Title : Non-hydrolytic sol-gel synthesis of oxide and mixed oxide catalytic materials
Abstract:
Oxides and mixed oxides are used as catalytic supports or as catalysts in all the fields of heterogeneouscatalysis. Sol-gel processing is widelyused for the synthesis of these catalytic materials. Conventional sol-gel typically involves the hydrolysis and polycondensation of precursors (e.g. silicon or metal alkoxides), but several alternative non-hydrolyticsol-gel (NHSG) routes have been developed over the last decades. NHSG routes involve the reaction in non-aqueous media of precursors (e.g. chlorides, alkoxides) with an organic oxygen donor (e.g. ether, alcohol). In this presentation I wish to show the potential of NHSG in the synthesis of catalytic materials. In particular, the reaction of chloride precursors with an ether provides a simple and cost effective route to non-ordered mesoporous mixed oxide xerogels, avoiding the use of multi-step procedures, expensive precursors, reactivity modifiers, templating agents or supercritical drying. This non-hydrolytic route has been applied to the design of mesoporous mixed oxide catalysts: SiO2 -TiO2 (-Me3 SiO0.5), TiO2 -V2 O5 , SiO2 -Al2 O3 -MoO3 , SiO2 -Al2 O3 -Re2 O7 , Al2 O3 -Nb2 O5 -AgO, SiO2 -ZrO2 , etc. In terms of texture, structure and catalytic performances, the catalysts obtained by non-hydrolytic sol-gel compare well with catalysts prepared by impregnation of supports or by state of the art methods.
