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951.
CuO/CeO2和CuO/Al2O3催化剂的催化性能 总被引:13,自引:0,他引:13
本文以CO氧化为模式反应考察了CeO2和Al2O3负载氧化铜催化剂的氧化活性,运用XRD和TPR技术研究了催化剂的还原性能和物相结构,结果表明:载体性质对负载CuO催化剂的CO氧化活性有很大影响,CuO/CeO2催化剂活性明显高于CuO/Al2O3催化剂.催化剂的还原特性随载体不同而不同.同时发现,热处理对催化剂铜物种的存在形式,晶粒大小、还原特性及其催化活性有明显影响,CuO/Al2O3催化剂活性下降的主要因素是生成了活性较低的CuAl2O4相,而CuO/CeO2催化剂活性下降是由于CuO和CeO2发生烧结,晶粒变大 相似文献
952.
The intermolecular interaction energy for reacting systems in singlet, triplet and doublet states was partitioned by the perturbation expansion method into the chemically meaningful five interaction terms: the Coulomb, exchange-repulsion, induction, dispersion, and charge-transfer energies. In the local ZDO approximation, these energy terms were evaluated for the dimerization of methylenes (1,3CH2), the additions of carbenes (1,3CH2 and1,3CF2) as well as amino radicals (2NH2 and2NF2) toward ethylene, and the hydrogen abstractions by methylenes (1,3CH2), nitrene (3NH), and hydroxyl radical (2OH) from methane. It has been found that the reaction path is much influenced by the spinmultiplicity, and that the charge-transfer and exchange-repulsion terms play a dominant role in determining the course of reactions. 相似文献
953.
Rudolf Wagner 《Fresenius' Journal of Analytical Chemistry》1976,282(4):315-321
Summary Problems, techniques and means of water sampling are reviewed. Applicability and performance are discussed with regard to individual and composite samples, and also to automatic sampling. Storage and preservation of samples are dealt with.
Probenahme und Behandlung von ProbenWasser
Zusammenfassung Probleme, Verfahren und Hilfsmittel bei der Probenahme von Wasser werden behandelt. Ausführung und Anwendbarkeit von Einzel und Mischproben sowie der automatischen Probenahme werden diskutiert, ebenso die Aufbewahrung und Konservierung von Proben.
Start of discussion held at the 6th Annual Symposium on Recent Advances in the Analytical Chemistry of Pollutants, April 21–23, 1976; Vienna, Austria. 相似文献
954.
Summary The influence of chemical reactions in d.c. arc plasma on the atomic emission determination of traces has been investigated. The effect of added NH4F on the intensity of spectral lines of Ca and Al was examined. A decrease of the spectral line intensities of Ca and Al in the presence of NH4F occurred, if the sample had not been mixed in the electrode with NH4F. The AlF band spectrum, transition A
1
X
1
, was observed in absorption of the arc radiation. Further, the axial intensity distribution of Ca, Al, Ga and Ag spectral lines and of the head of the green system of CaF band, has been measured. The depressive effect of fluorine on spectral line intensities of Ca, Al, Ga and Ag has to be connected with the processes in plasma. It is suggested that the formation of fluoride radicals could take part in this effect.
Bildung von CaF und AlF im Bogenplasma und spektrochemische Bestimmung von Ca und Al
Zusammenfassung Der Einfluß von chemischen Reaktionen im Lichtbogenplasma auf die spektrochemische Spurenanalyse wurde erörtert. Die Wirkung einer Zugabe von Ammoniumfluorid auf die Intensitäten der Spektrallinien des Calciums und Aluminiums wurde untersucht. Wenn die Probe nicht in der Elektrode mit NH4F gemischt war, wurde eine Intensitätserniedrigung von Ca- und Al-Spektrallinien in Anwesenheit von NH4F beobachtet. Das AlF-Bandenspektrum, Übergang A 1 X 1 , wurde in Absorption der Bogenstrahlung beobachtet. Die Axialverteilung der Linienintensitäten von Ca, Al, Ga und Ag wie auch der Intensität der Kante des grünen Systems der CaF-Banden wurde untersucht. Die depressive Wirkung des Fluors auf die Linienintensitäten von Ca, Al, Ga und Ag sollte mit den Vorgängen im Plasma in Zusammenhang gebracht werden. Es kann vorausgesetzt werden, daß die Bildung der Fluoridradikale bei diesem Effekt eine Rolle spielt.相似文献
955.
A heated injection system for a microprocessor-controlled GC has been developed for the (GC)2 analysis of the volatile phase of whole smoke of a cigarette. Effects of injection port temperature and the presence of a Cambridge filter pad are demonstrated. Chromatograms are shown for smoke samples with and without a Cambridge Filter with the sample valve oven at 25°, 165° and 205°C. The use of a flame ionization and a nitrogen-phosphorous detector is illustrated. 相似文献
956.
A method for the determination of cadmium microamounts in mixtures with metallic ions withE
1/2 near toE
1/2 of cadmium is discussed. For higher selectivity cadmium was extracted in the form of the pyridin-thiocyanate complexes prior to polarography.
Bestimmung von Cadmium(II) neben anderen Metallionen
Zusammenfassung Es wird eine polarographische Methode zur Bestimmung von Cd(II) neben anderen Metallionen mitE 1/2 naheE 1/2(Cd) diskutiert. Zur Erhöhung der Selektivität und Genauigkeit wird eine Pyridin-Thiocyanat-Extraktion vorgeschalten.相似文献
957.
958.
The structure elucidation and 1H and 13C assignments of the new triterpenes 3beta-palmitoxy-7beta-hydroxyolean-12-ene (1) and its hydrolysis product 3beta,7beta-dihydroxyolean-12-ene (2) and 3beta-sn-glyceroyl-(1'-palmitoxy)urs-12-ene (3), isolated from the aerial parts of Cladocolea grahami (Loranthaceae), are reported. 相似文献
959.
Kozhevnikov D. N. Kataeva N. N. Rusinov V. L. Chupakhin O. N. 《Russian Chemical Bulletin》2004,53(6):1295-1300
A simple procedure was developed for the synthesis of 1,2,4-triazines and their 4-oxides containing the ClCH2, Cl2CH, or CCl3 group at position 3 by cyclization of 2-aryl-2-hydrazono-1-oximinoethanes with the corresponding chloroacetonitriles. The reaction pathway depends on the number of halogen atoms in the acetonitrile used. The reactions with trichloroacetonitrile, monochloroacetonitrile, and dichloroacetonitrile afford 3-trichloromethyl-1,2,4-triazines, 3-chloromethyl-1,2,4-triazine 4-oxides, and a mixture of the corresponding dichloromethyltriazines and their 4-oxides, respectively. The reactions of 3-trichloromethyl-1,2,4-triazines with indoles and phenols are accompanied by tele-substitution with elimination of halogen from the trichloromethyl group to give 5-indolyl- (or 5-hydroxyphenyl)-3-dichloromethyl-1,2,4-triazines. 相似文献
960.
Cossy J 《Chemical record (New York, N.Y.)》2005,5(2):70-80
The synthesis of optically active substituted piperidines has been achieved by using four different methodologies. The first one is an intramolecular nucleophilic displacement of activated alcohol moieties that was used to build up the piperidine ring of (-)-prosophylline and (-)-slaframine, and the second one is a ring-closing metathesis of unsaturated amines which was employed in the synthesis of (+)-sedamine and 4a,5-dihydrostreptazoline. The third methodology is the alpha-functionalization of N-Boc piperidines which was particularly useful in the synthesis of argatroban, and the fourth one is a ring expansion of prolinols to 3-chloropiperidines or 3-hydroxypiperidines which was utilized to synthesize (-)-paroxetine, (-)-pseudoconhydrine, the piperidine ring of (-)-velbanamine and (+)-zamifenacin. 相似文献