The structure of porous silica gel/titania synthesized using chemical vapor
deposition (CVD) of titania via repeated reactions of TiCl4 with the surfa
ce and subsequent hydrolysis of residual Ti-CI bonds at different temperatu
res was investigated by means of low-temperature nitrogen adsorption-desorp
tion, X-ray diffraction (XRD), IR spectroscopy, and theoretical methods. A
globular model of porous solids with corpuscular structure was applied to e
stimate the porosity parameters of titania/silica gel adsorbents. The utili
zation of this model is useful, for example, to predict conditions for synt
hesis of titania/silica with a specified structure. Analysis of pore parame
ters and fractal dimension suggests that the porosity and fractality of sam
ples decrease with increasing amount of TiO2 covering the silica gel surfac
e in a nonuniform layer, which represents small particles embedded in pores
and larger particles formed at the outer surface of silica globules. Theor
etical simulation shows that the Si-O-Ti linkages between the cover and the
substrate can be easily hydrolyzed, which is in agreement with the IR data
corresponding to the absence of a band at 950 cm(-1) (characteristic of Si
-O-Ti bridges) independent of the concentration of CVD-titania. (C) 1999 Ac
ademic Press.