介孔复合金属氧化物三维结构的构筑与双金属纳米颗粒的限域调控制备及应用
发布时间：2018-09-19 06:13
【摘要】：介孔复合金属氧化物材料(2-50 nm)由于其大的比表面、灵活可调的孔径与组成,以及在催化、能量转换及生物技术方面的应用潜力,越来越引起人们的广泛关注。但是由于本身有机模板剂的尺寸限制,目前合成的孔径都在16nm以下。而在催化反应中,反应物和产物的传输效率直接影响最后的催化性能,所以孔径上的难突破极大的限制了它们在大分子催化中的应用。另一方面,催化剂一般是由活性位点和载体两大部分组成,金属纳米颗粒是活性位点的重要组成部分,而双金属纳米颗粒所表现出的协同作用有着比单金属更好的催化表现,所以,人们越来越多致力于研究双金属纳米颗粒的设计合成。目前,绝大多数的双金属颗粒是通过溶液相方法得到,这些颗粒在高温苛刻催化环境下易发生烧结长大,直接导致催化活性的下降甚至丧失,所以,如何制备高温稳定的双金属是这一领域的一大难点。更重要的是,催化领域研究的最终目标是能够根据催化反应所需要的空间结构设计并控制合成出具有所需构架的双金属颗粒,这样就可以省去大量盲目尝试的时间,各取所需,使合成更具有目的性和方向性。本论文致力于解决如上问题,即大孔介孔复合金属氧化物的合成与双金属纳米颗粒的可控合成,分为六章。第一章是课题相关文献综述,对所做工作的历史背景、最新进展及后期展望做了大体的概括；第二章介绍实验过程中用到的主要试剂、仪器设备、表征方法及催化反应条件；第三章介绍三维大孔介孔复合金属氧化物的普适性合成及催化应用；第四章介绍三维介孔限域空间内复合双金属纳米颗粒的合成及应用；第五章介绍调变初始纳米金尺寸实现金镍复合双金属的结构控制合成及其应用；第六章是总结与展望。论文得到的结论主要有以下几点：我们借助本身具有三维开放孔道的介孔氧化硅EP-FDU-12为骨架,将金属氧化物前驱体通过AcHE溶剂挥发的方法涂覆在其内表面,然后通过焙烧后处理得到结构复制的三维大孔介孔复合金属氧化物。此法成功的关键因素有两点：一是EP-FDU-12的开放孔道结构可以有效防止涂覆过程中金属氧化物前驱体单独聚集而引起的相分离现象,二是在AcHE体系中形成的非常稳定的金属氧化物前驱体纳米颗粒。通过一系列表征,证实EP-Al2O3, EP-TiO2, EP-ZrO2,二元EP-Cu-TiO2及三元EP-K-Cu-TiO2等都可以通过此法成功合成,并且涂层的厚度可以通过改变前驱体初始加入量灵活调控；将所得到的EP-Al2O3材料用于在强酸或中强B酸位点上进行的大分子傅-克烷基化反应中,并以纯EP-FDU-12和部分涂覆部分相分离的Al2O3@EP-FDU-12-100℃(1/9)为对比样品,发现EP-Al2O3催化活性比后两者都高出很多,说明此反应不仅需要酸性位点的存在,而且需要三维开放的孔道结构促进过程中物质的顺利传输,EP-Al2O3正是将两个必不可少的条件集为一身,从而得到非常可观的催化活性；将其用作载体负载PdNPs用于VOC正已烷的催化氧化中,也得到了高于对比样品的催化活性。为了得到高温条件下依然稳定的双金属纳米颗粒,我们采取了一种新的合成策略。将两种金属组分(Au,Pd或Ni,Pd等)直接负载到一种载体孔内进行高温焙烧,通过后续系列材料表征,证实这种高温冶炼合成双金属合金的方法是非常可行的。并且在我们所采用的EP-FDU-12限域空间内,得到的合金颗粒非常均,尺寸大都在5 nm左右,有效的防止了高温催化下颗粒发生聚集长大的问题。在Au-Pd体系中,不同的Au-Pd摩尔比可以有效控制Pd的抗氧化能力,O2-TPO证实当Au与Pd的摩尔比为1时,对于Pd的抗氧化温度提高了50℃之多,为330℃左右(纯Pd约260℃)。而后我们将所合成的Au-Pd体系用于Pd0为活性位的正已烷催化氧化中,证实了我们所得到的Au-Pd在富氧环境下,依然可以稳定绝大部分Pd0存在,从而很好的保持了高的催化活性；通过调变AuNPs的初始尺寸,并在相同的EP-FDU-12限域空间内,实现金镍复合双金属的结构控制合成,通过XRD,XPS等表征手段得到了初步结果,并且在苯甲醇的气相选择性氧化反应中得到了彼此不同的催化活性,间接证实AuNPs的不同初始尺寸可以影响与NiNPs在焙烧过程中的相互作用,此工作还在继续研究中。
[Abstract]:Mesoporous composite metal oxides (2-50 nm) have attracted more and more attention due to their large specific surface area, flexible and adjustable pore size and composition, as well as their potential applications in catalysis, energy conversion and biotechnology. However, due to the size limitation of their organic templates, the pore sizes are all below 16 nm. The transport efficiency of reactants and products has a direct impact on the final catalytic performance of the reactions, so the difficulty in breaking through the pore size limits their application in macromolecular catalysis. The synergistic effect of nanoparticles is better than that of single metal, so more and more people are devoting themselves to the design and synthesis of bimetallic nanoparticles. Therefore, how to prepare high temperature stable bimetallic particles is a major difficulty in this field. More importantly, the ultimate goal of catalytic research is to be able to control the synthesis of bimetallic particles with the required framework according to the space structure of catalytic reaction. This paper is devoted to solve the above problems, namely, the synthesis of macroporous mesoporous composite metal oxides and the controllable synthesis of bimetallic nanoparticles, which can be divided into six chapters. Chapter 1 is a literature review of the subject, the historical background of the work done, the latest progress and the future. In the second chapter, the main reagents, apparatus, characterization methods and catalytic reaction conditions used in the experiment are introduced; in the third chapter, the universality of synthesis and catalytic application of three-dimensional macroporous mesoporous composite metal oxides are introduced; in the fourth chapter, the suitability of composite bimetallic nanoparticles in three-dimensional mesoporous confined space is introduced. In the fifth chapter, the structure-controlled synthesis of gold-nickel composite bimetals by adjusting the initial size of gold nanoparticles and its application are introduced; in the sixth chapter, the summary and prospect are given. Three-dimensional macroporous mesoporous composite metal oxides were prepared by evaporation of AcHE solvent and then calcination. The key factors for the success of this method are as follows: 1. The open-channel structure of EP-FDU-12 can effectively prevent the aggregation of metal oxide precursors during the coating process. Phase separation, and the formation of very stable metal oxide precursor nanoparticles in AcHE system. Through a series of characterization, it is confirmed that EP-Al2O3, EP-TiO2, EP-ZrO2, binary EP-Cu-TiO2 and ternary EP-K-Cu-TiO2 can be successfully synthesized by this method, and the coating thickness can be flexibly changed by the initial addition of precursor. The obtained EP-Al2O3 material was used in the macromolecular Fourier-Crafts alkylation reaction at strong acid or moderate B acid sites, and compared with pure EP-FDU-12 and partially coated Al2O3@EP-FDU-12-100 C(1/9) samples, it was found that the catalytic activity of EP-Al2O3 was much higher than that of the latter two, indicating that the reaction needed not only acid. EP-Al2O3 is used as a carrier to support PdNPs in the catalytic oxidation of VOC n-hexane, and the catalytic activity of EP-Al2O3 is higher than that of the control sample. Activity. In order to obtain stable bimetallic nanoparticles at high temperature, we adopted a new synthetic strategy. Two metal components (Au, Pd or Ni, Pd, etc.) were directly loaded into a carrier pore for high-temperature roasting. The subsequent characterization of a series of materials confirmed that this method of high-temperature metallurgical synthesis of bimetallic alloys is very feasible. OK. And in the EP-FDU-12 confinement space we used, the alloy particles are very uniform, most of them are about 5 nm in size, which effectively prevents the agglomeration and growth of particles under high temperature catalysis. In the Au-Pd system, different Au-Pd molar ratio can effectively control the oxidation resistance of Pd, O2-TPO confirmed when the molar ratio of Au to Pd. For Pd, the antioxidant temperature increased by 50 C to about 330 C (pure Pd about 260 C). Then we applied the synthesized Au-Pd system to the catalytic oxidation of n-hexane with Pd0 as the active site, which confirmed that most of the Pd0 could still be stable in the oxygen-enriched environment, thus maintaining the high catalytic activity. By changing the initial size of AuNPs and in the same EP-FDU-12 confinement space, the structure-controlled synthesis of Au-Ni composite bimetals was realized. The preliminary results were obtained by XRD, XPS and other characterization methods, and the catalytic activities of AuNPs were different from each other in the gas-phase selective oxidation of benzyl alcohol. The initial size can affect the interaction between NiNPs and calcination. This work is still under study.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB383.1
[Abstract]:Mesoporous composite metal oxides (2-50 nm) have attracted more and more attention due to their large specific surface area, flexible and adjustable pore size and composition, as well as their potential applications in catalysis, energy conversion and biotechnology. However, due to the size limitation of their organic templates, the pore sizes are all below 16 nm. The transport efficiency of reactants and products has a direct impact on the final catalytic performance of the reactions, so the difficulty in breaking through the pore size limits their application in macromolecular catalysis. The synergistic effect of nanoparticles is better than that of single metal, so more and more people are devoting themselves to the design and synthesis of bimetallic nanoparticles. Therefore, how to prepare high temperature stable bimetallic particles is a major difficulty in this field. More importantly, the ultimate goal of catalytic research is to be able to control the synthesis of bimetallic particles with the required framework according to the space structure of catalytic reaction. This paper is devoted to solve the above problems, namely, the synthesis of macroporous mesoporous composite metal oxides and the controllable synthesis of bimetallic nanoparticles, which can be divided into six chapters. Chapter 1 is a literature review of the subject, the historical background of the work done, the latest progress and the future. In the second chapter, the main reagents, apparatus, characterization methods and catalytic reaction conditions used in the experiment are introduced; in the third chapter, the universality of synthesis and catalytic application of three-dimensional macroporous mesoporous composite metal oxides are introduced; in the fourth chapter, the suitability of composite bimetallic nanoparticles in three-dimensional mesoporous confined space is introduced. In the fifth chapter, the structure-controlled synthesis of gold-nickel composite bimetals by adjusting the initial size of gold nanoparticles and its application are introduced; in the sixth chapter, the summary and prospect are given. Three-dimensional macroporous mesoporous composite metal oxides were prepared by evaporation of AcHE solvent and then calcination. The key factors for the success of this method are as follows: 1. The open-channel structure of EP-FDU-12 can effectively prevent the aggregation of metal oxide precursors during the coating process. Phase separation, and the formation of very stable metal oxide precursor nanoparticles in AcHE system. Through a series of characterization, it is confirmed that EP-Al2O3, EP-TiO2, EP-ZrO2, binary EP-Cu-TiO2 and ternary EP-K-Cu-TiO2 can be successfully synthesized by this method, and the coating thickness can be flexibly changed by the initial addition of precursor. The obtained EP-Al2O3 material was used in the macromolecular Fourier-Crafts alkylation reaction at strong acid or moderate B acid sites, and compared with pure EP-FDU-12 and partially coated Al2O3@EP-FDU-12-100 C(1/9) samples, it was found that the catalytic activity of EP-Al2O3 was much higher than that of the latter two, indicating that the reaction needed not only acid. EP-Al2O3 is used as a carrier to support PdNPs in the catalytic oxidation of VOC n-hexane, and the catalytic activity of EP-Al2O3 is higher than that of the control sample. Activity. In order to obtain stable bimetallic nanoparticles at high temperature, we adopted a new synthetic strategy. Two metal components (Au, Pd or Ni, Pd, etc.) were directly loaded into a carrier pore for high-temperature roasting. The subsequent characterization of a series of materials confirmed that this method of high-temperature metallurgical synthesis of bimetallic alloys is very feasible. OK. And in the EP-FDU-12 confinement space we used, the alloy particles are very uniform, most of them are about 5 nm in size, which effectively prevents the agglomeration and growth of particles under high temperature catalysis. In the Au-Pd system, different Au-Pd molar ratio can effectively control the oxidation resistance of Pd, O2-TPO confirmed when the molar ratio of Au to Pd. For Pd, the antioxidant temperature increased by 50 C to about 330 C (pure Pd about 260 C). Then we applied the synthesized Au-Pd system to the catalytic oxidation of n-hexane with Pd0 as the active site, which confirmed that most of the Pd0 could still be stable in the oxygen-enriched environment, thus maintaining the high catalytic activity. By changing the initial size of AuNPs and in the same EP-FDU-12 confinement space, the structure-controlled synthesis of Au-Ni composite bimetals was realized. The preliminary results were obtained by XRD, XPS and other characterization methods, and the catalytic activities of AuNPs were different from each other in the gas-phase selective oxidation of benzyl alcohol. The initial size can affect the interaction between NiNPs and calcination. This work is still under study.
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB383.1
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