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41.
Yang L Mayr M Wurst K Buchmeiser MR 《Chemistry (Weinheim an der Bergstrasse, Germany)》2004,10(22):5761-5770
The synthesis of novel ruthenium-based metathesis catalysts containing the saturated 1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene ligand, that is, [RuCl2(NHC)[=CH-2-(2-PrO)-5-NO(2)-C6H3]] (1) and [Ru(CF3COO)2(NHC)[=CH-2-(2-PrO)-5-NO2-C6H3]] (2) (NHC=1,3-bis(2,4,6-trimethylphenyl)-3,4,5,6-tetrahydropyrimidin-2-ylidene) is described. Both catalysts are highly active in ring-closing metathesis (RCM) and ring-opening cross-metathesis (ROCM). Compound 1 shows moderate activity in enyne metathesis. Compound 2 is not applicable to enyne metathesis since it shows high activity in the cyclopolymerization of diethyl dipropargylmalonate (DEDPM). Poly(DEDPM) prepared by the action of 2 consists of 95% five-membered rings, that is, poly(cyclopent-1-enevinylene)s, and 5 % of six-membered rings, that is, poly(cyclohex-1-ene-3-methylidene)s. The polymerization proceeds in a nonliving manner and results in polyenes with broad polydispersities (1.9< or =PDI< or =2.3). Supported analogues of 2 were prepared by immobilization on hydroxymethyl-Merrifield resin and a monolithic support derived from ring-opening-metathesis polymerization (ROMP). Catalyst loadings of 1 and 2.5%, respectively, were obtained. Both supported versions of 2 showed excellent reactivity. With 0.24-2% of the supported catalysts, yields in RCM and ROCM were in the range of 76-100%. Leaching of ruthenium was low and resulted in Ru contaminations of the products of less than 0.000014% (0.14 ppm). 相似文献
42.
Ryashentseva M. A. Egorova E. V. Trusov A. I. Antonyuk S. N. 《Russian Chemical Bulletin》2002,51(9):1698-1701
The activity and selectivity of mono- and bimetallic catalysts containing copper and rhenium on sibunite were studied in the decomposition of methanol to methyl formate (MF), water, H2, CO, and CO2at 200—400 °C. Methane is also formed on rhenium-containing catalysts at 300—400 °C. The dehydrogenating activity and selectivity to form MF are higher on the copper-sibunite catalysts than on the rhenium-sibunite samples. The introduction of 0.25% Re into the 4% copper-containing catalyst enhances its total activity and stability. 相似文献
43.
Éder Lisandro de Moraes Flores Juliano Smanioto Barin Érico Marlon de Moraes Flores Valderi Luiz Dressler 《Spectrochimica Acta Part B: Atomic Spectroscopy》2007
This work deals with the determination of fluorine by solid sampling graphite furnace molecular absorption spectrometry. The molecular absorbance of aluminum monofluoride (AlF), which is produced in the vapor phase in the presence of Al3+, is measured at 227.5 nm, a non-resonant platinum line. A conventional graphite furnace program has been used with pyrolysis and vaporization temperatures of 800 and 2300 °C, respectively. Solutions of Ba2+ and Al3+ have been used to avoid fluorine losses during the pyrolysis stage and to produce AlF in the vaporization stage, respectively. Certified coal and alumina samples were analyzed using aqueous standards for calibration. The agreement between the found concentration and the certified value, or the value obtained by another method ranged from 92 to 105%, with a relative standard deviation less than 8.5%. The limit of detection and the characteristic mass was 0.17 μg g− 1 and 205 pg, respectively. 相似文献
44.
45.
A polystyrene-bonded stannic chloride catalyst was synthesized by the method of lithium polystyryl combined with stannic chloride. This catalyst is a polymeric organometallic compound containing 0.25 mmol Sn (Ⅳ)/g catalyst. The catalyst showed sufficient stability and catalytic activity in organic reaction such as esterification, acetalation and ketal formation, and it could be reused many times without losing its catalytic activity. 相似文献
46.
N. A. Prokudina E. A. Paukshtis R. A. Buyanov V. V. Chesnokov T. A. Konovalova 《Reaction Kinetics and Catalysis Letters》1996,59(1):187-192
The role of carbonate-carboxylate species on alumina surface has been studied during alumina coking. The species are intermediates poisoning the active sites. Little O2 added to the hydrocarbon feedstock causes further oxidation of the species and promotion of the active sites. 相似文献
47.
溶胶凝胶法制氧化铝负载铜基超细粒子催化剂的研究 总被引:9,自引:1,他引:9
采用溶胶凝胶法制氧化铝负载铜基超细粒子催化剂的制备了氧化铝负载的铜基超细粒子催化剂,用TG-DTA,XRD,BET以及TEM等技术手段,对催化剂的物相结构,表面孔结构,粒子形貌以及催化性能等进行了研究。结果表明,利用溶胶凝胶法,可以直接帛备出高比表面积,低堆积密度的纤维状纳米级负载型Cu/Al2O3超细粒子;活性组分以远低于纳米级的微晶粒子簇状态,均匀地分散在纳米级氧化铝载体表面上,而且在低于50 相似文献
48.
49.
The Incorporation of Titania into Modified Silicates for Solar Photodegradation of Aqueous Species 总被引:2,自引:0,他引:2
Lowell R. Matthews David Avnir Alexander D. Modestov Srinivasan Sampath Ovadia Lev 《Journal of Sol-Gel Science and Technology》1997,8(1-3):619-623
A new class of sol-gel-derived photocatalytic materials has been synthesized and used in solar-assisted photodegradation studies. The materials are comprised of a homogeneous dispersion of commercial TiO2 powder into silica and organically modified silicate (Ormosil) hosts. The efficiency of the photocatalytic properties of these TiO2-containing materials was determined by their relative performance in the solar photodecomposition of aqueous rhodamine B. The improved adsorption properties of the modified materials compared to commercial TiO2 increase the photodecomposition rate and the buoyancy properties, although excess hydrophobicity decreases the wetted section of the catalyst and its photocatalytic performance. These materials can be used as floatable catalysts for solar-assisted water purification. 相似文献
50.
V. I. Simagina V. V. Litvak I. V. Stoyanova V. A. Yakovlev V. M. Mastikhin I. V. Afanasenkova V. A. Likholobov 《Russian Chemical Bulletin》1996,45(6):1321-1324
Hydrodechlorination of chlorobcnzene by chemically bound hydrogen in the presence of transition metal compounds was studied. Alkali and alkaline earth metal hydrides (NaH, MgH2, LiAlH4, NaH(LiAlH4)/12) were used as the sources of the chemically bound hydrogen. The effect of the natures of the hydride and of the transition metal on the activity was studied under comparable conditions. The Pd/C-NaH(LiAlH41/2 catalytic system was found to be the most active. This system made it possible to perform the quantitative dechlorination of 2,3-dichlorodibenzo-p-dioxin at 70 °C.Deceased.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1391–1394, June, 1996. 相似文献