TiO₂-SiO₂ 및 H₂SO₄으로 개질된 TiO₂-SiO₂의 촉매특성과 산 성질

Catalytic and Acidic Properties of TiO₂-SiO₂ Unmodified and Modified with H₂SO₄

일련의 $TiO_2-SiO_2$촉매를 $TiCl_4$와 $Na_2SiO_3$혼합용액을 공침전시켜 제조하였으며 이중 일부의 촉매는 1N $H_2SO_4$로 처리하여 촉매표면을 개질하였다. 개질된 촉매의 촉매활성은 개질 안된 촉매보다 높은 촉매활성을 나타내었으며 cumene dealkylation 반응에서 보다 2 - propanol dehydration 반응에서 더욱 효과가 크게 나타났다. 개질 안된 촉매의 상기 두 반응에 대한 촉매활성은 산의 양과 관계가 있었다. $TiO_2-SiO_2$촉매는 비교적 많은 양의 약한 산자리와 작은 양의 강한 산자리를 가졌기 때문에 cumene dealkylation 반응에서 보다 2 - propanol dealkylation 반응에 더 높은 촉매활성을 나타내었다. 촉매활성에 미치는 $H_2SO_4$의 개질효과는 $TiO_2$ 함량에 비례하였으며 $92-TiO_2-SiO_2/SO_4^2$가 2 - propanol dealkylation 반응에 가장 큰 촉매활성의 증가를 나타내었다.

A series of $TiO_2-SiO_2$catalysts were prepared by coprecipitation from the mixed solution of titanium tetrachloride and sodium silicate. Some of the samples were treated with 1N $H_2SO_4$ and used as modified catalysts. The catalytic activities of modified catalysts were higher than those of unmodified catalysts, and the effect of modification on the catalytic activity was higher for 2 - propanol dehydration than for cumene dealkylation. The catalytic activity of unmodified catalysts was correlated with their acid amount for the above two reactions. As $TiO_2-SiO_2$ catalysts had relatively large amount of weak acid sites and small amount of strong acid sites, the catalytic activity for 2 - propanol dehydration was higher than that for cumene dealkylation. The effect of modification on catalytic activity increased with increasing $TiO_2$content of the catalysts. Actually, $92-TiO_2-SiO_2/SO_4{^2}$had the highest increment in catalytic activity and $10-TiO_2-SiO_2/SO_4{^2}$had the lowest increment for the 2 - propanol dehydration.