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1.
P. Dubois M. Mariaud R. Ceolin B. Prost 《Journal of Thermal Analysis and Calorimetry》1987,32(5):1489-1503
A mixture of 9,3-diacetylmidecamycin with 9.1% (by weight) ethylcellulose is used for its antibiotic properties, but it is only active in a non-crystalline state, which is a glassy one: DTA showsT
g at 99<T°C< 106.DTA has been used to develop a quantitative method of non-crystallinity control based upon' a linear relation between the crystallinity percentage and the computed algebraic sum of the enthalpies of recrystailization and fusion.It is shown that for binary mixtures with liquidus-type melting curves this procedure is to be preferred to the measurement of recrystailization enthalpy vs. crystallinity percentage.
Zusammenfassung Ein Gemisch von 9,3-piacetylmidecamycin mit 9,1 Gew.-% Ethylcellulose wird wegen dessen antibiotischen Eigenschaften angewandt, ist aber nur im nicht-kristallinen, glasigen Zustand aktiv. DTA ergibt fürT g99<T°C<106. Die DTA wurde zur Entwicklung einer quantitativen Methode zur Kontrolle der Nicht-Kristallinität herangezogen, die auf einer linearen Beziehung zwischen dem in % ausgedrückten Kristallinitätsgrad und der berechneten algebraischen Summe der Rekristallisations- und Schmelzenthalpie beruht. Es wird gezeigt, daß bei binären Mischungen mit Schmelzkurven des Liquidustyps diesem Verfahren gegenüber der Messung der Rekristallisationsenthalpie in Abhängigkeit vom Kristallisationsgrad der Vorzug zu geben ist.
9,3- 9,1 % g , , 99<T°< 106°. , . , , .相似文献
2.
G. Ya. Popova T. V. Andrushkevich G. A. Metalkova 《Reaction Kinetics and Catalysis Letters》1979,12(4):469-473
Acrolein is oxidized to acrylic acid over a V–Mo catalyst by lattice oxygen, while the formation of CO2 also involves gas phase oxygen. The steady state of catalyst reduction is about 5% monolayer and is characterized by an oxygen binding energy of 61 kcal/mol.
V–Mo- , CO2 . 5% 61 /.相似文献
3.
V. B. Okhotnikov N. A. Simakova B. I. Kidyarov 《Reaction Kinetics and Catalysis Letters》1989,39(2):345-350
The initial stage of the Li2SO4·H2O single crystal isothermal dehydration has been studied by means of quartz crystal microbalance. As found, weight loss in the initial process may be considered as H2O molecule diffusion from a semiinfinite medium. The numerical values of the H2O molecule diffusion in Li2SO4·H2O have been calculated from the results obtained.
. - - - -. - Li2SO4·H2O.相似文献
4.
N. M. Korotaeva V. V. Shereshovets V. D. Komissarov 《Reaction Kinetics and Catalysis Letters》1992,48(2):397-399
Rate constants for the reaction of singlet oxygen with a series of diazocompounds and diazoketones have been measured. Diazoketones were found to possess lower reactivity than diazocompounds.
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5.
Electron paramagnetic resonance studies on intermediates and final active catalyst material used for partial oxidation of anthracene to anthraquinone are reported.
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6.
L. A. Vostrikova K. G. Ione V. M. Mastikhin A. V. Petrova 《Reaction Kinetics and Catalysis Letters》1984,26(3-4):291-295
The dependence of the state of boron atoms on the preparation conditions of borosilicates and the effect of this state on their catalytic properties in methanol conversion have been studied.
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7.
The thermal decomposition of MgCl2·6H2O (non-dried and partly dried) and the kinetics of the process were studied by DTA, TG, DTG, IR, X-ray diffraction and chemical analysis of Mg and Cl. The reactions which occurred in the course of the thermal analysis were identified as dehydration (in steps), thermal hydrolysis of MgCl2·H2O and dehydrochloridization of magnesium hydroxy chlorides. Melting of the phases MgCl2·6H2O, MgCl2·4H2O and MgCl2 was also identified in the thermal curves. Thermal weight loss continued up to 800 °C in flowing air or nitrogen, but only up to 700 °C in static air. MgO was the end-product of thermal treatment in both cases.The kinetic parameters of the reaction, the activation energyE, pre-exponential factorA and apparent order of reactionb, were computed by several methods. The activation energy and the apparent reaction order of dehydration were found to increase with decreasing hydration number of the Mg. The dehydrochloridization process had the highest activation energy.
The authors express their appreciation to Dr. Jacob Nathan and Mr. Yoetz Deutch from th Geological Survey, Jerusalem, for the use of the thermal analysis instrument and for useful discussion, and to Mrs. Sarah Erlich from the same institute, for the chemical analysis. The financial support by Everyman's University, Tel-Aviv, and by the Hebrew University of Jerusalem is acknowledged. 相似文献
Zusammenfassung Die thermische Zersetzung von MgCl2·6H2O (nicht und teilweise getrocknet) und die Kinetik dieses Prozesses wurden mittels DTA, TG, DTG, IR, Röntgendiffraktometrie und chemischer Analyse von Mg und Cl untersucht. Die im Verlaufe der thermischen Analyse vor sich gehenden Reaktionen sind Dehydratisierung (in Schritten), thermische Hydrolyse von MgCl2·H2O und Chlorwasserstoffaustritt aus Magnesiumhydroxychloriden. Das Schmelzen der Phasen MgCl2·6H2O, MgCl2·4H2O und MgCl2 ist in den thermischen Kurven ebenfalls zu erkennen. Im Luft- und Stickstoffstrom erfolgt ein Gewichtsverlust bis 800 °C, in statischer Luftatmosphäre dagegen nur bis 700 °C. MgO war in beiden Fällen Endprodukt der thermischen Behandlung. Die kinetischen Parameter der Reaktion (AktivierungsenergieE, präexponentieller FaktorA, scheinbare Reaktionsordnungb) wurden nach verschiedenen Methoden berechnet. Aktivierungsenergie und scheinbare Reaktionsordnung der Dehydratisierung nehmen mit abnehmendem Hydratationsgrad des Mg zu. Die Chlorwasserstoffabspaltung erfordert die höchste Aktivierungsenergie.
, , , , ( ) . : ( ), . , . 800 °C, - 700 °C. B . , . , . .
The authors express their appreciation to Dr. Jacob Nathan and Mr. Yoetz Deutch from th Geological Survey, Jerusalem, for the use of the thermal analysis instrument and for useful discussion, and to Mrs. Sarah Erlich from the same institute, for the chemical analysis. The financial support by Everyman's University, Tel-Aviv, and by the Hebrew University of Jerusalem is acknowledged. 相似文献
8.
V. A. Gruznykh F. K. Shmidt V. V. Saraev M. V. Ustinov 《Reaction Kinetics and Catalysis Letters》1987,33(1):17-21
ESR studies of the interaction between Co(C5H7O2)2 and Al(C2H5)3 in presence of CO reveal the formation of paramagnetic tri- and tetra-nuclear carbonyl compounds and the consecutive formation of complexes including one, two and three cobalt atoms. Al(C2H5)3 decomposition is suggested to take place on the reduced transition metal to form Co–Al clusters. Structures for the paramagnetic heteronuclear clusters is proposed.
- . - . , , . , - -. .相似文献
9.
A new Ru–Co–Mo/Al2O3 catalyst has been prepared by impregnation of Ru salt as a secondary promoter onto Co–Mo/Al2O3 catalyst, and it was found that the Ru–Co–Mo/Al2O3 exhibited higher activity than Co–Mo/Al2O3 in hydrodesulfurization of thiophene to hydrocarbons. Ir studies on Ru–Co–Mo/Al2O3 revealed that the Co and NO adspecies increased significantly in intesnities and displayed a bathochromic shift in frequencies, as compared with Co–Mo/Al2O3.
Ru–Co–Mo/Al2O3 Ru, , Co–Mo/Al2O3. Co–Mo/Al2O3. CO NO, Co Mo, Co–Mo/Al2O3. , Mo , Mo3+ Mo3+ Co Ru–Co–Mo/Al2O3.相似文献
10.
G. Golonka P. Kaczala P. Lamy D. Siguret 《Journal of Thermal Analysis and Calorimetry》1984,29(4):807-813
Purity determination by DSC is possible if the impurity concentration lies within the limits 0.01 to 20 mole%. The thermodynamic equation of Schröder-Van Laar was used.This equation takes into account the effect of the departure of solutions from ideality, and the difference between the heat capacities in the solid and molten states.
Zusammenfassung Eine Reinheitbestimmung mittels DSC ist möglich, wenn die Konzentration der Verunreinigung zwischen 0.01 und 20 Mol-% liegt. Es wurde die thermodynamicshe Gleichung von Schröder-Van Laar angewandt. Diese Gleichung berücksichtigt den durch die Abweichung der Lösungen vom idealen Zustand bedingten Effekt und den Unterschied der Wärmekapazität im festen Zustand und in der Schmelze.
, 0.01–20 %. --, .相似文献
11.
S. Hochevar G. V. Echevskii B. Drzaj K. G. Ione 《Reaction Kinetics and Catalysis Letters》1980,13(4):425-429
The directions of methanol conversion on Pt, Pd, Zn, Ni metals and Y zeolites and on bifunctional metal-Y-zeolite catalysts have been studied. The increase of the hydrogenation activity of bifunctional catalysts enhances the rate of methanol conversion and decreases the selectivity of hydrocarbon formation.
- Y, - Y.相似文献
12.
E. N. Yurchenko O. G. Korolkova N. G. Zubritskaya 《Reaction Kinetics and Catalysis Letters》1991,44(1):215-222
IR spectroscopic and kinetic studies of the interaction between basic carbonates of Cu and Ni and H2CrO4 allows to suppose that catalyst formation is affected by different structures of the initial substances. The formation of mixed Ni–Cu–Cr phases is observed during the step of chromate formation and is preserved after treatment by ammonium.
Cu Ni H2CrO4. , . Ni–Cu–Cr- .相似文献
13.
S. G. T. Bhat 《Reaction Kinetics and Catalysis Letters》1981,17(1-2):93-96
The promotion of catalytic activity of zeolites by CCl4 was studied in a pulse reactor using aromatic alkylation as model reaction. The reaction of surface OH groups with CCl4 produced HCl which increased the catalytic activity. The maximum enhancement of activity occurred when the catalyst was weakly acidic.
CCl4 , . OH CCl4 HCl, . , .相似文献
14.
P. G. Firuzi V. P. Vislovskii E. A. Mamedov R. G. Rizaev 《Reaction Kinetics and Catalysis Letters》1981,18(3-4):401-404
Acidity and basicity of binary oxide catalysts measured by the CO2 and NH3 thermodesorption method are compared with their catalytic activity in oxidative conversion of toluene. The rate of toluene dehydrodimerization is shown to increase with the catalyst basicity.
CO2 NH3 . , .相似文献
15.
The catalytic hydrogenation of cyclopentadiene to cyclopentene was investigated under atmospheric pressure and 20°C in liquid phase with palladium carrier catalysts. The reaction was carried out in methanol and toluene in the presence of n-octylcatechol as a polymerization inhibitor. Using 0.56% Pd/Al2 O3, a 100% selectivity of the hydrogenation of cyclopentadiene to cyclopentene was achieved in toluene. In methanol, the selectivity of hydrogenation was lower and a partial polymerization of cyclopentadiene took place.
20° C Pd- . -. 0,56% Pd/Al2 O3 100%. , .相似文献
16.
The molar heats for the reactions of borate with the polyhydroxy compounds pentaerythritol, L-arabinitol, xylitol, sorbitol and meso-inositol were determined by thermometric titrimetry. By means of the equilibrium constants, the corresponding Gibbs functions and entropies were also obtained. The results refer to aqueous medium at 25 °C and 0.1 M. The present data, together with previous data from this laboratory, lead to the conclusion that the differences in stability of these complexes are mainly determined by entropy, rather than by enthalpy factors. Unlike the other ligands (which are bidentate), pentaerythritol and meso-inositol seem to behave as tridentate ligands with borate. Nevertheless, their complexes exhibit very different stabilities, probably due to the different conformational freedoms of the two ligands in the uncomplexed form.
Zusammenfassung Mittels thermometrischer Titration wurden die molaren Reaktionswärmen für die Reaktionen von Borat mit den Polyhydroxyverbindungen Pentaerythrit, L-Arabinit, Xylit, Sorbit und meso-Inosit bestimmt. Mittels der Gleichgewichtskonstanten erhielt man auch die entsprechenden Gibbsschen Funktionen und Entropien. Die Ergebnisse beziehen sich auf 25 °C undI=0,1 M. Auf Grund dieser und früherer Resultate der gleichen Autoren kann geschlußfolgert werden, daß die unterschiedliche Stabilität dieser Komplexe eher durch Entropieals durch Enthalpiefaktoren bestimmt wird. Im Gegensatz zu den anderen Liganden (die zweizählig sind) scheinen sich Pentaerythrit und meso-Inosit gegenüber Borat als dreizählige Liganden zu verhalten. Trotzdem zeigen ihre Komplexe eine sehr unterschiedliche Stabilität, wofür der Grund wahrscheinlich in dem unterschiedlichen Freiheitsgrad der zwei nicht im Komplex gebundenen Liganden liegt.
, L- , , -. . 25° I=0,1 M. , , , , . , , - . , .相似文献
17.
V. P. Sokolov N. M. Zaidman N. V. Elokhina N. V. Savostina E. V. Kuznetsova 《Reaction Kinetics and Catalysis Letters》1982,20(3-4):313-316
General forms of the kinetic equations for the conversion of various hydrocarbons in reforming of multicomponent gasoline fractions on platinum/alumina catalysts have been confirmed experimentally by using a gradientless method.
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18.
Experimental setup to study catalysts by combined pulse microcatalytic and ESR spectroscopic methods
A setup consisting of an ESR spectrometer and a pulse microcatalytic installation is suggested for simultaneous kinetic and spectral measurements directly in catalytic processes.
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19.
Nonsteady state activity during the gas phase oxidation of ethanol in a simple flow reactor and its dependence on pretreatment and reaction conditions can be explained utilizing the previously presented model of possible surface vanadia phases on silica.
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20.
A. Spojakina S. Damyanova D. Shopov T. Kh. Shokhireva T. M. Yurieva 《Reaction Kinetics and Catalysis Letters》1985,27(2):333-336
Studies of the catalysts obtained by supporting P–Mo, Si–Mo and Ti–Mo heteropolyacids on anatase in thiophene hydrodesulfurization have revealed that the presence of HPA in the initial catalysts promotes the formation of the molybdenum state ensuring high reaction rates. A possibility for HPA synthesis when supporting paramolybdate on TiO2, accounts for the great effect of the support on the properties of the catalyst.
, -, -, - , . , , . .相似文献