Physicochemical properties of TiO2SiO2 unmodified and modified with H2SO4 and activity for acid catalysis

A series of TiO₂SiO₂ catalysts were prepared by coprecipitation from the mixed solution of titanium tetrachloride and sodium silicate. Some of the sample were modified with 0.5 M H₂SO₄ and used as modified catalysts. The addition of TiO₂ to SiO₂ caused the increase of acidity and acid strength, and the shifts of OH and SiO stretching bands of silanol group to lower frequencies in proportion to the TiO₂ content. Catalytic activities for 2-propanol dehydration and cumene dealkylation increased in relation to the increase of acidity and the band shifts to lower frequencies. The catalytic activities of modified catalysts were higher than those of unmodified catalysts, and the effect of modification on catalytic activity was higher for 2-propanol dehydration than for cumene dealkylation. The effect of modification on catalytic activity increased with increasing TiO₂ content of the catalysts. Actually, 92-TiO₂SiO₂/SO²⁻₄ had the highest increment in catalytic activity and 10-TiO₂SiO₂/SO²⁻₄ had the lowest increment for the 2-propanol dehydration.