Catalysts for Alkylbenzene and Alkylpyridine Ammoxidation

<p>An increase of effectivity of binary and ternary vanadium containing oxide catalysts can be achieved by a regulation of chemical and phase catalyst composition during their preparation. Activity and selectivity of V-Ti catalysts depend on the ratio of V₂O₅ to VO₂ in the succession of substitutional solid solutions VO₂- TiO₂, as well as on the crystal modification of TiO₂. It was investigated the influence of vanadium oxides over the rate of the polymorfous conversion from anatase to rutile and the kind of TiO₂ crystal modification over V₂O₅ reduction degree during the thermal treatment of V-Ti catalysts. The synthesized catalysts offered producing nicotinonitrile from 3-methylpyridine with 93-95% mol. yield. Modifying of V-Ti catalysts by SnO₂ increased their activity. The reason is V=O bond weakening under the influence of SnO₂. That was verified by increasing of V₂O₅ dissociation rate almost by an order in comparison with V-Ti catalysts. SnO₂ in the ternary catalysts exists as individual phase and acts as a donor of oxygen for the lower vanadium oxides. It provides the high stability of V-Ti-Sn catalysts and possibility of obtaining isonicotinonitrile with 95-97% mol. yield from 4-methylpyridine. The investigation of the mutual influence of starting components in the ternary V-Ti-Zr catalysts showed that ZrO₂ prevented the polymorphous transformation from anatase into rutile. In its turn, anatase stabilized baddeleyite, which has a higher catalytic activity than ruffite. Taking into account the mutual influence of the components, it was able to prepare the selective V-Ti-Zr catalyst. It offered obtaining nicotininitrile from 3-methylpyridine with 92-96% mol. yield. </p>

Polymorphous transformation of rod-shaped iron oxides and their catalytic properties in selective reduction of NO by NH3

Polymorphous transformation of rod-shaped γ-Fe2O3 was applied to fabricate Fe3O4/Fe2O3 nanorods and their activities in NH3-SCR followed the order γ-Fe2O3 > α-Fe2O3 > Fe3O4.

Impeded solid state reactions and transformations in ceramic catalysts supports and catalysts

Impeded chemical reactions and impeded polymorphous transformation in materials are discussed, as desired effects, for stabilization of ceramic catalyst supports and ceramic based catalysts. This paper gives a short overview about the possibilities of slowing down the aging processes in ceramic catalyst supports and catalysts. Special attention is given to alumina and titania based catalysts.

Amorphous Ta-N as a Diffusion Barrier for Cu Metallization

ABSTRACTAmorphous Ta-N thin films (14 and 62 nm thick) are deposited on Si substrates by reactive magnetron sputtering followed by Cu film deposition. The interlayer reaction and failure mechanism of the annealed metallization stacks are investigated by resistance measurements, xray diffraction (XRD) and detailed electron microscopy analysis accompanied with electron energy-loss spectroscopy (EELS). Amorphous Ta-N crystallizes at 600°C by a polymorphous transformation to Ta2N. The crystallized Ta2N barrier prevents Cu-Si interaction and intermixing up to 700-800°C, depending on the barrier thickness. Copper appears to be the main diffusing species and reacts with Si at the Ta-N/Si interface to form η˝-Cu3Si. Local Cu-Si reaction enhances the formation of TaSi2 precipitates. Silicon also diffuses, though at a much slower rate, to the surface and reacts with Cu. Local oxidation of Cu3Si occurs upon exposure to air, accompanied by SiO2 formation.