Effect of vanadium content on the character of acidic sites on V2O5/Al2O3 catalysts

By IR spectroscopy and TPD the effect of vanadium content on the relative proportion of strongly acidic sites of V₂O₅/Al₂O₃ catalyst was studied.

---

- - V₂O₅/Al₂O₃.

     

Spectroscopic studies of the state of Cu2+ ions in Cu?Zn?Al oxide catalysts

ESR and electronic spectroscopy have reveled that in low-temperature ZnO the copper ions form Cu–O–Cu type cluster structures with highly covalent bonds and strong exchange interaction between the ions. The nearer environment of the Cu²⁺ ions is an octahedron with distortion towards square planar coordination.

---

, ZnO Cu–O–Cu . Cu²⁺- , .

     

High temperature thermal decomposition of propane

The thermal decomposition of propane has been studied by pulse chromatographic method within the temperature range of 975–1083 K. The kinetic parameters of the reaction have been determined.

---

- 975–1083 . .

     

Thermoanalytical investigations on lithium stearate,lithium 12-hydroxystearate and related greases

TG and DSC techniques proved useful in the study of the thermal properties of lithium stearate, lithium 12-hydroxystearate and related greases. Under an inert atmosphere, the stearates decompose into the oxalate prior to the formation of the carbonate. For the related greases, oil degradation-volatilization shows a discontinuity under ambient conditions, because of oxidation and carboxylic acid formation. The atmosphere and the concentration of the soap affect the chemical kinetics of thermal decomposition of the stearates and the greases.

---

Zusammenfassung TG- und DSC-Techniken haben sich als nützlich für die Untersuchung der thermischen Eigenschaften von Lithiumstearat, Lithium-12-hydroxystearat und der entsprechenden Schmierfette erwiesen. In inerter Atmosphäre zersetzen sich die Stearate über Oxalate als Zwischenprodukt zu Carbonaten. Under Umgebungsbedingungen verläuft die Ölzersetzung-Verflüchtigung der entsprechenden Schmierfette wegen der Oxydation und der Bildung von Carboxylsäure diskontinuierlich. Atmosphäre und Konzentration der Seife beeinflussen die Kinetik der thermischen Zersetzung der Stearate und der entsprechenden Schmierfette.

---

, 12- . , . , . .

     

Das System KNbO3-Nb2O5

Zusammenfassung Das System KNbO₃–Nb₂O₅ wurde mit thermoanalytischen, dilatometrischen und röntgenographischen Methoden neu untersucht. Acht ternäre Verbindungen werden im Bereich von 0–50 Mol-% K₂O gefunden. Nur K₄Nb₆O₁₇ schmilzt kongruent, alle anderen zersetzen sich peritektisch. Bei den beiden niobreichaten ternären Verbindungen handelt es sich um Hochtemperaturphasen, die sich erst oberhalb 1273 bzw. 1551 K bilden. Drei der acht Verbindungen wandeln sich mit steigender Temperatur in ihre Hochtemperaturmodifikation um.

---

The KNbO₃-Nb₂O₅ system was studied by thermal analysis, dilatometry and X-ray techniques. Eight ternary compounds were found in the range from 0 to 50 mol% K₂O. Only K₄Nb₆O₇ was found to melt congruently, the other compounds decomposed peritectically. For the two ternary compounds with the highest percentage of niobium high-temperature phases were observed which were formed only above 1273 and 1551°, respectively. Three of the compounds studied transformed into their high temperature modifications on heating.

---

, $ KN₃-Nb₂O₅. 0 50 % . , K₄Nb₆O₇ , $ . $ $ 1273 1551°. $ $ .

     

Thermochemical studies on the systems ACl/CeCl3 (A=Na-Cs)

The pseudobinary systems ACl/CeCl₃ (A=Na-Cs) were reinvestigated by means of DTA. The following compounds were found and identified through their X-ray patterns (primarily detected compounds in italics):NaCe _1.67 Cl ₆; K₃CeCl₆, K₂CeCl₅,KCe _1.67 Cl ₆;Rb ₃ CeCl ₆, Rb₂CeCl₅,RbCe ₂ Cl ₇; Cs₃CeCl₆, Cs₂CeCl₅,CsCe ₂ Cl ₇. The compounds A₂CeCl₅ crystallize with the K₂PrCl₅ structure. The high-temperature modifications of the compounds A₃CeCl₆ have the cubic elpasolite structure. The hexagonal unit cell of KCe_1.67Cl₆ is related to the CeCl₃ structure: 0.33 Ce³⁺ are substituted by one K^s+. The structure of CsCe₂Cl₇ can be described with a hexagonal subcellZ=4,a=9.72 andc=14.94 Å; however, small superstructure reflexions reduce the symmetry.The thermodynamic functions for the reactionsnACl+CeCl₃=A _n CeCl _n+3(A=K, Rb) were determined by means of e.m.f. measurements.Measurements of the e.m.f.E vs. T yielded the Gibbs enthalpiesG ^r . The temperature-dependence was found to be linear.The most important result is the formation of the elpasolites (A₃CeCl₆) and ACe₂Cl₇.

---

Zusammenfassung Die pseudobinären Systeme ACl/CeCl₃ (A=Na-Cs) wurden mittels Differenzthermoanalyse (DTA) neu untersucht. Folgende Verbindungen wurden gefunden und durch ihre Röntgenbeugungsmuster charakterisiert (erstmalig nachgewiesene Verbindungen sind kursiv):NaCe _1.67 Cl ₆; K₃CeCl₆, K₂CeCl₅,KCe _1.67 Cl ₆;Rb ₃ CeCl ₆, Rb₂CeCl₅,RbCe ₂ Cl ₇; Cs₃CeCl₆, Cs₂CeCl₅,CsCe ₂ Cl ₇. Die Verbindungen A₂CeCl₅ kristallisieren im K₂PrCl₅-Typ. Die Hochtemperaturmodifikationen der Verbindungen A₃CeCl₆ liegen in der kubischen Elpasolith-Struktur vor. Die hexagonale Elementarzelle des KCe_1.67Cl₆ ist mit der CeCl₃-Struktur verwandt: 0,33 Ce³⁺ sind durch ein K⁺ ersetzt. Die Struktur des CsCe₂Cl₇ kann mit einer hexagonalen Pseudozelle beschrieben werden:a=9,72;c=14,94Å;Z=4; schwache Überstrukturreflexe reduzieren jedoch die Symmetrie. Die thermodynamischen Funktionen für die Reaktionen:n ACl + CeCl₃=A _n CeCl _n+3 (A=K, Rb) wurden durch EMK-Messungen bestimmt. Messungen der Abhängigkeit von e. m. f.E gegenT ergaben die Gibbs-EnthalpienG ^r . Es wurde eine lineare Temperaturabhängigkeit gefunden. Als wichtigstes Resultat ist die Bildung von Elpasoliten (A₃CeCl₆) und von Verbindungen (ACe₂Cl₇) anzusehen.

---

ACl/CeCl₃, A . - ( ):NaCe _1.67 Cl ₆; K₃CeCl₆, K₂CeCl₅,KCe _1.67 Cl ₆;Rb ₃ CeCl ₆, Rb₂CeCl₅,RbCe ₂ Cl ₇; Cs₃CeCl₆, Cs₂CeCl₅ CsCe ₂Cl₇. A₂CeCl₅ K₂PrCl₅. A₃CeCl₆ . KCe_1.67Cl₆ CeCl₃, 0,33 Ce³⁺ . CsCe₂Cl₇ a=9,72 Å,c=14,94 Å Z=4. , . n ACl + CeCl₃=A _n CeCl _n+3(A=K, Rb) . . . . . .E , G ^r . ACe₂Cl₇.

---

---

Presented as a poster at the 8th ICTA, Bratislava, 1985.

---

This work was supported by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie.     

On theC v toC p conversion for solid linear macromolecules

TheC _v toC _p conversion for solid linear macromolecules via the Nernst-Lindemann equationC _p -C _v =A ₀,C _p ² T/T_m is discussed on hand of data for 10 crystals and seven glasses. An average value ofA ₀=(5.11±2.41) · 10^–3 mol K J^–1 was calculated if the mole is assumed to refer to heavy atoms only. ThisA ₀ is numerically equal to the original Nernst—Lindemann constant.

---

Zusammenfassung An Hand von sich auf 10 Kristalle und 7 Gläser beziehenden Daten wird die Umrechnung vonC _v -inC _p -Werte für feste lineare Makromoleküle mittels der Nernst-Lindemann-GleichungC _p -C _v =A ₀ C _p ² T/T _m diskutiert. Ein Durchschnittswert vonA ₀=(5.11±2.41) · 10^–3 mol K J^–1 wurde unter der Annahme berechnet, daß sich das Mol nur auf schwere Atome bezieht. DieserA ₀-Wert ist numerisch gleich der ursprünglichen Nerns-Lindemann-Konstanten.

---

10 , - C _v C _p , —C _p –C _v = _{0 p} ² / . , , ₀ (5.11±2.41) · 10^–3 · ^–1. ₀ — .

---

---

Support by the National Science Foundation, Polymers Program (Grant No. DMR 83-17097) is gratefully acknowledged.     

Studies on thermal stability and knot formation in the TG curves of Co(III) model complexes

TG studies of vitamin B₁₂ coenzyme model complexes, BrCo(diacetylmonoximeiminatodiacetylmonoximatoiminobenzene-1,6)L have been carried out with different heating rates and sample sizes. The trans ligand, L, is bromine, imidazole, methylimidazole, pyridine or triphenylphosphine. The decompositions of the complexes (except for the triphenylphosphine complex) are associated with the formation of a knot at the point of completion of the inflection of the TG curve at a heating rate of 20 deg/min; such a phenomenon is not observed for rates of 10 and 5 deg/min. The formation of a knot with increase in weight and decrease in temperature is attributed to the transition from high-energy six-coordinate Co(III) species to low-energy five-coordinate Co (II) species. The triphenylphosphine complex is found to deviate from these characteristics of decomposition.

---

Zusammenfassung TG-Untersuchungen von Vitamin-B₁₂-Coenzymkomplexen — BrCo (Diacetylmonoxim-iminato-diacetylmonoximato-iminobenzol-1,6)L wurden bei verschiedenen Aufheizgeschwindigkeiten und mit unterschiedlichen Probenmengen ausgeführt. Der trans-Ligand L ist mit Brom, Imidazol, Methylimidazol, Pyridin bzw. Triphenylphosphin modifiziert. Mit Ausnahme des Triphenylphosphinkomplexes geht die Zersetzung der Komplexe bei einer Aufheizgeschwindigkeit von 20 °/min mit der Ausbildung einer Schleife an der Stelle des TG Kurve einher, an der die Inflektion beendet ist. Solch ein Effekt ist nicht bei Aufheizgeschwindigkeiten von 10 und 5 °/min zu beobachten. Das eten einer Schleife mit zunehmenden Gewicht und abnehmender Temperatur ist der Umwandlung von 6-fach koordinierten Co(III)-Species hoher Energie in 5-fach koordinierte Co (II) -Species niedriger Energie zuzuschreiben. Der Triphenylphosphinkomplex weicht von dieser Zersetzungscharakteristik ab.

---

- ₁₂, r(- - -- -1,6)L, . - L , , , . , , 20°/. 10 5°/. () ((II) . , .

---

---

The author acknowledges the help of Mr. V. Alexander, who provided gift coenzyme model complex samples.     

Thermal behaviour of some new hydrazinium fluorometallates

Three new hydrazinium(1+) fluoro complexes, N₂H₅AsF₆, (N₂H₅)₂ZrF₆ and (N₂H₅)₂HfF₆, were prepared and characterized by means of chemical analysis, IR and Raman spectroscopy and X-ray powder diffraction. Study of their thermal behaviour via TG, DTG and DTA measurements showed that they decompose in stages; the decomposition of N₂H₅AsF₆ proceeded in two steps, through the intermediate NH₄AsF₆; (N₂H₅)₂ZrF₆. Decomposed in three steps, through (NH₄)₂ZrF₆ and NH₄ZrF₅. The thermal decomposition of (N₂H₅)₂HfF₆ is more complex; in the first step (NH₄)₂HfF₆ with some N₂H₅HfF₅ was obtained, and in the second NH₄HfF₅. The intermediates were identified by means of chemical analysis and vibrational spectroscopy.

---

Zusammenfassung Die Hydrazinium(1+)-fluorokomplexe N₂H₅AsF₆, (N₂H₅)₂ZrF₆ und (N₂H₅)₂HfF₆ wurden dargestellt und durch chemische Analyse, IR- und Ramanspektren sowie Röntgenbeugungsdiagramme charakterisiert. Die Untersuchung ihres thermischen Verhaltens durch simultane TG-DTG-DTA-Messungen zeigte, dass sie sich schrittweise zersetzen: N₂H₅AsF₆ zersetzt sich in 2 Stufen mit NH₄AsF₆ als Zwischenprodukt; (N₂H₅)₂ZrF₆ zersetzt sich in 3 Stufen über (NH₄)₂ZrF₆ und NH₄ZrF₅. Die thermische Zersetzung von (N₂H₅)₂HfF₆ ist komplizierter, der erste Schritt liefert (NH₄)₂HfF₆ mit wenig N₂H₅HfF₅, der zweite NH₄HfF₅. Die Zwischenprodukte wurden durch chemische Analyse und Schwingungsspektroskopie identifiziert.

---

N₂H₅AsF₆, (N₂H₅)₂ZrF₆ (N₂H₅)₂HfF₆, - , ., , . , N₂H₅AsF₆ NH₄AsF₆, (N₂H₅)₂ZrF₆ — (NH₄)₂ZrF₆ NH₄ZrF₅. (N₂H₅)₂HfF₆ : (NH₄)₂HfF₆ N₂H₅HfF₅, NH₄HfF₅. .

---

---

We thank Miss B. Sedej for chemical analysis. The work was financed through the Research Community of Slovenia.     

The thermal analysis of “argentic oxynitrate” and silver oxides

The precise stoichiometry of argentic oxynitrate has been elucidated by analytical and thermal analytical techniques. A decomposition path of the oxynitrate has been proposed and values of the enthalpy changes obtained. TG has been used as the criterion of purity of silver(II) oxide and new values for the heat of formation of silver(I) and silver(II) oxide are reported.

---

Zusammenfassung Die genaue Stöchiometrie des Silberoxynitrats wurde durch analytische und thermoanalytische Prüfung geklärt. Der Zersetzungsvorgang des Oxynitrats wurde verfolgt und die Enthalpieänderungen beobachtet. Die Reinheit von Silber(II)oxyd läßt sich thermogravimetrisch kontrollieren. Es wurden neue Werte für die Bildungswärmen des Silber(II)oxyds und Silber(I)oxyds gefunden.

---

Résumé Etude de la stoechiométrie précise de l'oxynitrate argentique par les techniques analytiques et thermoanalytiques. On propose un schéma de décomposition de l'oxynitrate et l'on évalue les variations d'enthalpie. Emploi de la TG comme critère de pureté de l'oxyde d'argent(II). Communication de nouvelles valeurs pour les chaleurs de formation des oxydes d'argent (I) et d'argent (II).

---

. . (II) . (I) (II).

---

---

The authors wish to thank Mr. J. McEwan and Mrs. I. M. Walker for valuable practical assistance and the United Kingdom Atomic Energy Authority for financial support.     

Thermoanalytical studies of substances liberating aggressive gases

A modification to the derivatograph has been designed that allows thermoanalytical investigations of chemical compounds, including sulphides and acids, that evolve aggressive gases such as CO, SO₂, S, etc. during warming. Application of this modification is exemplified by studies on the thermal dehydrogenation of titanium hydride (TiH_1.85) and on the interaction of rhenium disulphide (ReS₂) with concentrated sulphuric acid.

---

Zusammenfassung Es wird über die Modifizierung eines Derivatografen berichtet, die die Thermoanalyse von Stoffen ermöglicht, die wie z. B. Sulfide oder Säuren beim Erhitzen aggressive Gase wie z. B. CO, SO₂, S usw. freisetzen. Als Beispiel für die Anwendung dieser Modifizierung dienten Untersuchungen der thermischen Dehydrogenierung von Titanhydrid (TiH_1.85) und des Einwirkens von konzentrierter Schwefelsäure auf Rheniumsulfid (ReS₂).

---

, , , , , SO₂, S . . 2- , - (³_1,85) (ReS₂) (H₂SO₄).

---

---

Presented as a poster at ESTAC-4, Jena, GDR, 1987.     

Synthesis of Δα,β-butenolides by oxidative dehydrocarboxylation of paraconic acids

Conclusions A new method is proposed for the synthesis of -alkyl-,-butenolides by oxidative dehydrocarboxylation of -alkylparaconic acids by the S₂O₈ ^2–-AgNO₃-CuSO₄ system.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No.1, pp.117–120, January, 1976.     

Crystal structure of the synthetic analog of radtkeite Hg<Subscript>3</Subscript>S<Subscript>2</Subscript>Cl<Subscript>1.00</Subscript>I<Subscript>1.00</Subscript>

The results of structural studies of the synthetic analog of the radtkeite mineral Hg₃S₂Cl_1.00I_1.00 are analyzed. The crystal structure of the compound has been refined; the unit cell parameters are a _m = 16.827(4) , b _m = 9.117(1) , c _m = 13.165(5) , = 130.17(2)°, V = 1543.3(8) ³, space group C2/m, Z = 8, R = 0.0527. A possible transition a ₀ = a _m; b ₀ = a _m + 2c _m; c ₀ = –b _m to the pseudo-orthorhombic F cell previously determined for radtkeite, where one of the angles ( ₀ ) is slightly different from 90° (89.55°), has been found. Each sulfur atom in the structure is bonded to three mercury atoms, forming SHg₃ umbrellas with distances 2.240(6) –2.474(8) and angles HgSHg 94.7(2)°–102.9(2)°. The SHg₃ fragments are linked through Hg vertices to form corrugated [Hg₁₂S₈] layers. The halogen atoms lie inside and between the [Hg₁₂S₈] layers; the distances are Hg-Cl and Hg-I 2.783(7) , 2.961(7) , and 3.083(4) –3.311(3) , respectively.Original Russian Text Copyright © 2004 by N. V. Pervukhina, S. V. Borisov, S. A. Magarill, D. Yu. Naumov, V. I. Vasiliev, and B. G. NenashevTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 4, pp. 755–758, July–August, 2004.This revised version was published online in April 2005 with a corrected cover date.     

Kinetic and mechanistic studies on the interaction of thymidine with the hydroxopentaaquarhodium(III) ion

The interaction of thymidine, a nucleoside, with hydroxopentaaquarhodium(III), [Rh(H₂O)₅(OH)]²⁺ ion in aqueous medium is reported and the possible mode of binding is discussed. The kinetics of interaction between thymidine and [Rh(H₂O)₅OH]²⁺ has been studied spectrophotometrically as a function of [Rh(H₂O)₅OH²⁺], [thymidine], pH and temperature. The reaction has been monitored at 298 nm, the _max of the substituted complex, and where the spectral difference between the reactant and product is a maximum. The reaction rate increases with [thymidine] and reaches a limiting value at a higher ligand concentration. From the experimental findings an associative interchange mechanism for the substitution process is suggested. The activation parameters (H=47.8 ± 5.7 kJ mol^–1, S=–173 ± 17 J K^–1 mol^–1) supports our proposition. The negative G⁰ (–13.8 kJ mol^–1) for the first equilibrium step also supports the spontaneous formation of the outer sphere association complex.     

Quantum chemical calculations on the catalytic dehydration of 2-propanol

The charge on atoms and the bond strengths in CH₃CHOHCH₃, CH₃ CH₃, CH₃CHOHCH ₂ ^– , CH₃ CH ₂ ^– and CH₃ CH₃...O(H)CH(CH₃)₂ have been calculated by the CNDO/2 method. The results are in agreement with published experimental observations on catalytic dehydration. A modified mechanism of anti-elimination on solid catalysts is proposed.

---

CH₃CHOHCH₃, CH₃ CH₃, CH₃CHOHCH ₂ ^– , CH₃ CH ₂ ^– CH₃ CH₃...O(H)CH(CH₃)₂, CNDO/2. . .

     

Gibbs Energy and Entropy of Mixing in the NaNO2-KNO3 System

The activity and activity coefficients of the components of the NaNO₂-KNO₃ system, determined from the experimental data on the saturated vapor pressure at 798, 823, and 848 K, are used to calculate the relative and excess partial molar Gibbs energies (G _i and G _i ^{e x c}), entropies (S _i and S _i ^{e x c}), and integral relative and excess thermodynamic functions (G, G ^{e x c}, S, and S ^{e x c}) of the system.     

Catalytic decomposition of N2O on La2CuO4 in the presence of LaNi5 alloy

Decomposition of N₂O has been studied on pure La₂CuO₄, La₂CuO₄ with 5 and 10 wt. % LaNi₅ and oxidized LaNi₅ in the temperature range of 240–490 °C at 50 and 200 Torr initial pressures of N₂O. The addition of LaNi₅ decreases the energy of activation compared to that of La₂CuO₄ which has been explained based on the dispersity of NiO over La₂CuO₄.

---

N₂O La₂CuO₄ La₂CuO₄ LaNi₅ 5–10 .%, 240–490°C N₂O 50 200 . LaNi₅ , . NiO La₂CuO₄.

     

A mechanistic study of cycloaddition of carbon dioxide to propyne over supported Rh4 and Fex Rhy carbonyl cluster derived catalysts

CO₂ undergoes cycloaddition to propyne on a cationic rhodium site with the assistance of O^2–/OH^– of support or iron oxide over Rh₄ and Fex Rhy carbonyl clusterderived catalysts.¹³CO₁₂ labeling and FTIR studies suggest that monodentate carbonate formed on the catalyst surface is most likely a key species to offer an active CO₂ to be converted into a carbonyl intermediate prior to the product 4,6-dimethyl-2-pyrone.

---

CO₂ O^2–/OH Rh₄ Fex Rhy. ¹³CO₂ , CO₂ , 4,6--2-.

     

State of components in group IV A metal modified nickel catalysts prepared via decomposition of metal complexes

The dispersity and state of components in (M+Ni)/SiO₂ catalysts (M=Ge, Sn, Pb), prepared via the reduction of anchored complexes, have been studied by chemisorption and electron microscopy. High dispersity of metallic particles (6Å) has been revealed. According to Mössbauer spectroscopy, in (Ni+Sn)/SiO₂ catalysts reduced at 873 K, a partial reduction of Sn to the metallic state is observed.

---

(M+Ni)/SiO₂ ( M=Ge, Sn, Pb), , , - . 873 ° K (Sn+Ni)/SiO₂ , , , 6 Å.

     

Kinetics and mechanism of OsO4 catalyzed oxidation of chalcones by Ce4 in aqueous acetic sulfuric acid media

Kinetics of OsO₄ catalyzed oxidation of chalcones by Ce⁴⁺ has been studied in aqueous acetic-sulfuric acid medium in the temperature range 313 to 338 K. The order in [oxidant] is zero while the order with respect to [substrate] and [catalyst] are each fractional. The rate of the reaction decreased with increase in percentage of acetic acid while [H⁺] had practically no effect on the rate The rates of various substituted chalcones (with substituents in the phenyl. ring attached to the moiety) are in the orderp-CH₃>m-CH₃>H>p-Cl>m-Cl>m-NO₂>p-NO₂. A mechanism in which formation of a cyclic ester between chalcone and OsO₄ in a fast step followed by its decomposition in a rate-determining step is envisaged.

---

Ce⁴⁺, OsO₄, - 313–338 . —, —. , [H⁺] . ( , : -CH₃>-CH₃>H>-Cl>-NO₂>-NO₂. , OsO₄ , , .