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221.
苯酐催化剂表面纹理的表征及表面纹理模型的探讨 总被引:1,自引:0,他引:1
大多数实用催化剂均为复杂体系,对其结构和性能进行表征并加以关联是一个重要的问题~[1].表征催化剂可提供化学组成及结构、催化剂纹理及机械性质、催化活性等信息.催化剂纹理是指其几何结构和表面形貌,包括宏观及微观尺度,如颗粒形状、表面积、孔结构、物 相似文献
222.
稀土有机化合物在催化聚合反应中的应用 总被引:6,自引:3,他引:6
本文综述了稀土有机化合物作为单组份催化剂用于聚合反应的进展。它包括:烯烃和α-烯烃聚合、甲基丙烯酸酯类的均聚合及共聚合、乙与人烯酸酯及含官能团烯的共聚合、内醌的开环均聚合及共聚合等。茂基稀土氢化物是乙烯聚合的高活性催化剂,对茂基结构作一定调节,可催化α-烯烃的规整聚合。这类氢化物、茂基稀土甲基化合物和二价稀土配合物都是人烯酸酯类及内酯聚合的有效催化剂,并显示活性聚合特点给出高分子量、窄分子量分布的 相似文献
223.
Polyethylene terephthalate in the form of waste fibres and disposable soft drink bottles was subjected to depolymerisation through aminolysis using excess of ethanolamine in the presence of different simple chemicals, namely glacial acetic acid, sodium acetate and potassium sulphate, as catalysts. The product bis(2-hydroxy ethylene)terephthalamide (BHETA) obtained was in its pure form with sufficiently high yields with all the catalysts. The purified product was characterised by elemental analysis, melting point, IR spectroscopy, Nuclear Magnetic Resonance (NMR) and Differential Scanning Calorimetry (DSC). The process of aminolysis reported here is economically viable since yields of BHETA are as high as 91%, it has potential for further reactions to obtain useful products and the chemicals used as catalysts are common and cheaply available. 相似文献
224.
Ryoji Nomura Hideo Nakako Toshio Masuda 《Journal of molecular catalysis. A, Chemical》2002,190(1-2):197-205
In this review article, we summarize our recent efforts on the design and synthesis of helical polymers from propiolic esters. Stereoregular cis-transoidal poly(propiolic esters) prepared with Rh catalysts have proven to possess semiflexible main chain, which drives the main chain to the helical conformation with long persistence length. Based on the chiroptical properties of poly(propiolic esters) bearing various chiral pendants, we established the design strategy for the production of well-ordered helical poly(propiolic esters). NMR study of various poly(propiolic esters) enabled estimation of not only the activation energy of helix reversal, but also the free energy difference between the helical and disordered states. The helix sense of poly(propiolic esters) is determined by the configuration of the chiral center, structure of the pendant groups, temperature, and solvent. 相似文献
225.
Namdu Kim 《Tetrahedron letters》2004,45(38):7057-7059
Palladium nanoparticles were generated from tetrakis(triphenylphophine)palladium in a mixture of tetra(ethylene glycol) and tetramethoxysilane (or titanium(IV) isopropoxide), then encapsulated in silica matrix (or titania matrix) by the treatment with water. The resulting heterogeneous material showed high catalytic activity in the hydrogenations of various alkene and alkynes and in the carbon-carbon cross-coupling reactions such as the Suzuki-Miyaura, the Sonogashira, the Heck-Mizoroki, and the Stille reactions. 相似文献
226.
双核茂金属催化剂催化聚合反应进展 总被引:2,自引:0,他引:2
综述了双核茂金属化合物的研究进展及其在烯烃和极性单体聚合方面的应用及双核茂金属化合物的合成及性能研究;并对双核催化剂的作用机理、催化剂结构与性能的关系也做了介绍。 相似文献
227.
Summary. A novel ionic catalyst, 1-butyl-4-aza-1-azoniabicyclo[2.2.2]octane chloride based on 1,4-diazabicyclo[2.2.2]octane was synthesized
and applied in the Baylis-Hillman reaction, which occurred readily at room temperature to afford the corresponding adducts in good yield. The ionic catalyst
could be recycled for seven runs without diminution in its catalytic activity. 相似文献
228.
Fe(Ⅱ)pyridinebisimine complexes activated with trialkylaluminium or modified methylaluminoxane(MMAO)ascatalysts were employed for the polymerization of butyl methacrylate(BMA).Polymer yields,catalytic activities andmolecular weights as well as molecular weight distributions of BMA can be controlled over a wide range by varying thereaction parameters such as cocatalyst,Al/Fe molar ratio,monomer/catalyst molar ratio,monomer concentration and reactiontemperature used in the polymerization.The catalytic activity of Fe(Ⅱ)complex was 11.1 kg_(polym)/mol_(Fe)h and the highestyield could reach 99.1% under optimum condition. 相似文献
229.
230.
A new kind of hybrid catalyst, TiO2-carbon nanotubes, was prepared via sol-gel method for the first time. Its photocatalytic activity in the photodegradation of acridine dye aqueous solution at
low concentration was tested. There was no measurable effect on the formation of crystalline phase of TiO2 catalyst with the addition of 10 wt.% carbon nanotubes to TiO2 samples. AFM photograph of TiO2-carbon nanotubes sintered at 300°C showed that the carbon nanotubes were enwrapped by TiO2, which greatly increased the adsorbing ability of the catalyst and was in favor of photocatalytic reaction. Compared with
naked TiO2 powder the hybrid catalyst prepared in this way showed high efficiency in the photodecomposition of acridine dye. 相似文献