ZIF-8包覆的核—壳结构材料的合成及其应用

发布时间：2018-04-17 00:16

本文选题：ZIF-8材料 + 核壳结构　；参考：《大连理工大学》2015年博士论文

【摘要】：核-壳结构材料作为众多形式复合材料中最为常见的一种,通常是由内部的“核心”与外部的“壳层”组成,而且由于两种不同性质材料之间的结合,核壳结构材料在一些领域的应用过程中会展现出一些独特的性能,使其在很多领域具有潜在应用价值。以ZIF-8为代表的沸石咪唑酯骨架结构材料由于其规则的孔道结构、大的比表面积与孔容、良好的热稳定性与化学稳定性,被广泛应用于催化、气体吸附和气体分离等方向的研究。本论文主要围绕ZIF-8包覆的核-壳结构粒子的设计、合成及其应用展开,通过“核”材料与“ZIF-8壳”材料两者性质的结合,赋予该类核-壳粒子更多新颖的功能。主要内容如下：(1)以Fe304磁性粒子为核、ZIF-8为壳层包覆形成Fe3O4@ZIF-8磁性核壳粒子。壳层成功包覆的关键是采用聚电解质——聚苯乙烯磺酸钠(PSS)对Fe304表面进行修饰；然后考察了合成温度、合成时间、Fe304与ZIF-8合成液固液比、合成次数对于ZIF-8壳层包覆的影响。通过外加磁场成功将Fe3O4@ZIF-8磁性核壳粒子固载至不锈钢毛细管管壁组装成了微反应器,并应用于催化苯甲醛与氰乙酸乙酯间的Knoevenagel缩合反应,表现出优异的催化活性,而且具有磁性催化剂装填／卸载的简易操作性。(2)以水热碳球(Collodial carbon sphere, CCS)负载钯形成的Pd/CCS为核、ZIF-8膜为壳层制备了Pd/CCS@ZIF-8核壳结构粒子。采用葡萄糖水热法制备了粒径均一的CCS,以其为载体通过自还原反应进行Pd纳米粒子的负载在CCS表面形成Pd/CCS微球；利用Pd/CCS粒子丰富的表面官能团及其表面较大的负电荷密度,使ZIF-8在Pd/CCS微球表面原位生长成膜得到完整包覆的Pd/CCS@ZIF-8核壳粒子。在催化液相烯烃加氢反应时,Pd/CCS@ZIF-8核壳粒子表现出良好的抗Pd团聚、防Pd流失功能,而且循环6次催化性能几乎无降低。(3)以介孔二氧化硅微球形(Mesoporous silica sphere, MSS)为载体负载钯形成的Pd/MSS为核、ZIF-8为壳层,结合聚电解质表面修饰法与两步变温合成法成功制备了连续、完整ZIF-8壳层包覆的Pd/MSS@ZIF-8核壳粒子。聚电解质(PDDA和PSS)修饰增加了Pd/MSS核粒子与ZIF-8壳层间的亲和力和结合力；而采用低温有利于成核、高温有利于生长的两步变温ZIF-8壳层合成策略能有效减少壳层中的晶间缝隙和缺陷。该Pd/MSS@ZIF-8核壳催化剂应用于烯烃液相加氢反应,不仅具有良好的防Pd流失功能：循环使用5次后该核壳催化剂依然保持良好的催化活性；而且完整的ZIF-8壳层还赋予了该核壳催化剂择形催化和抗硫中毒功能。(4)结合聚电解质表面修饰法与两步变温合成法合成了一种新型的Fe3O4@Pd/SiO2@ZIF-8磁性核／壳／壳结构粒子。它综合了Fe304核的磁性、Pd纳米粒子的催化性能以及微孔ZIF-8壳层的固定和筛分功能,因此在烯烃液相加氢反应中该核／壳／壳结构粒子表现出良好的磁性回收、择形催化、抗Pd团聚、防Pd流失、抗硫中毒和多次重复使用功能。(5)探索了在非球型载体——ZSM-5分子筛粒子表面生长ZIF-8壳层的可行性,并合成了Pd/ZSM-5@ZIF-8核壳粒子。首先通过晶种诱导合成法成功合成出了粒径均一、单分散好且具有典型六棱型形貌的ZSM-5分子筛；然后对ZSM-5分子筛进行Pd纳米粒子负载和聚电解质表面修饰后,进行ZIF-8壳层的包覆得到了具有择形催化和可重复利用性的Pd/ZSM-5@ZIF-8核壳催化粒子。
[Abstract]:Core-shell structure materials as many forms in composite materials is one of the most common, usually is composed of internal and external "core" of "shell", but due to the combination of two different properties of materials, application of core shell structure material in some areas in the exhibition show some unique properties it has potential applications in many fields. With ZIF-8 as the representative of the zeolitic imidazolate frameworks as the pore structure of the rules, the specific surface area and pore volume, thermal stability and good chemical stability, widely used in catalysis, gas adsorption and separation of the design direction. This paper mainly focuses on the core-shell particles coated with ZIF-8, launches the synthesis and application, through the combination of nuclear materials and "ZIF-8" shell "to the nature of the material, giving the core-shell particles more novel main function. Contents are as follows: (1) with Fe304 magnetic particles as the core, ZIF-8 as shell coated Fe3O4@ZIF-8 magnetic core-shell particles. The key is the shell successfully coated by the polyelectrolyte -- sodium polystyrene sulfonate (PSS) was modified on the surface of Fe304; then the synthesis temperature, synthesis time and synthesis of ZIF-8 Fe304, the ratio of solid to liquid. The number of synthetic effects on ZIF-8 shell coated by the external magnetic field. The success of the Fe3O4@ZIF-8 magnetic core-shell particles immobilized to the stainless steel capillary wall assembled into a micro reactor, and applied to the Knoevenagel condensation reaction of benzaldehyde and ethyl cyanoacetate in between, showed excellent catalytic activity, easy to operate and has a magnetic catalyst uninstall /. (2) by hydrothermal carbon spheres (Collodial carbon sphere, CCS) supported palladium formed Pd/CCS as core and ZIF-8 films prepared Pd/CCS@ZIF-8 core-shell particles as shell. Preparation of uniform size CCS by glucose hydrothermal method, with its carrier to load Pd nanoparticles by self reduction reaction in CCS formed on the surface of Pd/CCS microspheres; using Pd/CCS particle rich surface functional groups and surface negative charge density, the ZIF-8 in the Pd/CCS in situ surface ball film Pd/CCS@ZIF-8 core-shell particles complete coating. In liquid phase catalytic hydrogenation of olefin, Pd/CCS@ZIF-8 core-shell particles showed good anti Pd aggregation, anti Pd loss function, and 6 cycles of catalytic performance almost no decrease. (3) using mesoporous silica microspheres (two - Mesoporous silica sphere, MSS) supported palladium the formation of Pd/MSS core and ZIF-8 shell, were prepared with continuous polyelectrolyte surface modification method and two step temperature synthesis method successfully, Pd/MSS@ZIF-8 core-shell particles ZIF-8 shell coated. Polyelectrolyte (PDDA and PSS) Modified increased Pd/MSS core particles and ZIF-8 shell between the affinity and binding force; and the low temperature nucleation, high temperature is in favor of the two step temperature ZIF-8 shell synthesis strategy can effectively reduce the growth in the shell of intergranular cracks and defects. The Pd/MSS@ZIF-8 core shell catalyst used in olefin hydrogenation reaction, not only can prevent Pd loss function good: after 5 recycles the nuclear shell catalyst still maintain good catalytic activity; and the complete ZIF-8 shell also gives the core-shell catalyst bedfor catalytic function and resistance to sulfur poisoning. (4) a new type of Fe3O4@Pd/SiO2@ZIF-8 magnetic core / shell / shell particles synthesized by synthetic method polyelectrolyte surface modification method and two step temperature. It combines the magnetic core of Fe304, the catalytic properties of Pd nanoparticles and porous ZIF-8 shell fixed and screening function, so in olefin liquid phase The core / shell / shell particles in hydrogenation reactions showed good magnetic recovery, selective catalysis, anti Pd aggregation, anti Pd loss, resistance to sulfur poisoning and used repeatedly. (5) explored in the non spherical carrier - ZSM-5 molecular sieve particles grown on the surface of feasibility of ZIF-8 shell, and synthesized. Pd/ZSM-5@ZIF-8 core-shell particles. Firstly through seed mediated synthesis method was successfully synthesized with uniform size and monodisperse ZSM-5 molecules and six typical prismatic morphology screen; then the ZSM-5 molecular sieve Pd nanoparticles and polyelectrolyte surface modified by ZIF-8 shell coating is obtained and shape selective catalysis reusable Pd/ZSM-5@ZIF-8 core shell catalyst particle.

【学位授予单位】：大连理工大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB33;O643.36

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