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1.
A. S. Belyi 《Reaction Kinetics and Catalysis Letters》1996,57(2):349-359
Some peculiarities of adsorption and catalytic properties of electron deficient platinum atoms (Pt) in reforming catalysts are presented. It appears possible to improve catalysts modifying Pt centers with -donor molecules. 相似文献
2.
Summary Handy et al. have shown that the asymptotic behavior of Hartree-Fock orbitals is controlled by the energy of highest occupied molecular orbital, except for the atomic case in which onlys-orbitals are occupied. However, their proof is not complete at one point. This point is clarified, and a more unified derivation is given. Further, we discuss the preexponential factorr
of the leading asymptotic termr
exp[–r], where =(–2HOMO)1/2 and HOMO is the orbital energy of HOMO. New results are obtained for linear molecules, and the results of several authors for atoms and non-linear molecules are reproduced. 相似文献
3.
It has been shown by the MNDO method that in allyl compounds of tin, the atomic orbitals of the heteroatom interact with the -orbital through the bridge group, but interact with the *-orbital mainly through space. The position and intensity of the long-wave electronic transitions for methylvinylstannane should not depend on the conformation, with the ,- and , pseudo--conjugation effects being approximately identical, whereas for allylstannane, the ,-conjugation is considerably stronger. In molecules containing several allyl fragments bonded to heavy atoms, ,-conjugation is far weaker than ,-conjugation in polyenes.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2071–2076, September, 1991. 相似文献
4.
R. Kieffer J. P. Hindermann R. El Bacha A. Kiennemann A. Deluzarche 《Reaction Kinetics and Catalysis Letters》1982,21(1-2):17-21
By chemical trapping, an acyl species has been evidenced in the oxidation of alcohols to carboxylate on an alumina surface. A possible reacton scheme is discussed.
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5.
T. A. Konovalova A. M. Volodin V. V. Chesnokov E. A. Paukshtis G. V. Echevskii 《Reaction Kinetics and Catalysis Letters》1991,43(1):225-229
A method to measure concentrations of strong surface acceptor centers on aluminosilicate catalysts by their titration with a solution of TEMPON (2,2,6,6-tetramethyl-4-oxypiperidine-1-oxyl) is suggested. The concentration of these centers corresponds to that of CO test molecules for the strongest acceptor centers (CO 2210 cm–1) obtained using IR spectroscopy. It is shown that for ZSM-5 zeolites most of these centers are localized on their external surface.
. - - CO (CO 2210 cm–1). , ZSM-5 .相似文献
6.
A method has been developed for the determination of the concentration of basic sites on white and deeply colored solid porous materials, which is based on the displacement of adsorbed benzoic acid by acetic acid. The determination is rapid and gives results comparable with those obrained by the titration with benzoic acid using thymolphthalein as indicator.
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7.
L. Ya. Leitis K. I. Rubina M. V. Shimanskaya V. V. Kharlamov Kh. M. Minachev 《Reaction Kinetics and Catalysis Letters》1985,29(1):175-179
It has been established that zeolites containing Pd and Cu ions catalyze the vapor phase oxidation of methylpyridines. In oxidation of 2-methylpyridine on PdCuNa-mordenite at 375 °C the yield of 2-pyridinecarbaldehyde is 40 % of its theoretical values.
, , Pd Cu, . 2- PdCuNa- 2- 375°C 40% .相似文献
8.
Rodriguez Roldan A. M. Auffrédic J. -P. Louër D. 《Journal of Thermal Analysis and Calorimetry》1983,28(1):131-146
The solid solid equilibria in the binary system Ca3(PO4)2-CaNaPO4 have been studied. Different diagrams have been proposed for this system. The differences relate to the limits of the field of existence of a non-stoichiometric phase (phase A) stable at high temperature and undergoing eutectoid decomposition during cooling; they can be explained by the existence of two metastable equilibria diagrams which are superposed in the stable diagram. These metastabilities depend on both the cooling rates and the maximum temperatures reached before this cooling.
Zusammenfassung Fest fest Gleichgewichte des binären Systems Ca3(PO4)2-CaNaPO4 wurden untersucht. Verschiedene Diagramme wurden für dieses System vorgeschlagen. Diese Unterschiede beziehen sich auf die Grenzen des Existenzbereiches einer nichtstöchiometrischen, hochtemperaturstabilen Phase (Phase A), die sich beim Abkühlen nach einer eutektoiden Reaktion zersetzt; sie können durch die Existenz von zwei dem stabilen Diagramm überlagerten metastabilen Gleichgewichtsdiagrammen erklärt werden. Diese metastabilen Zustände hängen sowohl von der Abkühlungsgeschwindigkeit als auch von den vor dem Abkühlen erreichten maximalen Temperaturen ab.
Ca3(PO4)2-CaNaPO4 — . . / A/, , - , , . , , .相似文献
9.
V. K. Ryabchuk L. L. Basov Yu. P. Solonitsyn 《Reaction Kinetics and Catalysis Letters》1989,39(2):331-337
An analysis of the correlation suggests that the common stages in photosorption, photooxidation and photodecomposition of some simple molecules on alkali metal halides are connected with catalyst photoexcitation.
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10.
J. ?vachula B. Králíková J. Tichy J. Machek 《Reaction Kinetics and Catalysis Letters》1991,44(1):45-49
The acidity and basicity of Sn–Mo–Ox catalysts with different Mo/Mo+Sn atomic ratios were measured by determining the adsorption isotherms of pyridine and acetic acid by chromatographic method. It was found that acidity and basicity go through a maximum at a Mo content of 15–20 at.%.
Sn–Mo–Ox Mo/Mo+Sn, . Mo=15–20 at.%.相似文献
11.
Phase transitions of pure water and aqueous Fe(II) perchlorate solutions, frozen between 1 and 5 kbar were detected by the DTA method at atmospheric pressure. Only the crystal structure of the primarily formed ice varies with the pressure, while water molecules remaining in the near eutectic solution — which solidifies into a glassy state — show no sensitivity towards pressure.
The authors are indebted to Dr. L. Keszthelyi for his extensive help and to Mr. I. Klim. Mr. B. Molnár and Mr. T. Grünstein for their assistance in the measurements. 相似文献
Zusammenfassung Phasenübergänge von reinem Wasser und zwischen 1 und 5 kbar gefrorenen wäßrigen Eisen(II)perchlorat Lösungen wurden durch DTA bei atmosphärischem Druck nachgewiesen. Nur die Kristallstruktur des primär segregierenden Eises wird durch den Druck beeinflußt. Die in der beinahe eutektischen Lösung zurückbleibenden Wassermoleküle, die in einem glasartigen Zustand erstarren, scheinen nicht druckempfindlich zu sein.
Résumé Mise en évidence par ATD à la pression atmosphérique des transitions de phase de l'eau pure et de solutions aqueuses de perchlorate de fer(II) préalablement congelées sous une pression allant de 1 à 5 kbar. Seule la structure cristalline de la phase qui se dépose la première dépend de la pression. Par contre, les molécules qui restent dans la solution presque eutectique — qui se solidifie à l'état vitreux — ne sont pas sensibles à la pression.
, 1 5 . , , , , .
The authors are indebted to Dr. L. Keszthelyi for his extensive help and to Mr. I. Klim. Mr. B. Molnár and Mr. T. Grünstein for their assistance in the measurements. 相似文献
12.
S. Yu. Burylin Z. G. Osipova V. D. Sokolovskii I. P. Olenkova 《Reaction Kinetics and Catalysis Letters》1982,18(1-2):7-11
Studies of the phase composition and catalytic properties of several complex oxide catalysts for oxidative ammonolysis of propane indicate that the active phases of these catalysts are antimonates of the respective metals. Phosphorus and tungsten additives to the catalysts promote the formation of such phase compositions, i.e. the formation of antimonates and the binding of excess antimony oxide.
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13.
L. P. Davydova G. K. Boreskov V. V. Popovskii T. M. Yurieva V. F. Anufrienko 《Reaction Kinetics and Catalysis Letters》1982,18(1-2):203-207
The bond energy of surface oxygen in a copper-magnesium catalyst and its reactivity are shown to be greatly dependent on the structure of the nearer environment of copper ions. For catalysts prepared at low temperatures (773 K) this structure changes from a symmetrical square planar in CuO to an octahedral with various degrees of axial distortion depending on the copper content.
, . , (773 ), CuO .相似文献
14.
A novel method is described, consisting in the determination of admolecules which are the most loosely bonded on the surface. This permits a better characterization of active centers on catalysts.
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15.
V. I. Zaikovskii V. I. Kovalchuk Yu. A. Ryndin L. M. Plyasova B. N. Kuznetsov Yu. I. Yermakov 《Reaction Kinetics and Catalysis Letters》1980,14(1):99-103
Reduced alumoplatinum and alumoplatinum-tin catalysts prepared via interaction of an organometallic platinum complex and platinum-tin compounds of various composition with Al2O3 mainly contain platinum particles of 10 Å.
, Al2O3, , , 10 Å.相似文献
16.
Interaction of both satured and unsaturated hydrocarbons with tetrahedral Co2+ ion complexes lodged in the zeolite skeleton is reported on the basis of diffuse reflectance spectra. While saturated hydrocarbons do not affect the coordination sphere of the Co-complex, the unsaturated hydrocarbons change considerably the distortion of the tetrahedral Co-complex.
- Co2+ - . - Co-, - - Co-.相似文献
17.
M. Sh. Yagpharov 《Journal of Thermal Analysis and Calorimetry》1982,23(1-2):111-121
The literature data on the degree of crystallinity of non-deformed poly(ethylene terephthalate) measured at various temperatures have been subjected to comparative analysis. There is no correlation between the results obtained by the different methods. The reason for this is shown to be the imperfections in the methods of determining the degree of crystallinity, which do not provide the true composition of the crystalline phase. Consideration has been paid to the validity of the main principles involved in the thermal method of determining the degree of crystallinity, so as to eliminate the imperfections in the existing methods and to provide the correct value of the mass of the crystalline phase. The phase composition of PET has been analyzed by the thermal method at different temperatures and conditions of crystallization. A marked difference from the literature data is observed in the range of low temperatures.
Zusammenfassung Eine vergleichende Analyse der Literaturangaben bezüglich des bei verschiedenen Temperaturen gemessenen Kristallisationsgrades von nicht-deformiertem Poly(äthylen-terephthalat) wurde durchgeführt. Zwischen den mit verschiedenen Methoden erhaltenen Ergebnissen besteht keine Korrelation. Es wurde gezeigt, daß der Grund hierfür in der Unvollkommenheit der Methoden zur Bestimmung des Kristallisationsgrades liegt, da diese nicht die wahre Zusammensetzung der Kristallinen Phase angeben. Die Gültigkeit der wichtigsten Prinzipien, welche die thermische Bestimmung des Kristallisationsgrades unter Ausschaltung der Unvollkommenheit der bestehenden Methoden gewährleisten und den richtigen Wert der Masse der kristallinen Phase angeben, wurden in Erwägung gezogen. Die Analyse der Phasenzusammensetzung von PET wurde durch die thermische Methode bei verschiedenen Temperaturen und Kristallisationsbedingungen durchgeführt. Ein deutlicher Unterschied zu den Literaturangaben kann im Bereich der niedrigen Temperaturen beobachtet werden.
. , , . , , . , , . . .相似文献
18.
Catalytic activity of honeycomb catalysts, I. The benzene-cyclohexane (de)hydrogenation reaction 总被引:1,自引:0,他引:1
A. Parmaliana C. Crisafulli R. Maggiore J. C. J. Bart N. Giordano 《Reaction Kinetics and Catalysis Letters》1981,18(3-4):295-299
Monolithic supported platinum catalysts were investigated with respect to their hydrogenation and dehydrogenation activity towards benzene and cyclohexane, respectively, between 250° and 350°C. Conversion of benzene to cyclohexane is optimal for the volume ratio H2/Bz=5 at lower temperatures. In the cyclohexane dehydrogenation reaction, high temperatures, associated with lower N2/Cy ratios, are beneficial. No byproducts were observed in the two reactions.
, , 250 °C 350 °C. H2/=5. N2/ . .相似文献
19.
J. Brandštetr 《Journal of Thermal Analysis and Calorimetry》1978,14(1-2):157-160
A review is given of recently developed instruments used in thermometric analysis and new methods of direct injection enthalpimetry.In the past two years, several types of Tronac (Orem, Utah) and Setaram (Lyon, France) calorimeters have been developed. A new mixing cell construction led to development of a flow instrument for automated thermometric analyses (Technicon, Tarrytown N. Y.). A new type of Hungarian instrument, Ditermanal (Orion, Budapest) permits arbitrary analyses.At the Technical University in Brno, small table twin isoperibol instruments allowing the direct analyses of solid samples have been developed. The use of PTC thermistors and a calibration device improved the accuracy of measurements.Many new methods of silicate and lime analysis, water determination, etc. have been elaborated.
Zusammenfassung Eine Übersicht über die zur thermometrischen Analyse eingesetzten, entwickelten Instrumente und neuen Methoden der Direkt-Injektion Enthalpimetrie wird gegeben.In den zwei vergangenen Jahren wurden verschiedene Kalorimetertypen TRONAC (Orem, Utah) und SETARAM (Lyon, France) entwickelt. Eine neue Mischzellenkonstruktion ermöglichte es ein Durchflussinstrument für automatische thermometrische Analysen (TECHNICON, Tarrytown, N. Y.) zu entwickeln. Ein neuer ungarischer Instrumententyp, DITERMANAL (ORION, Budapest), ermöglicht die Durchführung von Schiedsanalysen.An der Technischen Universität Brno wurden kleinen Zwillings-Isoperibol-Tisch Instrumente entwickelt, welche auch die direkten Analysen fester Proben ermöglichen. Der Einsatz von PTC-Thermistoren und einer Eichvorrichtung erhöhte die Messgenauigkeit.Viele neue Methoden der Silikat- und Kalkanalyse, Wasserbestimmungen usw. wurden erarbeitet.
Résumé On passe en revue les instruments récemment mis au point et utilisés en analyse thermométrique ainsi que les nouvelles méthodes d'enthalpimétrie par injection directe.Dans les deux dernières années, divers types de calorimètres ont été mis au point: TRONAC (Orem, Utah) et SETARAM (Lyon, France). La réalisation d'une nouvelle cellule de mélange a permis de mettre au point un appareil à flux pour les analyses thermométriques automatiques (TECHNICON, Tarrytown, N. Y.). Un nouveau type d'instrument hongrois, DITERMANAL (ORION, Budapest) permet d'effectuer des analyses arbitrales.A l'université technique de Brno de petites tables instruments jumeaux isopériboliques permettant aussi d'effectuer des analyses directes des corps solides ont été réalisés. L'application de thermistors PTC et un dispositif pour l'étalonnage augmentent l'exactitude des mesures.Des méthodes nouvelles nombreuses pour l'analyse des silicates, des pierres calcaires, de l'eau, etc., ont fait l'objet d'études.
, . (, ) (, ). (H, , -). (, ) . , . . , , .相似文献
20.
V. V. Azatyan V. A. Kalkanov A. A. Shavard 《Reaction Kinetics and Catalysis Letters》1980,15(3):367-372
The polymerization of acrylonitrile has been studied in dimethylformamide in the presence of the complex catalyst tris-(-allyl/chromium and pyridine. The structure of the active sites of polymerization is discussed on the basis of experimental data.
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