Cl+C2H6→HCl+C2H5反应的准经典轨线研究

用三原子模型的准经典轨线方法研究了Ｃｌ与Ｃ２Ｈ６（ｖ＝０，ｊ）的反应。计算结果表明，反应产物ＨＣｌ的角度分布基本上为各向同性，其振动分布处于基态，与实验结果相一致。对反应轨线的研究表明，该反应为一直接反应，而且反应碰撞在低及高的碰撞参数下的机理不一样，在低碰撞参数下反应碰撞是直接完成的，产物ＨＣｌ以向后散射为主，转动基本上是冷的，但比高碰撞参数下的热。在高的碰撞参数下则生成短寿命的碰撞复合物，产物     

CO2选择性氧化甲烷制C2烃催化剂La2O3/ZnO的氧化还原和CO2吸附性能

Ｌａ２Ｏ３／ＺｎＯ催化剂体系在以二氧化碳作为氧化剂的甲烷氧化偶联反应中具有很高的Ｃ２烃选择性和稳定性．采用ＣＯ２－ＴＰＤ－ＭＳ和ＴＰＲ技术考察了Ｌａ２Ｏ３／ＺｎＯ对ＣＯ２的吸附性质及其氧化还原行为．结果表明：（１）Ｌａ２Ｏ３／ＺｎＯ催化剂体系存在着强、弱两种碱中心，其中弱碱中心数量随样品中Ｌａ２Ｏ３含量增加而减少，强碱中心强度随样品中Ｌａ２Ｏ３含量增加而增强．（２）由于组分相互作用，高温下，Ｌａ２Ｏ３／ＺｎＯ易产生晶格氧空位，使之对ＣＯ２的吸附增强，吸附后的ＣＯ２与晶格氧作用形成立方晶型Ｌａ２Ｏ２ＣＯ３．（３）Ｌａ２Ｏ３／ＺｎＯ表面的Ｌａ３＋和Ｚｎ２＋可以部分被还原，由于组分间的相互作用，使得二者的还原都较单一组分存在时更难．（４）Ｈ２－ＣＯ２－Ｈ２氧化还原循环实验表明，Ｌａ２Ｏ３／ＺｎＯ表面被部分还原后，ＣＯ２可以将部分被还原的表面再氧化．在此基础上对Ｌａ２Ｏ３／ＺｎＯ催化剂上甲烷与ＣＯ２转化为Ｃ２烃的机制也进行了讨论．     

Synthesis and Structure of the Hexanuclear Diazenido－oxomolybdate ［（n－C_4H_9）_4N］_3［Mo_6O_（18）（N_2C_6H_4－p－NO_2）］

ＳｙｎｔｈｅｓｉｓａｎｄＳｔｒｕｃｔｕｒｅｏｆｔｈｅＨｅｘａｎｕｃｌｅａｒＤｉａｚｅｎｉｄｏ－ｏｘｏｍｏｌｙｂｄａｔｅ［（ｎ－Ｃ_４Ｈ_９）_４Ｎ］_３［Ｍｏ_６Ｏ_（１８）（Ｎ_２Ｃ_６Ｈ_４－ｐ－ＮＯ_２）］ＬｉＨａｉ－Ｌｉａｎ；ＹｏｕＸｉａｏ－Ｚｅｎｇ；...     

LOW DENSITY POLYETHYLENE/CLAY NANOCOMPOSITES MODIFIED BY ETHYLENE COPOLYMERS： EFFECTS OF FUNCTIONALIZED SEGMENTS ON MORPHOLOGY

Melt extrusion was used to prepare binary nanocomposites of ethylene copolymers and organoclay and trinary nanocomposites of low-density polyethylene （LDPE）, ethylene copolymer and organoclay. X-ray diffraction （XRD） and transmission electron microscopy （TEM） were used to analyze the structure of the clay phase and the morphology of the nanocomposites. Influences of the comonomer in the copolymer and the content of the copolymer on the morphology of the resulting nanocomposites were discussed. The binary and the trinary composites may form intercalated or exfoliated structures depending on the interaction between the copolymer and the clay layers and the content of the copolymer.     

Effects of Calcination Temperature on the Acidity and Catalytic Performances of HZSM-5 Zeolite Catalysts for the Catalytic Cracking of n-Butane

The acidic modulations of a series of HZSM-5 catalysts were successfully made by calcination at different treatment temperatures, i.e. 500, 600, 650, 700 and 800 ℃, respectively. The results indicated that the total acid amounts, their density and the amount of B-type acid of HZSM-5 catalysts rapidly decreased, while the amounts of L-type acid had almost no change and thus the ratio of L/B was obviously enhanced with the increase of calcination temperature (excluding 800 ℃). The catalytic performances of modified HZSM-5 catalysts for the cracking of n-butane were also investigated. The main properties of these catalysts were characterized by means of XRD, N2 adsorption at low temperature, NH3-TPD, FTIR of pyridine adsorption and BET surface area measurements. The results showed that HZSM-5 zeolite pretreated at 800 ℃ had very low catalytic activity for n-butane cracking. In the calcination temperature range of 500-700 ℃, the total selectivity to olefins, propylene and butene were increased with the increase of calcination temperature, while, the selectivity for arene decreased with the calcination temperature.The HZSM-5 zeolite calcined at 700 ℃ produced light olefins with high yield, at the reaction temperature of 650 ℃ the yields of total olefins and ethylene were 52.8% and 29.4%, respectively. Besides, the more important role is that high calcination temperature treatment improved the duration stability of HZSM-5zeolites. The effect of calcination temperature on the physico-chemical properties and catalytic performance of HZSM-5 for cracking of n-butane was explored. It was found that the calcination temperature had large effects on the surface area, crystallinity and acid properties of HZSM-5 catalyst, which further affected the catalytic performance for n-butane cracking.     

Orientational ordering of a bent-core mesogen by two-dimensional 13C NMR spectroscopy

Various two-dimensional (2D) NMR techniques are reported on a bent-core mesogen 4,6-dichloro-1,3-phenylenebis[4'-(9-decenyloxy)-1,1'-biphenyl] carboxylate in its nematic and solid phases in order to unambiguously assign its carbon-13 NMR spectrum. The (13)C chemical shifts from the molecular core were studied as a function of temperature to extract its molecular geometry and orientational order tensor. To this end, the chemical shift anisotropy tensors of some carbon sites were measured in the solid state of this mesogen using a recent method called the separation of undistorted powder patterns by effortless recoupling (SUPER). The average bending angle subtended by the two arms of the bent-core structure is determined to be 148.7 degrees. The C-H dipolar couplings obtained from the separated local field (SLF) experiment for the aromatic rings are used to find the local order parameter tensors.     

Neutron activation analysis of extractable organohalogens in milk from China

Instrumental neutron activation analysis (INAA) has been used for the determination of extractable organohalogens (EOX) in milk. The detection limits are 50 ng, 8 ng and 3.5 ng for Cl, Br and I, respectively. The EOX concentrations in milk samples from various regions of China were determined. Meanwhile, organochlorine pesticides residues were detected by gas chromatography. The concentrations of the EOX in the milk samples are decreasing in the order of EOCl >> EOBr > EOI, and EOCl accounts for 95% of the total EOX. The average concentration of EOCl in milk is 4.44 ·g/g expressed as fat weight basis, with the highest value of 17.6 ·g/g from South China. The mean concentrations of total HCH and DDT are 0.038 ·g/g and 0.046 ·g/g, respectively. Organochlorine pesticides account only for 1.6% of the EOCl, indicating the very high proportion of the unknown EOCl in the milk sample. This revised version was published online in August 2006 with corrections to the Cover Date.     

Low‐Temperature Facile Template Synthesis of Crystalline Inorganic Composite Hollow Spheres

This report presents a facile approach for the low‐temperature synthesis of crystalline inorganic‐oxide composite hollow spheres by employing the bulk controlled synthesis of inorganic‐oxide nanocrystals with polymer spheres as templates. The sulfonated polystyrene gel layer can adsorb the target precursor and induce inorganic nanocrystals to grow on the template in situ. The crystalline phase and morphology of the composite shell is tunable. By simply adjusting the acidity of the titania sol, crystalline titania composite hollow spheres with tunable crystalline phases of anatase, rutile, or a mixture of both were achieved. The approach is general and has been extended to synthesize the representative perovskite oxide (barium and strontium titanate) composite hollow spheres. The traditional thermal treatment for crystallite transformation is not required, thus intact shells can be guaranteed. The combination of oxide properties such as high refractive index, high dielectric constant, and catalytic ability with the cavity of the hollow spheres is promising for applications such as opacifiers, photonic crystals, high‐κ‐gate dielectrics, and photocatalysis.     

Alginic acid–silica hydrogel coatings for the protection of osmotic distillation membranes against wet-out by surface-active agents

The formulation of organic–inorganic polymer composites can be used to enhance selected properties, such as susceptibility to microbial attack, thermal stability, mechanical strength and water sorption capability. Accordingly, a series of alginic acid–silica hydrogel films was prepared for testing as protective coating materials for PTFE osmotic distillation membranes. Unprotected hydrophobic membranes are subject to wet-out when contacted by surface-active agents, such as oils and detergents. Films containing 5, 10, 15 and 20 wt.% silica, with and without the addition of glycerol for plasticisation, moisturisation and silica dispersion, were characterised using scanning electron microscopy, X-ray diffraction, differential scanning calorimetry, mechanical strength measurements, and water-swelling measurements. Composites prepared with glycerol addition had better thermal stability, mechanical strength and water sorption capability than those prepared without glycerol addition. Uncoated membranes and membranes coated with composites prepared with glycerol addition were tested for OD performance and resistance to surface-active agents using pure water, orange oil (limonene)–water mixtures, and sodium dodecylbenzene sulfonate detergent solutions. Uncoated membranes showed immediate hydrophobicity loss in the presence of orange oil and detergent. For coated membranes, no wet-out occurred over the 15 h duration of three consecutive 5 h OD trials using orange oil–water mixtures. In the case of detergent solutions, the coating afforded protection to the membrane for 4–5 h. In a separate trial, no wet-out occurred when the coated side of the membrane was placed in contact with 1.2 wt.% orange oil for 72 h.     

Novel sequence for generating glycopolymer tethered on a membrane surface

Cell surface carbohydrates, usually binding with other biomacromolecules (such as lipids and proteins), are involved in numerous biological functions, including cellular recognition, adhesion, cell growth regulation, and inflammation. Synthetic carbohydrate-based polymers, so-called glycopolymers, are emerging as important well-defined tools for investigating carbohydrate-based biological processes and for simulating various functions of carbohydrates. In this study, a novel two-step sequence for the generation of a glycopolymer layer tethered on a polypropylene microporous membrane is described. First, a UV-induced graft polymerization of 2-aminoethyl methacrylate hydrochloride (AEMA) was carried out on the membrane to generate an amino-functionalized surface, and the effects of polymerization factors (monomer/initiator concentration and UV irradiation time) on the grafting density were studied. Second, sugar moieties were bound with the grafted functional layer to form glycopolymer by the reaction between the amino groups on the membrane surface and carbohydrate lactones. Chemical analysis by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy combined with surface morphology observation by scanning electron microscopy confirmed the graft polymerization of AEMA and the formation of glycopolymer. The decreases of water contact angle and protein adsorption on the membrane revealed the enhancement of hydrophilicity and protein resistance due to the typical characteristics of the glycopolymer tethered on the surface. These results indicated that the novel sequence reported in this work is a facile process to form glycopolymer-modified surfaces.