Bobrysheva, A.A. Selyutin, I.A. Grigorov, 2009, published in Zhurnal Obshchei Khimii, 2009, Vol. 79, No. 4, pp. 538–541. For communication III, see [1].