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11.
《高分子科学杂志,A辑:纯化学与应用化学》2013,50(9):1171-1180
Polymerization of ethylene and propylene with VCl4-BuLi (Bu = n-Bu, sec-Bu, tert-Bu) catalysts was investigated. The VCl4-BuLi catalysts were found to initiate the polymerization of ethylene and propylene. The VCl4-BuLi catalysts gave an ultra high molecular polyethylene. The effect of the Li /V mole ratio on the polymerization of ethylene with the VCl4-BuLi catalysts was observed, an the catalyst gave an optimum rate at the Li/V ratio of about 3.0. The polyethylene obtained with the VCl4-BuLi catalyst was found to be a linear structure. In the polymerization of propylene with the VCl4-BuLi catalyst, the polymers contain mm contents of 56–66% were produced. 相似文献
12.
《高分子科学杂志,A辑:纯化学与应用化学》2013,50(1-2):133-143
New silicon-containing disubstituted polyacetylene was prepared by the polymerization of BTMSA having two bulky substituents (n-butyl and trimethylsilyl) using transition metal catalysts. The polymerization proceeded in a mild manner and the final polymer yield was generally lower than those of silicon-containing monosubstituted acetylenes by the similar catalyst system. The characterization on the polymer structure revealed that the resulting poly(BTMSA) have a conjugated backbone system, but the polymers have peculiar copolymer composition of poly-(BTMSA) and poly(1-hexyne) due to the spontaneous desilylation during the polymerization. The fluoride-ion induced desilylation of poly(BTMSA) using n-Bu4N+F? in THF yielded a completely desilylated product, pure poly(1-hexyne). 相似文献
13.
Nashaat N. Nassar 《Journal of Dispersion Science and Technology》2013,34(12):1714-1720
Water-in-oil (w/o) microemulsions are very appealing reaction media due to their ability to provide huge surface of contact between water-soluble and oil-soluble reactants. Their application as reaction media, including the preparation of nanoparticles, is, however, limited to water soluble precursors. In this study, we present a first step scheme in a two-step process for the preparation of metal oxide nanoparticles starting from their water-insoluble metal oxide bulk powder. This step involves solubilizing the metal oxide in the water pools of the microemulsion with the aid of a solubilizing agent. The variables affecting the solubilizing capacity of iron and copper oxides, as examples of important metal oxides, in single HCl-containing AOT/water/isooctane microemulsions were investigated. The effect of the following variables on the solubilization capacity is reported, namely, mixing time, surfactant concentration, water to surfactant mole ratio (R), and the nominal concentration of HCl in the water pool. At 300-rpm, time-invariant concentration of the metals in the microemulsions was achieved in about 6 hours. These values were quoted as the solubilization capacity of the metal oxide at the corresponding conditions. Solubilization capacity increased linearly with the surfactant concentration and R, and portrait a power function with the nominal concentration of HCl in the water pool. A mathematical model previously derived to describe nanoparticle uptake by single microemulsion accurately accounted for the effect of the aforementioned variables on the solubilization capacity. 相似文献
14.
15.
S. Pisana M. Cantoro A. Parvez S. Hofmann A.C. Ferrari J. Robertson 《Physica E: Low-dimensional Systems and Nanostructures》2007,37(1-2):1
Catalyst films undergo considerable surface morphology restructuring prior to carbon nanotube nucleation, deeply influencing the nanostructures obtained. Here we study the influence of different gaseous atmospheres on the structure of thin Fe films. The morphology is influenced by process temperature and substrate interactions and varying the gas type and pressure can control the average catalyst island height. 相似文献
16.
Mohammad Shakirullah Imtiaz Ahmad Habibur Rahman M. Arsala Khan M. Ishaq Amjad Ali Shah 《中国化学会会志》2006,53(5):1059-1066
This paper demonstrates the spectral analysis of some distillates obtained from asphalt cracking in the presence of a conventional expensive catalyst, i.e., HZSM‐5, and local cheap and readily available clay, i.e., UTIMAC. Each distillate was fractionated into pentane soluble (PI) and pentane insoluble (PI) fractions based on solubility in n, pentane. Both PS and PI obtained in the case of HZSM‐5 and UTIMAC were analyzed by 1H‐NMR spectrophotometry using CDCl3 as dissolving solvent and tetramethylsilane (TMS) as internal standard. It is evident from the profiles that both catalysts caused the generation of some peaks ascribed to methylene and methene configurations in the aliphatic region. Bands corresponding to aromatic configurations were also generated. The results indicate that the cheap local catalyst used has comparable suitability with the conventional expensive catalyst in terms of asphalt cracking. 相似文献
17.
Aligned multi-walled carbon nanotubes (MWCNTs) with high purity and bulk yield were achieved on a silicon substrate by an aerosol-assisted chemical vapor deposition. The introduction of specific amounts of water vapor played a key role in in situ controlling the purity and surface defects of the nanotubes. The morphology, surface quality and structure of MWCNTs were characterized by secondary and backscattered electron imaging in a field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM). Crystallinity and defects of the MWCNTs’ were investigated by high-resolution transmission electron microscopy (HRTEM) and Raman spectroscopy. In this work, water vapor was found to provide a weak oxidative environment, which enhanced and purified the MWCNTs’ growth. However, excessive water vapor would inhibit the MWCNTs growth with a poor surface quality. In addition, it has been found that the surface morphology of the CNTs can be modified intentionally through producing some surface defects by tuning the amount of the water vapor, which may offer more nucleation sites on the chemically inert CNT surface for various applications such as catalyst support. 相似文献
18.
Mixed oxides composed of Zn-Sn, Ti-Sn and V-Sn were prepared by a co-precipitation method and evaluated as catalysts for methanol oxidation in an ambient fixed-bed reactor. Surface analysis by X-ray photoelectron spectroscopy (XPS) revealed an electronic interaction between dopant and Sn atoms in the oxide structure and showed the formation of surface states associated with the dopants. Oxygen vacancies were present on the Zn-doped oxide, and the oxidation of methanol to carbon oxides was favored. The Ti-doped oxide exhibited a favorable selectivity to dimethyl ether, related to the oxygen anions near Ti centers. Vanadium dopants not only dramatically increased the catalytic activity but also promoted the partial oxidation of methanol to formaldehyde. Results demonstrate that the bridging dopant-O-Sn bond acts as active sites and influences product distribution. 相似文献
19.
Youji Li Mingyuan Ma Shuguo Sun Wenbin Yan Yuzhu Ouyang 《Applied Surface Science》2008,254(13):4154-4158
TiO2-carbon surface (TCS) composites were prepared by pretreatment of a sealing substrate in supercritical carbon dioxide using paraffin as a plugging agent, and sol-gel processing using tetrabutyl orthotitanate as a precursor. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectrum (XPS), optical absorption spectroscopy and nitrogen absorption. The photoactivity of TCS was checked by monitoring the decomposition of methylene blue (MB) in aqueous solution under UV irradiation. The results indicated that compared with TC prepared only by the sol-gel method, the small nanosize TiO2 particles are well dispersed on carbon surface with large amount of micropores and high Eg values, meanwhile TCS have high Ti3+ concentration due to supercritical pretreatment providing a amount of carbon on the composite surface with interfacial energy effects, which controls the growth of TiO2 nanoparticles, baffles the agglomeration of TiO2 nanoparticles and easily produces Ti3+ ions. These are reasons why TCS has a higher efficiency of decomposing MB than TiO2-carbon (TC) composites and pure TiO2. Additional, it is also attributed to the fact that TCS produce a high concentration of organic compounds near TiO2 in comparison with TC and pure TiO2, because their surface area are greater than that of TC and pure TiO2. 相似文献
20.
Nanoparticle zinc-titanium oxide materials were prepared by the aerogel approach. Their structure, surface state and reactivity were investigated. Zinc titanate powders formed at higher zinc loadings possessed a higher surface area and smaller particle size. X-ray photoelectron spectroscopy (XPS) revealed a stronger electronic interaction between Zn and Ti atoms in the mixed oxide structure and showed the formation of oxygen vacancy due to zinc doping into titania or zinc titanate matrices. The 8-45 nm aerogel particles were evaluated as catalysts for methanol oxidation in an ambient flow reactor. Carbon dioxide was favorably produced on the oxides with anion defects. Titanium based oxides exhibited a high selectivity to dimethyl ether, so that a strong Lewis acidic character suggested for the catalysts was associated primarily with the Ti4+ center. Both methanol conversion and dimethyl ether formation rates increased with increasing the zinc content added to the oxide support. Results demonstrate that cubic zinc titanate phases produce new Lewis acid sites having also a higher reactivity and that the nature of the catalytic surface transforms from Lewis acidic to basic characters due to the presence of reactive oxygen vacancies. 相似文献