The role played by an iodine-containing promoter in the formation of active polycrystalline silver catalyst surface

The programmed temperature desorption method was used to study the interaction of oxygen with the surface of a polycrystalline silver catalyst promoted with iodine. Ethyl iodide almost did not interact with the unoxidized surface of silver. The adsorption of C₂H₅I on the oxidized catalyst surface resulted in the formation of two adsorbed iodine forms, silver iodide and iodine deeply dissolved in subsurface silver crystal lattice layers. The character of oxygen adsorption from the iodine-containing surface of the catalyst was determined by the amount and form of adsorbed iodine. In the presence of a iodine-containing promoter, the concentration of oxide-like oxygen sharply decreased, and the amount of strongly bound atomically adsorbed oxygen responsible for the selective transformation of ethylene glycol into glyoxal increased.     

Photocatalytic properties of electric-explosion-produced TiO<Subscript>2</Subscript> nanopowder

Structural features and physicochemical and photocatalytic properties of an electric-explosion-produced titanium dioxide powder were studied by means of X-ray phase and X-ray diffraction analyses, transmission electron microscopy, thermal analysis, and optical spectroscopy.     

Coking during ethylene glycol oxidation to glyoxal on a silver catalyst

The influence of major parameters of ethylene glycol oxidation to glyoxal on a silver catalyst on catalyst coking has been studied. On the basis of experimental data obtained, methods decreasing the coking have been suggested.     

FePO<Subscript>4</Subscript>/SiO<Subscript>2</Subscript> Catalysts for Propylene Glycol Oxidation

FePО₄/SiO₂ supported catalysts with a different content of iron phosphate are prepared. The properties of the catalyst are changed by the introduction of alkali metal compounds (Na or Cs) on its surface. The samples obtained are characterized by X-ray diffraction, low-temperature nitrogen adsorption, temperatureprogrammed reduction by hydrogen, and temperature-programmed desorption of ammonia. The catalytic properties are investigated in the reaction of gas-phase propylene glycol oxidation. It is shown that the selectivity of methylglyoxal formation on the unmodified catalysts is determined by the state of the supported active component and by its reduction–oxidation ability under the action of a reaction mixture.     

Structural-phase and morphological characteristics of silver catalysts on modified ceramic supports for selective oxidation of alcohols

New ceramic materials based on silicon nitride and obtained by self-propagating high-temperature (SPHT) synthesis were investigated. The Si₃N₄ materials modified with Zr and Al compounds were used as supports for silver-containing catalysts of selective oxidation of ethyleneglycol into glyoxal. The procedure for the synthesis of supported silver-containing catalysts affected the structural and morphological states of the active component before and after the catalytic reaction.     

Cleaning of the Surface of Silver Crystals Used as Catalysts of Gas-Phase Oxidation of Ethylene Glycol to Glyoxal

The procedure for cleaning polycrystalline fibers of electrolytic silver used as a catalyst for gas phase oxidation of ethylene glycol to glyoxal was developed with the aid of X-ray photoelectron spectroscopy.