SO_4~(2-)/ZrO_2固体超强酸催化剂上的酯化反应机理

与液体酸和酸性树脂催化剂相比,固体超强酸催化剂具有许多优点,如无腐蚀性、不污染环境、易与产物分离和重使用性等。通过沉淀、老化、过滤、洗涤、干燥、浸渍、焙烧等过程,从ZrOCl2·8H2O和(NH4)2SO4制备了SO42-/ZrO2固体超强酸催化剂;使用Hammett指示剂法和吡啶吸附的FT-IR光谱法测定了其酸强度和酸中心类型;以甲醇、乙酸和乙酸乙酯吸附在SO42-/ZrO2固体超强酸催化剂上的FT-IR光谱,推测酯化反应机理。结果表明,当焙烧温度高于500℃,SO42-/ZrO2可以形成超强酸,其表面上同时存在Lewis酸和Bronsted酸中心;在SO42-/ZrO2固体超强酸催化剂上,酯化反应既可以在Lewis酸中心进行,也可以在Bronsted酸中心上进行。

Esterification Reaction Mechanism on the Surface of SO42-/ZrO2 Solid Superacid Catalysts

Compared to liquid acids and acidic resins,solid superacid catalysts has many advantages(such as non-corrosion, non-polluting enviroment, easy of separation and reusability etc.). The SO42-/ZrO2 solid superacid catalysts was prepared from ZrOCl2·8H2O and(NH4)2SO4 by precipitation, aging, filtering, washing,maceration and calcination processes. Their acidities were determined by Hammett indicators and FT-IR spectroscopy of pyridine adsorption methods. The reaction mechanism were determined with FT-IR spectroscopy of methanol,acetic acid,acetic ester on the SO42-/ZrO2 solid superacid catalyst. The results show that the SO42-/ZrO2 solid superacid was formed when calcination temperatures was higher than 500 ℃ and their surfaces has Lewis and Bronsted acidic centers; the estreification takes place not only on the Bronsted acidic centers but also on the Lewis acidic centers of the SO42-/ZrO2 solid superacid catalyst.