51V NMR studies of systems V2O5-KHSO4 and V2O5?K2SO4

Systems V₂O₅–KHSO₄ and V₂O₅–K₂SO₄ have been studied by the⁵¹V NMR method. The first system demonstrates the same states of vanadium as the previously studied V₂O₅–K₂S₂O₇, in this system a compound with an equimolar ratio of components has been found. In V₂O₅–K₂SO₄ the state of vanadium differs from the above systems and the formation of a compound with V/K=4 is observed.

---

⁵¹V KHSO₄–V₂O₅ K₂SO₄–V₂O₅. , K₂S₂O₇–V₂O₅, . K₂SO₄–V₂O₅ V/K4.

     

Upper limits of magnetic anisotropy of molecule with closed electron shell

Two simple upper limits have been established for the anisotropy of magnetic susceptibility of linear molecules with closed electron shells; these can be used to estimate the top limit on magnetic anisotropy of a molecule = – if its mean magnetic susceptibility is known, without any information whatever on the electronic wave function. The first of these limits is valid for the magnetic anisotropy of the ground electronic state X¹, and the second is valid for any ¹ state, including the excited state. The application of these limits to the evaluation of magnetic anisotropy is illustrated in the examples of the molecules of CO₂, FCCF, HCCF, FCN, LiH, and the excited state of the H₂ molecule. It is shown that these limits are useful for revealing cases of internal contradictions (or error) in individual values of magnetic anisotropy, including very rough values obtained in calculations of the magnetic properties of molecules in a limited basis set.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 24, No. 2, pp. 143–149, March–April, 1988.     

Thermal analysis by EMF-measurements on solid electrolytes

Galvanic cells of the type (C+Cl₂)(NaCl_(s))(MCl_2(s))(C+Cl₂) give e. m. f. 's above 280°, which are due to the formation of ternary chlorides Na_nMCl_n+2. By the change in slope of continuously measured e.m.f.vs. T curves, the temperatures of solid-state reactions in systems NaCl-MCl₂ can be found. This method was applied for the systems of NaCl with NiCl₂, CoCl₂ and CdCl₂, and for KCl-NiCl₂. With the exception of the system NaCl-NiCl₂, all phase diagrams must be corrected.

---

Zusammenfassung Mit galvanischen Zellen des Typs (C+Cl₂)/NaCl_(s)/MCl_2(s)/(C+Cl₂) lassen sich oberhalb 280° EMK's messen, die auf der Bildung ternärer Chloride Na_nMCl_n+2 beruhen. Durch die Änderung der Steigung kontinuierlich gemessener EMK- gegen T-Kurven lassen sich in Systemen NaCl/MCl₂ die Temperaturen von Festkörperreaktionen nachweisen. Diese Methode wurde auf die Systeme des NaCl mit NiCl₂, CoCl₂ und CdCl₂ sowie auf das System KCl-NiCl₂ angewendet. Alle Phasendiagramme, mit Ausnahme des Systems NaCl-NiCl₂, mußten auf Grund dieser Messungen revidiert werden.

---

(C+Cl₂)/NaCl./MCl₂./(C +Cl₂) 280 °C . . , Na_nMCl_n+2. . . , NaCl-MCl₂. NaCl NiCl₂, CoCl₂, CdCl₂ KCl-NiCl₂. NaCl-NiCl₂,ce .

---

---

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

Thermal analysis of ferrous sulphate heptahydrate in air

The thermal decomposition of ferrous sulphate heptahydrate was carried out in air under dynamic and isothermal conditions. The intermediate phases were identified by chemical analysis and an X-ray technique. Ferrous sulphate heptahydrate is converted to tetrahydrate and monohydrate, but this conversion is accompanied by oxidation. Fe(OH)SO₄ and Fe₂O(SO₄)₂ are formed as oxidation products, and the latter decomposes to ferric oxide directly and/or through Fe₂(SO₄)₃.

---

Zusammenfassung Die thermische Zersetzung von Eisen(II)sulfat Heptahydrat wurde in Luft unter dynamischen und isothermen Bedingungen durchgeführt. Die Intermediärphasen wurden durch chemische Analyse und Röntgentechnik identifiziert. Eisen(II)sulfat Heptahydrat wird in Tetrahydrat und Monohydrat überführt, doch wird diese Umwandlung durch eine Oxidation begleitet. Fe(OH)SO₄ und Fe₂O(SO₄)₂ werden als Oxidationsprodukte gebildet und letzteres wird unmittelbar und/oder über Fe₂(SO₄)₃ zu Eisen(III)oxid zersetzt.

---

Résumé La décomposition thermique dans l'air du sulfate de fer(II) heptahydraté a été étudiée en conditions dynamiques et isothermes. Les phases intermédiaires ont été identifiées par analyse chimique et par rayons X. Le sulfate de fer(II) heptahydraté se transforme en tétrahydrate et en monohydrate mais cette conversion s'accompagne d'une oxydation. Il se forme Fe(OH)SO₄ et Fe₂O(SO₄)₂ comme produits d'oxydation et ce dernier se décompose en oxyde de fer(III) directement ou quelquefois avec formation intermédiaire de Fe₂(SO₄)₃.

---

(II) . . (II) . Fe(OH)SO₄ Fe₂O(SO₄)₂. (III) Fe₂(SO₄)₃.

---

---

The authors express their grateful thanks to Prof. P. K. Jena, Director, for his keen interest and permission to publish the paper, and to Dr. A. Lakshminarayana for the X-ray measurements. One of us (MSRS) also thanks the Regional Research Laboratory (CSIR) for a fellowship.     

Catalytic properties of V?Mo?O systems in acrolein oxidation

Catalytic properties of V–Mo–O systems have been studied in acrolein oxidation. When catalysts are activated in reaction mixtures at 673 K, then a solid solution of molybdenum oxides in reduced vanadium oxides is formed, which is responsible for deep oxidation. Also, several compounds are produced, which by their activity and selectivity to acrylic acid formation are arranged in the sequences VMo₃O₁₁VMo₂O_8+x>V₆Mo₄O₂₅, and VMo₃O₁₁>VMo₂O_8+xV₆Mo₄O₂₅, respectively.

---

V–Mo–O . 673 K , , , : VMo₃O₁₁VMo₂O_8+x>V₆Mo₄O₂₅, : VMo₃O₁₁>VMo₂O_8+xV₆Mo₄O₂₅.

     

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.     

Comments on the approximate calculation of lattice potential

The potential of a charge distribution due to a lattice of point charges may be evaluated by the classical multipole expansion method. The leading terms in the resultant expressions are just those used in some of our previous calculations [1–3]. In addition, for cases where the leading terms vanish because of the effect of orthogonality of the basis functions upon the Mulliken expansion (this being especially serious in the case of a one-centre charge distribution), we have derived the first nonvanishing term, involving |r|. In other cases it may be necessary to proceed to still higher multipole terms before a non-zero contribution is obtained. The entire procedure is formulated in such a way that it can be easily applied to LCAO-MO calculations for polyatomic ions in ionic lattices.     

Effect of ligands on the hydrogenation selectivity in the presence of rhenium catalysts

It has been established that the catalytic activity of rhenium oxohalide complexes with phosphorus- or sulfur-containing ligands in hydroganation of C₆–C₁₀ olefins, nitrobenzene and p-nitrotoluene is primarily determined by the original ligand to rhenium ion bond. Chain length of olefins does not affect their hydrogenation rate.

---

- C₆–C₁₀, - - . .

     

Mechanism of the thermal decomposition of 3CaO·Al2O3·6D2O

The mechanism of the step I and step II of thermal decomposition of 3CaO · Al₂O₃ · 6D₂O was studied. The presence of Ca(OD)₂ was proved in the products of the first step of decomposition. In the calorimeter cell of the Dupont 990 thermoanalyser the enthalpy changesH _r,I=59.2kJ/mole D₂O for step I (210–410°) andDH _rII,1=69.0 kJ/mole D₂O for the first fast part of the step II (stage 1 of the step I, encompassing the temperature interval 410–560°) were measured. This indicates that the dissociation of Ca(OD)₂ is not the only transition taking place in the first fast part (stage 1) of the step II.

---

Zusammenfassung Der Mechanismus der I und II Stufe der thermischen Zersetzung von 3CaO · Al₂O₃ · 6D₂O wurde untersucht. Die Gegenwart von Ca(OD)₂ wurde in den Produkten der ersten Zersetzungsstufe nachgewiesen. In der Kalorimeterzelle des Thermoanalysers Dupont 990 wurde die EnthalpieänderungenH _r,i 59.2 kJ/Mol D₂O für Stufe I (210 bis 410°) undH _r,II,I=69.0 kJ/Mol D₂O für den ersten schnellen Teil der Stufe II (»Etappe 1 der Stufe II «) im Temperaturbereich von 410 bis 560° gemessen. Dies zeigt, daß die Dissoziation von Ca(OD)₂ nicht der einzige Übergang in der ersten, schnellen Phase (Etappe 1) der Stufe II ist.

---

Résumé On a étudié le mécanisme des deux premières étapes de la décomposition thermique de 3CaO · Al₂O₃ · 6D₂O. La présence de Ca(OD)₂ a été mise en évidence dans les produits de la première étape de décomposition. Les variations d'enthalpie correspondant à la première et à la deuxième étape de la décomposition ont été mesurées à l'aide de la cellule calorimétrique du thermoanalyseur Dupont 990; elles s'élèvent respectivement àH _i,I= 59.2 kJ/mole D₂O pour l'étape I (210–410°) etH _r,II,1= 69.0 kJ/mole D₂O pour la première partie, rapide, de l'étape II («stade l de l'étape II », couvrant l'intervalle 410–560°). Ceci indique que la dissociation de Ca(OD)₂ n'est pas la seule transition qui ait lieu dans la première partie (stade 1) de l'étape II.

---

I II · l₂₃ · 6D₂O. I Ca(OD)₂. 990 (210–410°) H_r,I=59.2 / D₂O, II ( 1 II 410–560°) _r,II,I= =69.0 / D₂O. , Ca(OD)₂ , ( I) II.

     

Influence of rare earth ions on the properties of Pd/SiO2 in CO hydrogenation

Systematic studies of the effect of the lanthanoid (Ln) nature on the activity and selectivity of (Pd+Ln)/SiO₂ catalysts obtained by decomposition of anchored Ln and Pd complexes in methanol synthesis from CO and H₂ have been carried out. It has been established that the highest promoting effect is observed for Pr and Ho ions.

---

(Ln) (Pd+Ln)/SiO₂ , Ln Pd, CO H₂. Pr Ho.

     

Variation of the surface potential of zinc oxide under illumination

Spectral and kinetic dependences of the decrease in the surface potential (SP) of ZnO under illumination and processes of SP relaxation in the dark have been studied. A significant contribution to the decrease of SP in the less-than-bandgap light absorption region is shown to be due to the photodissociation of specific surface bonds with the formation of localized Zn _s ⁺ and O _s ^– .

---

() ZnO . , Zn _s ⁺ O _s ^– .

     

Non-empirical calculations of adsorbability of paired Lewis acid sites of alumina

The non-empirical LCAO SCF MO method on the STO-3G basis was applied to calculate adsorption of H₂O, NH₃ and CO molecules on paired Lewis acid sites (LAS) of alumina formed as a result of the removal of the OH groups which are common for two aluminium atoms.

---

, STO-3G, H₂O, NH₃, CO () Al₂O₃, OH. , H₂O, NH₃, CO .

     

Dehydroxylation and catalytic activity of dealuminated Y zeolites

Dehydroxylation and catalytic conversion of m-xylene over dealuminated zeolites were studied.

---

- .

     

Epoxidation of propylene with tert-butyl hydroperoxide in the presence of heterogeneous polymeric catalysts

A series of heterogeneous polymeric molybdenum containing catalysts on the basis of weak acid cation exchanger Amberlite IRC-84 in an organic and water medium was prepared. The catalysts activity and selectivity in the epoxidation of propylene with tert-butyl hydroperoxide are compared. Data about the chemical structure of catalytically active molybdenum containing centres of the modified cation exchanger were obtained.

---

, , IRC-84 . .. , .

     

Activity of γ-Al2O3 modified by NaOH in disproportionation of methanethiol

Na⁺/Al₂O₃ catalysts in disproportionation of methanethiol are highly selective towards dimethyl sulfide but less active compared to -Al₂O₃. Their activity falls with increasing Na⁺ in the sample. This decrease is due to the neutralization of Brönsted acid centers on the catalyst.

---

Na⁺/Al₂O₃ , , -Al₂O₃. Na⁺ . .

     

Propylene oxidation over tin-molybdenum oxide catalysts

The influence of preparation of tin-molybdenum catalysts on their phase composition and activity has been elucidated. The mutual dissolution of Sn and Mo oxides leads to a considerable increase in their activities and selectivities in the partial oxidation of propylene to acetone.

---

. , .

     

Shape selectivity and maximum molecular size in methanol to hydrocarbons transformation

The maximum product size obtained during methanol to hydrocarbons transformation on medium and large pore zeolites and amorphous silica-aluminas is not governed by shape selectivity but it is a consequence of operational conditions and other process characteristics such as the occurrence of cracking reactions.

---

, , , .

     

Study of the combustion of a fire retardant coating by thermal analysis and different complementary techniques

An intumescent fire retardant coating can effectively control fire spread and damage. Its dual purpose is to confine the surface spread of flame to the boundaries of an already established fire, and to retard the penetration of heat and flame to and through the coated surface. Our composition expanded and provided an insulation layer between the flame source and the combustion substrate, and liberated a quantity of primarily non-flammable decomposition products which tended to extinguish the flame. The main ingredients of the coating were cellulose acetate butyrate and HMDI (Desmodur N) for Polyurethane, and Chlorowax-70 (chlorinated paraffins) as fire retardant component. This fire retardant coating was applied to wood panels, and tested in a 2-foot tunnel, its flame spread rating being measured. The effects of three parameters of interest were investigated: the type of wood used, the percentage of Chlorowax, and the coating thickness. It was found of interest to study the oxidation of the coating using different techniques, e.g. flash pyrolysis under oxygen and GC/MS for analysis of the decomposed products. Combustion studies of the coating were also conducted using DSC and thermogravimetry, either with the scanning mode or under isothermal conditions. Comparisons were made between the results obtained from pyrolysis and combustion.

---

Zusammenfassung Ein schwellender feuerhemmender Überzug kann Ausbreitung und Schäden von Feuer wirksam einschränken und wird zwei Zwecken gerecht: Verhinderung der Ausbreitung von ausgebrochenem Feuer und Schutz der überzogenen Oberfläche vor Hitze- und direkter Flammeneinwirkung. Die beschriebene Komposition quillt und bildet eine Isolationsschicht zwischen der Flammenquelle und dem brennbaren Material, liefert zugleich aber auch eine gewisse Menge von nichtbrennbaren, die Flamme erstickenden primären Zersetzungsprodukten. Die Hauptbestandteile des Überzugs sind Celluloseacetat und -butyrat und HMDI (Desmodur N) für Polyurethan sowie Chlorowax-70 (chlorierte Paraffine) als feuerhemmende Komponente. Dieser feuerhemmende Überzug wurde auf Holzplatten aufgebracht und in einem 2ft-Tunnel getestet, wobei die Flammenausbreitungsgeschwindigkeit gemessen wurde. Der Einfluß von drei interessierenden Parametern wurde untersucht: Typ des benutzten Holzes, Anteil von Chlorowax und Überzugsschichtdicke. Es erwies sich als interessant, die Oxydation des Überzugmaterials mit verschiedenen Techniken zu untersuchen, z.B. durch Schnellpyrolyse und Analyse der Zersetzungsprodukte mittels GC/MS. Verbrennungsuntersuchungen des Überzugmaterials wurden auch mittels DSC und Thermogravimetrie entweder nach der scanning-Arbeitsweise oder unter isothermen Bedingungen ausgeführt. Die bei Pyrolyse und Verbrennung erhaltenen Ergebnisse werden miteinander verglichen.

---

. -, , — . , . - ( ) ( ) . , . : , . , , , - . . , .