超分子结构水杨酸根插层水滑石的组装及结构与性能研究

以锌铝水滑石ZnAl-CO3 LDHs为前体（主体），以乙二醇为分散介质，用离子 交换法组装了水杨酸根（客体）插层水滑石ZnAl-[o-HO(C6H4)COO]LDHs，并用XRD ，FT-IR，TG-DTA等手段对样品进行了表征。结果表明，能过控制离子交换条件， 水杨酸根阴离子可取代锌铝水滑石前体层间的CO3^2-离子，组装得到晶体结构良好 的水杨酸根插层水滑石。通过研究发现，主体水滑石层板与客体以静电力和氢键相 互作用，得到的超分子结构材料紫外阻隔作用增强并具有较好的稳定性，从而成为 一种集屏蔽和吸收双重功能的新型无机-有机得合紫外阻隔材料。     

水滑石层间碘酸根离子的还原性机理研究

通过X射线衍射(XRD)和傅里叶变换红外(FTIR)光谱仪表征发现,经水合肼(N2H4·H2O)和亚硫酸钠(Na2SO3)两种还原剂处理碘酸根插层水滑石的产物分别为碘离子插层的水滑石(ZnAl-I LDHs)和硫酸根离子插层水滑石(ZnAl-SO4LDHs)。进一步研究表明,N2H4·H2O和水滑石的反应为D7模型的核外层扩散反应,N2H4·H2O在水滑石微球界面和IO3-发生反应。而Na2SO3则先进入了水滑石层间,然后与层间的IO3-反应,其模型符合D11动力学模型。     

过氧杂多阴离子柱撑水滑石的合成、表征及催化性能的研究

通过离子交换法, 将含钛过渡金属离子一、三取代钨硅、钨磷过氧杂多配合物嵌入Zn2Al类水滑石中, 获得了柱撑化合物, 并用XRD, IR, XPS, 元素分析等手段对产物的结构和组成进行了表征。结果表明, 过氧杂多阴离子进入水滑石层间后, 水滑石的层间距从0.92nm增大到1.47nm, 且O2^2^-链没有被破坏。柱撑产物在环己烯氧化反应中显示优良的催化性能。     

阳离子掺杂水滑石的制备及其性质研究

研究了掺杂阳离子水滑石的制备及阳离子对水滑石性质的影响. 分别制备了掺杂Zn2+、Ni2+、Fe3+型的水滑石, 考察了掺杂阳离子对水滑石晶相结构、层间距、层间阴离子含量、水滑石表面形态、水滑石碱性的影响, 结果表明, 由于阳离子的引入, 导致水滑石层间距减小及层间阴离子结合量降低, 且使水滑石培烧产物电负性提高, 并最终降低其碱性. 以上述水滑石培烧产物作为固体碱催化剂促进苯甲醛和丙醛缩合, 合成α-甲基肉桂醛, 关联了水滑石培烧产物碱性与反应活性的关系.     

Cu-Ni-Mg-Al-CO3四元水滑石的合成及结构分析

以Cu(NO3)2·2H2O,Ni(NO3)2·6H2O,Mg(NO3)2·6H2O和Al(NO3)3·9H2O为原料 ，以NaOH和Na2CO3为沉淀剂，采用成核／晶化隔离法合成了Cu-Ni-Mg-Al-CO3四元 水滑石，通过XRD，FT－IR，TG－DTA，ICP等手段对样品进行测试和表征，并且对 水滑石结构的层板和层间阴离子相互作用进行分析和讨论。结果表明，控制Cu^2+ 离子与其它二价金属离子的配比，可制备晶体结构规整的M(Ⅱ）4M(Ⅲ)2(OH) 12CO3·4H2O型水滑石；Cu^2+离子的引入导致了明显的Jahn-Teller效应；且随 Mg^2+量的增加，使得这种效应更加显著，另一方面Mg^2+量的增加有利于Cu-Ni- Mg-Al-CO3四元水滑石晶体在a方向上生长，增强其热稳定性。     

乙二胺四乙酸柱撑镁锌铝三元水滑石的制备与表征

采用共沉淀法合成了Mg2ZnAl-CO3水滑石;以其为前驱体,利用离子交换法进行插层组装得到Mg2ZnAl-EDTA三元柱撑水滑石;采用X射线衍射仪和傅立叶变换红外光谱仪对产物进行了表征.结果表明,合成的Mg2ZnAl-CO3水滑石纯度高、晶型良好,其层间CO32-可被乙二胺四乙酸(EDTA)阴离子取代形成Mg2ZnAl-EDTA三元柱撑水滑石;柱撑水滑石的层间距离明显增加,EDTA阴离子在层间倾斜排列.     

己二酸柱撑水滑石的制备及表征

水滑石（Layered Double Hydroxidex,简称LDHs）是一类具有层状结构的阴离子型粘土^[1]。水滑石的一个重要性质是层间阴离子具有可交换性,引入不同的阴离子,能够得到不同结构和功能和柱撑水石滑,因而阴离子插层是水滑石研究的一个重要方向。各类阴离子如有机和无机阴离子、同多和杂多阴离子以及金属配合物阴离子的柱撑水滑石在文献中都有报道^[2-5]。其中有机阴离子由于在结构上的多样性,使有机阴离子柱撑水滑石具有巨大的应用开发潜力,已经引起了人们的广泛关注^[6-12]。     

杂多阴离子柱撑水滑石的合成、热稳定性、酸碱性研究

采用水溶液中阴离子直接交换法合成了过渡金属单取代Keggin结构杂多阴离子SiW11M(H2O)O39^6^- (M=Mn^2^+, Fe^2^+, Co^2^+, Ni^2^+, Cu^2^+,Zn^2^+)柱撑水滑石。用元素分析、XRD和IR对产物的组成与结构进行了表征。XRD结果给出柱撑产物的底面间距达1.47nm。DTA结合不同温度下焙烧样品的XRD、IR研究表明, 柱撑水滑石在低于250℃时脱除物理吸附水和层间水; 在400~500℃之间脱除层上羟基, 形成一个无定形的混合氧化物状态; 在600℃以上无定形态结晶为晶态氧化物混合物。异丙醇探针反应表明, 柱撑水滑石具有高于水滑石前驱体和相应杂多酸盐的催化活性, 且同时存在酸碱两类催化活性中心, 但酸中心明显较强。     

含钴铜镍类水滑石焙烧产物催化分解N2O的研究

 合成了含Co，Cu和Ni的M／Mg－Al－HTL类水滑石，并将其焙烧产物用于N2O催化分解反应．实验结果表明，Co／Mg－Al－HTL对N2O分解反应的催化活性明显高于Cu／Mg－Al－HTL和Ni／Mg－Al－HTL的活性．在保持样品中Al含量不变的条件下，催化活性随着Co含量的增加及Mg含量的减少而升高，各催化剂的活性顺序为：Co／Al－HTL＞Co／Mg－Al－HTL＞Cu／Mg－Al－HTL＞Ni／Mg－Al－HTL．在此基础上，进一步考察了Co／Al－HTL中Co／Al原子比调变对催化剂活性的影响．对含Co类水滑石及其焙烧产物进行了XRF，XRD和N2O－TPD表征．结果表明，含Co类水滑石具有典型的水滑石结构，其高温焙烧产物都含尖晶石相．由于尖晶石相中Co－O－Al活性中心的作用，含Co类水滑石对N2O分解反应表现出较高的催化活性．随着Co／Al原子比的增大，含Co类水滑石焙烧产物的尖晶石相特征更加突出，Co－O－Al活性中心数目随之增多，催化剂的活性也相应升高．     

水滑石层间碘酸根离子的还原性机理研究

通过X射线衍射（XRD）和傅里叶变换红外（FTIR）光谱仪表征发现,经水合肼（N₂H₄·H₂O）和亚硫酸钠（Na₂SO₃）两种还原剂处理碘酸根插层水滑石的产物分别为碘离子插层的水滑石（ZnAl-ILDHs）和硫酸根离子插层水滑石（ZnAl-SO₄LDHs）。进一步研究表明,N₂H₄·H₂O和水滑石的反应为D₇模型的核外层扩散反应,N₂H₄·H₂O在水滑石微球界面和IO₃^-发生反应。而Na₂SO₃则先进入了水滑石层间,然后与层间的IO₃^-反应,其模型符合D₁₁动力学模型。     

The synthesis and spectroscopic characterisation of hydrotalcite formed from aluminate solutions

Raman spectroscopy has been used to characterise nine hydrotalcites prepared from aluminate and magnesium solutions (magnesium chloride and seawater). The aluminate hydrotalcites are proposed to have the following formula Mg(6)Al(2)(OH)(16)(CO(3)(2-))·xH(2)O, Mg(6)Al(2)(OH)(16)(CO(3)(2-),SO(4)(2-))·xH(2)O, and Mg(6)Al(2)(OH)(16)(SO(4)(2-))·xH(2)O. The synthesis of these hydrotalcites using seawater results in the intercalation of sulfate anions into the hydrotalcite interlayer. The spectra have been used to assess the molecular assembly of the cations and anions in the hydrotalcite structures. The spectra have been conveniently subdivided into spectral features based upon the carbonate anion, the hydroxyl units and water units. This investigation has shown the ideal conditions to form hydrotalcite from aluminate solutions is at pH 14 using a magnesium chloride solution at a volumetric ratio of 1:1. Changes in synthesis conditions resulted in the formation of impurity products aragonite, thenardite, and gypsum.     

Minimising reversion, using seawater and magnesium chloride, caused by the dissolution of tricalcium aluminate hexahydrate

The increase in pH and aluminium concentration after the neutralisation of bauxite refinery residues is commonly known as reversion. This investigation reports the extent of reversion in synthetic supernatant liquor and possible methods to reduce reversion. This work is based on bauxite refinery residues produced from alumina refineries, where reversion is a real life situation in neutralised refinery residues. Tricalcium aluminate hexahydrate, a common phase in bauxite refinery residues, has been found to cause reversion. It has been established that reductions in both pH and aluminium from the seawater neutralisation process are due to the formation of 'Bayer' hydrotalcite Mg(7)Al(2)(OH)(18)(CO(3)(2-),SO(4)(2-))·xH(2)O. This is the primary mechanism involved in the removal of aluminium from solution. Increasing the volume of seawater used for the neutralisation process minimises the extent of reversion for both synthetic supernatant liquor and red mud slurry. The addition of MgCl(2)·6H(2)O also showed a reduction in reversion and confirmed that the decrease in aluminium and hydroxyl ions is due to the formation of Bayer hydrotalcite and not simply a dilution effect.     

Thermal decomposition of hydrotalcite with hexacyanoferrate(II) and hexacyanoferrate(III) anions in the interlayer

The mechanism for the decomposition of hydrotalcite remains unsolved. Controlled rate thermal analysis enables this decomposition pathway to be explored. The thermal decomposition of hydrotalcites with hexacyanoferrate(II) and hexacyanoferrate(III) in the interlayer has been studied using controlled rate thermal analysis technology. X-ray diffraction shows the hydrotalcites have a d(003) spacing of 10.9 and 11.1 Å which compares with a d-spacing of 7.9 and 7.98 Å for the hydrotalcite with carbonate or sulphate in the interlayer. Calculations show dehydration with a total loss of 7 moles of water proving the formula of hexacyanoferrate(II) intercalated hydrotalcite is Mg₆Al₂(OH)₁₆[Fe(CN)₆]_0.5·7H₂O and 9.0 moles for the hexacyanoferrate(III) intercalated hydrotalcite with the formula of Mg₆Al₂(OH)₁₆[Fe(CN)₆]_0.66·9H₂O. CRTA technology indicates the partial collapse of the dehydrated mineral. Dehydroxylation combined with CN unit loss occurs in two isothermal stages at 377 and 390°C for the hexacyanoferrate(III) and in a single isothermal process at 374°C for the hexacyanoferrate(III) hydrotalcite.     

Memory effect of activated Mg-Al hydrotalcite: in situ XRD studies during decomposition and gas-phase reconstruction

The thermal decomposition of Mg-Al hydrotalcite and the subsequent reconstruction of the decomposed products in the presence of water vapor (2 vol. % H(2)O in N(2)) have been investigated by in situ XRD. Thermographic analysis and temperature-programmed desorption MS results complemented the diffraction data. Valuable mechanistic and kinetic insights into these processes, which are of prime importance for optimal activation of this type of material for catalytic applications, were obtained. Hydrotalcite decomposition to the mixed oxide proceeds via formation at 423-473 K of an intermediate phase, consisting of a highly disordered, dehydrated, layered structure. The latter evolves by removal of interlayer water on heating, causing a shrinking of the interlayer space (it is up to 45 % smaller than in the as-synthesized hydrotalcite). Above 623 K, Mg(Al)O(x) oxide with the periclase structure is formed. Reversion of the intermediate dehydrated structure to hydrotalcite upon contact with water vapor is complete and very fast at room temperature. Recovery of hydrotalcite from the oxide calcined at 723 K is two orders of magnitude slower than rehydration of the intermediate layered structure and one order of magnitude slower than the typically practiced liquid-phase reconstruction. In contrast to the decomposition, the reconstruction mechanism does not involve an intermediate phase. The gas-phase rehydration and reconstruction was interrupted above 303 K. This is attributed to the poor wetting of the surface of the decomposed materials induced by hampered H(2)O adsorption above room temperature at the water vapor pressure applied. The Avrami-Erofe'ev model describes the reconstruction kinetics well.     

镁铝型水滑石水热合成

水滑石是一类具有特殊结构的层状无机材料 .具有可调变的组成及独特的结构和性能 ,在离子交换、吸附分离、催化、医药等领域得到广泛应用 [1～ 4 ] .特别是水滑石类材料所具有的选择性、红外吸收性和离子交换性等一些特殊性能 ,使其作为新型无机功能材料已应用于 PE农膜 (保温剂 )和 PVC(无毒热稳定剂 )等高分子材料中 ,显示了独特的性能[5] .作为无机功能材料 ,水滑石在复合材料中的应用必然涉及其粒子尺寸和分布 ,因此对水滑石晶化规律的研究非常重要 .水滑石成熟的合成方法是共沉淀法[6] ,如单滴法、双滴法 .由于沉淀粒子是渐次产生 ,…     

The role of water in synthesised hydrotalcites of formula Mg(x)Zn(6 - x)Cr2(OH)16(CO3) x 4H2O and Ni(x)Co(6 - x)Cr2(OH)16(CO3) x 4H2O--an infrared spectroscopic study

Infrared spectroscopy has been used to characterise synthesised hydrotalcites of formula Mg(x)Zn(6 - x)Cr2(OH)16(CO3) x 4H2O and Ni(x)Co(6 - x)Cr2(OH)16(CO3) x 4H2O. The infrared spectra are conveniently subdivided into spectral features based (a) upon the carbonate anion (b) the hydroxyl units (c) water units. Three carbonate antisymmetric stretching vibrations are observed at around 1358, 1387 and 1482 cm(-1). The 1482 cm(-1) band is attributed to the CO stretching band of carbonate hydrogen bonded to water. Variation of the intensity ratio of the 1358 and 1387 cm(-1) modes is linear and cation dependent. By using the water bending band profile at 1630 cm(-1) four types of water are identified (a) water hydrogen bonded to the interlayer carbonate ion (b) water hydrogen bonded to the hydrotalcite hydroxyl surface (c) coordinated water and (d) interlamellar water. It is proposed that the water is highly structured in the hydrotalcite interlayer as it is hydrogen bonded to both the carbonate anion, adjacent water molecules and the hydroxyl surface.     

Raman spectroscopic study of the hydrotalcite desautelsite Mg6Mn2CO3(OH)16 x 4H2O

The structure of the hydrotalcite desautelsite Mg6Mn2CO3(OH)16.4H2O has been studied by a combination of Raman and infrared spectroscopy. Three intense Raman bands are observed at 1086, 1062 and 1055 cm(-1). A model based upon the observation of three CO3 stretching vibrations is presented. The CO3 anion may be (a) non-hydrogen bonded, (b) hydrogen bonded to the interlayer water and (c) hydrogen bonded to the brucite-like hydroxyl surface. Two intense bands at 3646 and 3608 cm(-1) are attributed to MgOH and MnOH stretching vibrations. Infrared bands at 3476, 3333, 3165 and 2991 cm(-1) are assigned to water stretching bands. Raman spectroscopy has proven a powerful tool for the study of hydrotalcite minerals.     

Molecular assembly in synthesised hydrotalcites of formula Cu(x)Zn(6 - x)Al2(OH)16(CO3) x 4H2O--a vibrational spectroscopic study

Infrared and Raman spectroscopy have been used to characterise synthetic hydrotalcites of formula Cu(x)Zn(6 - x)Al2(OH)16(CO3) x 4H2O. The spectra have been used to assess the molecular assembly of the cations in the hydrotalcite structure. The spectra may be conveniently subdivided into spectral features based (a) upon the carbonate anion (b) the hydroxyl units (c) water units. The Raman spectra of the hydroxyl-stretching region enable bands to be assigned to the CuOH, ZnOH and AlOH units. It is proposed that in the hydrotalcites with minimal cationic replacement that the cations are arranged in a regular array. For the Cu(x)Zn(6 - x)Al2(OH)16(CO3) x 4H2O hydrotalcites, spectroscopic evidence suggests that 'islands' of cations are formed in the structure. In a similar fashion, the bands assigned to the interlayer water suggest that the water molecules are also in a regular well-structured arrangement. Bands are assigned to the hydroxyl stretching vibrations of water. Three types of water are identified (a) water hydrogen bonded to the interlayer carbonate ion (b) water hydrogen bonded to the hydrotalcite hydroxyl surface and (c) interlamellar water. It is proposed that the water is highly structured in the hydrotalcite as it is hydrogen bonded to both the carbonate anion and the hydroxyl surface.