多級孔納米分子篩的快速合成、表征及催化性能研究
發(fā)布時間：2018-12-18 13:18
【摘要】：多級孔分子篩的合成一直以來都是研究的熱門方向,通常制備多級孔分子篩可分為'由上而下'和'由下而上'兩種策略。前者指的是先合成分子篩,再通過溶硅溶鋁或者二者結(jié)合引入介孔,但這種方法存在一定的弊端,如硅鋁比需要在一定的范圍內(nèi),容易破壞微孔結(jié)構(gòu)等。后者是在合成起始步驟中加入可以導向介孔的模板劑(軟模板或者硬模板)。也可以合成雙功能的模板劑一步導向微孔和介孔復合的分子篩。但是高昂的模板劑價格以及繁瑣的模板劑制備過程限制模板劑法的實際應用�？刂凭Щ瘲l件直接合成小晶粒分子篩堆積形成晶間介孔也是一種高效的制備多級孔分子篩的方法。探索一條經(jīng)濟簡便、收率高、快速合成多級孔(包括晶間與晶內(nèi))納米分子篩的路線是當前研究的重點課題。第一部分主要是以層狀硅酸鹽H-kanemite為硅源,在常規(guī)小分子季銨鹽四乙基氫氧化銨(TEAOH)的導向作用下快速合成多級孔納米Beta分子篩。在堿性晶化母液中,H-kanemite易于溶解成硅基碎片并且能4 h內(nèi)快速重新組裝形成納米Beta分子篩。納米Beta分子篩晶粒大小在20 nm左右,晶間堆積介孔均勻分布在20 nm左右,比表面積為703 m2 g-1,總孔容達0.86 cm3 g-1,微孔孔容為0.21 cm3 g-1。與常規(guī)及商業(yè)Beta相比多級孔納米Beta分子篩的介孔孔容及比表面積更高。多級孔納米Beta在大分子的傅克酰基化反應中也顯示比常規(guī)及商業(yè)Beta分子篩更優(yōu)異的催化性能。第二部分是在第一部分的基礎上繼續(xù)以H-kanemite作為硅源,通過低溫預晶化和干膠法相結(jié)合的晶化方式試圖進一步合成出晶粒更小并且更為均一的超納米Beta分子篩。經(jīng)過預晶化溫度、時間等參數(shù)的調(diào)控,成功地實現(xiàn)了～10 nm納米Beta分子篩的合成,并形成了均勻的～7nm的晶間介孔。且在傅克酰基化反應中具有比常規(guī)及商業(yè)Beta更為優(yōu)異的催化性能。第三部分以H-kanemite作為母體,通過加入常規(guī)表面活性劑十六烷基三甲基溴化銨CTAB及小分子模板劑TEAOH,原位合成含晶內(nèi)介孔的多級孔全硅PLS-3分子篩,為進一步引入活性中心探索其催化性能提供了基礎。
[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.
【學位授予單位】：華東師范大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：O643.36
，
本文編號：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.
【學位授予單位】：華東師范大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：O643.36
，
本文編號：2385911
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