多酸插层水滑石从合成方法到功能材料应用

发布时间：2018-04-20 17:58

本文选题：多金属氧酸盐 + 层状双金属氧化物　；参考：《北京化工大学》2015年博士论文

【摘要】：多金属氧酸盐(POMS)是一类复杂的阴离子,通过第五和第六主族元素形成的金属氧化物阴离子缩聚而形成的。他们拥有特殊的物理化学性质,如强的Brcpnsted酸性,较强的氧化还原性,它们可以在很广的分子结构范围内合成。因此,他们已经在工业生产中得到应用,譬如高效吸附剂,污染物降解,绿色催化剂,及精细化工产品的生产。然而,多金属氧酸盐是高度可溶的并且容易在溶液中结晶。此外,多酸晶体中的阴阳离子之间的静电作用很弱,因而导致多酸晶格能很低。上述多酸的性质很大程度上限制了其在实际中的应用。在催化反应中,如果想要实现在工业生产中大规模使用多酸,就必须将多酸阴离子多相化,以达到催化剂的高效回收,高效率重复使用,有效的选择性和热稳定。多酸在一些基质上的固载化和固相化,可以形成多功能的多相材料,这是研究中应用较广泛的两种技术。这些技术生产了具有广泛应用的多酸基功能材料,而且这种材料可以在保持多酸优点的同时克服它的局限性。因此将多酸插层到水滑石层间的这种固载化显得尤为重要。多酸／水滑石材料具有特殊的性质,如高的热稳定性,选择性和重复利用性。然而,由于多金属氧酸盐大多是酸性的,插入过程是伴随着碱性的LDH材料的流失。此外,多酸会和水滑石中的铝离子反应,形成孔隙堵塞的POMs/LDHs多酸盐化合物。这些盐化合物除了由于孔隙堵塞造成的多酸暴露的问题,还会影响POMs/LDHs材料的功能。目前报道的几种多金属氧酸盐插层水滑石技术包括离子交换,重组,共沉淀法,电化学还原,超声合成,分层。最近报道的是2011年的分层技术,这一报导实现了多金属氧酸盐/水滑石材料的合理设计,这一过程中没有多酸盐的形成或LDH材料的流失。因此,在这项工作中,我们采用分层技术合成一些新的多金属氧酸盐/水滑石材料,使用它们来解决各种环境污染问题。’首先,从含铕的水滑石材料合成单层纳米片。首次成功地分离并鉴定纳米片为带正电荷的单层式[Eu_8(OH)_(20) nH_2O]Cl4(LEuH)。单层纳米片成功用于从水介质中吸附对环境有害的氟离子。通过在480℃焙烧吸附氟的材料,在氟的吸附过程中纳米片可以循环使用。其次,WO_4~(2-)多酸的结构单元在pH=5的条件下,通过在LRH纳米片上浓缩制得一种新的多功能POMs/LDH材料,Eu_2(OH)_5[H_2W_(12)O_(40)]0.17 7H_2O (LEuH-H_2W_(12)O_(40)),含有有序的多层次通道。这种多孔材料具有高的比表面积,可以提高其液态/分子/离子的运输能力。这种材料吸附重金属离子的能力是Cd~(2+)1.8 mmol/g,Pb~(2+)2.4 mmol/g和Cr~(6+) 4.1mmol/g,反应时间分别为18,25和20分钟。吸附机理是二级反应,服从朗格缪尔吸附模型。此外,多酸阴离子PW_(10)O_(36)7-被成功地固载在Fe_3O_4@SiO_2磁性纳米球上,核心使用带正电的LRH纳米片合成一个新的Fe_3O_4@SiO_2@LEuH@PW_(10)磁性纳米复合材料。这种特殊的新材料已被证明是一个有效的溴化催化剂。实验证明Fe_3O_4@SiO_2@LEuH@PW_(10)这种材料可以使溴酚红99%的转变为溴酚蓝,反应条件是298 K,1 atm,反应速率为5.5×10-mmol/L g~(-1)s~(-1),此材料可回收至少十次而不损失其催化活性。而且,这种新合成的纳米复合材料Fe_3O_4@SiO_2@LEuH@PW_(10)可以有效地从水溶液中吸附铬酸根阴离子。吸附等温线符合朗格缪尔吸附模型,42分钟内吸附容量为23 mmol/g,反应温度为25℃C,活化能为44.22 kJ mol~(-1)。此外,在40℃下加热吸附铬离子后的复合材料,将导致铬酸盐阴离子和纳米复合材料的离解,因此Fe_3O_4@SiO_2@LEuH@PW_(10)可以重复使用来除去水溶液中的Cr(Ⅵ)。总而言之,该纳米复合材料提供了一种从含水介质中可逆吸附Cr(Ⅵ)的新途径。最后,我们通过重组法将[EuW_(10)O_(36)]~(9-)多酸插入到各类水滑石中,并进行了大量地研究。稀土多酸,特别是含铕多酸,因为其线性发光、衰减时间长以及氧化还原的特性,已经在发光、催化等工业领域获得了大量的应用。然而,含铕多酸(Eu-POM)因为较短的红光发射,限制了其在农业以及园艺方面的进一步应用。通过将[EuW_(10)O_(36)]~(9-)多酸阴离子插入到限域的水滑石层间,能够增强其红光发射。带正电的水滑石纳米层板为~5D_0→~7F_2轨道的电子转移提供了一个有利的环境,从而使得红光发射成为可能。含铕多酸[EuW_(10)O_(36)]~(9-)的I(~5D_0→~7F_2)/I(~5D_0→~7F_1)为0.44,而将其插入MgAl-LDH, LYbH, ZnAl-LDH和LEuH中的I(~5D_0→~7F_2)/I(~5D_0→~7F_1)则分别为14.08,6.20,1.75,1.59。另外,将[EuW_(10)O_(36)]~(9-)阴离子插入到水滑石层间,并未影响到它的氧化还原性质。利用MgAl-EuW_(10)为催化剂,我们实现了模拟油中BT,4,6-DMDBT以及DBT在120,125,25分钟内的脱硫率分别达到90%,94%,和99%。
[Abstract]:Polyoxometalate (POMS) is a complex type of anions, formed by anionic polycondensation of metal oxides formed by fifth and sixth main elements. They have special physical and chemical properties, such as strong Brcpnsted acidity, strong oxidation-reduction, and they can be synthesized in a wide range of molecular structures. It is used in industrial production, such as efficient adsorbents, pollutants degradation, green catalysts, and production of fine chemical products. However, polyoxometalates are highly soluble and easily crystallized in solutions. In addition, the electrostatic interaction between the ions and the ions in the polyacid crystals is very weak, resulting in the low lattice energy of polyacid. The nature of acid greatly limits its application in practice. In the catalytic reaction, polyacid is multiphased in order to achieve large-scale use of polyacid in industrial production to achieve high efficiency recovery of the catalyst, high efficiency reuse, effective selectivity and thermal stability. The immobilization of polyacid on some substrates And solid phase formation can form multi-functional multiphase material, which is the two widely used technology in the study. These technologies produce widely used polyacid based functional materials, and this material can overcome its limitations while maintaining the advantages of polyacid. Therefore, the immobilization of polyacid intercalation to the layer of hydrotalcite appears to appear. It is particularly important that polyacid / hydrotalcite materials have special properties, such as high thermal stability, selectivity and reutilization. However, because polyoxometalates are mostly acidic, the insertion process is the loss of alkaline LDH materials. In addition, polyacid will react with aluminum ions in hydrotalcite to form a porous POMs/LDHs polyacid. Salt compounds. These salts can also affect the function of POMs/LDHs materials in addition to the problems of polyacid exposure due to pore blockage. Several polyoxometalate intercalated hydrotalcite technologies reported at present include ion exchange, recombination, co precipitation, electrochemical reduction, ultrasonic synthesis, and stratification. Recently, the stratification technology was reported. This report has realized the rational design of Polyoxometalates / hydrotalcite materials. In this process, there is no polyacid formation or loss of LDH materials. Therefore, in this work, we use stratified technology to synthesize some new polyoxometalates / hydrotalcite materials and use them to solve various environmental pollution problems. The synthesis of single layer nanoscale with europium hydrotalcite material. First successfully isolated and identified as a positive charge single layer [Eu_8 (OH) nH_2O]Cl4 (20) nH_2O]Cl4 (LEuH). Single layer nanoscale was successfully used to adsorb harmful fluorine ions from water medium. By baking the fluorine at 480 centigrade, the nanoscale film could be followed by the adsorption process of fluorine. Second, WO_4~ (2-) polyacid structure unit, under the condition of pH=5, produces a new multi-functional POMs/LDH material by concentrating on LRH nanoscale, Eu_2 (OH) _5[H_2W_ (12) O_ (40)]0.17 7H_2O (LEuH-H_2W_ (12) 40), containing an ordered multilevel channel. This porous material has a high specific surface area and can improve its liquid / fraction. The transport capacity of the sub / ion is Cd~ (2+) 1.8 mmol/g, Pb~ (2+) 2.4 mmol/g and Cr~ (6+) 4.1mmol/g, and the reaction time is 18,25 and 20 minutes respectively. The adsorption mechanism is two order reaction, obeying the Langmuir adsorption model. Moreover, polyanic anion PW_ (10) O_ (36) is successfully immobilized in the magnetic field. On sex nanospheres, a new Fe_3O_4@SiO_2@LEuH@PW_ (10) magnetic nanocomposite is synthesized by the core with positive LRH nanoscale. This special new material has been proved to be an effective bromination catalyst. The experiment has proved that Fe_3O_4@SiO_2@LEuH@PW_ (10) can change bromine phenol red 99% to bromine blue, the reaction condition is 298 K, 1 atm, the reaction rate is 5.5 * 10-mmol/L g~ (-1) s~ (-1). This material can be recovered at least ten times without losing its catalytic activity. Moreover, the newly synthesized nanocomposite Fe_3O_4@SiO_2@LEuH@PW_ (10) can effectively adsorb chromate detachment from aqueous solution. The adsorption isotherm conforms to the Langmuir adsorption model and is absorbed within 42 minutes. The attached capacity is 23 mmol/g, the reaction temperature is 25 C C, the activation energy is 44.22 kJ mol~ (-1). In addition, the composite after heating adsorption of chromium at 40 C will lead to the dissociation of chromate anions and nanocomposites, so Fe_3O_4@SiO_2@LEuH@PW_ (10) can be repeated to remove Cr (VI) in the aqueous solution. The composite provides a new way of reversible adsorption of Cr (VI) from water containing medium. Finally, we insert [EuW_ (10) O_ (36)] (9-) polyacid into various hydrotalcite by recombinant method and have carried out a great deal of research. A lot of applications have been obtained in the fields of luminescence, catalysis and other industries. However, Eu-POM containing europium polyacid (Eu-POM) has limited its further application in agriculture and horticulture because of its shorter red light emission. By inserting [EuW_ (10) (36)] ~ (9-) polyanic anions into the restricted water talcum layer, the red light emission can be enhanced. It provides a favorable environment for the electron transfer of ~5D_0 to ~7F_2 orbits, making it possible for the red light emission to be possible. The I (~5D_0 to ~7F_2) /I (~5D_0 to ~7F_2) of the europium polyacid (10) O_ (9-)) is 0.44, and it is inserted into MgAl-LDH. 1.75,1.59., in addition, inserts [EuW_ (10) O_ (36)] ~ (9-) anions into the hydrotalcite layer and does not affect its redox properties. Using MgAl-EuW_ (10) as a catalyst, the desulfurization rate of BT, 4,6-DMDBT and DBT in the simulated oil is 90%, 94%, and 99%. in 120125,25 minutes.

【学位授予单位】：北京化工大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TB34

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