Preparation and Photocatalytic Application of the Microporous Decatungstate, Na4W10O32/SiO

The photochemical behavior of polyoxometalates（POMs）have been studied extensivelyIn homogeneous solutions［1-3]．However,the major drawback to the practical applications ofthe homogeneous systems is the high water solubility of POMs,which impedes the readyrecovery and the reuse of the photocatalysts．Therefore,the preparation of insoluble POMs Isconsidered．More recently,we haveprepared insoluble POMs,i．e,Keggin－type microporousPOMs,H3PW12O40／SiO2 or H4SiW12O40／SiO2,and paratungstate A－containing pillaredcompound,Mg12Al6（OH）36（W7O24）·4H2O,for the purpose of photo－oxidation of aqueous     

用十聚钨酸季铵盐催化过氧化氢氧化环己烯为己二酸

己二酸是重要的化学品.开发绿色、洁净的氧化方法合成己二酸,一直吸引着许多化学工作者的注意.1998年,Noyori等[1]报道了使用钨酸钠和甲基三辛基硫酸氢铵作为催化剂把环己烯氧化为己二酸的方法.1999年邓友全等[2,3]报道了在钨酸钠和草酸等形成原位过氧钨酸有机配合物催化剂存在下,使用30%过氧化氢由环己烯合成己二酸的方法.姜恒等[4,5]先后在甲基三辛基硫酸氢铵替代物的选择上和过氧钨酸有机配合物有机配体的作用方面进行了较为系统的工作.这些研究工作虽然都能直接获得高质量和高产率的己二酸,但是都存在着催化剂难于分离的问题.重复…     

Hydrogen generation from methanol reforming under unprecedented mild conditions

A homogeneous catalyst [Cp^*Rh(NH₃)(H₂O)₂]³⁺ has been found for the clean conversion of methanol and water to hydrogen and carbon dioxide.The simple and easily available reaction steps can circumvent the formation of CO,therefore,making it possible to avoid inactivating catalysts and contaminating the hydrogen fuel.Different from conventional reforming method for hydrogen production,no additional alkaline or organic substances are required in this method.Valuable hydrogen can be obtained under ambient pressure at 70℃,corresponding TOF is 83.2 h^-1.This is an unprecedented success in reforming methanol to hydrogen.Effects of reaction conditions,such as reaction temperature,initial methanol concentration and the initial pH value of buffer solution on the hydrogen evolution are all systematically investigated.In a certain range,higher reaction temperature will accelerate reaction rate.The slightly acidic condition is conducive to rapid hydrogen production.These findings are of great significance to the present establishment of the carbon-neutral methanol economy.     

Decatungstate as a direct hydrogen atom transfer photocatalyst for synthesis of trifluromethylthioesters from aldehydes

We have developed a versatile, mild protocol for trifluoromethylthiolation reactions of aldehydes with catalysis by a decatungstate hydrogen atom transfer photocatalyst under redox-neutral conditions. The protocol is highly selective, operationally simple, and compatible with a wide array of sensitive functional groups. It can be used for late-stage functionalization of bioactive molecules, which makes it convenient for drug discovery.     

Solid deformation induced by the adsorption of methane and methanol under sub- and supercritical conditions

Carbonaceous materials with some degree of flexibility in their physical structure can expand or contract under the influence of the forces exerted by adsorbed molecules. To gain insight into how adsorption of non-polar and polar fluids could deform a carbon solid, we present GCMC simulations of sub- and supercritical adsorption of methane and methanol in slit-shaped pores whose walls are made of graphene layers. Our extensive simulation study shows that there is a strong correlation between solvation pressure and solid deformation, and that the expansion or contraction of the pore strongly depends on adsorbate loading, temperature and pore size.     

基于甲醇自由基还原波的甲醇极谱测定

利用过硫酸根在电极上还原产生的硫酸根自由基SO4· - 将甲醇氧化成甲醇自由基HC·HOH ,该自由基还原产生极谱还原波 ,拟定了极谱测定甲醇的新方法。在 0 .0 33mol/LKH2 PO4+Na2 HPO4(pH 6.1± 0 .1 ) + 1 .6× 1 0 - 2 mol/LK2 S2 O8介质中 ,甲醇自由基还原波峰电流与甲醇浓度在 3.1 5× 1 0 - 4 mol/L～ 9 46× 1 0 - 3mol/L范围呈线性关系。用该方法测定了甲醇生产车间空气中的甲醇含量     

多金属氧酸盐光催化降解有机污染物研究进展

光催化作为一种高级氧化技术在有机污染物的降解方面得到广泛研究。本文概述了多金属氧酸盐光催化降解有机卤化物、染料、农药等有机污染物的研究进展,介绍了多金属氧酸盐与半导体氧化物、层状双氢氧化物、分子筛与介孔材料、离子交换树脂形成的复合材料,以及与半导体氧化物、聚乙烯醇等形成的复合膜材料的相关研究。     

光催化Suzuki偶联反应的非均相催化剂研究进展

Suzuki偶联反应作为构建C-C键的最有效的手段之一,在医药、染料和电子工业等领域扮演着重要的角色。传统的Suzuki偶联反应催化体系需要依赖化石能源产生的热能来驱动,不仅造成了不可再生资源的消耗,还会导致相应的环境问题。近年来,光催化技术和绿色有机合成化学蓬勃发展,利用可再生的太阳能光催化Suzuki偶联反应不但可以解决在催化反应过程中的能源与环境问题,还可以在温和条件下获得高产率的联苯化合物产物,正在受到人们的广泛关注。与均相光催化剂相比,非均相光催化剂具有良好的化学稳定性、便捷的可回收性与优异的循环利用性能等优点,因此成为光催化Suzuki偶联反应的研究重点。本文总结了非均相催化剂光催化Suzuki偶联反应的基本原理,介绍了近年来科研工作者对光催化Suzuki偶联反应中非均相催化剂的制备方法、催化性能以及可循环利用性等方面做的一系列研究。     

Degradation of rhodamine B photocatalyzed by Eu-doped CdS nanowires illuminated by visible radiation

CdS nanowires doped with different contents of Eu dopant were synthesized by solvothermal method. XRD, SEM, TEM and Raman analyses certified that the as-synthesized samples were hexagonal CdS uniform nanowires. The pure CdS nanowires were 1–3 ?μm long and 80 ?nm diameter with the 1st and 2nd order longitudinal phonon modes at 298 and 594 ?cm^?1. The 3% Eu-doped CdS wires were 800 ?nm–2.5 ?μm long and 75 ?nm diameter with the 1st and 2nd order longitudinal phonon modes at 296 and 593 ?cm^?1. CdS nanowires grew along the [001] direction due to the surface energy effect. The photocatalytic properties of CdS and Eu-doped CdS nanowires were investigated for the degradation of rhodamine B (RhB) illuminated by visible radiation. In this research, Eu dopant played the role in promoting the photocatalytic kinetics because Eu³⁺ ions act as an electron acceptor to promote charge separation and photocatalytic activity. Both ^●OH and ^●O₂^? were the main active radicals used to transform RhB molecules into CO₂, H₂O and other intermediates.     

A comparative study of the performance of acetonitrile and methanol in the multi-linear gradient separation of proteic primary amino acids

The performance of the separation of proteic primary amino acids using multi-linear gradients of acetonitrile and methanol was studied under an experimental-design basis, using an Inertsil ODS-3 column and pre-column derivatization with o-phthaldialdehyde (OPA) and N-acetyl-l-cysteine (NAC). Elution strength, peak properties, resolution, and analysis time, were examined. The optimal separation was established through modeling, using information obtained from isocratic data. By optimizing the separation with gradients of increasing complexity, acceptable resolution was possible, being glycine/threonine the critical pair. Multi-criteria decision-making (Derringer desirabilities) was applied to balance resolution and analysis time. The more favorable peak distribution for methanol gradients allowed a larger reduction of analysis times, keeping satisfactory resolution, but its smaller elution strength forces the use of concentrations significantly larger. Methanol is, however, less toxic, and the final cost is similar for both solvents.     

Solvation of perfluorooctane and octane in water, methanol, acetonitrile, and aqueous mixtures of methanol and acetonitrile

Molecular dynamics simulations are used to examine the local solvation structure of single octane and perfluorooctane molecules in liquid water, methanol, acetonitrile, and aqueous mixtures of methanol and acetonitrile. The motivation is to obtain baseline information about the solvation of perfluorooctane by liquids used as the mobile phase in liquid chromatography and how it differs from the solvation of octane. While octane is uniformly solvated by both water and the second component, perfluorooctane is solvated by methanol and acetonitrile with the exclusion of water from the first solvation layer when the solvent is a mixture.     

Synthesis and catalytic performance on methanol conversion of NiAPSO-34 crystals (II): catalytic performance under various reaction conditions

This work has been focused on the catalytic performance for methanol conversion of NiAPSO-34 catalysts which had been synthesized by various preparation methods. The deposited coke during the hydrocarbon transformation was analyzed by temperature-programmed oxidation (TPO) method. For a catalyst with small acid sites and sharp particle size distribution, the catalytic activity and selectivity to ethylene increased compared with other catalysts. It could be confirmed that the catalysts having different acidic densities on external surface and internal surface represented different catalytic activities. Furthermore, it was elucidated that amount of coke formation was strongly related to acidic density on the external crystal surface. On the other hand, catalytic performances under various reaction conditions were exhibited variously and the deposited coke amount was also various. In particular, a surprising result was that the catalytic performance was not changed on the revived catalyst by thermal treatment at 600°C for 3 h.     

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。     

Ionothermal synthesis and characterization of two new heteropolytungstates with 1-ethyl-3-methylimidazolium bromide ionic liquid as solvent

In this article, we have synthesized two new heteropolytungstate-based compounds [EMIM]₄[SiW₁₂O₄₀] (1) and [EMIM]₆[P₂W₁₈O₆₂] · 4H₂O (2) using the ionic liquid (IL) [EMIM]Br (EMIM = 1-ethyl-3-methylimidazolium) as a solvent and characterized them by infrared (IR) and ultraviolet (UV) spectra, thermogravimetric (TG) and elemental analyses, electrochemistry, and single-crystal X-ray analyses. Compound 1 is constructed from one [SiW₁₂O₄₀]^4? and four [EMIM]⁺. In the structure, [SiW₁₂O₄₀]^4? and [EMIM]⁺ are connected by hydrogen bonds with the surface oxygens of the polyoxoanion to form a 3-D supramolecular framework. The heteropolyanion of 2 is a classical Dawson-type structure [P₂W₁₈O₆₂]^6? and connected with six cations through hydrogen bonds. The structures of these two heteropolyanions are consistent with those synthesized by traditional methods, indicating that ionothermal synthesis is an effective method for the preparation of heteropolyoxometalates. The photocatalytic properties of these compounds have also been investigated.     

Electron solvation in methanol revisited

Suggestions for the mechanism of electron solvation in methanol during the last three decades were mostly based on limited time resolution measurements, or indirect observations. The two-channel solvation scheme proposed by Lewis and Jonah (1986) based on indirect observations in electron scavenging experiments is checked here to see if it is in accordance with recent sub-picosecond pump-and-probe laser experimental results. We confirm the applicability of this solvation mechanism and calculate quantitative kinetic and spectral parameters involved.     

Catalytic reaction of methanol with alkanethiols

Methanol reacts with primary alkanethiols (R=C₁–C₃) over alumina catalysts to yield dialkyl sulfides. Methanethiol is completely converted to dimethyl sulfide. Ethane-and 2-propanethiols give methyl alkyl sulfides. However, the process is complicated by side reactions producing olefins and dimethyl sulfide. If mixed thiols are used, their transformations hinder each other.     

Electrochemical oxidation of carbon monoxide, methanol, formic acid, ethanol, and acetic acid on a platinum electrode under hot aqueous conditions

Using a pressure cell equipped with an Ag AgCl 0.1 M KCl external pressure-balanced reference electrode (EPBRE), hydrogen, methanol, formic acid, carbon monoxide, ethanol, acetic acid, and glucose were electrochemically oxidized on a Pt electrode under hot aqueous conditions (365−525 K), and the polarization curves were obtained at a sweep rate of 1 or 10 mV s⁻¹. The potential measured versus EPBRE was corrected to the RHE scale based on the experimentally or theoretically calculated pH of the solution at high temperature. During methanol and carbon monoxide oxidation, a strongly adsorbed intermediate presumably CO, was formed but it was oxidized at a lower potential than under ambient temperature. Formic acid was rapidly oxidized around 0 V versus RHE without formation of this adsorbed intermediate. Using a gas mixture of hydrogen and carbon monoxide, it was confirmed that the surface coverage by CO was decreased dramatically with a temperature increase from 425 to 475 K under hot aqueous conditions. Ethanol and acetic acid were also satisfactorily oxidized, but the trial to measure the electrochemical oxidation behavior of glucose was not successful due to the adhesion of char-like compounds to the electrode.     

The torsion-vibration spectrum of methanol trapped in neon matrix

The spectra of six isotopic species of methanol trapped in neon matrix have been recorded between 30 and 11,000 cm⁻¹. Noticeable temperature effects are observed for the OH species. They allow two kinds of absorptions to be identified for most of the vibrational transitions: those low temperature (LT) predominating at 2.7 K and those high temperature (HT) significantly increasing in intensity when varying temperature from 2.7 to 7 K. The conversion is perfectly reversible and has been examined from two points of view: the kinetics of interconversion and the activation energy associated to the process. The kinetic study shows that the limiting factor of the measurements is the time required for spectral acquisition (about 5 s). The activation energy deduced from Arrhenius plots is found equal to 6.7 ± 0.5 cm⁻¹. From the comparison with gas phase data one concludes that the internal rotation about the C–O bond is not strongly altered by the matrix surrounding, the activation energy corresponding to the E–A tunneling splitting of the ground state (9.12 cm⁻¹ for CH₃OH in the gas phase). The pure torsion and the torsion-vibration spectra are generally consistent with those in the gas phase. In particular the complex structure of the COH bending mode is well reproduced, with a clear identification of the transitions issuing from the A and E sublevels of the ground state.