A. S. Kovalenko

Interrelationship of Structural-Adsorption Characteristics of Titanium Dioxide and Its Photocatalytic Activity in the Gas-Phase Oxidation of Acetone and Ethanol

X-ray phase analysis and adsorption techniques were used to study the effect of heat treatment of starting amorphous titanium dioxide on its structural-adsorption characteristics, which determine the photocatalytic activity in the gas-phase oxidation of acetone and ethanol. In addition to the specific photocatalytic activity of the samples due to the amount of the active anatase TiO2 modification, the adsorption capacity of the photocatalysts, which is a function of the specific surface and pore adsorption volume, affects the rate of the reactions studied.

Effect of Metal Inclusions on the Porous Structure and Photocatalytic Activity of Titanium Dioxide

A study was carried out on the effect of the inclusion of a series of transition metals (V, Cr, Mn, Fe, Ni, Cu, Zr, Mo) and also Al, Si, Zn, and Sn into titanium dioxide on its porous structure, anatase formation, and photocatalytic activity in the generation of molecular hydrogen from aqueous ethanol. An increase in the content of these metals leads to a decrease in photocatalytic activity, while an increase in the anatase content in titanium dioxide leads to an increase in such activity.

FEATURES OF FUNCTIONALIZATION OF MCM-41 SILICA MESOPOROUS MOLECULAR SIEVES DURING THEIR TEMPLATE SYNTHESIS

We have shown that functionalization of MCM-41 mesoporous molecular sieves during their template synthesis using the effect of solubilization of organic hydrophobic co-condensing compounds makes it possible to obtain highly ordered mesoporous molecular sieves, with concentrations of vinyl or allyl groups covalently bonded to the surface of the silica matrix of about 3.5 mmol/g, which after sulfonation have acidic properties and exhibit catalytic activity in the process of ethyl tert-butyl ether synthesis.

Effect of Phosphorylation of Si-MCM-41 and Ti-Si-MCM-41 Mesoporous Molecular Sieves on Their Structure-Adsorption and Acid Properties

Transmission electron microscopy, X-ray diffraction, nitrogen and argon adsorption, thermal analysis, thermoprogrammed ammonia desorption, and 1H MAS NMR spectroscopy were used to show that phosphorylation by POCl3 yields MCM-41 silica gel and Ti-MCM-41 titanium-silica gel mesoporous molecular sieves with about 1.1 mmol/g acid sites consisting largely of hydroxyl group protons of supported phosphoric acid. These materials display catalytic activity in the esterification of acetic acid by ethanol.

Preparation of hybrid organo-inorganic catalysts based on MSM-41 mesoporous molecular sieves and their properties in synthesis of ethyl tert-butyl ether

A series of sulfoorganosilica (vinyl-containing) catalysts based on MSM-41 mesoporous molecular sieves were prepared by template synthesis. The structure and properties of these catalysts and their catalytic characteristics in synthesis of ethyl tert-butyl ether were examined.

Structural Features of Grafted Phosphates in Mesopores of Si-MCM-41 and Ti,Si-MCM-41 Molecular Sieves

We have used 31P NMR (MAS) and IR spectroscopy and also chemical analysis to show that when Si- and Ti,Si-MCM-41 mesoporous molecular sieves are treated with phosphorus oxychloride, surface-anchored silicophosphate and titanophosphate compounds are formed of the type ≡(Si—O)x—{PO(OH)3−x} and ≡(Ti—O)x—{PO(OH)3−x} (x = 1, 2), and also compounds with the structure of titanium hydrophosphate and pyrophosphate.

Effects of template synthesis conditions on TiO2 gel structuring

Studies have been made on the effects of template synthesis conditions (initial substances, SA/TiO2 ratio, and pH) on TiO2 gel formation; under certain conditions, a nanoperiodic structure is formed in the presence of a cationic surfactant SA (ethonium, cetyltrimethylammonium chloride) and in the presence of anionic SA (sodium dodecylsulfat, and dodecylbenzenesulfonic acid). A feature of the TiO2 gels made in the presence of a crown ether (dibenzo-18-crown-6) is that it contains a nanoperiodic structure and a crystalline one (anatase).

Effects of synthesis conditions on titanogel sorption characteristics

Studies have been made on how synthesis conditions (gelling pH, washing pH, and drying temperature) affect the textural characteristics of titanogels; transparent monolithic gels are formed at pH≤5, while coagels are formed at pH>5. The porous structure parameters are substantially influenced only by the washing pH. XRD indicates that there is some ordering: weak long-range order.