Application of natural zeolites for air separation

The application for air separation purposes of modified versins of clinoptilolite and mordenite containing tuffs, deposited in the Tokaj Mountains (Hungary), is demonstrated. The importance of adsorption kinetics in the design of any pressure swinging adsorption (PSA) operation is shown.

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, , (), . .

     

Effect of P2O5 content in phosphogypsum on its thermal decomposition to CaCO and SO2

The effect of P₂O₅ on the thermal decomposition of phosphogypsum to phospholime and sulphur dioxide has been studied.

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Zusammenfassung Es wurde der Einfluß von P₂O₅ auf die thermische Zersetzung von Phosphogips zu Phospholim und Schwefeldioxid untersucht.

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.

     

Fluctuations and dynamics of chemical reactions near neutral steady-state

The effect of fluctuations on the behavior of a simple kinetic model of catalytic reactions allowing a neutral steady-state, is analyzed.

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, , .

     

Photochemical reactions of anthraquinone with hydrocarbons in the presence and absence of oxygen: Trapping of radical intermediates

Radical intermediates formed at 25°C in the presence and absence of oxygen during the photolysis of anthraquinone in aromatic, cyclic and aliphatic hydrocarbon solvents were trapped by 2,6-dichloronitrosobenzene, 2,6-dibromonitrosobenzene and 2,4,6-tribromonitrosobenzene. The resulting nitroxide radicals have been characterized in situ by ESR spectra.

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: 2,6-, 2,6- 2,4,6-— , , 25°C. .

     

Catalytic activity of transition metal silicides in hydrogen oxidation

The catalytic activity of transition metal silicides in H₂ oxidation is much higher compared to metal-like carbides, which can be due to the lower electronegativity of silicon compared to carbon.

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, , .

     

High-temperature pyrolysis of polymers

The experimental results on the pyrolysis of thermoplastic polymers under high-temperature heating and burning conditions are discussed. The reaction of polymer degradation in this case proceeds in the same way as in a low-temperature region.

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Zusammenfassung Die experimentellen Ergebnisse der Pyrolyse von thermoplastischen Polymeren unter Erhitzungs- und Brehnbedingungen hoher Temperatur werden besprochen. Die Reaktion der Polymerzersetzung verläuft in diesem Falle genau so wie in der Niedrigtemperaturzone ab.

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Kinetic conversion of complex hydrocarbon mixtures in reforming on platinum/alumina catalysts

General forms of the kinetic equations for the conversion of various hydrocarbons in reforming of multicomponent gasoline fractions on platinum/alumina catalysts have been confirmed experimentally by using a gradientless method.

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.

     

Hydrogenation of CO2

The hydrogenation of CO₂ has been studied on three different series of catalysts: Fe/MgO, Ni/Ti, Cr/Zn doped with potassium. Reaction was carried out in a conventional flow microreactor system at 15 bar at 250–350°C. Three independent competing reactions: Reverse gas-water shift (RGWS), Fischer-Tropsch (FT) and methanol synthesis were observed.

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CO₂ : Fe/MgO, Ni/Ti, Cr/Zn . 15 250–350°C. : RGWS, F.T. .

     

Parametric analysis of eigenvalues of matrices corresponding to linear one-route catalytic reaction mechanism

The parametric analysis of accepted eigenvalues of matrices observed in chemical kinetics and corresponding to the linear n-stage one-route mechanisms with irreversible stages has been conducted. Relaxation times with varying one of the rate constants are given. The possibility of nonmonotonic change of relaxation times with growing rate constants is shown.

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, n- . . .

     

Lack of influence of the diffusion of free radicals in some photoreactions

Numerous authors have attempted to demonstrate, using theoretical calculations, the influence exerted by the diffusion of free radicals in the liquid phase upon chain photoreactions. We demonstrate here, after defining a coefficient of chemical diffusion, that the importance of diffusion processes can be neglected in the majority of cases.

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Kinetics of perborate oxidation of quinol

The perborate oxidation of quinol in aqueous acetic acid is first order with respect to perborate, zero order with respect to quinol, and first order with respect to H⁺. The oxidation is faster than H₂O₂ oxidation. Breakdown of protonated perboric acid is suggested as the rate-limiting step.

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, H⁺. . , , , .

     

Conversion of dehydrolinalyl acetate in catalytic hydrogenation on metals

Low selectivity of dehydrolinalyl acetate (DeHLA) hydrogenation into linalyl acetate and ester group detachment are predicted in accordance with quantum-chemical data obtained for its homologue dimethyl ethynyl carbinol acetate. Experimental data are confirmed by theoretical calculations. DeHLA hydrogenation produces a variety of products.

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, - . . .

     

A thermoanalytical study of treated wools

Previous studies of fibrous keratins have enabled assignments to be proposed for the endothermic processes identified in the relatively complex DTA curve. From this base, the influence of well defined chemical modifications to keratin on their observed DTA curves has been discussed. Wools are specifically treated commercially to improve shrink resistance and machine washability. To achieve these desired characteristics wools are treated, (a) by special oxidative processes, (b) with specific polymers, and (c) by combinations of (a) and (b). The DTA curves of wool samples which have been subjected to each of the three different treatments were reproducibly recorded. The significance of differences between these curves and that for the untreated fibre are discussed. Although characteristic differences in the DTA curves of wools after specific treatments can be distinguished, differential thermal analysis cannot be regarded as a general tool for such treatment characterisation. It is considered that thermogravimetry should offer a greater potential for this purpose.

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Zusammenfassung Vorangegangene Untersuchungen über faserige Keratine ermöglichten Zuordnungsvorschläge für die in der verhältnismässig komplexen DTA-Kurve befindlichen endothermen Vorgänge. Auf dieser Basis wurde der Einfluss gut definierter chemischer Veränderungen in Richtung Keratin auf ihre beobachteten DTA-Kurven erörtert. Die Wollen werden im Handelsmaßstab spezifisch behandelt um ihre Widerstandsfähigkeit gegenüber dem Eingehen zu erhöhen und ihre Waschbarkeit in der Maschine zu fördern. Um diese erwünschten Charakteristika zu erreichen werden die Wollen a) durch spezielle Oxidationsvorgänge, b) mittels spezifischer Polymere und c) mit kombinierten Verfahren von a) und b) behandelt. Die DTA-Kurven von jedem dieser drei verschiedenen Behandlungen unterworfenen Wollproben wurden reproduzierbar aufgezeichnet. Die Signifikanz der Unterschiede dieser Kurven gegenüber denen der unbehandelten Fasern wird erörtert. Obwohl sich charakteristische Unterschiede in den DTA-Kurven der spezifisch behandelten Wollen beobachten lassen, kann die Differentialthermoanalyse nicht als ein allgemein anwendbares Verfahren zur Charakterisierung solcher Behandlungen betrachtet werden. Es wird angenommen, dass die Thermogravimetrie für diesen Zweck grössere Möglichkeiten bietet.

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Résumé Des études antérieures sur les kératines fibreuses ont permis de proposer des interprétations sur les effects endothermiques identifiés sur la courbe ATD relativement complexe. Sur cette base, l'influence de modifications chimiques bien définies de la kératine sur les courbes ATD observées est discutée. Les laines, à l'échelle commerciale, sont traitées spécifiquement pour augmenter leur résistance au rétrécissement ainsi que pour améliorer leur faculté de lavage en machine. Afin d'atteindre ces caractéristiques, elles sont traitées soit par des procédés oxydants spéciaux, soit par des polymères spécifiques soit par les deux. Les courbes ATD d'échantillons de laines traitées par chacune de ces méthodes ont été enregistrées de façon reproductible. Les différences observées entre les courbes obtenues avec les fibres traitées et non traitées sont discutées. Malgré des différences caractéristiques, l'analyse thermique différentielle ne peut pas être considérée comme une méthode universelle pour caractériser de tels traitements. La thermogravimétrie pourrait être potentiellement plus adaptée.

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, DTA. , DTA. , , . : ) , ) ) ) ). DTA , . . DTA , . , .

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Paper presented at the 1^st ESTA, Salford U.K.

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We wish to thank Precision Processes (Textiles) Ltd., and the International Wool Secretariat for samples and information. Their co-operation is gratefully acknowledged. One of us (WMF) wishes to record her thanks to the I.W.S. for their support of a research studentship.     

Structure of Pt/ZnAl2O4 catalysts

The effect of the support preparation technique (solgel and coprecipitation) on the final Pt/ZnAl₂O₄ catalyst is presented. The structural properties of the solids obtained are correlated to the selectivity and activity for isobutane dehydrogenation in H₂ and He reaction media. If a highly dispersed catalyst is suitable, the support has to be prepared by the sol-gel method.

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( — ) Pt/ZnAl₂O₄. H₂ He. , — .

     

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.

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

     

Flow reactor for kinetic studies with simultaneous X-ray phase analysis of a catalyst

A flow reactor for kinetic studies of heterogeneous catalytic reactions with simultaneous X-ray phase analysis of the catalyst is described. As an example, the correlation between the selectivity of acetylene hydrogenation and the -Pd hydride concentration in palladium catalysts is shown.

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, . -Pd .

     

Reaction between the OH group of hydroxyproline and diisocyanate catalyzed by an organotin compound

We have studied the kinetics of the reaction of L-hydroxyproline with OCH(CH₂)₆NCO, catalyzed by organotin, avoiding side reactions by protecting the other active hydrogens of the aminoacid, and comparing it with the MeOH/n-BuNCO system.

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L-- -OCN(CH₂)₆NCO, , . . - .

     

Oxidative dehydrogenation of ethylbenzene of Fe?Sb?O catalysts

The conversion and selectivity to styrene in the oxidative dehydrogenation of EtPh at 800 K has been foudn to depend on the x=[Sb]/[Sb]+[Fe] ratio in the catalyst, being the highest at x0.8. The observed increase in specific catalytic activity is probably caused by the formation of a solid solution of FeSb₂O₆ in the catalyst.

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800°, x[Sb]/[Sb]+[Fe] . x=0,8. FeSb₂O₆ .

     

Compounds responsible for the deactivation of H-USY zeolite during the alkylation of phenol with methanol

H-USY deactivates very rapidly during the alkylation of phenol with methanol at 200°C. The retention in the pores of compounds resulting from successive O- and C-alkylation of phenol (such as polymethylphenols and polymethylanisoles) is responsible for this deactivation. The retention of these compounds in the pores is not due to their steric blockage but to their low volatility and their strong adsorption.

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H-USY 200°C. , - - , ( -). , .

     

Thermal stability and phase transformations in a commercial vanadia-molybdena alkali-promoted catalyst

Temperature-programmed decomposition, thermal analysis, thermogravimetry and high-temperature X-ray analysis have been used to investigate a commercial catalyst for the selective oxidation of benzene into maleic anhydride. It was shown that phase transformations took place in the vanadia-molybdena alkali-promoted catalyst. The transformations were caused either by high-temperature treatment or by catalytic work in an industrial plant. As a result, the-bronze phase was formed. In the high-temperature region a reversible transformation of the bronze phase was observed. This was interpreted as the phase transformation.

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Zusammenfassung Temperaturprogrammierte Zersetzung, Thermoanalyse, Thermogravimetrie und Hochtemperatur-Röntgenanalyse wurden zur Untersuchung eines kommerziellen Katalysators für die selektive Oxydation von Benzol zu Maleinsäure herangezogen. Es wird gezeigt, daß in dem einen Alkalipromotor enthaltenden Vanadinoxid-Molybdänoxid-Katalysator Phasenübergänge vor sich gehen. Die Phasenübergänge, als deren Ergebnis eine-Bronzephase gebildet wird, wurden entweder durch Hochtemperaturbehandlung oder durch sich in einer industriellen Anlage während des Betriebes abspielenden Vorgänge verursacht. Im Bereich hoher Temperaturen wurde eine reversible Umwandlung der Bronzephase beobachtet, die als Phasenübergang interpretiert wurde.

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