层间模板剂导向合成新型多孔蒙脱石材料的研究

Synthesis of Novel Porous Silica/Montmorillonite Composites by Gallery-Template Structure-Directing Method

采用提纯后天然蒙脱石为原料,经十六烷基三甲基溴化铵和十八烷基三甲基氯化铵改性后,分别以C8～C14中性伯胺为结构导向剂,蒙脱石/胺/正硅酸乙酯摩尔比为1:20:150,搅拌反应时间为8h,经分离、干燥、焙烧,成功制备出新型多孔氧化硅/蒙脱石复合材料.用XRD、TG、FT-IR、N_2等温吸附-脱附和酸催化烷基化探针反应等表征了其结构和性能.结果表明,合成材料具有高比表面积、大层间通道、孔径分布较窄且依据模板导向剂分子尺寸可调,其酸催化活性和选择性较普通的酸活化蒙脱石有较大的提高.

The purified natural montmorillonites were modified by cetyltrimethylammonium bromide (CTAB) and octadecyltrimethylammonium chloride respectively. Mixtures of the modified montmorillonites, neutral amine and tetraethylorthosilicate (TEOS at a molar ratio of 1:20:150 were allowed to react for 8h. The resulting intercalates were centrifuged, dried in air and calcined at 540degreesC for 4h to burn off the organic templates, a series of novel porous silica/montmorillonites composites were successfully synthesized by the gallery-template structure-directing process. The structure of the samples was characterized by XRD, TG, FT-IR, N-2 adsorption-desorption isotherms and acid-catalyzed alkylation probe reaction. The results show that the samples synthesized have a narrowly pore distribution and super-gallery height, a large BET specific area. With the increasing of chain length of neutral amine, the pore size and gallery height increase accordingly. The synthetic materials are potentially effective solid acid catalysts for the Friedel-Crafts alkylation of catechol with tert-butyl alcohol to synthesize butyl 4-tert-butylcatechol (4-TBC). Over synthetic porous material by using CTAB and hexylamine as template, the selectivity to 4-TBC of 78.5% and catechol conversion of 45.5% can be obtained under experimental condition.