Formation of hexagonal MoO3 upon the decomposition of silica-supported ammonium paramolybdate

Upon the decomposition of silica-supported ammonium paramolybdate, hexagonal MoO₃ is formed at 300–350 °C. Irreversible transformation of hexagonal to rhombic MoO₃ is observed with increasing calcination temperature. The hexagonal MoO₃ structure is probably stabilized by the insertion of ammonium and silicon ions into the lattice of molybdenum trioxide.

---

, , 300–359 °C . MoO₃ . MoO₃, , MoO₃.

     

Unexpected variations of the rate of catalytic ethylene hydrogenation on nickel versus the flow-rate of the reacting mixture

Different shapes of the plot rate vs. flow-rate can be obtained for ethylene hydrogenation on nickel. They relate to the presence of oxygen traces and the way they are introduced into the reacting mixture. A previous statement according to which active centers are produced by the conversion of oxygen into water is thus confirmed.

---

. . , . ., , .

     

On the quantitative reliability of heat flux DSC

In an attempt to explain how the calibration factor of a heat flux DSC cell depends both on the standard utilized and on the experimental variables, a study has been undertaken of the entire DSC trace.This report deals with the second half of the peak and shows that, other experimental conditons being fixed, the peak area increases with increasing heating rate.This accounts for the observed decrease in the calibration factors with increasing heating rate.

---

Zusammenfassung Die gesamte DSC-Kurve wurde untersucht, um zu klären, wie der Eichfaktor einer Wärmefluss-DSC vom verwendeten Eichstandard und von den Versuchsbedingungen abhängt. Der vorliegende Teil behandelt den zweiten Abschnitt eines DSC-peaks (vom Maximum an). Es wird gezeigt, dass bei Konstanthalten aller anderen Versuchsbedingungen die peak-Flächen mit steigender Aufheizgeschwindigkeit zunehmen. Das wird als Ursache für die beobachtete Verringerung des Eichfaktors mit steigender Aufheizgeschwindigkeit angesehen.

---

, . . , - , . .

     

Effects of exposure of chloroquine picrate to the sun: A differential scanning calorimetric study

In a continuing study of the effect of exposure of chloroquine and its salt derivatives to the sun, the picrate was investigated. The picrate gives a sharp endothermic effect of melting at 209.2 °C, before it decomposes, to give an exothermic peak at 255.6 °C. The endothermic peak of melting at 209.2 °C was found suitable for the quantitative determination of chloroquine picrate in sun-exposed samples.

---

Zusammenfassung In Fortführung einer Untersuchung über Veränderungen von Chloroquin und dessen Derivaten, wenn diese der Sonne ausgesetzt werden, wurden die Pikrate untersucht. Bei den Pikraten werden ein scharfer, dem Schmelzvorgang zuzuschreibender Effekt bei 209.2 °C und ein mit der Zersetzung einhergehender exothermer Peak bei 255.6 °C beobachtet. Der endotherme Peak bei 209.2 °C erwies sich als geeignet zur quantitativen Bestimmung von Chloroquinpikrat in der Sonne ausgesetzten Proben.

---

, . 209,2 ° 255,6 ° . , 209,2 ° , .

     

Isoparametric kinetic relations for chemical transformations in condensed substances (Analytical survey). II. Reactions involving the participation of solid substances

Various manifestations of the kinetic compensation effect are considered in reactions involving the participation of solid substances under isothermal and nonisothermal conditions, as well as manifestations of other isoparametric correlations. It is shown that isoparametric correlations can be used for the analysis of solid-phase reactions and the exclusion of artefacts in nonisothermal kinetics.

---

Zusammenfassung Verschiedene Erscheinungen des kinetischen Kompensationseffektes bei unter Beteiligung von festen Substanzen unter isothermen und nichtisothermen Bedingungen verlaufenden Reaktionen werden erörtert, ebenso Erscheinungen anderer isoparametrischer Korrelationen. Es wird gezeigt, daß isoparametrische Korrelationen zur Analyse von Festphasenreaktionen und zum Ausschluß von Artifakten in der nicht-isothermen Kinetik herangezogen werden können.

---

, , . .

     

Proof of the kinetic reaction mechanism of PVC degradation using TA

The possibility of describing the kinetics of thermal degradation of PVC samples under both isothermal and nonisothermal conditions with a unique model and using the same set of parameters was investigated. Analysis of the experimental data revealed good agreement at higher temperatures (above 175 °C) when the catalytic action of generated HCl and its distribution in the sample were considered. At lower reaction temperatures, further experimental conditions and/or sample characteristics must be considered, and a modification of the model is necessary.

---

Zusammenfassung Es wird die Möglichkeit untersucht, die Kinetik des thermischen Abbaus von PVC sowohl unter isothermen wie unter nichtisothermen Bedingungen durch ein einziges Modell und unter Verwendung des gleichen Parametersatzes zu beschreiben. Die Analyse der Messdaten zeigt gute Übereinstimmung bei hohen Temperaturen (über 175 °C), wenn die katalytische Aktivität des entwickelten HCL und seine Verteilung in der Probe berücksichtigt werden. Bei tieferen Temperaturen müssen weitere experimentelle Bedingungen und/oder Probeneigenschaften berücksichtigt werden, was eine Modifizierung des Modells erforderlich macht.

---

. ( 175°), . , .

     

Effect of inorganic salts on the process of competitive hydrogenation of 2-methyl-3-butene-2-ol and 2-phenylpropene on a platinum catalyst

The effect of inorganic salts (NaNO₃, NaCl, Na₂SO₄, NaHCO₃ and Na₃PO₄) on the selectivity of competitive hydrogenation of 2-methyl-3-butene-2-ol and 2-phenylpropene at 20 °C and atmospheric pressure on a 5%Pt/act. C catalyst in methanol solution was investigated. The dependence of the selectivity and of the initial rate of hydrogenation of the given equimolar mixture on the amount of sodium phosphate used in the modification of the platinum catalyst was measured.

---

(NaNO₃, NaCl, Na₂SO₄, NaHCO₃, Na₃PO₄) 2--3--2- 2- 20 °C 5% Pt . Na₃PO₄ .

     

Effect of dentate number of anchored phosphine ligands on the composition and catalytic properties of their palladium complexes

Mono-, di- and triphosphine ligands anchored by a Si–C bond to the surface of silica have been synthesized. Complexes of Pd(II) and Pd(O) with these ligands have been obtained. On the basis of elemental analysis and UV spectroscopy, structures of the complexes formed are suggested. The catalytic properties of the above complexes in the selective hydrogenation of cyclopentadiene are compared.

---

-, - , Si–C . Pd(II) Pd(O) . - . .

     

Effect of molybdenum catalysis on the perborate-bromide reaction. Kinetics and mechanism and some theoretical considerations

In the presence of molybdenum, both the uncatalyzed and the catalyzed reactions proceed simultaneously. An equation for k_cat was derived and the effect of temperature was described through a temperature function F(T) by the use of the Arrhenius-Eyring equation. A plausible mechanism is postulated and the theoretical background given for the analytical application of molybdenum.

---

. k_cat, -. .

     

Kinetic investigations of the formation of carbonate sodalite

The kinetics of sodium carbonate formation within a sodalite matrix by an intracage reaction of hydrothermally grown basic nitrite sodalite and carbon dioxide has been studied. This heterogeneous reaction inside the sodalite cages was followed in the 773 K–1153 K temperature interval by thermogravimetry, IR-spectroscopy, as well as X-ray powder diffraction. The weight uptake during heating and the increase of the unit cell volume has been discussed to describe the imbibition of CO₂ and the resulting intra-cage carbonate formation.

---

. 773–1153 , . CO₂, .

     

Effect of rare earth ions on the catalytic activity of Ln2MnNiO6 perovskites

Abstract A series of rare earth transition metal perovskites has been synthesized and the catalytic activity tested for 2-propanol decomposition. The effect of rare earth ions on the catalytic activity can been understood from the correlations obtained between the physico-chemical properties and the catalytic activity of the perovskites.

---

, , 2-. , - .

     

Possibilities of applying the Piloyan method of determination of decomposition activation energies in the differential thermal analysis of polynitroaromatic compounds and their derivatives

By means of non-isothermal DTA in its simple form the initial exotherm temperaturesT _D of 2,4-dinitrotoluene, 2,6-dinitrotoluene, 2,4,6-trinitrotoluene, 1,5-dinitronaphtalene, 1,8-dinitronaphthalene and 1,4,5,8-tetranitronaphthalene have been determined. By application of the Piloyan method to these measurements, the activation energiesE arising from the decompositions of these compounds were established. The results are discussed from the point of view of the molecular structures of the polynitro compounds.

---

Zusammenfassung Durch nicht-isotherme DTA in ihrer einfachen Form wurde der BeginnT _D der Exothermen von 2,4-Dinitrotoluol, 2,6-Dinitrotoluol, 2,4,6-Trinitrotoluol, 1,5-Dinitronaphthalin, 1,8-Dinitronaphthalin, 1,4,5-Trinitronaphthalin und 1,4,5,8-Tetranaphthalin bestimmt. Durch Anwendung der Methode von Piloyan auf diese Messungen wurden die aus der Zersetzung o.a. Verbindungen herrührenden AktivierungsenergienE spezifiziert. Die erhaltenen Ergebnisse werden unter dem Aspekt der Molekularstruktur der untersuchten Polynitroverbindungen erörtert.

---

Résumé On a déterminé par ATD les températures initialesT _D des phénomènes exothermiques du 2,4-dinitrotoluène, 2,6-dinitrotoluène, 2,4,6-trinitrotoluène, 1,5-dinitronaphtalène, 1,8-dinitronaphtalène, 1,4,5-trinitronaphtalène et 1,4,5,8-tétranitrophtalène. Les énergies d'activationE de la décomposition de ces composés ont été déterminées à l'aide de la mé thode de Piloyan. Les résultats obtenus sont discutés sous l'aspect de la structure moléculaire de ces composés.

---

T _D 2,4-, 2,6-, 2,4,6- , 1,5- 1,8- , 1,4,5- 1,4,5,8- . , E .

     

On stochastic models of solid-state reactions

The Avrami model of solid-state reactions or transformations has frequently been presented and compared with other stochastic models. The equation often applied is shown to be merely a simplification of the full Avrami model equation (FAME). A convenient procedure for application of the FAME to the kinetics of solid-state reactions is proposed.

---

Zusammenfassung Das Avrami'sche Modell von Festkörperreaktionen wurde häufig dargestellt und mit anderen stochastischen Modellen verglichen. Hier wird gezeigt, dass die häufig verwendete Gleichung eine Vereinfachung der Vollständigen Avrami'schen Modellgleichung (FAME) darstellt. Die Anwendung der FAME auf die Kinetik von Festkörperreaktionen wird vorgeschlagen und eine geeignete Verfahrensweise empfohlen.

---

, . , . , .

     

Temperature dependence of the X-ray induced adsorption of oxygen and methane on ZnO

The capacity of ZnO with respect to the photo- and X-ray adsorbed, as well as postadsorbed oxygen is shown to depend on the temperature. It is suggested that this dependence cannot be attributed to either the thermal annealing of the induced sites or the thermal desorption of the adsorbed molecules.

---

O , - , , , . , .

     

On the application of exponential kinetic equations

An exponential kinetic equation for complex chemical reactions in solid-liquid heterogeneous systems is discussed. The integral form of the equation is analyzed and the conditions specified for the application of an approximate form. The meaning of constant t₀ is explained.

---

, . . t₀.

     

Effect of medium composition on the monooxygenase activity of immobilized hemin in aniline oxidation

The effect of the composition of the reaction medium on the rate of aniline oxidation to p-aminophenol by hydrogen peroxide on hemin immobilized on -propylimidazole-modified silica has been studied. Organic solvent additives (alcohols, esters and nitriles) are shown to increase the reaction rate. The observed effect is attributed to the decrease of the medium dielectric constant.

---

- , , --. , (, , ) . .

     

Kinetics of the thermal decompositions of MC2O4 to MCO3 (M=Ca,Sr AND Ba)

The kinetics of the thermal decompositions of CaC₂O₄, SrC₂O₄ and BaC₂O₄ to their carbonates were studied by thermogravimetry at constant and at linearly increasing temperatures. Isothermally, the three oxalates decompose according to A_1.43, R_1.54 and R₁ laws, respectively. Dynamically, the decompositions of the first two oxalates proceed in a similar way as under the isothermal conditions, whereas BaC₂O₄ decomposes according to a different law.Kinetic compensation laws were established for the decomposition of CaC₂O₄ and SrC₂O₄ under both isothermal and non-isothermal conditions. Such a compensation law is considered to result if correct kinetic model functionsF () are used when the isothermal and non-isothermal decompositions are regulated by the sameF().

---

Zusammenfassung Die Kinetik der thermischen Zersetzung von CaC₂O₄, SrC₂O₄ und BaC₂O₄ zu den entsprechenden Carbonaten wurde durch Thermogravimetrie bei konstanter und linear ansteigender Temperatur untersucht. Isotherm werden die drei Oxalate entsprechend A_1.43, R_1.54 bzw. R₁ zersetzt. Dynamisch verläuft die Zersetzung der ersten zwei Oxalate auf ähnlichem Wege, während BaC₂O₄ nach einem davon verschiedenem Gesetz abgebaut wird. Kinetische Kompensationsgesetze wurden sowohl unter isothermen als auch unter nicht-isothermen Bedingungen für die Zersetzung von CaC₂O₄ und SrC₂O₄ ermittelt. Ein solches Kompensationsgesetz wird als Ergebnis eines solchen Vorgehens angesehen, bei dem richtige kinetische ModellfunktionenF() benutzt werden, wenn die nicht-isothermen Zersetzungen durch die gleichenF() bestimmt sind.

---

- , . , , A_1.43, R_1.54 · R₁- , . , . F() «» , F().

     

Rapid determination of vapor adsorption properties of ultramicroporous solids: An application to the zeolite affinity of adsorption

Adsorption capacities of zeolites are rapidly determined by a vapor sorption apparatus which can be used as an ultramicroporosimeter. From the sorption data, it is possible to calculate the zeolite affinities toward various adsorbates in comparison with water. The n-hexane affinity index of the new ZSM zeolites has values always higher than those of X, Y or Zeolon zeolites. This fact is attributed to the unusual framework structure of the silica-rich ZSM zeolites.

---

, . . - ZSM , X, Y . ZSM , .

---

---

Presented in part at the I⁰ Convegno nazionale di Catalisi-II⁰ Simposio Italo/Cecoslovacco di Catalisi, held in Bologna (Italy) on June 1979.     

Kinetic parameters of the thermal decompositions of nitritonickelates(II)

Kinetic parameters of thermal decomposition of compounds of general formulaM ₂ ^I M ^II[Ni(NO₂)₆], whereM ^I= K⁺, Rb⁺ or Cs⁺ andM ^II= Ca²⁺, Sr²⁺ or Ba²⁺, were investigated on the basis of the respective thermal curves. Calculations of the reaction order and activation energy carried out by the Coats-Redfern method and by Doyle's method (modified by Zsakó) gave similar results, The reaction order is 2 for all the compounds investigated. In the group of potassium salts the activation energy increases fromM ^II=Ca²⁺ toM ^II=Ba²⁺. In the groups of rubidium and caesium salts, the lowest activation energy is observed whenM ^II=Sr²⁺. Such behaviour of the nitritonickelates is explained in terms of structures and the principle of maximum density.

---

Zusammenfassung Die kinetischen Parameter der thermischen Zersetzung von Verbindungen der allgemeinen FormelM ₂ ^I M ^II [Ni(NO₂)₆] (M ^I= K⁺, Rb⁺ oder Cs⁺ und M^II = =Ca²⁺, Sr²⁺ oder Ba²⁺) wurden auf Grund der entsprechenden thermischen Kurven untersucht. Die an Hand der Coats-Redfern Methode und der durch Zsakó modifizierten Doyleschen Methode durchgeführten Berechnungen der Reaktionsordnung und der Aktivierungsenergie ergaben ähnliche Resultate. Die Reaktionsordnung ist 2 für sämtliche untersuchten Verbindungen. In der Gruppe der Kaliumsalze steigt die Aktivierungsenergie vonM ^II=Ca²⁺ in RichtungM ^II=Ba²⁺ an. In der Gruppe der Rubidium- und Caesiumsalze wird die niedrigste Aktivierungsenergie beiM ^II=Sr²⁺ beobachtet. Dieses Verhalten der Nitritonickelate wird durch die Strukturen und das Prinzip der maximalen Dichte erklärt.

---

₁ ^{2 II}[Ni(NO₂)₆], ^I= ⁺, Rb⁺Cs⁺,a ^II= ²⁺,8r²⁺²⁺. , - ( ), . 2. ^{+ 2+}. ^II=S²⁺. .