PREPARATION OF SOL-GEL SULFATED ZRO2-SIO2 AND CHARACTERIZATION OF ITSSURFACE-ACIDITY

Zr-Si mixed oxides containing 1.3 to 6.7 wt.-% Zr have been prepared b y a sol-gel technique, using tetraethoxysilane and zirconium acetate a s precursors. Zirconium is incorporated into the lattice of silica, bu t can easily be extracted either by self steaming or by acid treatment . The solids obtained in basic medium show a low surface area and low acidity. The samples prepared in acidic medium show large surface area s between 410 and 740 m(2)/g and can be converted to strong acids by c ontact with a solution of sulfuric acid. They retain pyridine up to 77 3 K and contain a total number of acid sites comparable to that of HY zeolites i.e. 1.7 meq/g. The catalytic activity for the bifunctional i somerization of n-hexane expressed per gram of zirconium is comparable for the sample containing 4wt.-% Zr and sulfated zirconia.