A method for the construction of kinetic graph determinants

A new approach for the deduction of kinetic equations based on graph theory is suggested.

---

, .

     

Kinetics of isotope exchange of dioxygen with a powdered high-temperature superconducting material Ba2YCu3O7?x

It has been found that the rate of isotope exchange in Ba₂YCu₃O_7–x–O₂ system is high. Its kinetics is exponential, first order with respect to dioxygen and the exchange is of the mixed first/third type.

---

Ba₂YCu₃O_7–x–O₂ . -, -, - .

     

DTA and chemical characteristics of YBa2Cu3O6.5+γ superconductor processing from different raw materials

The YBaCu=123 coprecipitates of carbonates (precipitated with Na₂CO₃ or Na₂CO₃-NaOH solution) and of oxalates (obtained in aqueous, partly aqueous and non-aqueous media) were investigated as concerns the yield and stoichiometry of the precipitates, including their transmission electron microscopy and DTA characteristics. Oxalates coprecipitated from acetate solutions in non-aqueous media provide fine samples with increased reactivity. For comparison, when thermally treated, an oxide ceramic mixture containing aged BaO (with some Ba(OH)₂ and BaO₂) exhibits increased reactivity due to the formation of a liquid phase in the temperature range 400–500°.

---

Zusammenfassung Gemeinsam gefällte Carbonate (aus Na₂CO₃- bzw. Na₂CO₃-NAOH-Lösung) und Oxalate (aus wässeriger, wässerig-akoholischer bzw. alkoholischer Lösung) von Y, Ba und Cu im Molverhältnis 123 wurden untersucht in Bezug auf die Ausbeute und Stöichiometrie der Fällungsprodukte, mittels Transmission-Elektronenmikroskopie und DTA. Durch Oxalatfällung aus Acetaten in nichtwässeriger Lösung wurden feinteilige Proben erhöhter Reaktivität erhalten. Zum Vergleich wurden oxidkeramische BaO-haltige Mischungen (die infolge Alterung durch Ba(OH)₂ und BaO₂ verunreinigt waren) thermisch behandelt und zeigten infolge Bildung einer flüssigen Phase im Temperaturbereich 400–500 °C ebenfalls erhöhte Reaktivität.

---

, , 1:2:3 Na₂CO₃ Na₂CO₃-NaOH, , , . , . . , ()_{2 2}, , 400–500°.

     

Methods for finding steady-state solutions of mathematical models for chemico-technological schemes

Gradient and Newton methods are suggested for searching for steady-state solutions of chemico-technological schemes to obtain synthetic fuels.

---

- .

     

Mass-spectrometric detection of an unstable product in silver-methanol interaction

The low pressure interaction of methanol vapors with a silver catalyst was studied by mass spectrometry. An unstable product contributing to m/e-15 was detected in this reaction. While yield of formaldehyde increased with addition of oxygen, the unstable product showed towards oxygen a reversed, decreasing trend.

---

- , m/e=15. , .

     

Thermal properties of the clathrate compounds of binary cyanides

The stoichiometry of thermal decomposition of a particular group of clathrate compounds, of the type Cd(en)Pd(CN)₄·2G, with the same coordination component but different clathrate-enclosed components, was investigated. Irrespective of the experimental conditions, the liberation of the enclosed component G always proceeded in one step. Thermal investigation of the decomposition stoichiometry under identical experimental conditions showed that the temperature intervals in which the enclosed components are given off shift to lower temperatures in the order C₆H₅OH=> C₆H₆ > > C₄H₅N > C₄H₄S. Diffraction measurements indicated a considerable change in the structures of the original clathrate compounds after thermal release of the enclosed componentG.

---

Zusammenfassung Die Stöchiometrie der thermischen Zersetzung einer bestimmten Gruppe von Klathratverbindungen vom Typ Cd(en)Pd(CN)₄·2G mit der gleichen Koordinationskomponente und verschiedenen Klathrat-Einschlußkomponenten wurde in dieser Studie untersucht. Ungeachtet der Versuchsbedingungen vollzieht sich die Freisetzung der eingeschlossenen KomponenteG stets in einer Stufe. Die unter gleichen Versuchsbedingungen durchgeführte thermische Untersuchung der Zersetzungsstöchiometrie zeigte, daß die Temperaturbereiche, in denen die eingeschlossenen Komponenten freigesetzt werden in der Reihenfolge C₆H₅OH > C₆H₆ > C₄H₅N > C₄H₄S in Richtung der niedrigeren Temperaturwerte verschoben werden. Die Diffraktionsmessungen weisen darauf hin, daß eine beträchtliche Änderung der Struktur der ursprünglichen Klathratverbindung nach thermischer Freisetzung der eingeschlossenen KomponenteG sichtbar wird.

---

Résumé Dans cette étude on a établi la stoechiométrie de la décomposition thermique d'un groupe particulier de clathrates du type Cd(en)Pd(CN)₄·2G, avec le même composant de coordination et différents composants occlus. Indépendamment des conditions d'expériences, la libération du composant occlusG s'effectue toujours en une étape. L'étude thermique de la stoechiométrie de la décomposition effectuée dans les mêmes conditions d'expériences, a montré que les intervalles des températures dans lesquels les composants occlus sont libérés, se déplacent vers les températures plus faibles dans l'ordre suivant: C₆H₅OH > C₆H₆ > > C₄H₅N > C₄H₄S. Les mesures de diffraction indiquent qu'après la libération thermique du composant occlusG, une variation considérable de la structure initiale des clathrates originaux apparaît.

---

Cd(en)Pd(CN)₄. 2G . , G . , , , ] ₆₅>₆₆>C₄H₆N>C₄H₄S. - , G.

     

On the catalytic system MgO?Na

Acid-base and radical properties of two sets of MgO–Na catalysts have been studied. The catalysts were prepared (I) by impregnation of MgO with NaOH in aqueous solution, and (II) by evaporation of metallic sodium onto a MgO surface. The catalyst prepared by the second method was much more basic than pure MgO (H_o=35) and showed a high activity in olefin isomerization.

---

- MgO–Na. 1) MgO (NaOH) 2) MgO. , , , MgO(H₀=35), .

     

Catalytic ammoxidation of coal

Ammoxidation of coal on oxide catalyts has shown the possibility of hydrocyanic acid formation at sufficiently low temperatures.

---

. .

     

Modification of Fe species in FeNaY zeolite by NaCl treatment

The treatment of Fe(III)NaY zeolite with NaCl solution does not lead to a back-exchange of ferric species but the cationic Fe rearranges into new complexes which are more deeply reduced by hydrogen and less self-reduced by vacuum heat treatment than the parent Fe species in FeNaY zeolite.

---

Fe(III)NaY NaCl . , Fe , , , Fe FeNaY.

     

A note on diffusion stabilized Pt/C oxidation catalysts: Absence of gas-liquid boundary deactivation results in relatively high efficiency (Pt/C oxidation catalysts; Part 6)

Deactivation of Pt/C aqueous phase oxidation catalysts may occur at the gas-liquid boundary. This feature explains the relatively high and stable activity of diffusion stabilized Pt/C catalysts in the oxidation of substrates with a low reactivity.

---

, Pt/C : . Pt/C, , .

     

Mechanism of alkyl iodide reduction to alkanes in aqueous solutions of Na2PtCl4?NaI?HClO4

Platinum(II) catalyzes the reduction of alkyl iodides to alkanes according to a mechanism involving oxidative addition of RI to Pt(II), reduction of the product complex RPt(IV) to RPt(II) by iodide ions and protolysis of the latter particle.

---

(II) , RI Pt^II, - RPt^IV RPt^II .

     

Thermal and photochemical stability of polystyrene and its blends with polyvinyl chloride

The influence of some irregularities in polystyrene (PS) and polyvinyl chloride (PVC) chains on their thermal stability was investigated. UV irradiation caused an increase in the content of these irregularities in the polymers. It was found that the presence of carbonyl groups and crosslinking of the polymer chains hamper the thermal dehydrochlorination of PVC and the total decomposition of both polymers. On the other hand, weak peroxy linkages (which facilitate degradation processes) and conjugated double bonds decrease the temperature of total decomposition of PS and PVC blends.

---

Zusammenfassung Es wurde der Einfluß von Unregmlmäßigkeiten in Polystyrol (PS)- und Polyvinylchlorid (PVC)-Ketten auf deren thermische Stabilität untersucht. UV-Bestrahlung verursacht ein Ansteigen des Gehaltes an Unregelmäßigkeiten in den Polymeren. Es wurde festgestellt, daß die Gegenwart von Carbonylgruppen und Querverbindungen der Polymerketten die thermische Dehydrochlorierung von PVC und eine vollständige Zersetzung beider Polymere verhindern. Andererseits senken Peroxidverknüpfungen (die die Degradierungsvorgänge erleichtern) und konjugierte Doppelbindungen die Temperatur für eine vollständige Zersetzung von PS und PVC Gemischen.

---

. - . , . , , , .

     

Binding energy of oxygen to the surface of promoted V?Mo?O catalysts for acrolein oxidation to acrylic acid

It has been established that P, Cs and Cu additives to V–Mo–O catalysts affect essentially both binding energy of surface oxygen and mobility of bulk oxygen.

---

P, Cs Cu V–Mo–O .

     

Electronic state of the active site of A V?P?O/SiO2 catalyst in oxidation of chlorine-containing hydrocarbons

V⁴⁺ ions in slightly associated states are supposed to play the role of V–P–O/SiO₂ active sites. V⁴⁺ ions are reduced to V³⁺ during deactivation of the V–P–O/SiO₂ catalyst.

---

V–P–O/SiO₂ V⁴⁺ . V–P–O/SiO₂ V⁴⁺ V³⁺.

     

Some aspects of mathematical statistics as applied to nonisothermal kinetics V

The paper gives a quantitative comparison of two methodological approaches to the solution of the inverse kinetic problem: the traditional approach and the nontraditional approach suggested by the authors. It is shown that the amount of information (in the sense of Shannon) obtained within the scope of the nontraditional approach is always greater than that obtained with the use of the traditional approach.

---

Zusammenfassung Zwei methodologische Näherungen der Lösung des inversen kinetischen Problems werden quantitativ verglichen, nämlich die traditionelle und die von den Autoren vorgeschlagene nicht-traditionelle Näherung. Es wird gezeigt, daß mit der nicht-traditionellen Näherung erhaltene (im Sinne von Shannon verstandene) Informationsmenge immer größer als die durch Anwending der traditionellen Näherung erhaltene ist.

---

: . , ( ), , , .

     

Silane-silanol condensation catalyzed by organotin compounds

The rate of condensation of H–SiR₂–(OSiR₂)_n–H (n=2, 3 or 4 and R=CH₃) and HO-SiRR–(OSiRR)₃–OH (R=C₆H₅) in xylene at 100 °C, catalyzed by dibutyltin diacetate, dilaurate and di-(2-ethyl)hexanoate, has been studied by infrared spectroscopy. The kinetic law is first order in each reactant and the reaction is accompanied by autocondensation of the silanol. The mecha nism involves complexation of the silanol with the catalyst, followed by the attack of a silane or silanol molecule.

---

H–SiR₂–(OSiR₂)_n–H ( n=2,3 4 R=CH₃) HO–SiRR–(OSiRR)₃–OH ( R=C₆H₅) 100° C, , -(2-) , . . .

     

Effect of pretreatment in benzene hydrogenation on Pt/nylon catalyst

Benzene hydrogenation on Pt/nylon catalyst produced cyclohexene and cyclohexane, in contrast to Pt/SiO₂ on which only cyclohexane was detected. Higher selectivity to cyclohexene was found at higher temperature and after air pretreatment. It is suggested that an oxidized platinum species is responsible for cyclohexene formation.

---

Pt/ , Pt/SiO₂, . . , .

     

ESR studies of photoinduced centers on weakly reduced anatase

The paramagnetic centers of reduced anatase (g₁=1.999, g₂=1.984, g₃=1.979) and (g₁=2.046, g₂=2.008), assigned to the stabilization of photoinduced holes near anion vacancies, have been studied. For the reduced oxide a new type of O₂ photoadsorption at h >1 eV due to the generation of only electron surface centers has been discovered.

---

, : (g₁=1,999, g₂=1,984, g₃=1,979) (g₁=2,046, g₂=2,008), . O₂ h>1 , .

     

A rapid method for catalyst testing. Zeolite catalysts for methanol conversion to hydrocarbon

A rapid method for testing catalysts is suggested, which permits a 30-fold reduction in the time of their examination. The method is recommended for studying catalytic processes taking place with either evolution or absorption of heat.

---

- , Qj 30 . , .