One-phase supported titanium-based catalyst for polymerization of ethylene. IV. Effect of alkyl group at organoaluminium compound on catalyst performance

The effect of a basic layer (SiO₂—R₃Al intermediate) in the one-phase silica supported titanium-based catalyst was investigated using the simple model catalyst systems obtained by reacting the activated silica gel consecutively with R₃Al and TiCl₄. Mode of the interaction of SiO₂ with R₃Al—resulting in the formation of the basic layer—was observed via analysis of the concentration of the unreacted OH groups on the silica surface employing IR spectroscopy and via analysis of the concentration of aluminium in solvent using AA spectroscopy. It was found that nature of the alkyl group in R₃Al modified the structure of the basic layer, thus influencing the catalyst performance including the concentration of both the sum of Ti²⁺ and Ti³⁺ and the ESR-active Ti (III) centers. The sum of Ti²⁺ and Ti³⁺ ranged from 45 to 52 mol % and the amount of the ESR-active Ti (III) species ranged from 6 to 17 mol % of the all titanium content. A significant effect of alkyl group at organoaluminium compound on the molecular weight distribution of the resulting polymer was observed. © 1996 John Wiley & Sons, Inc.     

Preparation of styrene–divinyl benzene copolymer-supported platinum complexes and their catalytic properties in hydrosilylation

A new type of catalyst for the hydrosilylation of unsaturated monomers with dichloromethylsilane (DCMS) was prepared, which consisted of thiolmethylene-substituted styrene–divinyl benzene copolymer and platinum. When using DCMS as a hydrosilylation agent, these catalysts showed a high activity in the hydrosilylation of vinyl and acetylene monomers as styrene, alkyl vinyl silanes, acetylene, phenyl acetylene, butyl acrylate. The activities of catalysts were not significantly reduced even after 20 reuse cycles.     

天然气管道泄漏可调谐二极管激光遥感探测的研究

天然气管道泄漏不仅造成经济损失而且是危险之源。传统的天然气管道泄漏检测技术效率低、速度慢,难以满足实际应用的需要。近年来以近红外二极管激光吸收光谱为基础的光学传感器由于具有灵敏度高、体积小、重量轻和无需维护等优点而得到了广泛的应用。文章以可调谐二极管激光吸收光谱和谐波探测技术为基础进行天然气管道泄漏遥感探测技术的研究,采用二次谐波与一次谐波信号的比值作为系统浓度标定,结果显示浓度与比值之间具有较好的一致性。文章还就不同地形散射体对探测结果的影响进行了测量和分析,实验结果表明二次谐波与一次谐波信号比值标定技术对便携式二极管激光光学测量能够很好的满足实际应用的需要。     

Vapor-phase synthesis of V-butylaniline from aniline and 1-butanol over Cu/SiO2 catalyst

The Cu/SiO2 catalyst prepared by incipient wetness method exhibited very high activity and selectivity for the vapor-phase synthesis of JV-butylaniline from aniline and 1-butanol. When Cu loading was 0.70 mmol/g-SiO2 and the catalyst precursor was calcined at 500 ℃, 1-butanol conversion reached 99%, and the selectivity of JV-butylaniline exceeded 97%.     

氮杂环卡宾-钯配合物催化Buchwald-Hartwig偶联反应最新研究进展*

钯催化的Buchwald-Hartwig偶联反应是用于构建C-N键非常直接有效的方法。氮杂环卡宾-钯配合物具有性能稳定、催化活性高等优点,是Buchwald-Hartwig偶联反应的高效催化剂。对这一领域近3年的研究进展作简要介绍。     

Comparison of betaine and l-stachydrine as phase-transfer catalysts in Michael addition and Darzens reaction

Betaine and l-stachydrine have been tested as phase-transfer catalysts in Michael and Darzens reactions. The catalytic effect of l-stachydrine was found comparable to that of betaine in Michael addition and even higher when considering Darzens reaction. The desired products have been obtained in higher yields in solid-liquid system than under liquid-liquid bi-phase conditions. The influence of microwave irradiation and ultrasound on the reaction rate has been studied.     

In situ X-ray diffraction study of reduction processes of Fe3O4- and Fe1−xO-based ammonia-synthesis catalysts

The temperature-programmed reduction process of two types of industrial ammonia-synthesis catalysts, A110 and ZA-5, which are, respectively, based on Fe₃O₄ and Fe_1−xO precursors, were studied by in situ X-ray power diffraction (XRD). It has been found that the ZA-5 has lower reduction temperature and faster reduction rate, and its active phase α-Fe possesses a higher value of lattice microstrain than A110. The simulation based on Rietveld refinement has also shown that the shape of α-Fe grain of ZA-5 has a mixed shape of cube and sphere with more exposing (111) and (211) planes, while that of A110 looks like a concave cube with more exposing (110) planes. Based on the results obtained, a growth model of α-Fe during the reduction of Fe₃O₄- and Fe_1−xO-based ammonia-synthesis catalysts is proposed, and the origins for the activity difference has been also discussed.     

Natural Compound Curcumin-a Channel Potentiator Rather Than a Corrector of the Defective Intracellular Processing of △F508 Mutant Cystic Fibrosis Transmembrane Conductance Regulator

Cystic fibrosis(CF)is a severe genetic disease caused by the gene mutation of the cystic fibrosis transmembrane conductance regulator(CFTR)chloride channel.The most common point mutation △F508,which leads to impaired intracellular processing and channel gating of CFTR, appears in about 90? patients.The natural compound curcumin was reported to correct the processing defect of △F508-CFTR and proposed as a potential therapeutic drug to cure CF.In the present study.we analyzed the efrect of curcumin on △F508-CFTR and demonstrated that curcumin can restore the impaired chloride conductance of △F508 mutant CFTR.The activity is rapid,reversible and cAMP-dependent.However,we couldn't reproduce the previously reported correction of the defective membrane trafficking of △F508-CFTR by curcumin.Therefore,curcumin may not be a superior lead compound for developing anti-CF drugs.     

Cu-Mn-Zn/Y直接合成二甲醚催化剂中锌和锰的协同调节作用

通过对Y型分子筛负载Cu-Mn、Cu-Zn和Cu-Mn-Zn催化剂的结构、表面性质及其直接合成二甲醚反应活性的对比,发现Mn和Zn对催化剂还原性能的影响作用相反,对催化剂吸附H₂和CO的影响也不同。Mn和Zn的单独添加或共同添加引起催化剂结构和组分之间相互作用程度的改变,是造成催化剂活性和选择性变化的主要原因。两者的协同作用,能调整催化剂的还原性能和吸附性能达到适合的状态,从而使得催化剂具有高的二甲醚合成活性。