Studies On Preparation Of Mesoporous Solid Acid Catalyst SO₄～(2-)/Zr-CLC And Its Structure And Property

Mesoporous solid acid catalyst of SO42-/Zr-CLC prepared by the intercalation of polynuclear hydroxyl zirconium cation into the interlayer region of clay layers by means of a cation-exchange reaction for the small Na+ ions of Bentonites ,and dipped by SO42" accelerant, has excellent catalytic properties calcinated at high temperature. At last the properties and structure of catalyst of SO42- /Zr-CLC are investigated.The influence of preparation conditions,such as the type of pillaring agents , Zr/clay, the type, quantity and the importing way of accelerant, calcinating temperature on catalytic properties is studied when esterification of citric acid with n-butanol is used as probing reaction. The stability and deactivation of catalyst are also studied. The experimental results show that the optimum preparation conditions of catalyst of SO42- /Zr-CLC are achieved :pillaring material is 0.5mol/l ZrOCb,Zr/clay is 3mmol/g,accelerant is (NH4)2SO4 and the quantity of SO42- is 30% , the precursor of Zr-CLC is dipped by SO42- and is calcinated at temperature of 500 癈 for 2h. The catalyst of SO42- /Zr-CLC prepared under optimum preparation conditions is an excellent catalyst of esterification of citric acid with n-butano and don't induce pollution into environment. When the catalyst is used to esterify citric acid with n-butano,the conversion of citric acid amounts to 96.60% and the selectivity of catalyst amounts to 99.38%.The main reason of deactivation of catalyst is that the active centers are covered by organic substances.The elementary composition, acidity and the distribution of acid intensity, surface area and pores distribution, structure , heat stability and structure of SO42- at the surface of the catalyst are analyzed and characterized by using EDX, Py-IR> Py-TPD, AML XRTK TG, DTA, Frame-IR. The experimental results show that polynuclear hydroxyl zirconium cation is intercalated into the interlayer region of clay layers by means of a cation-exchange reaction for the small Na+ ions of Bentonites, the pillar of ZrO2 is formed by calcinating and fixed in the interlayer region of clay by chemical bond,therefore,the catalyst's surface area is larger ,the heat stability isimproved and mesoporous structure is formed.The catalytic activity is related to the pillar of ZrO2 and acid center formed by SO42- and ZrO2-The catalyst has two acid centers which are strong and feeble acid centers,at the same time the catalyst has B acid and L acid;and most feeble acid center is B acid,most strong acid center is L acid. The main resource of B acid is Zr-OH of polynuclear hydroxyl Zirconium cation, while the main resource of L acid is the pillar of ZrO2 and acid center formed by SO42-and ZrO2. The structure of organic sulfate is formed between SO42- and ZrO2 when the catalyst is calcinated at temperature of 500癈.