Rh/nylon catalysts for partial hydrogenation of benzene to cyclohexene

Hydrogenation of benzene on Rh/nylon produced cyclohexene with a high selectivity. The influence of contact time, pretreatment of catalyst and rhodium salt precursors have been studied. Samples prepared from Rh(III) were found more selective than catalysts obtained from Rh(I). It is suggested that electron deficient metal sites are responsible for cycloolefin formation.

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Rh/ . , . , Rh(III) , , Rh(I). , .

     

Cyclohexane photooxygenation by air oxygen in CH2Cl2 in the presence of chromium oxocomplex-iodosylbenzene system

Cyclohexane is oxidized by air oxygen in CH₂Cl₂ solution to yield cyclohexanol, cyclohexanone and cyclohexyl chloride when irradiated by light (>310 nm) in the presence of (Bu₄N)₂CrO₄ or (Bu₃SnO)₂CrO₂. The addition of PhIO greatly accelerates the reaction and increases the yield of products. The reaction mixture contains neither cyclohexanol nor cyclohexanone when the photoreaction in the presence of the Cr(VI)–PhIO system is carried out in argon atmosphere. Hence neither iodosylbenzene nor oxochromium compounds can be oxygen atom donors in alkane oxygenation. The accelerating effect of iodosylbenzene may be due to the enhanced oxidizing power of photo-excited oxochromium species when coordinated to iodosylbenzene.

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CH₂Cl₂ , , (>310 ) (Bu₄N)₂CrO₄ (Bu₃SnO)₂CrO₂. PhIO . Cr(VI)–PhIO , , . , ( ) . .

     

Catalytic properties of ion-exchanged carnegieite powders. Isomerization of n-butenes

The mist decomposition method was applied to the solgel type synthesis. Resulting carnegieite and its ionexchanged derivatives were tested by means of butene isomerization. Carnegieite showed weak but stable activity originating from its base sites. The results of the reaction suggested the development of more active sites by the magnesium ion exchange and new acid sites by the ammonium ion exchange. These are examined by acid-base measurements.

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. - . , , . , , — . — .

     

The role of lattice and adsorbed oxygen in the oxidation of n-butene-1 and furan with MnMoO4-based catalysts

In this paper the adsorption properties towards oxygen and the catalytic oxidation properties of furan and n-butene-1 on a MnMoO₄-based catalyst have been compared. Different forms of adsorbed oxygen are responsible either for the oxidation of furan to maleic anhydride or of furane and n-butene-1 to carbon oxides.

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--q MnMoO₄. , --1 .

     

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) , - .

     

Response studies of the mechanism of o-xylene oxidation over a vanadium-titanium oxide catalyst

A response method has been used to study the mechanism of o-xylene oxidation over a vanadium-titanium oxide catalyst. The products of partial and destructive oxidation are shown to be formed under the influence of molecular oxygen on the surface intermediates produced by the interaction between o-xylene and oxidized surface sites.

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- . , , - .

     

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. , - .

     

Differential thermoanalyse in der Strukturuntersuchung der als Formmassenbindestoffe in der Giessereitechnik angewandten montmorillonitischen Formlehme

Zusammenfassung Die Differentialthermoanalyse eignet sich zur Bestimmung der thermischen Stabilität der in Formmassen angewandten montmorillonitischen Bindestoffe. Mit der DTA-Methode können die bei hohen Temperaturen in diesen Bindestoffen auftretenden strukturellen Änderungen bestimmt werden. Waschöl erhöht die Dehydratisierungs- und Dehydroxylierungstemperatur des montmorillonitischen Bindestoffes. In der Folge steigert also die Suszeptibilität des Obigen zur Hydratation und auch die thermische Stabilität.

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The hitherto presented results of researches of DTA of montmorillonite binding agent, applied in the moulding sand for foundry practice. With the aid of this method the temperature of dehydratation and dehydroxylation of binding agent with the addition and without of wash oil have been defined.As a result of our investigations it has been found that the same oil rises the appearance of these effects.With the aid of DTA these has also been defined structural changes occurring in montmorillonite binding agent, subjected to the activity of high temperature.

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, . . , . , , .

     

Oxidative coupling of 5-membered heterocycles catalyzed by a Pd(II)-heteropolyacid system in dimethylformamide

Oxidative coupling of thiophene and 2-methylfuran to the corresponding dihetaryls in DMFA medium occurs in the presence of the homogeneous catalytic system Pd(II)-molybdovanodophosphoric heteropolyacid (HPA). The data obtained show that HPA may act as a reversible oxidant in polar aprotic media.

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, Pd(II)- 2- . , .

     

Phase coexistence and complicated dynamics in open catalytic systems

The simplest catalytic system with surface phase transitions in CSTR has been studied. It is shown that the possible number of steady states is directly determined by that of phase coexistence regions on the phase diagram of the adsorption layer.

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. , , .

     

Microcalorimetric studies of slag alkaline binders

Calorimetric measurements were carried out on the hydration of slag activated by sodium hydroxide, sodium carbonate and water glass at 60 °C. The results can be correlated with the mechanical properties of the cured cements. The studies confirmed the applicability of calorimetry in the testing of activators used in concrete technology.

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Zusammenfassung Die Hydratation von Schlacke bei 60 °C und Aktivierung mit Natriumhydroxid, Natriumcarbonat oder Wasserglas wurde durch kalorimetrische Messungen verfolgt. Die Ergebnisse lassen sich mit den mechanischen Eigenschaften der erhärteten Zemente korrelieren. Die Untersuchungen bestätigen die Brauchbarkeit der kalorimetrischen Methode zum Testen von Aktivatoren in der Betontechnologie.

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, 60° , . . , - .

     

Testing of nickel phosphate (NiP) catalyst for ethylbenzene oxydehydrogenation by means of isopropanol dehydration

It has been shown that NiP catalyst, if fresh, contains a high concentration of the same type acid-base surface centers as those participating in i-PrOH dehydration on -Al₂O₃. The concentration of these centers diminishes rapidly after a modification of NiP surface in a stream of ethylbenzene (EtPh) oxydehydrogenation products.

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, NiP - , , i-PrOH -Al₂O₃. NiP .

     

Influence of phosphorus additives on the properties of Fe?Sb?O oxide catalysts

Modification of the surface of Fe–Sb–O oxide catalysts by phosphorus additives increases the yield of acrylonitrile in the oxidative ammonolysis of propylene, which can be attributed to the increase of the surface concentration of weakly acidic aprotic centers, viz. Sb³⁺ ions.

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, --Sb³⁺.

     

Oxidation of hydrocarbon mixtures over a complex vanadium catalyst

Vapor-phase oxidation of hydrocarbon mixtures over vanadium oxide (promoted by potassium sulfate)-silica catalyst has been studied. It is shown that the inhibition of the rates of formation of individual products depends on the ability of the added hydrocarbons to similar specific interaction with the catalyst.

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. , , .

     

Mechanism of ascorbic acid oxidation by molecular oxygen in aqueous pyridine catalyzed by CO2+, Ni2+, Mn2+ and Zn2+

Data on the radical non-chain mechanism of ascorbic acid oxidation by molecular oxygen catalyzed by Co²⁺, Ni²⁺, Mn²⁺ and Zn²⁺ ions are reported.

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Co²⁺, Ni²⁺, Mn²⁺ Zn²⁺.

     

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.

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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.

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

     

How is an acceptable Nomenclature system achieved?

The philosophy and procedure adopted by the Nomenclature Committee of the International Confederation for Thermal Analysis are briefly outlined with illustrative examples taken from the contents of the two reports so far prepared.

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Zusammenfassung Prinzipien und Verfahrungsweise der Problembehandlung in dem Ausschuß für Nomenklatur der Internationalen Conföderation für Thermische Analyse werden erörtert, illustriert durch Beispiele [die zwei kürzlich entworfenen Referaten des Ausschusses entnommen wurden.

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Résumé On indique les principes dui ont guidé les travaux du Comité Nomenclature de l'ICTA et la préparation de deux rapports.

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, .