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Dehydrogenation of propane to propylene in absence and in presence of oxygen in the reaction mixture of propane-inert gas has been investigated on vanadium oxide supported on mesoporous H-Ti-MCM-41 titanosilicate prepared by hydrothermal synthesis from titanoaerosil. It has been shown that at increase of the amount of VxOy from 5 to 30 wt. %, supported by decomposition of vanadyl oxalate or acetylacetonate complexes, the orderliness of system H-Ti-MCM-41 is broken, the size of its surface, diameter and volume of mesopores are decreased. The maximum yield of propylene is reached at 650-675 °C. It is obtained on 20 % greater for dehydrogenation of propane in the absence of oxygen. It is dependent extremally on the formed volume of pores, on its relationship with the acidity of active surface sites and it is accounted for the certain optimum range of variation of these values. [ABSTRACT FROM AUTHOR]

Ti-MCM-41 silicate with vanadium introduced in mesoporous structure has been obtained by hydrothermal template synthesis with participation of VOSO4 and pyrogenic titanoaerosil with 1.4 wt. % tetrahedrally coordinated titanium. By the X-ray diffraction, X-ray fluorescent spectroscopy, DR UV-vis analysis and adsorption of nitrogen it has been shown that even 0.3 wt. % V causes raising spatial order and hydrolytic stability of Ti-MCM-41. It has been found that additional supporting of VOx groups on a surface of the synthesized bimetallic silicate allowed to obtain the catalyst 5 %VOx/V, Ti-MCM-41 which due to dehydrogenation of propane generated propylene with bigger selectivity and yield than those when VOx was supported on MCM-41 and Ti-MCM-41. [ABSTRACT FROM AUTHOR]

A series of fumed oxides such as silica, titania, alumina, silica/alumina (SA), silica/titania (ST), and alumina/silica/titania (AST), initial and hydrothermally treated (HTT) in the steam phase at T(HTT)=150, 250, and 350 degrees C was studied by adsorption, AFM, XRD, FTIR, and theoretical methods. Diminution of the size of primary particles (corresponding to increasing S(BET)) of initial silica and mixed oxides results in enhancement of their structural changes on HTT with elevating T(HTT) and increasing density of packing of primary particles in the secondary structures. Relative changes in the texture of treated fumed silicas are smaller than those of mesoporous silica gels occurring under similar HTT conditions. On HTT, aggregates of primary particles and their agglomerates become denser but their surface layers become looser because of transfer of silica fragments from one particle to another, and the smaller the initial primary particles, the greater the relative diminution of the specific surface area S(BET) for the same type of primary particle packing in aggregates. Relative changes in the pore volume V(p) (or V(BJHd)) on HTT are more complex than that of S(BET), as for many samples the V(p) value increases especially at T(HTT)=150 degrees C. Alumina and titania partially inhibit structural changes on HTT, which decrease in the series silica > SA > AST approximately ST.