Titania-induced changes of silica texture upon moderate heating

Induced changes in the texture of silica gel due to physically mixed titania (15–85 mol%) upon heating at 300°C or 600°C in air are inspected through a detailed pore structure analysis using adsorption of N2 at 77 K. The decreases in surface area and pore volume with the corresponding variations in the average hydraulic pore radius of silica recorded at both heating temperatures are attributed to the disturbance of the normal conditions of silica dehydration–dehydroxylation due to presence of titania. Water desorbed from titania upon heating up to 300°C alters the arrangement of siloxane links that form between primary particles of silica upon dehydroxylation. The active Lewis sites of titania surface that develop in the course of heating up to 600°C disturb the usual equilibrium between surface and bulk water of silica.