粉状白钨酸的研究(Ⅴ)——12-钨磷酸的直接制备以及用正丁醚的提纯法

12-钨磷酸的应用,近年来发展迅速,有从实验室合成转为工业生产的趋势。本报告从E.Drechsel法的以钨酸钠和磷酸氢二钠为原料,改为以活性粉状白钨酸为原料,与磷酸直接反应,即成12-钨磷酸溶液。这样便可以免除Drechscl乙醚萃取法中大量盐酸的使用。在提纯时,把在Drechsel方法中所用的乙醚,改为沸点高的正丁醚,配合适当少量的盐酸,可以得到相应的(钅羊)盐油状物。并由于该(钅羊)盐安定度较差,用水反萃取即可使12-钨磷酸转入水溶液,经过浓缩即可得到12-钨磷酸晶体。回收的正丁醚,毋需蒸馏,可以反复使用。     

GaxCs2.5-3xH0.5PW12O40的固相法制备及其催化正丁烷异构化反应的活性

利用室温固相法制备了一系列掺镓的钨磷酸铯盐催化剂GaxCs2.5-3xH0.5PW12O40(x=0.05,0.1,0.15).与钨磷酸铯盐相比,掺镓的钨磷酸铯盐催化剂的结构未产生变化,但其酸强度提高,在正丁烷异构化反应中催化活性增强,其中以Ga0.1Cs2.2H0.5PW12O40和Ga0.15Cs2.05H0.5P...     

杂多酸及其盐对异丁烯聚齐反应的催化作用

研究了12-钨磷酸及其14种盐以及其它3种Keggin型杂多酸对异丁烯齐聚反应的催化作用。发现12-钨磷酸的Fe(Ⅲ),La,Al,Cr(Ⅲ)和Cu(Ⅱ)盐对异丁烯齐聚反应有很高活性,可同12-鹤磷酸相媲美。各种12-钨磷酸盐的催化活性大体上随金属阳离子的电负性增大而增高,与盐的H_0≤ 4.8的酸量也有相似的关联。齐聚生成物的聚合度主要与酸强度有关,酸强度越大,聚合度越高。杂多阴离子不一样的几种Keggin型杂多酸的催化活性次序与它们的酸性强弱次序相一致。     

杂多酸催化剂上甲醇转化为烃的研究

Keggin型杂多酸化合物的热稳定性高,又具有强酸性和氧化还原性,故其催化作用很引人注目.由于其结构上的特点,反应物分子能出入催化剂的体相内部,因而体相中的活性中心也起作用,被称作“假液相”催化.杂多酸用于甲醇催化转化为烃的反应有不少研究.据报道,12-钨磷酸(H_3PW_(12)O_(40))和12-钨硅酸(H_4SiW_(12)O_(40))、12-钨磷酸铜(Cu_(3/2)PW_(12)O_(40))对甲醇转化反应都有相当高的活性.1,4-二嗪和1,3,5-三嗪的12-     

十二钨磷酸碱土金属盐与DMF和乙醇加合物的合成及反应热的测定

在非水溶剂中合成了十二钨磷酸碱土金属盐与DMF和EtOH的加合物Ca_3/2(PW₁₂O₄₀)·9DMF·EtOH、Sr_3/2(PW₁₂O₄₀)·8DMF·EtOH和Ba_3/2(PW₁₂O₄₀)·9DMF.通过元素分析和红外光谱确定了它们的组成和Keggin结构.测定了十二钨磷酸钙、十二钨磷酸锶和十二钨磷酸钡同DMF和EtOH的加合反应热.30℃下其反应热分别为-207.4±2.3、-197.1土5.4kJ/mol和-270.9±2.4kJ/mol.     

杂多酸催化剂作用下丙烯与醋酸的加成酯化反应

在较低压力(1.0—2.0mPa)下,研究了杂多酸对丙烯和醋酸的气-液加成酯化反应的催化作用。实验表明杂多酸具有很高的活性和选择性,其活性大小次序为:12-钨磷酸≈12-钨硅酸>10-钼磷酸≈12-钼磷酸,在以最佳反应温度(T_(opt))为界的两个温度段,温度的影响不同,即:TT_(opt)时随反应温度升高醋酸转化率降低,在液相中含水量低于1.0％时,醋酸转化率随含水量增加急剧增高;含水量在1.0～2.0％时达极大值;含水量进一步增加时,醋酸转化率减少,伴生的异丙醇量增加,还考察了反应压力和时间等因素的影响,提出了由丙烯与醋酸生成醋酸异丙酯和伴生异丙醇的反应机理。     

多酸含量对无机/高分子复合薄膜结构及光致变色性能的影响

制备了一系列不同浓度的钨磷酸/聚乙烯醇(PWA/PVA)复合薄膜, 通过红外光谱、原子力显微镜、紫外-可见吸收光谱对复合薄膜的结构和光致变色性能进行了研究. 红外光谱分析结果表明, Keggin结构钨磷酸和聚乙烯醇分子的基本结构在复合薄膜中仍然存在, 钨磷酸分子与高分子底物间存在氢键作用, 形成电荷转移桥. 原子力显微镜(AFM)结果表明复合前后PVA薄膜表面形貌发生了显著变化, 复合膜表面形貌随钨磷酸含量的不同而不同. 在紫外光照射下, 复合薄膜由无色变为蓝色. 复合膜的升色速度和褪色速度均随着钨磷酸含量的增加而加快. 这些结果表明钨磷酸含量对复合膜的微结构存在影响, 从而导致了复合膜具有不同的光致变色性能.     

钨磷酸(钨硅酸)/聚乙烯醇复合物的制备和光、电性质研究

Kessin型的杂多酸及其盐是多酸化学中研究得最多的物种[1],近年来,以Keggin型的钨磷酸、钨硅酸为代表的多种杂多酸在固体和材料化学领域受到人们的关注[2],并在固体修饰电极、光（电）致变色材料、离子选择性电极和传感器等方面得到了广泛应用[3-5]．本文报道了Keggin型的钨磷酸、钨硅酸／聚乙烯醇复合物的合成、表征、光致变色性质及导电性．1实验方法技文献[6]方法制备H4[SiW12O40]·mH2O和H2［PW12O40］·nH对晶体,含水量用热重分析测得．将聚合度为1800士100的聚乙烯酸（PVA）0．5g溶于200mL沸水中,在65C,搅拌条件下分批…     

乙醇在杂多酸上的氧化、脱水和程序升温脱附研究

合成了两个系列具有Keggin结构的12-钒钼磷酸和钨钼磷酸,研究了它们对乙醇氧化、脱水的催化反应。借助程序升温脱附技术研究了反应物及产物乙醇、乙烯、乙醚等在样品上的程脱作用。讨论了钨、钒取代部分钼原于后对杂多酸酸性及氧化性能的影响。     

离子液体型多金属氧酸盐[PyPS]nH3-nPW12O40·xH2O的合成及其对水溶液中染料的光催化脱色作用

以吡啶、丙磺酸内酯和钨磷酸为原料,合成了离子液体型多金属氧酸盐（POM-IL）化合物[PyPS]nH3-nPW12O40·xH2O（n=1,2,3）,用FT-IR、UV-Vis、1H NMR和元素分析等对其进行了表征。 结果显示,POM-IL化合物仍保持相应钨磷酸的Keggin结构,并存在吡啶丙磺酸的特征谱带,熔点均高于130 ℃,且随有机阳离子含量增加,熔点降低。 在紫外光下,n为1和2的POM-IL对水溶液中甲基橙的光催化降解活性与钨磷酸相似;在可见光下,POM-IL对水溶液中靛红的光催化降解活性相近,且均远高于钨磷酸。     

A kinetic study of the electron-transfer in the reaction of tribenzylchlorotin with[CoW_(12)O_(40)]~(5-)

A kinetic study of the electron-transfer in the reaction of tribenzylchlorotin with potassium 12-tungsto cobalt(Ⅲ) ate ion, K_5[CoW_(12)O_(40)],abbreviated as Co(Ⅲ)W,has been performed in different solvents.The studies were carried out in methanol, ethanol,acetonitrile and acetic acid/water.The rate constants,reaction rates and activation parameters were calculated. Our findings show that the rate of disappearance of the Co(Ⅲ) is pseudo-first order.The kinetic data is strongly affected by used solvents.T...     

Heterogeneous crystal growth of methane hydrate on its sII [001] crystallographic face

This paper presents a systematic molecular simulation study of the heterogeneous crystal growth of methane hydrate sII from supersaturated aqueous methane solutions. The growth of sII hydrate on the [001] crystallographic face is achieved through utilization of a recently proposed methodology, and rates of crystal growth of 1 A/ns were sustained for the molecular models and specific conditions employed in this work. Characteristics of the crystals grown as well as properties and structure of the interface are examined. Water cages with a 5(12)6(3) arrangement, which are improper to both sI and sII structures, are identified during the heterogeneous growth of sII methane hydrate. We show that the growth of a [001] face of sII hydrate can produce an sI crystalline structure, confirming that cross-nucleation of methane hydrate structures is possible. Defects consisting of two methane molecules trapped in large 5(12)6(4) cages and water molecules trapped in small and large cages are observed, where in one instance we have found a large 5(12)6(4) cage containing three water molecules.     

Computer simulation of the hydration of sulfocation exchanger containing imino acid

The mechanism of formation of hydrate structures in the system sulfo exchanger-imino acid was suggested. The mutual position of fixed ion, imino acid, and water molecules was determined in cation exchanger. The conclusion was made on the presence of water molecule between the functional group of sorbent and counterion of imino acid. It was demonstrated that the mechanism of sorption of proline and hydroxyproline is performed by the break of bond between water molecules and protonation of carboxylic group of imino acid.     

Raman spectra of vibrational and librational modes in methane clathrate hydrates using density functional theory

The sI type methane clathrate hydrate lattice is formed during the process of nucleation where methane gas molecules are encapsulated in the form of dodecahedron (5(12)CH(4)) and tetrakaidecahedron (5(12)6(2)CH(4)) water cages. The characterization of change in the vibrational modes which occur on the encapsulation of CH(4) in these cages plays a key role in understanding the formation of these cages and subsequent growth to form the hydrate lattice. In this present work, we have chosen the density functional theory (DFT) using the dispersion corrected B97-D functional to characterize the Raman frequency vibrational modes of CH(4) and surrounding water molecules in these cages. The symmetric and asymmetric C-H stretch in the 5(12)CH(4) cage is found to shift to higher frequency due to dispersion interaction of the encapsulated CH(4) molecule with the water molecules of the cages. However, the symmetric and asymmetric O-H stretch of water molecules in 5(12)CH(4) and 5(12)6(2)CH(4) cages are shifted towards lower frequency due to hydrogen bonding, and interactions with the encapsulated CH(4) molecules. The CH(4) bending modes in the 5(12)CH(4) and 5(12)6(2)CH(4) cages are blueshifted, though the magnitude of the shifts is lower compared to modes in the high frequency region which suggests bending modes are less affected on encapsulation of CH(4). The low frequency librational modes which are collective motion of the water molecules and CH(4) in these cages show a broad range of frequencies which suggests that these modes largely contribute to the formation of the hydrate lattice.     

Analysis of Decomposition for Structure I Methane Hydrate by Molecular Dynamics Simulation

Under multi-nodes of temperatures and pressures, microscopic decomposition mechanisms of structure I methane hydrate in contact with bulk water molecules have been studied through LAMMPS software by molecular dynamics simulation. Simulation system consists of 482 methane molecules in hydrate and 3027 randomly distributed bulk water molecules. Through analyses of simulation results, decomposition number of hydrate cages, density of methane molecules, radial distribution function for oxygen atoms, mean square displacement and coefficient of diffusion of methane molecules have been studied. A significant result shows that structure I methane hydrate decomposes from hydrate-bulk water interface to hydrate interior. As temperature rises and pressure drops, the stabilization of hydrate will weaken, decomposition extent will go deep, and mean square displacement and coefficient of diffusion of methane molecules will increase. The studies can provide important meanings for the microscopic decomposition mechanisms analyses of methane hydrate.     

A new waterNa(+) coordination motif in an unexpected diatrizoic acid disodium salt crystal form

The disodium salt of diatrizoic acid crystallises as a tetragonal channel hydrate structure. One of the incorporated water molecules is coordinated to three individual sodium cations in a unique geometry.     

Thermal degradation studies on some lanthanide—edta complexes containing hydrazinium cation

Lighter and heavier lanthanide(III) ions react with dihydrazinium salts of ethylenediaminetetraacetic acid (H4edta) in aqueous solution to yield hydrazinium lanthanide ethylenediaminetetraacetate hydrate, N₂H₅[Ln(edta)(H₂O)₃]·(H₂O)₅ where Ln=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb and Dy. The numbers of water molecules present inside the coordination sphere have been confirmed by X-ray single crystal studies. The presence of five water molecules as lattice water is clearly shown by the mass loss from the TG analyses. Dehydration of a known amount (1 g) of each sample were carried out at constant temperature (100–110°C) for about 5 min further confirms the number of non-coordinated water molecules. The complexes after the removal of lattice water undergo multi-step decomposition to give respective metal oxide as the final product. The DTA shows endotherms for dehydration and exotherms for the decomposition of the anhydrous complexes. The formation of the metal oxides was confirmed by X-ray powder diffraction studies.     

新型两亲性聚酰胺的合成及性质

为了设计天然气水合物抑制剂和了解作用机理提供依据,分析两亲性聚酰胺与水相互作用的特征与本质,本文合成了新型水溶性高分子聚柠檬酰丙二胺,在此基础上合成了一种含环己基基团的两亲性聚柠檬酰丙二胺。通过核磁共振波谱、凝胶渗透色谱和示差扫描量热法对产物的结构和性能进行了表征。研究表明,改性的聚柠檬酰胺能形成不可冰冻束缚水,而且比传统的天然气水合物抑制剂聚(N-乙烯基己内酰胺)和聚维酮形成的不可冰冻束缚水多1倍。改性后聚合物中水的比热容增加约36%。聚合物和水之间产生的疏水相互作用,可将水分子更紧密地束缚在聚合物中。改性后的聚合物的疏水性强,造成了水分子彼此紧密束缚程度提高,为不可冰冻束缚水含量的增加提供了必要的环境。     

Characterization of non-stoichiometric hydration and the dehydration behavior of sitafloxacin hydrate

Sitafloxacin (STFX) hydrate is a non-stoichiometric hydrate. The hydration state of STFX hydrate varies non-stoichiometrically depending on the relative humidity and temperature, though X-ray powder diffraction (XRPD) of STFX hydrate was not affected by storing at low and high relative humidities. The detailed properties of crystalline water of STFX hydrate were estimated in terms of hygroscopicity, thermal analysis combined with X-ray powder diffractometry, crystallography and density functional theory (DFT) calculation. STFX hydrate changed the water contents continuously and reversibly from an equivalent amount of dihydrate through that of sesquihydrate depending on the relative humidity at 25°C. Thermal analysis and X-ray powder diffraction (XRPD) simultaneous measurement also revealed that STFX hydrate dehydrated into a hydrated state equivalent to monohydrate by heating up to 100°C, whereas XRPD patterns were slightly affected. This indicated that the crystal structure of STFX hydrate was retained at the dehydration level of monohydrate. Single-crystal X-ray structural analysis showed that two STFX molecules and four water molecule sites were contained in an asymmetric unit. STFX molecules formed a channel structure where water molecules were included. At the partially dehydrated state, at least two of four water molecules were considered to be disordered in occupancy and/or coordinates. Insight into the crystal structure of STFX hydrate stored at low and high relative humidities and geometry of the hydrogen bond were helpful to estimate the origin of non-stoichiometric hydration of STFX hydrate.     

热力学抑制剂作用下甲烷水合物分解过程的分子动力学模拟

采用正则系综(NVT)分子动力学方法模拟研究277.0 K、11.45 mol·L-1的热力学抑制剂乙二醇(EG)溶液作用下甲烷水合物分解微观过程. 模拟显示甲烷水合物的分解从甲烷水合物固体表面开始, 逐渐向内部推移, 固态水合物在分解过程中逐渐缩小, 直至消失. 固态水合物的分解从晶格扭曲变形开始, 之后笼形框架结构破裂, 最后形成笼形结构碎片. 同时已经分解的甲烷水合物在外层形成水膜, 包裹里层正在分解的甲烷水合物, 增大里层甲烷水合物分解传质阻力.