Surface and bulk properties of silica-zirconia mixed-oxides: acid vs base catalysed condensation

The influence of acid and alkali catalysed condensation on the nature of silica-zirconia mixed oxides derived from sol-gel preparations has been compared. The bulk and surface properties have been characterised and where appropriate compared with results for a sample of Aerosil 200 where an equivalent zirconia loading was deposited by precipitation. Results indicate that the sol-gel preparations generate solids with similar surface areas, but only alkali catalysed condensation leads to solids with large mesopore volumes. Both solids give similar acid site densities although solids prepared by alkali catalysed condensation contained a higher proportion of strong Bronsted acid sites. An increased acid site density was not created by increasing the degree of mixing of the two components. (C) 1999 Elsevier Science B.V. All rights reserved.