本文選題：多金屬氧酸鹽 + 層狀雙金屬氧化物　； 參考：《北京化工大學(xué)》2015年博士論文

【摘要】：多金屬氧酸鹽(POMS)是一類復(fù)雜的陰離子,通過第五和第六主族元素形成的金屬氧化物陰離子縮聚而形成的。他們擁有特殊的物理化學(xué)性質(zhì),如強(qiáng)的Brcpnsted酸性,較強(qiáng)的氧化還原性,它們可以在很廣的分子結(jié)構(gòu)范圍內(nèi)合成。因此,他們已經(jīng)在工業(yè)生產(chǎn)中得到應(yīng)用,譬如高效吸附劑,污染物降解,綠色催化劑,及精細(xì)化工產(chǎn)品的生產(chǎn)。然而,多金屬氧酸鹽是高度可溶的并且容易在溶液中結(jié)晶。此外,多酸晶體中的陰陽離子之間的靜電作用很弱,因而導(dǎo)致多酸晶格能很低。上述多酸的性質(zhì)很大程度上限制了其在實際中的應(yīng)用。在催化反應(yīng)中,如果想要實現(xiàn)在工業(yè)生產(chǎn)中大規(guī)模使用多酸,就必須將多酸陰離子多相化,以達(dá)到催化劑的高效回收,高效率重復(fù)使用,有效的選擇性和熱穩(wěn)定。多酸在一些基質(zhì)上的固載化和固相化,可以形成多功能的多相材料,這是研究中應(yīng)用較廣泛的兩種技術(shù)。這些技術(shù)生產(chǎn)了具有廣泛應(yīng)用的多酸基功能材料,而且這種材料可以在保持多酸優(yōu)點(diǎn)的同時克服它的局限性。因此將多酸插層到水滑石層間的這種固載化顯得尤為重要。多酸／水滑石材料具有特殊的性質(zhì),如高的熱穩(wěn)定性,選擇性和重復(fù)利用性。然而,由于多金屬氧酸鹽大多是酸性的,插入過程是伴隨著堿性的LDH材料的流失。此外,多酸會和水滑石中的鋁離子反應(yīng),形成孔隙堵塞的POMs/LDHs多酸鹽化合物。這些鹽化合物除了由于孔隙堵塞造成的多酸暴露的問題,還會影響POMs/LDHs材料的功能。目前報道的幾種多金屬氧酸鹽插層水滑石技術(shù)包括離子交換,重組,共沉淀法,電化學(xué)還原,超聲合成,分層。最近報道的是2011年的分層技術(shù),這一報導(dǎo)實現(xiàn)了多金屬氧酸鹽/水滑石材料的合理設(shè)計,這一過程中沒有多酸鹽的形成或LDH材料的流失。因此,在這項工作中,我們采用分層技術(shù)合成一些新的多金屬氧酸鹽/水滑石材料,使用它們來解決各種環(huán)境污染問題�！紫�,從含銪的水滑石材料合成單層納米片。首次成功地分離并鑒定納米片為帶正電荷的單層式[Eu_8(OH)_(20) nH_2O]Cl4(LEuH)。單層納米片成功用于從水介質(zhì)中吸附對環(huán)境有害的氟離子。通過在480℃焙燒吸附氟的材料,在氟的吸附過程中納米片可以循環(huán)使用。其次,WO_4~(2-)多酸的結(jié)構(gòu)單元在pH=5的條件下,通過在LRH納米片上濃縮制得一種新的多功能POMs/LDH材料,Eu_2(OH)_5[H_2W_(12)O_(40)]0.17 7H_2O (LEuH-H_2W_(12)O_(40)),含有有序的多層次通道。這種多孔材料具有高的比表面積,可以提高其液態(tài)/分子/離子的運(yùn)輸能力。這種材料吸附重金屬離子的能力是Cd~(2+)1.8 mmol/g,Pb~(2+)2.4 mmol/g和Cr~(6+) 4.1mmol/g,反應(yīng)時間分別為18,25和20分鐘。吸附機(jī)理是二級反應(yīng),服從朗格繆爾吸附模型。此外,多酸陰離子PW_(10)O_(36)7-被成功地固載在Fe_3O_4@SiO_2磁性納米球上,核心使用帶正電的LRH納米片合成一個新的Fe_3O_4@SiO_2@LEuH@PW_(10)磁性納米復(fù)合材料。這種特殊的新材料已被證明是一個有效的溴化催化劑。實驗證明Fe_3O_4@SiO_2@LEuH@PW_(10)這種材料可以使溴酚紅99%的轉(zhuǎn)變?yōu)殇宸铀{(lán),反應(yīng)條件是298 K,1 atm,反應(yīng)速率為5.5×10-mmol/L g~(-1)s~(-1),此材料可回收至少十次而不損失其催化活性。而且,這種新合成的納米復(fù)合材料Fe_3O_4@SiO_2@LEuH@PW_(10)可以有效地從水溶液中吸附鉻酸根陰離子。吸附等溫線符合朗格繆爾吸附模型,42分鐘內(nèi)吸附容量為23 mmol/g,反應(yīng)溫度為25℃C,活化能為44.22 kJ mol~(-1)。此外,在40℃下加熱吸附鉻離子后的復(fù)合材料,將導(dǎo)致鉻酸鹽陰離子和納米復(fù)合材料的離解,因此Fe_3O_4@SiO_2@LEuH@PW_(10)可以重復(fù)使用來除去水溶液中的Cr(Ⅵ)�？偠灾�,該納米復(fù)合材料提供了一種從含水介質(zhì)中可逆吸附Cr(Ⅵ)的新途徑。最后,我們通過重組法將[EuW_(10)O_(36)]~(9-)多酸插入到各類水滑石中,并進(jìn)行了大量地研究。稀土多酸,特別是含銪多酸,因為其線性發(fā)光、衰減時間長以及氧化還原的特性,已經(jīng)在發(fā)光、催化等工業(yè)領(lǐng)域獲得了大量的應(yīng)用。然而,含銪多酸(Eu-POM)因為較短的紅光發(fā)射,限制了其在農(nóng)業(yè)以及園藝方面的進(jìn)一步應(yīng)用。通過將[EuW_(10)O_(36)]~(9-)多酸陰離子插入到限域的水滑石層間,能夠增強(qiáng)其紅光發(fā)射。帶正電的水滑石納米層板為~5D_0→~7F_2軌道的電子轉(zhuǎn)移提供了一個有利的環(huán)境,從而使得紅光發(fā)射成為可能。含銪多酸[EuW_(10)O_(36)]~(9-)的I(~5D_0→~7F_2)/I(~5D_0→~7F_1)為0.44,而將其插入MgAl-LDH, LYbH, ZnAl-LDH和LEuH中的I(~5D_0→~7F_2)/I(~5D_0→~7F_1)則分別為14.08,6.20,1.75,1.59。另外,將[EuW_(10)O_(36)]~(9-)陰離子插入到水滑石層間,并未影響到它的氧化還原性質(zhì)。利用MgAl-EuW_(10)為催化劑,我們實現(xiàn)了模擬油中BT,4,6-DMDBT以及DBT在120,125,25分鐘內(nèi)的脫硫率分別達(dá)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.

【學(xué)位授予單位】：北京化工大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2015
【分類號】：TB34

【參考文獻(xiàn)】

相關(guān)期刊論文 前1條

1 ;Supermolecular layered double hydroxides[J];Chinese Science Bulletin;2001年13期

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本文編號：1778812