多级孔纳米分子筛的快速合成、表征及催化性能研究
发布时间：2018-12-18 13:18
【摘要】：多级孔分子筛的合成一直以来都是研究的热门方向,通常制备多级孔分子筛可分为'由上而下'和'由下而上'两种策略。前者指的是先合成分子筛,再通过溶硅溶铝或者二者结合引入介孔,但这种方法存在一定的弊端,如硅铝比需要在一定的范围内,容易破坏微孔结构等。后者是在合成起始步骤中加入可以导向介孔的模板剂(软模板或者硬模板)。也可以合成双功能的模板剂一步导向微孔和介孔复合的分子筛。但是高昂的模板剂价格以及繁琐的模板剂制备过程限制模板剂法的实际应用。控制晶化条件直接合成小晶粒分子筛堆积形成晶间介孔也是一种高效的制备多级孔分子筛的方法。探索一条经济简便、收率高、快速合成多级孔(包括晶间与晶内)纳米分子筛的路线是当前研究的重点课题。第一部分主要是以层状硅酸盐H-kanemite为硅源,在常规小分子季铵盐四乙基氢氧化铵(TEAOH)的导向作用下快速合成多级孔纳米Beta分子筛。在碱性晶化母液中,H-kanemite易于溶解成硅基碎片并且能4 h内快速重新组装形成纳米Beta分子筛。纳米Beta分子筛晶粒大小在20 nm左右,晶间堆积介孔均匀分布在20 nm左右,比表面积为703 m2 g-1,总孔容达0.86 cm3 g-1,微孔孔容为0.21 cm3 g-1。与常规及商业Beta相比多级孔纳米Beta分子筛的介孔孔容及比表面积更高。多级孔纳米Beta在大分子的傅克酰基化反应中也显示比常规及商业Beta分子筛更优异的催化性能。第二部分是在第一部分的基础上继续以H-kanemite作为硅源,通过低温预晶化和干胶法相结合的晶化方式试图进一步合成出晶粒更小并且更为均一的超纳米Beta分子筛。经过预晶化温度、时间等参数的调控,成功地实现了～10 nm纳米Beta分子筛的合成,并形成了均匀的～7nm的晶间介孔。且在傅克酰基化反应中具有比常规及商业Beta更为优异的催化性能。第三部分以H-kanemite作为母体,通过加入常规表面活性剂十六烷基三甲基溴化铵CTAB及小分子模板剂TEAOH,原位合成含晶内介孔的多级孔全硅PLS-3分子筛,为进一步引入活性中心探索其催化性能提供了基础。
[Abstract]:The synthesis of multiporous molecular sieves has always been a hot research direction. Usually, the preparation of multilayered molecular sieves can be divided into 'top-down' and 'bottom-up' strategies. The former refers to the first synthesis of molecular sieve and then the introduction of mesoporous via dissolved silicon dissolved aluminum or the combination of the two. However this method has some disadvantages such as the ratio of silicon to aluminum needs to be within a certain range and the micropore structure can be easily destroyed. The latter is to add a template (soft template or hard template) that can be directed to mesoporous cells in the starting step of synthesis. Bifunctional templates can also be synthesized by one-step-oriented microporous and mesoporous composite molecular sieves. But the high price of template agent and the complicated process of template preparation limit the practical application of template method. Controlling the crystallization conditions directly to synthesize small grain molecular sieve to form intergranular mesoporous is also an efficient method to prepare multiporous molecular sieve. It is an important research topic to explore a simple and economical route for the rapid synthesis of multi-pore nanosieve (including intergranular and intragranular). In the first part, layered silicate H-kanemite was used as silicon source to rapidly synthesize multiporous Beta molecular sieve under the guidance of conventional quaternary ammonium salt tetraethylammonium hydroxide (TEAOH). In alkaline crystallization mother liquor, H-kanemite is easy to dissolve into silicon-based fragments and can be rapidly reassembled into nano-sized Beta molecular sieve in 4 h. The grain size of nanometer Beta molecular sieve is about 20 nm, the mesoporous distribution is about 20 nm, the specific surface area is 703 m ~ 2 g ~ (-1), the total pore volume is 0.86 cm3 g ~ (-1), and the micropore volume is 0.21 cm3 g ~ (-1). Compared with conventional and commercial Beta, the mesoporous volume and specific surface area of multiporous Beta molecular sieve are higher. Multiporous nano-sized Beta also showed better catalytic performance than conventional and commercial Beta molecular sieves in the Fourier acylation reaction of macromolecules. In the second part, on the basis of the first part, H-kanemite is used as the silicon source to synthesize ultrananocrystalline Beta molecular sieve with smaller and more uniform grain size through the combination of low temperature precrystallization and dry adhesive crystallization. The synthesis of ~ 10 nm nanocrystalline Beta molecular sieve was successfully realized by adjusting the temperature and time of pre-crystallization, and a uniform intergranular mesoporous structure of ~ 7nm was formed. Moreover, the catalytic properties of Beta in the Fourier acylation reaction were better than those in conventional and commercial Beta. In the third part, in situ synthesis of multiporous all-silicon PLS-3 molecular sieve containing intracrystalline mesoporous by adding conventional surfactant cetyltrimethylammonium bromide (CTAB) and small molecular template (TEAOH,) with H-kanemite as matrix. It provides a basis for the further introduction of active centers to explore its catalytic properties.
【学位授予单位】：华东师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36
，
本文编号：2385911
[Abstract]:The synthesis of multiporous molecular sieves has always been a hot research direction. Usually, the preparation of multilayered molecular sieves can be divided into 'top-down' and 'bottom-up' strategies. The former refers to the first synthesis of molecular sieve and then the introduction of mesoporous via dissolved silicon dissolved aluminum or the combination of the two. However this method has some disadvantages such as the ratio of silicon to aluminum needs to be within a certain range and the micropore structure can be easily destroyed. The latter is to add a template (soft template or hard template) that can be directed to mesoporous cells in the starting step of synthesis. Bifunctional templates can also be synthesized by one-step-oriented microporous and mesoporous composite molecular sieves. But the high price of template agent and the complicated process of template preparation limit the practical application of template method. Controlling the crystallization conditions directly to synthesize small grain molecular sieve to form intergranular mesoporous is also an efficient method to prepare multiporous molecular sieve. It is an important research topic to explore a simple and economical route for the rapid synthesis of multi-pore nanosieve (including intergranular and intragranular). In the first part, layered silicate H-kanemite was used as silicon source to rapidly synthesize multiporous Beta molecular sieve under the guidance of conventional quaternary ammonium salt tetraethylammonium hydroxide (TEAOH). In alkaline crystallization mother liquor, H-kanemite is easy to dissolve into silicon-based fragments and can be rapidly reassembled into nano-sized Beta molecular sieve in 4 h. The grain size of nanometer Beta molecular sieve is about 20 nm, the mesoporous distribution is about 20 nm, the specific surface area is 703 m ~ 2 g ~ (-1), the total pore volume is 0.86 cm3 g ~ (-1), and the micropore volume is 0.21 cm3 g ~ (-1). Compared with conventional and commercial Beta, the mesoporous volume and specific surface area of multiporous Beta molecular sieve are higher. Multiporous nano-sized Beta also showed better catalytic performance than conventional and commercial Beta molecular sieves in the Fourier acylation reaction of macromolecules. In the second part, on the basis of the first part, H-kanemite is used as the silicon source to synthesize ultrananocrystalline Beta molecular sieve with smaller and more uniform grain size through the combination of low temperature precrystallization and dry adhesive crystallization. The synthesis of ~ 10 nm nanocrystalline Beta molecular sieve was successfully realized by adjusting the temperature and time of pre-crystallization, and a uniform intergranular mesoporous structure of ~ 7nm was formed. Moreover, the catalytic properties of Beta in the Fourier acylation reaction were better than those in conventional and commercial Beta. In the third part, in situ synthesis of multiporous all-silicon PLS-3 molecular sieve containing intracrystalline mesoporous by adding conventional surfactant cetyltrimethylammonium bromide (CTAB) and small molecular template (TEAOH,) with H-kanemite as matrix. It provides a basis for the further introduction of active centers to explore its catalytic properties.
【学位授予单位】：华东师范大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：O643.36
，
本文编号：2385911
本文链接：https://www.wllwen.com/shoufeilunwen/boshibiyelunwen/2385911.html
