Adsorption and thermodynamic properties of active sites of a pyrogenic aluminium oxide surface

Differential isosteric adsorption heats and entropies of adsorption of both n-pentane and diethyl ether on hydrated and dehydrated surfaces of pyrogenic alumina (S=140 m²/g) in the coverage range of 0.15–1.0 have been calculated from the adsorption isotherms.     

Synthesis of polysiloxane xerogels with fluorine-containing groups in the surface layer and their sorption properties

Hydrolysis and polycondensation reactions of tetraethoxysilane (TEOS) with 3,3,3-trifluoropropyl-trimethoxysilane (TFMS) or 1H,1H,2H,2H-perfluorooctyltriethoxysilane (PFES) were used to synthesize xerogels functionalized with fluorine-containing groups. According to transmission electron microscopy, the skeletons of synthesized polysiloxane xerogels have globular structures and consist of agglomerates of particles with fluorinated groups on their surfaces. FTIR spectroscopy showed that primary xerogel particles possess spatial polysiloxane networks, with fluorinated groups along with silanol groups and water in the surface layer. According to thermal analyses, the water content was 3–8 wt.%, and it decreased with increasing length of the fluorinated chain. Thermal destruction of the surface layer starts above 300 °C. The sorbents that were obtained were predominantly mesoporous materials with well-developed porous structures (S_BET = 400–960 m² g⁻¹, V_s = 0.66–0.93 cm³ g⁻¹). The influence of the TEOS/functional silane ratio and the natures of the functional groups on the structural and adsorptive properties were shown. The samples synthesized are organophilic. The affinity for n-hexane increases with increasing length of the fluorine-containing chain (PFES) and the content of fluorinated groups in the surface layer. The hybrid organic–inorganic materials that were obtained can be used for adsorption of hydrocarbons, including oil, from water.     

New commercial technologies based on fundamental research in catalysis, designed at the Institute of Chemical Physics of Russian Academy of Sciences

Modern commercial technologies and catalysts of new generation designed using fundamental research in catalysis are presented. Technologies show high efficiency, low energy and material consumption, are friendly to the environment, and require low investment costs.     

Adsorption and Thermodynamic Study of Pyrogenic Alumina Properties

Adsorption of n-pentane, triethylamine, diethyl ether, acetonitrile and chloroform has been investigated on pyrogenic alumina (S=140 m² g⁻¹). The results of our studies have shown the presence of active sites on the surface of pyrogenic alumina with irreversible adsorption of electron-donating molecules and CHCl₃ and the dependence of energetic surface properties on electronic structure of adsorbate, quantity of adsorbed substance and hydration degree of the surface. On the hydrated oxide surface the water molecules screen the active sites of the surface, which resulted in changing of interaction energy of adsorbent-adsorbate and decreasing the region of irreversible adsorption of organic bases and CH-acid. This revised version was published online in August 2006 with corrections to the Cover Date.