Phase equilibria in the Tl2Te-Ag2Te system

The phase diagram for the Tl₂Te-Ag₂Te system has been established by thermal analysis and X-ray diffraction methods. The results obtained are compared with the data of other authors. Examples are given of using the disadvantages of thermal analysis for the correct interpretation of experimental data.

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Zusammenfassung Das Phasendiagramm von Tl₂Te-Ag₂Te wurde durch thermische Analyse und röntgendiffraktometrie ermittelt. Die erhaltenen Ergebnisse werden mit denen anderer Autoren verglichen. Beispiele werden angeführt, wie die Nachteile der thermischen Analyse zur korrekten Interpretation der experimentellen Daten benutzt werden können.

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Tl₂Te-Ag₂Te. . .

     

Sintering of supported palladium

Sintering results of Pd supported on carbon black at 723–973 K, in water vapor, in H₂ and under high vacuum are reported. They are compared with sintering data of Pd on other supports. The observed sequences are: SiO₂C>sepioliteAl₂O₃>AlPO₄ and H₂O>high vacuum>H₂.

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Pd 723–973 , , H₂ . Pd . : SiO₂Al₂O₃>AlPO₄ H₂O> >H₂.

     

X-ray studies of interaction between magnesium chloride and ethyl benzoate, components of the catalyst for propylene polymerization

X-ray studies of the interaction between highly dispersed magnesium dichloride and ethyl benzoate (EB) at different molar ratios EB/MgCl₂, and the effect of their grinding indicate that a new compound of MgCl₂ and EB is formed. Grinding destroys the crystal phase of the new compound, thus increasing the activity and stereospecificity of the catalyst obtained.

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() /MgCl₂, . , MgCl₂. , .

     

Determination of reaction kinetic parameters from variable temperature DSC or DTA

An equation is derived for evaluating the kinetic parameters of a transformation from variable temperature DSC or DTA, taking account of the variation in the reaction rate constant with time and temperature. Kinetic parameters for the crystallization of a ZrF₄-BaF₂-LaF₃ glass are calculated using this equation.

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Zusammenfassung Es wird eine Gleichung zur Bestimmung der kinetischen Parameter einer Umwandlung aus DSC- und DTA-Messungen bei variabler Temperatur abgeleitet, die den Veränderungen der Reaktionsgeschwindigkeit mit der Zeit und der Temperatur Rechnung trägt. Kinetische Parameter der Kristallisation von ZrF₄-BaF₂-LaF₃-Glas werden unter Benutzung dieser Gleichung berechnet.

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, , . , ZrF₄-BaF₂-LaF₃.

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This work was carried out under a grant from the National Aeronautics and Space Administration, Materials Processing in Space Program.     

Effect of bond energies of a catalyst with reacting atoms on the selectivity of CO hydrogenation over metals

In hydrogenation over metals (M)_j carbon monoxide is adsorbed as a molecule. C–O bond rupture in partially hydrogenated complex, MCHOH, leads to MO and MCH₂ and then to hydrocarbons, while transformation of MCHOH into MCH₂OH gives alcohols and other oxygen-containing compounds. Selectivity towards hydrocarbons increases with increasing energy of M–O bonds.

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(M) . C–O MCHOH MO MCH₂ — ; MCHOH MCH₂OH . M–O.

     

Kinetic analysis of thermogravimetric data XIX. Study of the thermal decomposition of some hexathiocyanatochromates

Ammonium and metal salts of the acid H₃[Cr(NCS)₆] have been obtained and characterized. Their thermal decomposition has been studied with a derivatograph. The thermal decomposition of the ammonium salts begins with an endothermic stage, leading to the formation of the intermediate Cr(NCS)₃, which in exothermic processes finally yields Cr₂O₃. The decomposition of the metal salts is exothermal and the polarizing effect of the cation plays an important part in this. Kinetic parameters have been derived by means of the nomogram method.

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Zusammenfassung Ammonium- und Metallsalze der Säure H₃[Cr(NCS)₆] wurden hergestellt und charakterisiert. Ihre thermische Zersetzung wurde mit einem Derivatographen verfolgt. Sie beginnt beiden Ammoniumsalzen mit einer endothermen Phase, welche zur Bildung des Zwischenprodukts Cr(NCS)₃ führt, das in exothermen Vorgängen als Endprodukt Cr₂O₃ ergibt. Die Zersetzung der Metallsalze ist exotherm und der Polarisationseffekt des Kations spielt hierbei eine wichtige Rolle. Kinetische Parameter wurden nach der Nomogramm-Methode abgeleitet.

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H₃[Cr(NCS)₆]. . , Cr(NCS)₆, ₂₃. .

     

Discrimination of active sites for ethylene homologation and ethylene metathesis on molybdena silica catalyst

Active sites for ethylene homologation (3C₂H₄2C₃H₆) and ethylene metathesis (C₂H₄–¹²C₂+C₂H₄–¹³C₂2C₂H₄–¹³C₁) were discriminated by adding platinum to a reduced molybdena silica catalyst, and the former was presumed to be composed of several molybdenum species, while the latter was presumed to be composed of one molybdenum species.

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(3C₂H₄2C₃H₆) (C₂H₄–¹²C₂+C₂H₄–¹³C₂2C₂H₄–¹³C₁) . , , .

     

Determination of hydroxyl groups and/or water on the surface of oxide catalysts by a pulse chromatographic method

A pulse chromatographic method based on the reaction of gaseous dimethylzinc tetrahydrofura nate was developed for the determination of surface hydroxyl groups and/or adsorbed water in solid porous materials. The procedure is rapid and gives results comparable to other methods. Some heterogeneous catalysts and supports have been analyzed.

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, , / , . , . .

     

Chemiluminescent method to measure generation rates of active centers in reaction of hydrogen peroxide with hemin and pyridinehemichrome

A chemiluminescent method was used to measure generation rates of active intermediates in the interaction of hemin with hydrogen peroxide with and without pyridine at pH=8–9. The effect of various inhibitors in these two cases has been examined.

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pH=8+9. .

     

Variations in electronic state of silver catalysts for methanol oxidation

Variations in the electronic state of silver catalysts for methanol oxidation under the effect of the reaction medium have been studied, using diffuse reflectance spectroscopy. The nature of active centers-Ag⁺ cations, Ag _n ⁺ complexes and clusters of various sizes for bulk and supported catalysts are shown to be identical.

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. - Ag⁺, Ag _n ⁺ .

     

Preparation of catalysts by spray decomposition

Spray decomposition of solutions is an uncommon but very promising technique for the preparation of multicomponent solid systems with welldefined structure. The experimental arrangement is described and a summary of the systems prepared until now is given. These are MgO–ZnO, CaO, CdO, Al₂O₃. Fe₂O₃ solid solutions and CdO. CdSO₄ and Al₂O₃. Al₂(SO₄)₃ systems.

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, , . : MgO·ZnO, CaO·CdO,. Al₂O₃·Fe₂O₃ CdO·CdSO₄ Al₂O₃·Al₂ (SO₄)₃.

     

A thermal X-RAY and resistivity study of the heusler alloy Cu2NiSn

The compound Cu₂NiSn was analyzed by DTA, X-ray and electrical resistivity measurements. No single-phase structure was found at room temperature. The alloy decomposes upon heating, starting at 160°, forming copper and two hcp structures. At 500° the Heusler structure is restored. Electrical resistivity results are discussed in terms of Markowitz's theory for disordered metals.

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Zusammenfassung Die Verbindung Cu₂NiSn wurde durch DTA, Röntgen- und elektrische Widerstandsmessungen analysiert. Keine Einphasenstruktur wurde bei Zimmertemperatur gefunden. Die Legierung zersetzt sich beim Erhitzen ab 160°, wobei Kupfer und zwei hcp-Strukturen gebildet werden. Bei 500° wird die Heusler-Struktur wieder hergestellt. Die Ergebnisse der elektrischen Widerstandsmessungen werden aufgrund der Markowitzschen Theorie für ungeordnete Metalle diskutiert.

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Résumé Le composé Cu₂NiSn a été examiné par ATD, rayons X et mesures de résistance électrique. A température ambiante on n'a pas trouvé de structure correspondant à une phase unique. L'alliage se décompose par chauffage à partir de 160° en formant du cuivre et deux structures hcp. A 500° la structure Heusler est rétablie. On discute les résultats des mesures de résistance électrique à partir de la théorie de Markowitz pour des métaux désordonnés.

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Cu₂NiSn , . . , 160° . 500° . a .

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Work supported in part by Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq) and Financiadora de Estudos e Projetos (FINEP).     

Study of the thermal decomposition of solids in a fluidized bed, III

The influence of the air humidity upon the thermal decomposition of diammonium hydrogen phosphate was studied in a fluidized bed, under isothermal conditions. It was found that the increase of the decomposition rate is influenced directly by the partial pressure of the water vapour in the air, and indirectly by the working temperature. The moisture effect is explained by the salt hydrolysis in the water condensed on the grain surface. The energy of activation of the thermal decomposition decreases when the air humidity increases.

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Zusammenfassung Der Einfluß der Luftfeuchtigkeit auf die thermische Zersetzung des Diammoniumhydrogenphosphats wurde in fluidisiertem Bett unter isothermen Verhältnissen studiert. Die Zunahme der Zersetzungsgeschwindigkeit war direkt proportional dem partialen Wasserdampfdruck in der Luft und indirekt proportional der Arbeitstemperatur. Diese Wirkung wird durch Salzhydrolyse in dem kondensierten Wasser an der Kernoberfläche erklärt. Die Aktivierungsenergie der thermischen Zersetzung nimmt mit zunehmendem Feuchtigkeitsgehalt ab.

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Résumé On a étudié l'influence de l'humidité atmosphérique sur la décomposition thermique de (NH₄)₂HPO₄ en lit fluidisé, en conditions isothermes. La pression partielle de la vapeur d'eau dans l'air intervient directement sur l'augmentation de la vitesse de décomposition et exerce une action indirecte sur la température de travail. On a expliqué l'effet de l'humidité par l'hydrolyse du sel dans l'eau condensée à la surface des grains. La valeur de l'énergie d'activation de la décomposition thermique diminue quand l'humidité atmosphérique augmente.

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. , , , , . , .

     

Some peculiarities in ESR spectra of titanium complexes in catalysts for isoprene polymerization in excess A1R3

It has been established that at low temperatures of TiCl₄+AOC catalyst preparation in solution (with Ti/Al1/15), ESR spectra exhibit rhombic anisotropy of the g-factor. Experiments with the sample having 61 % concentration of⁴⁷Ti isotopes suggest the formation of associates of Ti³⁺ with magnetic ordering, apparently due to the Jahn-Teller cooperative effect.

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TiCl₄+ AOC ( Ti/Al1/15) g-. ⁴⁷Ti (61%) Ti³⁺ , , -.

     

Influence of Pr ions on the properties of Pd/SiO2 and Pt/SiO2 catalysts in oxidation of n-butane

It has been established that (M_VIII+Pr)/SiO₂ catalysts (M_VIII=Pd or Pt) obtained from organometallic precursors, have increased the dispersity of Pt, but their TN in deep oxidation of n-butane is by 3–6 times lower than that of unmodified M_VIII/SiO₂.

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(M_VIII+Pr)/SiO₂ ( M_VIII=Pd, Pt), , Pt, 3–6 - M_VIII/SiO₂.

     

Heterogeneous reactions of solid nickel(II) complexes, IV

The decomposition heats (H) for complexes of the type Ni(NCS)₂L₂ were studied by means of a differential scanning calorimeter. From the decreasing values ofH the following order has been established:a) for pseudooctahedral complexes: py >-pic > > Q; andb) for square-planar complexes: 2,6-lut > Q >-pic. The results obtained are compared with the data from the TG, DTG, and DTA curves.

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Zusammenfassung Es erfolgte die Bestimmung der Zersetzungswärmen (H) der Komplexe vom Typ Ni(NCS)₂L₂ durch die Differential Scanning Calorimetrie. Mit abnehmendenH Werten ergab sich die Reihenfolge:a) Pseudooktaedrische Komplexe: Py >ß-Pic > Q;b) Quadratische Komplexe: 2,6-Lut. > Q >-Pic. Ergebnisse mit aus den DTA, TG und DTG-Kurven gewonnenen Resultaten wurden verglichen.

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Résumé Détermination par analyse enthalpique différentielle des chaleurs de décomposition (H) des complexes de formule générale Ni(SCN)₂L₂. Le classement des valeurs deH par ordre décroissant montre que pour les complexes pseudo-octaédriques py >gb-pic > Q et que pour les complexes plans carrés lut-2,6 > Q >-pic. Comparaison de ces résultats avec les données des courbes TG, TGD et ATD.

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(H) Ni(NCS)₂L₂. H : ) >-pic > Q; ) 2,6 lut > Q >-Pic. , , .

     

Effect of the state of vanadium cations on the IR spectra of adsorbed carbon monoxide

ESR and IR-spectrosocpic studies of the effect of the state of vanadium ions on the IR-spectra of adsorbed CO have revealed complex formation of CO with V⁴⁺ (vCO at 2192 and 2205 cm^–1) and V³⁺ (vCO at 2178 and 2185 cm^–1) ions.

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-- - CO. CO V⁴⁺ (vCO 2192, 2205 cm^–1) V³⁺ (vCO 2178, 2185 cm^–1).

     

Multiple rate resonance phenomena in the forced composition cycling of the Fischer-Tropsch synthesis over a supported cobalt oxide catalyst

Experimental investigation of hydrocarbon synthesis from a mixture of CO and H₂ over a supported cobalt oxide catalyst showed pronounced resonance of the rate of formation of individual hydrocarbons with respect to the frequency of the feed compositon changes. When the measured concentrations of the synthesis products are time-averaged, the mean rate of formation for methane increases fivefold when compared with rate at the mean composition of the feed at steady state for a cycling frequency of 0.017 c/s. Another maximum occurs at about 0.00056 c/s, where the mean rate is about twice the steady-state rate. Rate resonance was also observed for higher hydrocarbons at similar frequencies but with smaller time-average rates. Resonance of rates of reaction has been observed for other catalysts, but rarely with multiple peaks and with such large magnitudes of the rate change.

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CO H₂ . , 0,017 /. 0,00056 /, . , , . , .