孔壁含有沸石次级结构单元的MCM-48的合成及催化研究

以双表面活性剂（双极性头表面活性剂和三乙醇胺）为模板，以含有沸石次级结构单元的溶胶为前驱体，在碱性条件下合成了新型介孔分子筛MCM 48。研究了沸石前驱体和三乙醇胺对产物MCM 48形成的影响，XRD和TEM表征结果表明，样品具有较高的结晶度和规则的孔径；FTIR和N2吸附表征结果表明，产物MCM 48的孔壁中含有沸石的次级结构单元，从而使得样品具有更大的比表面积。产物的重芳烃轻质化反应催化活性表明，实验样品对重芳烃的转化率比常规的MCM 48高，转化率约高出11%，进一步证明了实验样品的孔壁中含有沸石的结构单元。

Synthesis of mesoporous MCM-48 containing zeolite secondary building units and it's catalytic properties

Mesoporous aluminosilicate MCM 48 containing zeolite secondary building units in the pore wall, has been synthesized in alkaline media by a two step procedure: the zeolite structure precursor was first synthesized by carefully controlling reaction conditions and then the pre synthesized zeolite precursor was assembled using mixed templates of gemini surfactant \C18H37N(CH3)2(CH2)3N(CH3)2 C18H37\]2+ and triethanolamine (TEA). Small angle XRD patterns of the as made samples display strong diffraction peaks, indicating the highly ordered mesostructured MCM 48 was formed. TEM images further show that the as made sample has uniform cubic pore channel system with the pore diameter of about 2.5nm. FT IR technique was employed to characterize the pore wall of the MCM 48 containing zeolite building units. IR spectra reveal an extra band at 520cm－1~600cm－1 assigned to five membered rings from zeolite structure, suggesting the presence of zeolite building units in the pore wall. N2 adsorption/desorption result shows the material has much higher specific surface area （1200m2/g）, compared with the reported data （1100m2/g） of MCM 48. This may be ascribed to the presence of micropores produced by zeolite secondary building units in its pore wall. The hydrogenation dealkylation reaction of heavy aromatic hydrocarbons on the as made MCM 48 catalyst gives higher conversion than that on traditional MCM 48. Thus, it is concluded that as made MCM 48 containing the secondary building units of zeolites is of potential application in the catalytic conversion of large molecules. The key factors in our synthesis of MCM 48 are the controlled preparation of zeolite precursor and the selection of auxiliary template.