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1.
C. Karunakaran K. Ganapathy P. Ramasasamy 《Reaction Kinetics and Catalysis Letters》1989,40(2):369-374
The perborate oxidation of quinol in aqueous acetic acid is first order with respect to perborate, zero order with respect to quinol, and first order with respect to H+. The oxidation is faster than H2O2 oxidation. Breakdown of protonated perboric acid is suggested as the rate-limiting step.
, H+. . , , , .相似文献
2.
The Michael addition of nitromethane to 3-buten-2-one has been carried out in the absence of solvent, using potassium fluoride supported on Al2O3, ZnO, SnO2, sepiolite, AlPO4, AlPO4–Al2O3 and AlPO4–ZnO catalysts. We found that KF/ZnO easily performed the Michael addition and thus, ZnO is a better support for the basic reagent than Al2O3. Besides, the Michael addition was not successful with AlPO4 or AlPO4-metal oxide acidic supports.
3--2- , , Al2O3, ZnO, SnO2, , AlPO4, AlPO4–Al2O3 AlPO4–ZnO. , KF/ZnO .. ZnO, , , Al2O3. , , AlPO4 AlPO4- .相似文献
3.
Using a crystal model with an adsorbed layer, the propagation of vibrational excitation induced by an adsorbed particle is considered. The relaxation times of excitation have been estimated. The role of excitation transfer processes in adsorption-desorption phenomena is discussed.
, . . - .相似文献
4.
A mordenite-containing rock from the Tokaj-mountains was investigated. The effect of the treatment with hydrochloric acid solutions of various molarity was established. From gas adsorption measurements, scanning electron microscopic investigations and measurements with a mercury porosimeter conclusions were drawn on the changes caused by acid treatment. Slight changes in the texture were found, but no damage in the crystal structure could be observed.
- . . , - , , . - .相似文献
5.
A. Broersma P. L. de Bruyn J. W. Geus R. J. Stol 《Journal of Thermal Analysis and Calorimetry》1978,13(2):341-355
Simultaneous DTA and DTG curves (Mettler TA-2) have been measured for one diaspore and four different boehmites at temperatures up to 750° in a flow of dried argon. The crystallographic structures of the materials were assessed by X-ray diffraction and the degree of clustering of the elementary particles by scanning electron microscopy. To get straight base-lines a calibration curve was used to correct the DTA curves. The usefulness of the correction was established by comparison with DTA curves obtained with a Mettler TA-2000.The diaspore contained occluded water. Expulsion of the water at 300–350° brought about fragmentation of the crystals. The DTA and DTG peaks that correspond to the dehydration to alumina both lie at 560°.There is a noticeable spread in the DTA and DTG peaks for the different boehmites in the temperature range 455–530°. All the DTA peaks lie close to the corresponding DTG peaks. One of the boehmites displayed a double peak (470° and 502°). To trace the origin of the variation in peak temperature, the porous structure of the boehmite having its peak at 530° was varied by ball-milling and by dispersion into water, neither of which markedly affected the crystallographic structure and the crystallite size. Whereas ball-milling did not change the peak temperature much, dispersion into water brought about a transition from a single peak at 530° to a double peak at 450° and 490°. Prolonged storage in air led to a shift of the peaks to 480° and 520°. It is concluded that the porous structure of boehmites can profoundly affect the appearance and the temperature of their dehydration peaks.
The authors are indebted to Dr. P. F. Elbers for placing the electron microscopic facilities of the University of Utrecht at their disposal. We especially wish to acknowledge the time and energy spent by Mr. J. Pieters in the preparation of samples and the investigation with the scanning electron microscope. The assistance given by Dr. A. Duisenberg in the measurement of the line-broadening is also gratefully acknowledged. 相似文献
Zusammenfassung Simultane DTA- und DTG-Kurven (Mettler TA-2) wurden für ein Diaspor und vier verschiedene Boehmite bei Temperaturen bis zu 750° in einem Strom von getrocknetem Argon aufgenommen. Die kristallographische Struktur der Substanzen wurde mittels Röntgendiffraktion und der Anhäufungsgrad der Elementarpartikel mittels Raster-Elektronenmikroskopie bestimmt. Um gerade Grundlinien zu erhalten wurde eine Eichkurve zur Korrektur der DTA-Kurven verwendet. Die Nützlichkeit der Korrektur wurde durch Vergleiche der in einem Mettler TA-2000 Gerät erhaltenen DTA-Kurven festgestellt.Der Diaspor enthielt eingeschlossenes Wasser. Das bei 300 bis 350° erfolgte Abspalten des Wassers brachte eine Fragmentierung der Kristalle mit sich. Die DTA- und DTG-Peaks, welche der Dehydratisierung zu Aluminiumoxid entsprechen, liegen beide bei 560°.Im Temperaturbereich von 455 bis 530° läßt sich ein Verbreitern der DTA- und DTG-Peaks der verschiedenen Boehmite wahrnehmen. Einer der Boehmite zeigte einen Doppel-peak (470° und 502°). Um dem Ursprung der Änderungen der Peak-Temperaturen festzustellen wurde die poröse Struktur des Boehmits mit einem Peak bei 530° mit Hilfe einer Kugelmühle und durch Dispersion in Wasser verändert. Keine dieser Behandlungen änderte merklich die kristallographische Struktur und die Kristallgröße. Während das Vermählen in der Kugelmühle die Peak-Temperatur nicht wesentlich änderte, erbrachte die Dispergierung in Wasser einen Übergang von einem einzigen Peak bei 530° zu einem Doppelpeak bei 450 und 490°. Längeres Lagern an der Luft führte zu einer Verschiebung der Peaks nach 480° und 520°. Es wird gefolgert, daß die Porösstruktur von Boehmiten das Erscheinen und die Temperatur ihrer Dehydratisierungspeaks stark beeinflussen kann.
Résumé Les courbes ATD et TGD d'une diaspore et de quatre boehmites différentes ont été enregistrées simultanément (Mettler TA-2) jusqu'à 750°, sous circulation d'argon desséché. La structure cristallographique de ces composés a été examinée par diffraction des rayons X et le degré de compacité a été évalué par microscopie électronique à balayage. Une courbe d'étalonnage a été utilisée pour corriger les courbes ATD et obtenir des lignes de base droites. L'utilité de cette correction est démontrée en comparant avec les courbes ATD obtenues à l'aide d'un appareil Mettler-TA-2000.La diaspore contenait de l'eau d'inclusion. L'élimination de l'eau à 300–350° a entraîné la fragmentation des cristaux. Les pics ATD et TGD qui correspondent à la déshydratation en oxyde d'aluminium se trouvent tous deux à 560°.Un étalement des pics ATD et TGD est perceptible pour les différentes boehmites dans l'intervalle de température 455–530°. Tous les pics ATD sont proches des pics TGD correspondants. L'une des boehmites a donné un pic double (470 et 502°). Afin de trouver l'origine de la différence de température entre les deux pics, la structure poreuse de la boehmite dont le pic se situait à 530° a été modifiée par traitement dans un broyeur à boulets et par dispersion dans de l'eau; ni l'un ni l'autre de ces deux traitements n'influence de façon apparente la structure cristallographique et la taille des cristaux. Alors que le traitement au broyeur à boulets ne change pas beaucoup la température du pic, la dispersion dans de l'eau fait apparaitre le passage d'un pic unique à 530° à un pic double à 450 et 490°. Le stockage prolongé dans l'air provoque un déplacement des pics à 480 et 520°. On en conclut que la structure poreuse des boehmites peut influer profondément sur l'apparition et la température de leurs pics de déshydratation.
— ( TA-2) 750° . - , — . . , TA-2000. . 300–350°C, . — , , 560°. - 455–530°. . (470° 502°). , 530°C . . , — 530° — 450° 490°. 480° 520°. , , .
The authors are indebted to Dr. P. F. Elbers for placing the electron microscopic facilities of the University of Utrecht at their disposal. We especially wish to acknowledge the time and energy spent by Mr. J. Pieters in the preparation of samples and the investigation with the scanning electron microscope. The assistance given by Dr. A. Duisenberg in the measurement of the line-broadening is also gratefully acknowledged. 相似文献
6.
The presence of hydrogen sulfide and oxygen in mixtures increases the number of sites for dissociative desorption on the surface of MoS2 as compared with the adsorption of individual hydrocarbons. This phenomenon can be explained by a change in the coordination state of the active sites (molybdenum ions) upon the adsorption of the gases mentioned.
, MoS2 . .相似文献
7.
Surface acidity of a series of silica-alumina mixed oxides have been investigated by IR-spectroscopy and catalytic measurements. Pure alumina was the most active catalyst in the conversion of butan-1-ol, but the E1 part in the reaction increased with increasing SiO2 content. It was concluded that the number of acidic sites increased with increasing Al2O3 content, while the strength of the acidic sites with the silica content.
- . -I-, E1 SiO2. , Al2O3, - .相似文献
8.
CpTiCl2-M-surface complexes (M=Al, Si, Mg, Cp=cyclopentadienyl) supported on Al2O3, SiO2, MgO gels are reduced by Et3Al, C3H5MgBr and BuLi to Ti3+ surface compounds which exhibit ESR signals. The g and g values and asymmetry of these signals depend on the kind of gel and reducing agent.
CpTiCl2-M ( M=Al, Si, Mg Cp=), Al2O3, SiO2 MgO, Et3Al, C3H5MgBr, BuLi (Et=–C2H5 Bu=–C4H9) Ti+3, . g g .相似文献
9.
M. Harmelin 《Journal of Thermal Analysis and Calorimetry》1972,4(4):403-415
Résumé Application de l'ATD quantitative à l'étude des transformations structurales du nitrate de potassium. Les échantillons (1 à 8 mg) sont chauffés et refroidis dans l'azote sec, à la pression atmosphérique. Au refroidissement, on observe toujours les transitions successives I III II. Le pic exothermique correspondant à I III apparaît dans un intervalle de température très reproductible (118 – 120°). Les mesures de surface confirment la parfaite réversibilité de I III déjà signalée par C. Mazières. Les transitions III I et II I ont lieu pratiquement à la même température (127–130°) mais l'aire du pic endothermique correspondant à III I est plus faible et représente 51.5 % de la valeur observée pour II I. En prenantH=13.2 cal/g comme valeur de référence pour la transition II I, on trouveH=6.8± 0.2 cal/g pour III I. La transformation III II suit un processus en deux étapes, fortement influencé par le traitement thermique antérieur de la phase I.
Mémoire présenté en l'honneur du 70e anniversaire du Professeur Clément Duval. 相似文献
The changes in the structure of potassium nitrate have been studied by differential thermal analysis. The samples were heated and cooled in a stream of dry nitrogen, at atmospheric pressure. On cooling, the following transformations have been observed: I III II. The exothermic peak corresponding to the I III transformation appeared at 118–120° with good reproducibility. Surface area measurements show the complete reversibility already observed by Mazières for the I III transformation. The III I and the II I processes take place at the same temperature (127–130°), but the peak corresponding to the III I change is of lower intensity, representing only 51.5% of that of the peak belonging to the II I transition. If the enthalpy change belonging to process II I,H=13.2 cal/g, that belonging to transition III I,H=6.8±0.2 cal/g. Transformation III II proceeds in two steps and is greatly influenced by the preceding heat treatment of phase I.
Zusammenfassung Quantitative Differentialthermoanalyse wurde zur Untersuchung der strukturellen Umwandlungen von Kaliumnitrat herangezogen. Die Proben (1–8 mg) wurden in trockenem Stickstoff bei atmosphärischem Druck erhitzt und abgekühlt. Beim Abkühlen lassen sich immer die sukzessiven Umwandlungen I III II beobachten. Die dem Übergang I III entsprechende exothermische Spitze erscheint sehr reproduzierbar bei 118–120°. Die Oberflächenmessungen bezeugen die vollständige Reversibilität von I III, schon früher angegeben von Mazières. Die Übergänge III I und II I erfolgen praktisch bei gleicher Temperatur (127–130°), doch die endothermische Spitze von III I ist schwächer und entspricht nur 51.5% des für II I beobachteten Wertes.H=13.2 cal/g als Referenzwert für Übergang II I genommen, ergibt sichH=6.8±0.2 cal/g für III I. III II Übergang verläuft in zwei Schritten, die durch das thermische Vorleben der Phase I stark beeinflußt sind.
. . I III II. , I III, 118–120°. , I III. III I II I (127–130°), , III I 51,5% III. II I H=13,2 /. III I 6,8 ± 0,2 /. III II I.
Mémoire présenté en l'honneur du 70e anniversaire du Professeur Clément Duval. 相似文献
10.
《Reaction Kinetics and Catalysis Letters》1975,3(3):277-283
, , , . 298–366°K. , H+O2+M=HO2+M .
The kinetics of the reaction between fluorine and hydrogen under conditions far from those of self-ignition can be described by a simple scheme of chain reaction over a wide range of concentrations. The probability of formation of fluorine atoms upon collision of F2 molecules with the reactor wall has been determined at 298–366 K. The effectivity of argon, nitrogen and carbon dioxide in trimolecular chain termination, H+O2+MHO2+M, is compared with that of helium.相似文献
11.
Coupled methanol/hydrocarbon cracking (CMHC) with n-butane as feed was carried out on fresh and steamed H-ZSM-5 zeolite catalysts in reaction cycles (including regeneration) of 150 min each. The deactivation of H-ZSM-5 zeolite during CMHC reaction is due to both coke deposition and dealumination of the zeolite framework.
/ , H-ZSM-5 ( ) 150 . H-ZSM-5 , , .相似文献
12.
Electrolytic supporting of metallic sodium on the surface of TiO2 and Pt/TiO2 films is shown to change significantly the Fermi level of the semiconductor substrate already at small concentrations of sodium. The steady-state catalytic activity changes only at high concentrations of supported sodium, varying the chemical composition of the active phase. The contact process does not play any significant role in the catalytic process.
, TiO2 Pt/TiO2 . , . .相似文献
13.
The effect of fluctuations on the behavior of a simple kinetic model of catalytic reactions allowing a neutral steady-state, is analyzed.
, , .相似文献
14.
A. La Ginestra C. Ferragina P. Patrono R. Dl Rocco 《Journal of Thermal Analysis and Calorimetry》1981,20(1):205-213
The thermal and redox behaviours of some Ag-low-converted zirconium phosphates have been investigated by thermoanalytical and X-ray methods: the conditions for obtaining Ag solid solutions in
phases are reported.
Paper in part presented at the 6th ICTA, in Bayreuth (Germany), July 1980.
We thank Dr. M. A. Massucci, of our Institute, for helpful discussions and suggestions. 相似文献
Zusammenfassung Das thermische und Redoxverhalten einiger Zirkoniumphosphate niedriger Ag-Konversion wurde durch thermoanalytische und Röntgenmethoden studiert; über die Bedingungen zum Erhalten von Ag-Festphasenlösungen in HH-Phasen wird berichtet
Résumé On a étudié le comportement thermique et oxydo-réducteur de quelques phosphates de zirconium faiblement converti par Ag, en se servant des méthodes d'analyse thermique et des rayons X: on communique les conditions permettant d'obtenir des solutions solides d'Ag dans les phases .
- Ag- . HH.
Paper in part presented at the 6th ICTA, in Bayreuth (Germany), July 1980.
We thank Dr. M. A. Massucci, of our Institute, for helpful discussions and suggestions. 相似文献
15.
J. J. Tondeur G. Vandendunghen M. Watelet 《Reaction Kinetics and Catalysis Letters》1988,36(1):125-129
We have studied the kinetics of the reaction of L-hydroxyproline with OCH(CH2)6NCO, catalyzed by organotin, avoiding side reactions by protecting the other active hydrogens of the aminoacid, and comparing it with the MeOH/n-BuNCO system.
L-- -OCN(CH2)6NCO, , . . - .相似文献
16.
V. N. Orlov 《Reaction Kinetics and Catalysis Letters》1980,14(2):149-154
A class of ordinary differential equations including nonideal nonisothermal kinetics is introduced. The behavior of their solutions for the system with a positive complex-balanced stationary point is studied. Sufficient conditions for this point to exist are described.
, . . .相似文献
17.
Arylazohydroxynaphthoic acids of general formula were subjected to thermal analysis. The decomposition temperatures of the compounds were found to be determined by the resonance and inductive interaction of substituent R with the benzene ring and the azo group of the arylazohydroxynaphthoic acid molecule. The results of DTG analysis correspond with the Hammet
H constants. The mechanism of thermal splitting is briefly discussed.
Zusammenfassung Die Thermoanalyse wurde zur Untersuchung der thermischen Zersetzung substituierter 4-Arylazo-3-hydroxy-2-Naphtoesäuren eingesetzt. Es zeigte sich, daß die Zersetzungstemperaturen der Verbindungen durch die Resonanz und induktiven Wechselwirkungen der Substituenten R mit dem Benzenring und den Azogruppen der Arylazohydroxy-naphthoesäure bestimmt wird. Zwischen den Versuchsergebnissen der Thermostabilität und den Hammetschen H-Konstanten besteht eine Korrelation. Der Zersetzungsmechanismus wird kurz diskutiert.
4--3- -2 , . . .相似文献
18.
Activity of CaO–CaF2 catalysts in the Claus reaction has been studied as a function of catalyst composition and of the time of catalyst operation in the reaction. Opposite effects of low and high fluoride content on the Claus activity have been found. A new type of reducing centers is suggested to be responsible for the increase in the activity observed in the case of fluorine-rich catalysts.
CaO–CaF2 . , . , , .相似文献
19.
O. V. Klimov E. A. Krivoshchekova A. N. Startsev 《Reaction Kinetics and Catalysis Letters》1991,43(1):19-23
New highly active catalysts for metathesis of olefins were obtained through the interaction of bis(acetylacetonato)dioxymolybdenum(VI) with surface OH groups of -Al2O3 and subsequent reduction in H2 or CO.
()(VI) OH -Al2O3 H2 CO .相似文献
20.
V. M. Vlasenko V. Ya. Volfson S. A. Soloviev G. F. Kalapusha 《Reaction Kinetics and Catalysis Letters》1979,11(2):179-182
1,1- (AH) ([AH]=6,9 /, 50°C). AH Wi/WO
3=0,40±0,16.
The kinetics and oxidation products of 1,1-diethoxyethane (AH) ozonolysis have been investigated at [AH]=6.9 mol/l and 50 °C. The initiation efficiency of radical oxidation by ozone is Wi/WO 3=0.40±0.16.相似文献