CVD-titania/silica gel carbonized due to pyrolysis of cyclohexene

Titania/silica gels covered by a carbon layer using pyrolysis of cyclohexen e at 973 K and containing different amounts of titania (C-TiO2) and carbon deposit (Cc) have been studied by means of pyrolysis kinetics, nitrogen ads orption/desorption, TEM, IR spectroscopy, differential thermogravimetry, an d theoretical methods. The pyrolysis rate depends on the concentration and the characteristics of a titania phase, as anatase, which forms at a lower synthetic temperature in comparison with rutile, catalyzes this process mor e strongly than rutile does. The adsorbent mesoporosity decreases with incr easing concentrations of titania and carbon covering the oxide surface main ly in mesopores, but in the case of C/SiO2, carbon can be also grafted onto the outer surface of silica. The microporosity (maximal for binary systems C/SiO2 or TiO2/SiO2) of carbon/titania/silica gels is relatively low and c hanges slightly with increasing deposit concentration. The influence of car bon on the specific surface area of the adsorbents is weaker than that of t itania due to not only the difference in the morphology of these deposits p er se but also the types of their distributions and contacts between grafte d matters and substrate surfaces. Carbon deposit reduces the amount of adso rbed water to a greater extent than titania does. Theoretical modeling of C /TiO2/SiO2 and pyrolysis of cyclohexene has been performed using different quantum chemical methods and molecular mechanics.