【作者】 徐海燕；

【导师】 阚秋斌；

【作者基本信息】 吉林大学 ， 物理化学， 2009， 博士

【摘要】 微孔沸石具有较大的比表面积、可调变的孔径、较强的酸性以及较高的热稳定性和水热稳定性,因而被广泛应用于吸附、分离、催化等领域。但由于它有限的孔径限制其实际应用范围。孔径在2-50纳米范围内的介孔材料可以克服微孔分子筛孔径的局限性。但是由于它的孔壁是无定形的,酸性和水热稳定性较差,因而也限制了其应用范围。因而,近年来,很多研究者致力于寻找一种材料能够兼具微孔和介孔材料优点。以纳米Beta沸石或碱处理纳米Beta沸石得到的微小沸石颗粒及其次级结构单元为硅、铝源,在模板剂十六烷基三甲基溴化铵(CTAB)的存在下,通过调pH值后晶化的方法合成了一系列具有六方状介孔结构MCM-41/Beta复合分子筛。复合分子筛的酸性和水热稳定性都比普通的MCM-41要高。在苯酚叔丁基化反应中,复合分子筛显示了更高的苯酚转化率及2,4-二叔丁基苯酚的选择性。同样以纳米Beta沸石或碱处理纳米Beta沸石得到的微小沸石颗粒为硅、铝源,在模板剂P123的存在下分别在强酸及弱酸条件下合成了两类分子筛。强酸条件下合成的样品具有类似SBA-15的六方介孔孔道,但是其酸性不高,主要原因可能是强酸性合成条件容易造成脱铝,从而削弱了其酸性。弱酸条件合成样品具有类似KIT-1的蠕虫状孔道,酸性较强。在苯酚叔丁基化反应中,弱酸条件下合成的样品比强酸条件下合成的样品显示了更高的苯酚转化率及2,4-二叔丁基苯酚的选择性。通过一步法合成了一种介孔分子筛,该系列分子筛具有较强的酸性,在苯酚叔丁基化反应中,该系列分子筛显示了较高的苯酚转化率及2,4-二叔丁基苯酚的选择性。更多还原

【Abstract】 Zeolites are widely used in industrial applications because they have many desirable properties, such as high surface area, adjustable pore size, acidity and high thermal and hydrothermal stability. However, the main drawback of zeolites is their small pore channels which make large sized reactants and products to and from the active sites of catalysts difficult. Mesoporous molecular sieves with pore diameters of 2–50 nm can overcome the pore size constraint of microporous zeolites and allow the diffusion of lager molecules. However, mesoporous materials have low acidity and hydrothermal stability because of their amorphous nature of frameworks, which limit their use as catalysts in industrial processes. Recently, much effort has been devoted to prepare new molecular sieves which combine the advantages of micro- and mesoporous materials.In the chapter three, Beta/MCM-41 micro/mesoporous composite materials have been prepared through assembly of zeolite Beta nanoclusters and their decomposed products by NaOH solution in the presence of CTAB under static or stirred conditions. The composite materials exhibit stronger acidity and higher hydrothermal stability than traditional mesoporous MCM-41. In the alkylation reaction of phenol with tert-butanol, composite materials display higher catalytic activities than that of Al-MCM-41.In the chapter four, micro/mesoporous composite materials have been prepared by using zeolite Beta nanoclusters and their decomposed products by NaOH solution as silica and aluminus source in the presence of P123 under strong or weak acidic condition. When it is synthesized under strong acidic condition, the resulting material exhibit highly ordered hexagonally arranged mesochannels similar to that of SBA-15. However, the acidity of the material is largely weakened by dealumination under strong acidic condition. The material synthesized under weak acidic condition shows disordered worm-like mesoporous channels. In the alkylation reaction of phenol with tert-butanol, the material syntheszed under weak acidic condition exhibits higher conversion of phenol and selectivity for 2,4-di-tert-butyl phenol (2,4-DTBP) than the material synthesized under strong acidic condition.In the chapter five, mesoporous molecular sieves with strong acidity have been prepared through a simple one step synthesis procedure in the presence of tetralkylammonium hydroxide. The resulting materials exhibit stronger acidity than conventional mesoporous MCM-41. All materials show high conversion of phenol and selectivity for 2,4-di-tert-butyl phenol (2,4-DTBP) in alkylation of phenol with tert-butanol.更多还原