TiCl3/PhN2-mediated radical addition of ethers to aldimines generated in situ under aqueous conditions

Ti(III)-mediated one-electron reduction of phenyldiazonium cation, followed by phenyl radical α-H atom abstraction from ethers, leads to one-pot radical addition of ethers to the C-atom of imines generated in situ from the corresponding aldehydes and imines under aqueous conditions. The reaction is not limited to aromatic aldehydes and may be applied to imines generated in situ from formaldehyde and enolizable aldehydes.     

高温气相合成纳米TiO2-Al2O3复合颗粒的形态

TiO2和 Al2O3复合陶瓷具有热膨胀系数小、熔点高、抗震性好等优良性能,是一种很有发展前途的高温结构材料 [1]。 Woignier等 [2]采用醇盐共水解的 Sol gel法制备 TiO2 Al2O3复合颗粒,原料成本高、反应时间长; Okumura等 [3]利用烷氧基钛的水解反应在 Al2O3颗粒表面包覆 TiO2得到 TiO2 Al2O3复合颗粒,该法均匀性差,且需要液固分离、干燥和煅烧等,干燥和煅烧极易导致颗粒凝并或烧结。 Hung等 [4]利用燃烧法制备 SiO2 GeO2、 TiO2 Al2O3等复合粒子,研究中未采取有效措施控制复合颗粒形貌和大小,也未对颗粒形态结…     

Photoactivity and phase stability of ZrO2-doped anatase-type TiO2 directly formed as nanometer-sized particles by hydrolysis under hydrothermal conditions

Anatase-type TiO₂ doped with 4.7 and 12.4 mol% ZrO₂ that were directly precipitated as nanometer-sized particles from acidic precursor solutions of TiOSO₄ and Zr(SO₄)₂ by simultaneous hydrolysis under hydrothermal conditions at 200°C, showed higher photocatalytic activity than pure anatase-type TiO₂ for the decomposition of methylene blue. The crystallite growth and the phase transformation from anatase-type to rutile-type structure caused by heating at high temperature were retarded by doping ZrO₂ into TiO₂. The anatase-type TiO₂ doped with ZrO₂ showed high phase stability and maintained anatase-type structure even after heating at 1000°C for 1 h.     

Influence of crystallite structure of nanometer TiO2 catalysts on photocatalyst reaction

25 samples of nanometer TiO₂ were prepared through modifying the preparation conditions including the concentrations of Ti(SO₄)₂ and NH₄HCO₃, the pH value at the end of precipitation operation, and sintering temperature and time by methods of orthogonal design. The relationships between their catalytic activities of photocatalytic degradation of sodium dodecyl benzene sulfonate (SDBS) and the normal crystallite size, lattice-strain and X-ray diffraction intensity of 10 crystal faces were analyzed. It was discovered that the photocatalytic degradation reaction of SDBS follows first-order kinetics. Crystal faces of catalysts’ (101) have greater influence than other crystal faces on the reaction. The photocatalytic reaction needs more perfect (101) crystal faces with less lattice-strain. Smaller normal crystallite size and greater specific surface area of (101) crystal face are better for increasing reaction rate. The photocatalytic reaction is mainly proceeded on the (101) crystal face, comparatively, amorphous TiO₂ has lower catalytic activity.     

C3H8 separation from CH4 and H2 using a synthesized PDMS membrane: Experimental and neural network modeling

A polydimethylsiloxane (PDMS) membrane was synthesized and permeation behavior of ternary gas mixtures including C₃H₈, CH₄ and H₂ through it was studied as a function of operating parameters. Mixed gas permeability values were also compared with pure gas data as well as literature to validate experimental results. The aim was to predict separation factor (SF) of C₃H₈ as a function of feed temperature, pressure, flow rate and C₃H₈ concentration with the aid of artificial neural network (ANN) technique. Multilayer perceptron (MLP), which is the most common type of feedforward neural network (FFNN), was used for prediction. The Levenberg–Marquardt training method was initially employed to train the net. Then, optimum numbers of hidden layers and nodes in each layer were determined. The selected structure (4:4:5:1) was finally used to predict SF of C₃H₈ for different inputs in the domain of training data. The modeling results showed that there is an excellent agreement between the experimental data and the predicted values, with mean absolute errors of less than 1%. Both modeling and experimental results confirmed that increasing feed temperature, feed pressure and C₃H₈ concentration in feed debilitates separation performance; however, SF increases with increasing feed flow rate. As a result, ANN can be recommended for the modeling of mixed gas transport through dense membranes such as PDMS.     

Synthesis and crystal structure of new layered BaNaSc(BO3)2 and BaNaY(BO3)2 orthoborates

Crystals of two new layered BaNaSc(BO₃)₂ (I) and BaNaY(BO₃)₂ (II) orthoborates are grown from the melt-solution by the spontaneous crystallization onto the platinum loop. Single crystal X-ray analysis showed that the compounds are isostructural with the space group R3¯, a=5.23944(12) and 5.3338(2) Å, and c=34.5919(11) and 35.8303(19) Å for I and II, respectively, Z=6. The distinctive feature of the structure is the close-packed composite anion-cation (Ba,Na)(BO₃) layers. The layers are combined into the base building packages of two types: {M³⁺[Ba²⁺(BO₃)³⁻]₂}⁺ and {M³⁺[Na⁺(BO₃)³⁻]₂}⁻, where M is Sc or Y. Neutral-charge two-package (four-layer) blocks are stacked by the rhombohedral principle into twelve layers of the cubic packing.     

Four isomers from the oxidative addition of Me3SnH to Os(CO)2(PPh3)3 and the crystal structure of Os(SnMeI2)I(CO)2(PPh3)2, in which the pairs of CO and PPh3 ligands are mutually trans

Reaction between Os(CO)₂(PPh₃)₃ and Me₃SnH produces Os(SnMe₃)H(CO)₂(PPh₃)₂ (1). Multinuclear NMR studies of solutions of 1 reveal the presence of four geometrical isomers, the major one being that with mutually cis triphenylphosphine ligands and mutually trans CO ligands. Os(SnMe₃)H(CO)₂(PPh₃)₂ undergoes a redistribution reaction, at the trimethylstannyl ligand, when treated with Me₂SnCl₂ giving Os(SnMe₂Cl)H(CO)₂(PPh₃)₂ (2). Solutions of 2 again show the presence of four isomers but now the major isomer is that with mutually trans triphenylphosphine ligands and mutually cis CO ligands. The redistribution reaction of 1 with SnI₄ produces Os(SnMeI₂)H(CO)₂(PPh₃)₂ (3) which exists in solution as only one isomer, that with mutually trans triphenylphosphine ligands and mutually trans CO ligands. Treatment of 3 with I₂ cleaves the Os-H bond with retention of geometry giving Os(SnMeI₂)I(CO)₂(PPh₃)₂ (4). The crystal structure of 4 has been determined. No isomerization of the trans dicarbonyl complex 4 occurs when 4 is heated, instead there is a formal loss of “MeSnI” and formation of OsI₂(CO)₂(PPh₃)₂ (5).     

Synthesis of vinyl sulfides via hydrothiolation of alkynes using Al2O3/KF under solvent-free conditions

We present here a clean, solvent-free hydrothiolation of alkynes using solid supported catalyst (Al₂O₃/KF). This efficient and improved method selectively furnishes the corresponding anti-Markovnikov vinyl sulfides in good to excellent yields. The method is applicable for aliphatic and aromatic thiols and the catalytic system can be re-used up to two times without previous treatment and with comparable activity.     

无溶剂条件下三聚氰胺-Br_3催化一锅法合成1-氨基烷基-2-萘酚(英文)

A facile and efficient method has been developed for the synthesis of 1-amidoalkyl-2-naphthols via the one-pot multi-component condensation of 2-naphthol with aromatic aldehydes and acetamide or thioacetamide in the presence of melamine-Br3 under solvent-free conditions. There are several advantages to this reaction, including high yields, short reaction time, and high catalytic efficiency.     

掺杂Fe2O3对吸附相反应技术制备TiO2的形貌和光催化性能的影响

利用吸附相反应技术制备得到了掺杂不同浓度的Fe₂O₃的TiO₂复合光催化剂。通过透射电子显微镜(TEM)、紫外可见光谱和X射线衍射(XRD)研究不同掺杂浓度对TiO₂形貌和结晶过程的影响,并利用3种波长光源下的甲基橙光降解实验考评了各个复合光催化剂的催化活性。结果表明,掺杂后复合光催化剂中Fe₂O₃分散性较好较均匀。在TiO₂紫外可见吸收光谱中由于Fe₂O₃的掺杂而出现了红移,而且随着掺杂浓度增加红移越来越明显,复合光催化剂的禁带宽度也越来越小。在焙烧过程中无定形Fe₂O₃或Fe³⁺进入了TiO₂的晶格结构,从而抑制了TiO₂的结晶过程。半导体禁带宽度的减少以及TiO₂结晶过程的抑制作用,都导致紫外光下复合光催化剂催化活性的降低。但Fe₂O₃的掺杂也使得复合光催化剂在可见光区出现了一定的光催化活性。     

Effect of sol-gel derived Al2O3-ZrO2 and Al2O3-TiO2 oxides on the selectivity of NO reduction by CO under oxidizing conditions

The role of Al₂O₃-ZrO₂ and Al₂O₃-TiO₂ sol-gel prepared supports in the activity of platinum for the NO reduction by CO under oxidizing conditions has been studied. ²⁷Al MAS-NMR spectra have shown the formation of pentacoordinate Al^V in alumina-zirconia support. ZrO₂ or TiO₂ crystalline phases cannot be identified by XRD diffraction, suggesting the formation of nanosized structures supported on alumina. When the reaction was carried out in presence of oxygen, large amounts of NO₂ were observed on Pt/Al₂O₃-ZrO₂catalyst, while the formation of N₂O is more prononced on Pt/Al₂O₃-TiO₂ catalyst. The effect of water during NO reduction is discussed. This revised version was published online in June 2006 with corrections to the Cover Date.     

The crystal structure of CuSb2O3Br: Slabs from cubic Sb2O3 interspersed between puckered hexagonal CuBr-type layers

The new compound CuSb₂O₃Br crystallize in the monoclinic space group Cc. The unit cell parameters are , , , β=90°, Z=16. The crystal structure is solved from single crystal data, R=0.0490. The compound show a layered structure with slabs from cubic Sb₂O₃ interspersed in between puckered layers of CuBr. The Sb(III) atoms have tetrahedral [SbO₃E] coordination where E is the 5s² lone pair, these units build up Sb₄O₄E₆ cages. The CuBr layers resemble those in hexagonal CuBr but the Cu(I) ions have actually tetrahedral [CuBr₃O] coordination. The Cu-O bonds link the Sb₄O₆ cages with the CuBr layers.     

Crystallization kinetics of Na7.4(AlSiO4)6(CO3)0.7·4H2O, an intermediate phase between cancrinite and sodalite, grown under low temperature hydrothermal conditions

During low temperature hydrothermal alkaline conversion of kaolinite in the presence of sodium carbonate a disordered phase crystallizes showing structural features between the sodalite and cancrinite minerals. A detailed study of its formation field and the kinetics of crystallization is the first step for further investigations of this zeolite-like material. The crystallization kinetics was investigated in the early stage of the reaction for times up to 192 h at a temperature of 353 K. Besides X-ray powder diffraction²⁷Al MAS NMR has been found to be the preferred method to follow the reaction kinetics because a signal assigned to six-coordinated aluminium of the starting kaolinite can be clearly distinguished from a second resonance, being typical for aluminium in four-coordinate position of an aluminosilicate framework structure. Important conclusions can also be drawn from the experiments for the synthesis of ideal ordered cancrinites.     

Synthesis of rare-earth selenate and selenite materials under “sol-gel” hydrothermal conditions: crystal structures and characterizations of La(HSeO3)(SeO4) and KNd(SeO4)2

Two rare-earth compounds containing selenium atoms, La(HSeO₃)(SeO₄) with a new open framework structure and KNd(SeO₄)₂ with a layered structure, have been synthesized under “sol-gel” hydrothermal conditions for the first time. Single-crystals of La(HSeO₃)(SeO₄) crystallize in the monoclinic system (P2₁, , , , β=104.91(3)°, Z=2, R_All=0.032). The structure contains puckered polyhedral layers made of LaO_x (x=9,10) and SeO₄ groups, which are connected via SeO₃-uints to the 3D structure. The crytal structure of KNd(SeO₄)₂ (monoclinc, P2₁/c, , , , β=91.38(3)°, Z=4, R_All=0.051) contains honeycomb-like six-ring NdO₉ polyhedra forming layers which are further decorated with SeO₄ tetrahedra. The K⁺ ions occupy the interspaces of these layers and provide the charge balance.     

Surface species and gas phase products in the preferential oxidation of CO on TiO2-supported Au-Rh bimetallic catalysts

The oxidation of CO in the presence of hydrogen (PROX process) was investigated on bimetallic Au-Rh catalysts at 300–373 K by Fourier transform infrared spectroscopy and mass spectroscopy. The effects of catalyst composition, reaction temperature and composition of the reacting gas mixtures have been studied. The IR studies revealed the formation of bi- and monodentate carbonates, bicarbonates and hydrocarbonates on the catalysts surfaces; these surface species proved to be not involved in the surface reactions. The formation of adsorbed formaldehyde was observed on all surfaces, except 1% (0.25Au+0.75Rh)/TiO₂. Adsorbed CO₂ (as the surface product of CO oxidation) was not detected on any surface. The presence of both O₂ and H₂ reduced the surface concentration of CO adsorbed on the metallic sites. Mass spectroscopic analysis of the gas phase showed that gaseous CO₂ was formed in the highest amount in the CO+O₂ mixture, the presence of H₂ suppressed the amount of CO₂ produced. This negative effect of H₂ was the lowest on the 1% Rh/TiO₂ and 1% (0.25Au+0.75Rh)/TiO₂ catalysts.     

CH3S与HO2气相反应机理的理论研究

采用密度泛函理论的B3LYP方法, 在6-311＋＋G(d,p)基组水平上研究了CH3S自由基与HO2自由基的微观反应机理, 全参数优化了反应势能面上各驻点的几何构型, 振动分析和内禀反应坐标(IRC)分析结果证实了中间体和过渡态的真实性, 计算所得的键鞍点电荷密度的变化情况也确认了反应过程. 找到了五条可能的反应通道, 对结果的分析表明: 单线态反应通道(5) CH3S＋HO2→CH3SOOH (1P), 是所有通道中的主要反应通道. 该通道不需要克服过渡态能垒, 属于放热反应, 在动力学和热力学上都是最为有利的. 对于三线态反应通道来说, 通道(1)CH3S＋HO2→COM11→TS1→COM12→CH3SH＋O2 (3P)为主要反应通道, 控制步骤的活化能为53.5 kJ/mol, 能垒最低, 属于放热反应, 在动力学和热力学上都是有利的.     

Highly selective oxidation of amines to imines by Mn2O3 catalyst under eco-friendly conditions

Mn₂O₃ calcined at 450 ℃ by a simple template-free oxalate route gave 96.2% selectivity of imine at 100% conversion of benzylamine. The high selectivity of the imines clearly depended on the Mn³⁺/Mn⁴⁺ ratio. The probable reaction pathway for amines oxidation catalyzed by manganese oxides was proposed for the first time. This catalytic process was carried out under milder conditions, no base additives, and air as the only oxidant.     

Recovery of indium from In2O3 and liquid crystal display powder via a chloride volatilization process using polyvinyl chloride

Indium (In) was recovered from indium oxide (In₂O₃) and liquid crystal display (LCD) powder via a chloride volatilization process using polyvinyl chloride (PVC) as the chlorination agent. The recovery of In from In₂O₃ increased with an increasing molar Cl/In ratio in N₂ and air atmospheres. The degree of In recovery at a Cl/In molar ratio of 11 and a temperature of 350 °C was 98.7% and 96.6%, for N₂ and air, respectively. The In recovery also increased notably with increasing temperature in N₂ atmosphere. In both atmospheres, the In recovery increased with an increasing degradation temperature of PVC. However, the In recovery from LCD powder was lower than that from In₂O₃. For LCD powder, the degree of In recovery at a Cl/In molar ratio of 11 and a temperature of 350 °C was 66.7% and 54.1%, for N₂ and air, respectively.     

Morphological and phase evolution of TiO2 nanocrystals prepared from peroxotitanate complex aqueous solution: Influence of acetic acid

Nanosized anatase and rutile TiO₂ having different shape, phase and size have been prepared from aqueous solutions of peroxo titanium complex starting from titanium(IV) isopropoxide (TTIP), acetic acid and hydrogen peroxide (H₂O₂) in water/isopropanol media by a facile sol-gel process. The TiO₂ nanocrystals are characterized by powder X-ray diffraction (XRD), Raman spectroscopy, FT-IR spectroscopy, TEM, high resolution transmission electron microscopy (HRTEM) and selected area electron diffraction (SAED) techniques. The influence of pH and the sequence of addition of reaction contents on the phase and morphology of TiO₂ are studied. The reasons for the observation of only anatase and/or mixture of anatase and rutile are given.     

镧石型碳酸镨钕向碱式碳酸镨钕的相转变反应特征及其应用

镧石型碳酸镨钕[(PrNd)2(CO3)3·8H2O,LPN]在95℃的不同起始pH值的溶液中陈化不同时间所得样品的XRD衍射图证明了LPN向碱式碳酸镨钕[(PrNd)(OH)(CO3),BPN]的相态转变。为此,详细研究了这一相态转变的反应条件以及粒子特征变化。结果表明:LPN是由片状或条状结晶连生而成的聚集体,具有大的粒度和小的堆密度。当在热的水溶液中陈化时,由于水解反应而发生由LPN向BPN的相转变。这一相转变可以在95℃下pH=7以上的溶液中发生,其转化率随起始溶液pH值的升高和陈化时间的延长而增大。随着相转变的进行,溶液的pH值开始下降明显,而后趋于平缓。相应地,大的团聚体颗粒解散成小的单个粒子,导致粒度减小,分布变窄,氯根含量降低和堆密度的增大。而且,这些变化直接与溶液pH值和陈化时间相关。据此,发展了一种新的制备具有高堆密度、低氯根含量、细粒度和窄分布的新方法,而且通过改变相转变条件可以方便地调谐颗粒特征。