Carbon-supported sulfide bimetallic catalysts for hydrodesulfurization

It has been established that the activity of carbon-supported sulfide Ni–Mo, Ni–W and Co–Mo catalysts is much higher compared to the traditional -Al₂O₃ and SiO₂ supported systems. The effect of surface area of the support and of the catalyst composition on their catalytic properties has been studied.

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, Ni–Mo, Ni–W Co–Mo , . .

     

Determination of the strength of Lewis acid centers via IR spectroscopic measurement of adsorbed pyridine

According to high-temperature IR spectroscopic studies, the isosteric heats of pyridine adsorption on the Lewis centers of Al₂ O₃, ZrO₂ and zeolite HNaY have been estimated. The dependence between the frequency _8a (1580–1630 cm^–1) and the adsorption heat is shown to take place only for centers formed by cations of the same metal.

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, - HNaY. , _8a (1580–1630 cm^–1) , - .

     

Metal dispersity and activity for methylcyclohexane dehydrogenation on Pt/NaY zeolite

By changing the conditions of calcination prior to reduction, three samples with different metal dispersity of Pt/NaY zeolite have been obtained. Their behavior in methylcyclohexane dehydrogenation shows an insensitive character if a second order mechanism with respect to the active site concentration is assumed.

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, , Pt NaY. , .

     

Reduction of carbon dioxide with methane over Ni-catalyst

The reaction CO₂+CH₄=2CO+2H₂+60 kcal/mol was carried out over some transition metal catalysts (Ni, Fe and Co) and Ni/Al₂O₃ catalyst was then found to be the best for the reaction. The reaction rate expression and the apparent activation energy were also obtained over the Ni catalyst.

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CO₂+CH₄=2CO+2H₂+60 / (Ni, Fe Co). Ni/Al₂O₃ . Ni-.

     

Hydrogenation of benzene on sulfide catalysts in the presence of thiophene

The principles of benzene hydrogenation have been studied with sulfide catalysts NI/MS₂, Ni/SiO₂, M/SiO₂ and (Ni, M)/SiO₂ (M=Mo, W) obtained via metal complex precursors or by impregnation. In bimetallic catalysts active sites of benzene hydrogenation are formed upon reduction of the active component for thiophene hydrogenolysis.

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Ni/MS₂, Ni/SiO₂, M/SiO₂, (Ni,M)/SiO₂, M=Mo W, , . , .

     

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.

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V–P–O/SiO₂ V⁴⁺ . V–P–O/SiO₂ V⁴⁺ V³⁺.

     

Correlation between structures and thermal properties of hydrated thallium(I) diborates; H2O-Tl2B4O7 phase diagram

Two synthetic hydrated thallium (I) diborates have been found in the liquidsolid equilibria of the 100° isotherm of the ternary system H₂O-B₂O₃-Tl₂O; they were characterized via the powder diagrams, but classical chemical analysis does not lead to the correct degree of hydration. Through TG of the powders, a complex process is found with no explanation. Structural resolution and TG of the monocrystals allow a correct explanation of the thermal dehydration: these thallium (I) diborates are two distinct compounds, Tl₂B₄O₇ · 3H₂O and Tl₂B₄O₇ · 1.5H₂O, which have their own process of dehydration; they contain infinite chains of polyanions and their structural formulae are Tl₂[B₄O₆ (OH)₂] · 2H₂O and Tl₄[B₈O₁₂ (OH)₄]H₂O; the latter polyanion may be considered as the dimer of the first.The H₂O-Tl₂B₄O₇ phase diagram was established by thermal analysis and solubility experiments, both under pressure; it allows the prediction that another hydrated thallium (I) diborate, Tl₂B₄O₇·H₂O, exists, with possible structural formula Tl₆[B₁₂O₁₈ (OH)₆]. Actually, only monocrystals of Tl₄[B₈O₁₂ (OH)₄]·H₂O have been obtained hydrothermally from Tl₂[B₄O₆ (OH)₂] · 2H₂O.

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Zusammenfassung Im ternären System H₂O-B₂O₃-Tl₂O liegen bei 100° bei Einstellung des Gleichgewichtes flüssig-fest zwei hydratisierte Thallium (I) -diborate vor; diese wurden durch Pulverdiagramme charakterisiert, die klassische chemische Analyse ergab jedoch nicht den richtigen Hydratationsgrad. Bei TGA von Pulvern verläuft ein komplexer Prozeß, für den keine mögliche Erklärung gegeben werden kann. Strukturaufklärung und TGA mit Einkristallen ermöglichen eine korrekte Erklärung der thermischen Dehydratisierung: die hydratisierten Thallium (I) -diborate sind zwei verschiedene Verbindungen der Zusammensetzung Tl₂B₄O₇· 3H₂O und Tl₂B₄O₇· 1.5H₂O mit unterschiedlichem Dehydratisierungsverlauf, die Polyanionketten enthalten und durch die Strukturformeln Tl₂[B₄O₆ (OH)₂] · 2H₂O bzw. Tl₄[B₈O₁₂ (OH)₄] · H₂O zu beschreiben sind. Das Polyanion der zweiten Verbindung kann als Dimeres des der ersten angesehen werden. Das Phasendiagram H₂O-Tl₂B₄O₇ wurde durch unter Druck ausgeführte thermische Analyse und Löslichkeitsexperimente aufgestellt. Aus diesem Phasendiagramm kann die Existenz eines anderen hydratisierten Thallium (I) -diborats, Tl₂B₄O₇ · H₂O, mit der möglichen Strukturformel Tl₆[B₁₂O₁₈ (OH)₆] vorausgesagt werden. In Wirklichkeit wurden aber nur Einkristalle von Tl₄[B₈O₁₂ (OH)₄]·H₂O durch hydrothermale Behandlung von Tl₂[B₄O₆ (OH)₂] · 2H₂O erhalten.

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₂-₂₃-l₂ 100° , . , . : l₂₄₇·₂ l₂₄₇·1.5₂, . l₂[₄₆()₂]· 2₂ l₄[₈₁₂()₄]·₂. . ₂-l₂₄₇. , l₂₄₇·₂ l₆[₁₂₁₈()₆]. , l₄[₈₁₂()₄]·₂ l₂[₄O₆()₂]·2₂O.

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Paper presented at the World Conference on Thermal Analysis Amsterdam, 1984.     

Reaction routes for hydrogenation of acetylene-ethylene mixtures using a double labelling method

Hydrogenation of C₂H₂:C₂H₄ mixtures using a double labelling method has been studied. Both in the presence and absence of ethylene the rate of acetylene hydrogenation on its partial pressure proceeds through a maximum and the rate is higher when ethylene is added. Using¹⁴C–C₂H₂ it was demonstrated that at low acetylene partial pressures the main route of acetylene hydrogenation was the formation of ethane and C₄ hydrocarbons. Using¹⁴C–C₂H₄ it was also shown that at certain acetylene partial pressures the formation of ethane from ethylene completely ceased. Different surface species are suggested and a reaction mechanism is proposed.

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C₂H₂:C₂H₄, . , , . C¹⁴–C₂H₂, , C₄. C¹⁴–C₂H₄, , . .

     

Influence of sodium salt addition on the morphological and catalytic properties (ethane hydrogenolysis) of aluminasupported cobalt

NaNO₃ addition to Co/Al₂O₃ results in an increase in the reducibility, in a smaller dispersity of the metal and in a decrease in the ethane hydrogenolysis rate due to a decorative effect.

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NaNO₃ Co/Al₂O₃ ,

     

Investigation of n-hexane dehydrocyclization over supported Pt catalyst modified by adsorbed Pd

A -Al₂O₃ supported Pd–Pt bimetallic catalyst prepared by electrochemical metal adsorption has been tested in n-hexane dehydrocyclization. The Pd–Pt/Al₂O₃ catalyst, after calcination in oxygen followed by hydrogen treatment, showed higher activities and better selectivities for benzene and iso-hexane formation. The Pd–Pt/Al₂O₃ catalyst appeared to be less sensitive to the changes in the temperature of hydrogen treatment than the base Pt/Al₂O₃ catalyst.

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Re–Pt, -Al₂O₃, . -. , Re–Pt/Al₂O₃, , , , . , Pt/Al₂O₃.

     

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.

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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.

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

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

Kinetics and selectivity of the oxidation of alkanes in Cl2?H2O and Cl2?Hg2+?H2O solutions

Relative oxidation rate constants of several normal, iso-, cyclo-and methylcycloalkanes have been measured in Cl₂–H₂O and Cl₂–Hg²⁺–H₂O solutions at 343K. The selectivity of C–H bond dissociation in both systems is the same. HOCl is assumed to be the active species for the two systems.

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Cl₂–H₂O Cl₂–Hg²⁺–H₂O 343 , -,- ; C–H . , HOCl.

     

Methanol oxidation on copper-oxide catalysts

Complete oxidation of methanol on CuO and CuO/Al₂O₃ catalysts has been studied. The main kinetic parameters have been determined. A possible mechanism and the nature of the rate-determining step are discussed.

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CuO CuO/Al₂O₃. . .

     

Photocatalytic electron transfer across the membranes of lipid vesicles mediated by diglycylamide of mesoporphyrin-IX N-metylglycomate

A peculiarity of the photocatalytic action of porphyrin molecules with different localization inside lipid bilayers of lecithin vesicles has been studied. The influence of an electrostatic field in the lipid membrane on the efficiency of electron photocatalytic transfer across the membrane is discussed.

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, - . . .

     

Reduction of an amorphous NiO?Al2O3/SiO2 catalyst by different olefins and hydrogen

By static magnetic measurements it was found that the ability to reduction of an amorphous NiO–Al₂O₃/SiO₂ catalyst decreases in the order: but-2-eneshydrogen isobutene>but-1-ene>propeneethene. The reduction temperatures are significantly higher than the dimerization reaction temperatures.

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, NiO–Al₂O₃/SiO₂ : -2>-1> . .

     

Chemical reaction and phase transformations of the components of low temperature shift catalyst in various atmospheres

The systems CuO–Al₂O₃ and ZnO–Al₂O₃, as model systems of low temperature shift catalysts, have been studied in the temperature interval 100–700°C. The changes of their phase composition and surface area, influenced by gas atmosphere have been studied by X-ray, IR analysis and low temperature nitrogen adsorption.

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CuO–Al₂O₃ ZnO–Al₂O₃ CO 100–700°C. , - .

     

Hydrogen exchange between tert-butyl cation and sulfuric acid

The D/H exchange between tert-butyl-d₉ cation and H₂SO₄ was investigated. The cation participating in the exchange was recovered in the form of p-di-tert-butylbenzene. The mass spectroscopic measurements show a continuous distribution, from zero to nine, of the deuterium atoms in the tert-butyl group originating from the cation.

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D/H --d, H₂SO₄. , , ---. — — - .

     

ESR study of the interaction of oxygen and propene with solid CoO?MgO solutions under pulse conditions

An ESR study has shown that under the action of oxygen pulses, radical ions O ₂ ^– with g_I=2.0085 and g_II=2.087 are generated at room temperature on the surface of 1% CoO–MgO. Heating of the sample to 150 °C in the spectrometer results in complete disappearance of the O ₂ ^– signal from the ESR spectra. The variation of the O ₂ ^– signal intensity with time due to the interaction between propene and oxygen adsorbed on the sample surface, has been measured.

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, 1% CoO–MgO - O ₂ ^– g_I=2.0085 g_II=2.087. 150 °C - O ₂ ^– . O ₂ ^– .

     

Crystallization of iron phosphate glasses

Differential thermal analysis (DTA), thermogravimetric analysis (TG), X-ray diffraction and Mössbauer spectroscopy were employed in the investigation of crystalline products of FeO_x-P₂O₅ glasses generated by various heat treatments. In glasses with a high value of =Fe²⁺/(Fe²⁺ + Fe³⁺), absorption of oxygen occurs in a broad temperature range identified by TG. Depending on the value of , two exotherms appear in the DTA curves, the low-temperature one corresponding to crystallization of the Fe₃(PO₄)₂ type regions, and the high-temperature one being related to various phases with dominating FePO₄. Each exotherm has its own transformation region, identical in absolute value. The Mössbauer spectra of glasses which underwent thermal treatment at higher temperatures exhibit some indication of phases of the types Fe₃(PO₄)₂ · xH₂O and FePO₄ · xH₂O.

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Zusammenfassung Differentialthermoanalyse (DTA), thermogravimetrische Analyse (TG), Röntgendiffraktion und Mössbauerspektroskopie wurden bei der Untersuchung (von kristalliner Produkte) durch verschiedene thermische Behandlungen hergestellten FeO_x-P₂O₅ Gläsern eingesetzt. In den Glasarten mit einem hohen Wert von =Fe²⁺/(Fe²⁺ + Fe³⁺) erfolgt die Sauerstoffabsorption in einem durch TG [nachgewiesenen breiten Temperaturbereich. In Abhängigkeit von dem -Wert erscheinen zwei Exothermen in den DTA-Kurven, von denen der bei niedriger Temperatur die Kristallisation des Fe₃(PO₄)₂ entspricht, und jener bei höheren Temperaturen in verschiedenen Phasen dem FePO₄. Jede Exotherme hat ihr eigenes Umwandlungsgebiet, das in absolutem Wert identisch ist. Die Mössbauer-Spektren der Gläser welche einer Wärmebehandlung bei höheren Temperaturen unterzogen worden sind, weisen einige Indikationsphasen der Typen Fe₃(PO₄)₂ · xH₂O und FePO₄ · xH₂O auf.

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, , FeO_x-P₂O₅, . , =Fe²⁺/(Fe²⁺+Fe³⁺) . , - : Fe₃(PO₄)₂, – FePO₄. , . , , Fe₃(PO₄)₂ · ₂ FePO₄ · ₂.

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The authors thank Mrs. Simonyiová for assistance in the experimental part of these investigations, and Dr. Horváth and Dr. Vondrovic for performing the X-ray and TG analyses.     

Vitreous phases of the Ag2O∶B22O3∶P2O5 system

Most optimized vitreous electrolytes are obtained by doping an oxide glass with a salt (MX); the resulting substance has an increased ionic conductivity, but a reduced thermal stability. On the other hand, this paper shows that it is possible to obtain vitreous electrolytes with enhanced electrical and thermal performances by mixing two glass formers. This phenomenon may be called the mixed anion effect. The Ag₂OB₂O₃P₂O₅ system is shown to offer a very interesting example of such a phenomenon.

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Zusammenfassung Optimale glasartige Elektrolyte werden durch Dopen eines Oxydglases mit einem Salz (MX) erhalten; die Produkte weisen eine erhöhte ionische Leitfähigkeit, jedoch auch eine verminderte thermische Stabilität auf. Andererseits wird gezeigt, daß glasartige Elektrolyte mit besseren elektrischen und thermischen Eigenschaften durch Mischen von zwei Glasbildnern erhalten werden können. Für dieses Phänomen wird die Bezeichnung mixed anion effect in Vorschlag gebracht. Es wird gezeigt, daß das System Ag₂OB₂O₃P₂O₅ ein sehr interessantes Beispiel dieses Phänomens bietet.

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MX. , . . . , Ag₂O₂₃₂₅ .

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The NMR data were collected at the Regional NMR Center of the Colorado State University (Fort Collins, Co, USA), funded by NSF Grant CHE-8208821). This research was funded in part by the Italian Department of Education (MPI 40%).