Interaction of super-finely dispersed Al powders with water

Interaction of super-finely dispersed Al powders (SFDP) with water is characterized by the presence of a considerable section on the kinetic curves, where the conversion rate is maximum and its degree is as high as =0.5–0.7. It is suggested that the essential factor accounting for the conversion kinetics and the phase composition of its products is the self-heating of Al particles.

---

() , , () 0,5–0,7. , .

     

Study of well-characterized Pt?Ru/C catalysts by oxygen electroreduction

A series of well characterized Pt–Ru bimetallic catalysts supported on graphite has been studied by means of the electroreduction of oxygen in a supporting electrolyte of 1 N H₂SO₄. A synergetic effect is observed when the activity per gram of catalyst is considered. However, this effect disappears when the activity values are corrected by the active surface area.

---

Pt–Ru, , 1N H₂SO₄. 1- , . , , .

     

Oxidative dehydrogenation of n-butane IV. Kinetic and catalytic activity of copper oxide

Copper oxide is moderately active and selective in the oxidative dehydrogenation of n-butane. Selectivity to C₄ olefin is almost constant in the range of 200–520°C. The apparent activation energy determined between 200 and 360°C was 18.8 kcal/mol, and 9.2 kcal/mol at higher temperatures.

---

-. C₄ 200–520°C. 200–360°C 18,8 /, 9,2 /.

     

Precipitation of iron catalysts for the Fischer-Tropsch synthesis

The batch Fischer-Tropsch wise precipitation of iron catalysts for the synthesis in the pH range of 4.60 to 7.91 is described in detail. Each step of the precipitation has been controlled by measurements of the relevant parameters to produce definite catalysts. Factors influencing the reproducibility are shortly discussed.

---

- pH=4,60–7,91. . , .

     

Effect of stirring on the Belousov-Zhabotinskii reaction: A problem of interpretation

It is probable that different phenomena attributed to mechanical stirring during the Belousov-Zhabotinskii (BZ) reaction are caused by atmospheric oxygen and, as far as our experiments show, they have nothing to do with dissipative structures or with the turbulence of the reacting mixture.

---

, , , -, .

     

Reactivity of electronically excited Br(2P1/2) atoms towards CH3F

The rate constants for Br(²P_1/2) and Br(²P_3/2) atoms in the reaction Br+CH₃FHBr+CH₂F in photobromination of CH₃F have been determined. Their ratio is 10^{–(2.6±0.5)} exp(10100±1000/RT) in the temperature range of 60–200 °C.

---

Br(²P_1/2) Br(²P_3/2) Br+CH₃FHBr+CH₂F CH₃F. 60–200 °C 10^{–(2,6±0,5)} exp (10100±1000/RT).

     

Relation between the catalytic and acidic properties of zeolite catalysts

Influence of the strength and concentration of non protic centers on the catalytic activity of metal-zeolite catalysts in isomerization of n-butane has been studied. A relationship between the specific activity and the center strength is suggested.

---

-. , .

     

Effect of surfactants on the cleavage of the N?O bond in O-(2,4-dinitrophenyl)-cyclohexanone oxime

Kinetics of cleavage of N–O bond in O-(2,4-dinitrophenyl)-cyclohexanone oxime with hydroxide ions both in the presence and absence of surfactants has been studied. The reaction is accelerated by cationic micelles, slightly by non-ionic micelles and there is no effect of anionic micelles. A plot of the rate constant vs. [surfactant] shows a maximum corresponding to the CMC of surfactant.

---

NO O-(2,4-) - , - (). , , - . , .

     

Evolved gas analysis for examination of surface oxides on alloys

Temperature programmed reduction in a hydrogen flow with simultaneous evolved gas analysis was employed to determine surface oxides on oxide dispersion strengthened (ODS) nickel containing TiO₂, A1₂O₃ or Cr₂O₃ particles, and on a Ni-2OCr alloy, after exposure to air at elevated temperatures. Oxides on particles of water-atomized (WA) Ni-2OCr powder were analysed similarly. Significant differences in starting temperatures of the reaction between hydrogen and phases present in oxide layers made identification of the phases possible. NiO or NiO doped with Ti, Al or Cr are the major constituents of the scale formed on ODS Ni. NiTiO₃, NiCr₂O₄ and NiAl₂O₄ are formed as a result of a reaction between TiO₂, A1₂O₃ or Cr₂O₃ particles in the scale with NiO. The oxide layer formed on Ni-2OCr alloy consists of Cr₂O₃ and of NiO doped with Cr. Surface oxides on WA Ni-2OCr contain Cr₂O₃ and a small amount of NiO.

---

Zusammenfassung Temperaturprogrammierte Reduktion im Wasserstoffstrom wurde zusammen mit gleichzeitiger Analyse des in Freiheit gesetzten Gases dazu benutzt, um Oberflächenoxide an Nickel enthaltenden TiO₂-, A1₂O₃- oder Cr₂O₃-Partikeln mit verstärkter Oxiddispersion (ODS) und an einer Ni-2OCr-Legierung nach Behandlung in Luft bei erhöhten Temperaturen zu bestimmen. Oxide auf Partikeln von wasser-zerstäubtem (WA) Ni-2OCr-Pulver wurden auf ähnliche Weise analysiert. Signifikante Unterschiede in der Starttemperatur der Reaktionen zwischen Wasserstoff und der in den Oxidschichten vorliegenden Phasen ermöglichen die Identifikation der Phasen. NiO oder mit Ti, Al oder Cr gedoptes NiO sind die Hauptbestandteile des auf ODS-Ni gebildeten Belags. NiTiO₃, NiCr₂O₄ und NiAl₂O₄ treten als Produkte der Reaktion von TiO₂-, Al₂O₃- oder Cr₂O₃-Partikeln mit NiO im Belag auf. Die auf der Ni-2OCr-Legierung gebildete Oxidschicht besteht aus Cr₂O₃ und aus mit Cr gedoptem NiO. Oberflächenoxide auf WA-Ni2OCr enthalten Cr₂O₂ und geringe Mengen an NiO.

---

- , , , , , , Ni-2r, . Ni-2OCr. , , . , , , , . NiTiO₃, NiCr₂O₄ NiAl₂O₄ , , . , Ni-2r, , . Ni-2r .

     

Toluene disproportionation and coke formation over fluorided alumina and hydrogen-mordenite

Toluene transformation was investigated on a fluorided alumina and a protonic mordenite under hydrogen (0.8, 12 bar) and under nitrogen (12 bar). Hydrogen pressure considerably improves the catalytic stability of H-mordenite by inhibiting the formation of coke. Moreover, hydrogen eliminates part of the coke deposited by reaction under nitrogen, and regenerates the activity of the mordenite. On the contrary, hydrogen has no effect in the case of fluorided alumina. The particular behavior of the mordenite is attributed to its very strong acidity.

---

(0,8, 12 ) (12 ). -, . , , , . , - . .

     

Thermal decomposition of 10-molybdo-2-vanadosilicic heteropolyacid:29Si and51V-NMR study

Thermal decomposition of 10-molybdo-2-vanadosilicic heteropolyacid has been studied by²⁹Si and⁵¹V-NMR method.²⁹Si-NMR MAS spectra of solid samples indicate that the HPA begins to decompose at T<300°C and the decomposition is complete at 300–400°C.

---

²⁹Si ⁵¹V Si–Mo-V () 12- . ²⁹Si MAS , 300°C 300–400°C.

     

Computation in kinetics V. A new KINDC computational method. Comparative study with other computer programs for kinetic treatment

A new KINDC kinetic computational method is proposed that offers a greatly improved version of the KILET program. A comparative study is made of its performance and those of the most recent computational methods reported in the literature.

---

, KINDC, KILET. .

     

Nonisothermal kinetics of zinc oxide nonstoichiometrization

The results obtained by studying zinc oxide non-stoichiometrization are presented. The kinetic parameters values under nonisothermal conditions were calculated too. Both the nonstoichiometric zinc oxide composition and the kinetic parameter values are depending on the generating substances.

---

Zusammenfassung Die Ergebnisse der Untersuchungen der Nichtstöchiometrisierung von Zinkoxid werden vorgeführt.Die Werte der kinetischen Parameter unter nicht-isothermen Bedingungen wurden eben falls berechnet.Sowohl die nichtstöchiometrische Zusammensetzung des Zinkoxids als auch die Werte der kinetischen Parameter hängen von der das Phänomen auslösenden Substanz ab.

---

Résumé On présente les résultats d'une étude sur la formation d'oxyde de zinc non-stchiométrique. Les valeurs des paramètres cinétiques en conditions non-isothermes sont égale ment calculées. La composition de l'oxyde de zinc non-stchiométrique ainsi que les valeurs des paramètres cinétiques dépendent du composé de départ.

---

, , . .

     

Modification effect of Cu upon Pt In Pt?Cu?Al2O3 catalysts

In Pt–Cu–Al₂O₃ catalysts Cu might display either Electronic Ligand Effect or Ensemble Effect, depending on the preparation method of catalysts. For catalysts with Pt added before Cu, the latter exhibits an Electronic Ligand Effect. However, for catalysts with Cu added before Pt or with co-added Pt and Cu, Cu mainly demonstrates an Ensemble Effect.

---

Pt–Cu/Al₂O₃ , . Pt Cu, , .

     

Effect of the medium on the oxidation of aliphatic monocarboxylic acids

Oxidation rates and k₂/k₆ ratios are given for some acids from propionic to lauric. The k₂/k₆ ratio is shown to be influenced by the electrostatic effect of the solvent. A linear dependence between the isodielectric values of k₂/k₆ and the number of methylene groups in the acid molecules is described.

---

k₂/k₆ . k₂/k₆ k₂/k₆ .

     

The thermal decomposition of thaumasite from Mothae kimberlite pipe,Lesotho, Southern Africa

The endothermic decomposition of thaumasite from Mothae which has been investigated by DTA and TG shows a peak temperature of 138–203°, and reaction orders of 0.45–1.00, depending on the heating rate employed. The activation energy of the reaction was found to be about 19 kcal/mole; the enthalpy is 246 cal/g.The decomposition seems to be divided into one reaction withn=0.90, immediately followed by one withn=1.59. The first reaction is attributed to the loss of H₂O, the second one to the (partial) release of OH and CO₂.

---

Zusammenfassung Die durch DTA und TG überprüfte endothermische Zersetzung von Thaumasit aus Mothae zeigt in Abhängigkeit der angewandten Aufheizgeschwindigkeiten Spitzentemperaturen zwischen 138 und 203° C, sowie Reaktionsordnungen von 0.45 bis 1.00. Die Aktivierungsenergie der Reaktion ergab sich zu 19 Kcal/Mol, die Enthalpie zu 246 cal/g.Die Zersetzung scheint in eine Reaktion vonn=0.90 und eine sofort darauffolgende vonn=1.59 geteilt zu sein. Die erste Reaktion wird dem Verlust von H₂O, die zweite der (teilweisen) Freisetzung von OH und CO₂ zugeschrieben.

---

Résumé La décomposition endothermique de la thaumasite de Mothae a été étudiée par ATD et TG. Suivant la vitesse de chauffage utilisée la température au sommet du pic varie de 138 à 203° C et l'ordre de réaction de 0.45 à 1.00. On a trouvé que l'énergie d'activation s'élevait à 19 kcal, mol^–1 et l'enthalpie à 246 cal. g^–1.Il semble que la décomposition s'effectue suivant une réaction d'ordren=0.90, immédiatement suivie par une autre oùn=1.59. On attribue la première réaction à la perte d'eau et la seconde à la libération (partielle) d'hydroxyles OH et d'anhydride carbonique CO₂.

---

, , 138–203° 0,45–1,00 . , 19 /, - 246 /. , n=0,90, n=1,59. , - OH CO₂.

---

---

The material used for this study has been kindly supplied by Dr. P. H. Nixon, former chief geologist, Department of Mines, Maseru, Lesotho.     

The applicability of DTA and DSC techniques to the study of the kinetics of phase transition reactions

Differential thermal analysis and differential scanning calorimetry techniques have been used to study the kinetics of phase transitions. The aragonite/calcite transformation was chosen as test reaction.Marked discrepancies were observed between the DTA kinetic results and those obtained from isothermal kinetic measurements. This disagreement is associated with the difficulty of determining accurately the reaction rate of the process from a DTA curve.In contrast, in DSC measurements, where the reaction rate is given by the height of the peak from the base-line, it is possible to get a satisfactory fit of the data, and the kinetic results obtained with this technique are in good agreement with the isothermal ones.

---

Zusammenfassung Die Differentialthermoanalyse und DSC wurden zur Untersuchung der Kinetik von Phasenübergängen eingesetzt. Die Umwandlung Aragonit/Calcit wurde als Testreaktion gewählt.Bedeutende Diskrepanzen wurden zwischen den kinetischen Ergebnissen der DTA und den durch isotherme kinetische Messungen erhaltenen Ergebnissen beobachtet. Diese Abweichungen sind damit verbunden, daß es schwierig ist, die Reaktionsgeschwindigkeit des Vorgangs aus einer DTA-Kurve genau zu ermitteln.Bei DSC-Messungen,wo die Reaktionsgeschwindigkeit durch die Höhe des Peaks von der Grundlinie gegeben ist, kann eine befriedigende Anpassung der Daten erhalten werden, und die durch diese Technik erhaltenen kinetischen Ergebnisse sind in guter Übereinstimmung mit den isothermen Ergebnissen.

---

. /. , . -. , , , , , .

     

Influence of the gas phase on metallic reference electrodes used in work function measurements

Contact potential differences between electrodes of Pt, Au and Ta of different surface finishing were measured by the dynamic condenser method in propylene and oxygen. Propylene is irreversibly adsorbed, thus changing the work function. This renders the electrodes unsuitable as standard electrodes for work function measurements on catalysts in the atmosphere of hydrocarbons, but they may be used in adsorption studies on oxygen.

---

Pt, Au Ta . , , . , .

     

Formation of nitrogen oxides during the oxidation of nitromethane on copper-chromium catalyst

Principles of the oxidation of nitromethane on a 30% CuCr₂O₄/-Al₂O₃ catalyst over the temperature range from 210 to 485 °C have been studied. The conversion of bound nitrogen to oxides depends on initial concentrations of nitromethane and oxygen in the range corresponding to the complete conversion of nitromethane (350–485 °C). The composition of oxidation products is determined by the oxygen to nitromethane ratio.

---

30% CuCr₂O₄/-Al₂O₃ 210–485°C. (350–485°C) . , .