Thermoanalytical investigation of ion exchange resins. The swelling water of anion exchange resins

The water uptakes of completely swollen and air dried anion exchange resins were investigated by traditional and also by thermoanalytical measurements. In investigations on the air dried resin samples of HSO₄, H₂PO₄, SO₄, HPO₄ and PO₄ forms, two types of water (strongly and loosely bound) were found. The sequence of water uptake on the resins investigated was compared to the opposite order of the adsorption strengths of the anions and to the entropies of the hydrated anions. A conclusion was made regarding the role of the hydration of the anions in the selectivity sequence of anion exchange.

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Zusammenfassung Die Wasseraufnahme vollständig angequollener und lufttrockener Anionenaustauscherharze wurde mittels herkömmlicher sowie auch thermoanalytischer Messungen untersucht. Bei den Prüfungen der lufttrockenen Harzproben in den HSO₄-, H₂PO₄-, SO₄-, HPO₄-, und PO₄-Formen wurden zwei Arten von Wasser gefunden: stark und schwach gebundenes. Die Reihenfolge der Wasseraufnahme wurde mit der umgekehrten Reihenfolge der Adsorptionsstärke der Anionen und mit der Entropie der hydratisierten Anionen verglichen. Schlüsse bezüglich der Rolle der Hydratisierung der Anionen bei der Selektvititätsreihenfolge des Anionenaustausch wurden gezogen.

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Résumé On a étudié par des mesures traditionnelles et par analyse thermique l'absorption d'eau par des résines échangeuses anioniques totalement gonflées et séchées à l'air. Lors de l'étude des échantillons de résines séchées à l'air, de formes HSO₄, H₂PO₄, SO₄, HPO₄ et PO₄, on a trouvé deux types d'eau: de l'eau fortement liée et de l'eau faiblement liée. On a comparé l'ordre de l'absorption d'eau des résines étudiées à l'ordre inverse des forces d'adsorption des anions et à l'entropie des anions hydratés. On en tire des conclusions sur le rôle de l'hydratation des anions sur la sélectivité de l'échange anionique.

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- , . - HSO₄-, H₂PO₄-, SO₄-, HPO₄-, PO₄- : . . .

     

Kinetics of Cr(VI) and V(V) oxidation of trans-stilbene and indene

Title reactions are acid catalyzed and strongly dependent on the permittivity of the medium. With Cr(VI) indene reacts faster than trans-stilbene, but with V(V), trans-stilbene reacts faster than indene. The mechanism is discussed.

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. Cr(VI) , -, V(V) - , . , .

     

Novel type of oscillatory chemical reactions

Chemical oscillations occur during the uncatalyzed oxidation of a number of phenol and aniline derivatives by acidic bromate.

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.

     

On a theorem of overshoot-undershoot kinetics

A lemma has been provided to completely prove and to extend the following theorem. In a closed system of first-order, reversible reactions involving n components the concentration vs. time curve of any component can exhibit at most n-2 relative strict extrema.

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: , n, n-2 .

     

Thermogravimetric and EPR study of the solid-state reactions between zinc chromate and zinc oxalate

The formation of some catalytically active Cr(V) and Cr(III) species is studied when the progressive thermal reduction of zinc chromate is enhanced by the addition of solid zinc oxalate, the reducing agent CO being formed in situ, during thermal analysis.When compared with the decomposition of pure ZnCrO₄, Cr(VI) reduction, as followed by EPR, is similar concerning the nature of the intermediate Cr species formed: Cr(V), Cr(III) in a Cr₂O₃-like bulk phase and Cr(III) dispersed in ZnO. However, the temperature range of Cr₂O₃ formation, as well as the magnitude of the Cr(III)-Cr(III) interaction in such a phase is found to be strongly dependent on the amount of ZnO formed. On the other hand, after the Cr(V) species resulting from progressive oxygen release have disappeared, some other stable Cr(V) species are formed again at higher temperatures. Their formation may be related to a further reduction of the remaining Cr(VI) species by CO stemming from the oxalate.

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Zusammenfassung Die Bildung einiger katalytisch aktiver Cr(V) und Cr(III) Species wird für den Fall untersucht, bei dem die progressive thermische Reduktion von Zinkchromat durch Zugabe von festem Zinkoxalat gefördert wird, wobei das Reduktionsmittel CO in situ, während der Thermoanalyse gebildet wird.Ein Vergleich mit der Zersetzung der reinen ZnCrO₄ ergibt die ÄhnIichkeit der durch EPR verfolgten Cr(VI)-Reduktion hinsichtlich der Beschaffenheit der gebildeten Cr Intermediärspecies: Cr(V), Cr(III) in einer Cr₂O₃-artigen Hauptphase und Cr(III) in ZnO dispergiert. Jedoch sind Temperaturbereich der »Cr₂O₃«-Bildung sowie der Umfang der Cr(III)-Cr(III) Wechselwirkung in einer solchen Phase stark von der Menge des gebildeten ZnO abhängig. Andererseits werden nach dem Verschwinden der durch die progressive Sauerstoff-Freisetzung entstandenen Cr(V)-Species wider einige andere stabile Cr(V)-Species bei höheren Temperaturen gebildet. Ihre Bildung mag mit einer weiteren Reduktion der noch vorhandenen Cr(VI)-Species durch aus dem Oxalat stammendes CO verbunden sein.

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Cr(V) Cr(III) , , , , . , Cr(VI), ZnCrO₄ . , Cr : Cr(V) Cr(III) , Cr₂₃, Cr(III) ZnO. , «Cr₂₃», Cr(III)-Cr(III) . , , Cr(V) , Cr(V) . Cr(VI) , .

     

Mo(V)/SiO2 supported catalysts for the epoxidation of allyl chloride

New Mo(V)/SiO₂ supported catalysts as the products of settlement of MoO(OH)₃ on silica were obtained and ESR examined. Catalytic activity in epoxidation of allyl chloride with cumene hydroperoxide was found.

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MoO(V)/SiO₂, MoO(OH)₃ S O₂. .

     

Combination and disproportionation of methyl and 2-propyl radicals with 1,1,2-trimethylallyl radicals

The combinations and disproportionations of the CH₃ and 2-propyl (iP) radicals with the 1,1,2-trimethylallyl (TMA) radical have been studied in the gas phase in the temperature interval of 389–451 K and 490–540 K, respectively. For the ratios of the terminal (t) and non-terminal (n) combinations of the CH₃ and iP radicals with the TMA radical, values of 1.9±0.1 and 2.84±±0.10 were obtained, respectively. The ratios of the tt and tn and nn to tn combinations of the TMA radical were 1.59 and 0.46, respectively. The disproportionation-combination rations were (CH₃ , TMA)=0.022±±0.012 and (iP, TMA)=0.026±0.011.

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CH ₃ 2- (iP) 1,1,2- (TMA) : 389–451 K 490–540 K. (t) (n) TMA 1,9±0,1 2,84±0,10, . tt tn nn tn TMA 1,59 0,46, . (CH ₃ , TMA)=0,022±0,012 (iP, TMA)=0,026±0,011.

     

Evaluation of quantum yields in the presence of an absorbing additive

A method is proposed for the evaluation of quantum yields of photochemical reactions studied in the presence of absorbing additives using cylindrical sample tubes.

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Reactions of C4?C6 alkanes on platinum and platium-gold films

Results are reported on the reactions of n-butane, n-pentane and n-hexane on Pt and Pt/Au alloy films. The results are compared with those obtained for Pt–Au alloys on a SiO₂ carrier. It is concluded that alloying can change the selectivity of the catalyst. No indication has been found for the possible role of oxygen in the high selectivity of Pt in non-destructive reactions.

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-, - - Pt . , Pt–Au SiO₂. , . - Pt .

     

Catalytic reaction of methane with carbon dioxide

High activities and selectivities of Ni on SiO₂ catalysts producing CO in the reaction of CH₄ with CO₂, have been obtained at relatively low temperatures. These aspects are considerably different from the activities or selectivities of other catalysts, and have been explained by assuming that the Ni on SiO₂ catalyst markedly suppresses carbon deposition.

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CO Ni SiO₂ CH₄ CO₂. , Ni SiO₂.

     

M?ssbauer spectroscopic studies of passivated layers of iron-containing catalysts for ammonia synthesis

Combined conversion electron (CEMS) and transmission -ray (MS) Mössbauer spectroscopy was used to study the structure of passivated layers of promoted and unpromoted iron-containing catalysts. In both catalysts the oxide-coated films were found to consist of small paramagnetic (at 300 K) clusters of ferric oxide.

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. , ( 300 ) .

     

Differential thermal analysis of the phase transition of dicalcium orthosilicate Ca2SiO4 under a reducing atmosphere

The transformation of Ca₂SiO₄ was investigated with regard to the disintegration of the sinter in alumina manufacturing. DTA was applied to study the effect of the reducing atmosphere upon the course of the polymorphic transitions of Ca₂SiO₄, and particularly the self-disintegration process. Pure synthetic dicalcium orthosilicate and blends of pure components from the system CaO-Al₂O₃-SiO₂-Fe₂O₃ were compared with technological mixtures of limestone and fly ash. Data obtained from the DTA runs allowed the specification of technical parameter for both firing and cooling of the sinter.

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Zusammenfassung Die -Umwandlung in Ca₂SiO₄ wurde im Hinblick auf den Zerfall von Sinter in der Tonerdeproduktion untersucht. Mittels DTA wurde der Einfluß einer reduzierenden Atmosphäre auf den Verlauf der polymorphen Umwandlungen von Ca₂SiO₄ und insbesondere auf den Zerrieselungsprozeß verfolgt. Reines synthetisches Ca₂SiO₄ und Gemische reiner Komponenten des Systems CaO-Al₂O₃-SiO₂-Fe₂O₃ wurden mit technischen Mischungen aus Kalk und Flugasche verglichen. Die Ergebnisse von DTA-Versuchen erlauben die Spezifizierung der technischen Bedingungen für das Brennen und Abkühlen des Sinters.

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. , , . -l₂₃-SiO₂-F23 . .

     

Integral invariants in chemical kinetics

Integral invariants of classical mechanical systems are used for the mathematical treatment of equilibrium systems of chemical reaction kinetics. Some conserved quantities and Hamilton equations in chemistry are shown.

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. .

     

Kinetics of ion exchange sorption of phosphate

The kinetics of phosphate sorption on Amberlite IRA-400 has been studied as a function of temperature, nature of counterions, at two different concentrations. The film and particle diffusion coefficients and the activation parameters of the process are calculated.

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IRA-400 , . .

     

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 behaviour of thallium(I) fatty acid salts,II

The electrical conductivity (EC) changes of thallium(I) salts of fatty acids, which possess liquid crystalline phases, were investigated as a function of temperature. It was found that sharp EC jumps are associated with the phase transitions. The EC of the liquid crystalline phases depended not only on the temperature, the molecular weight and the geometry of the measuring cell, but also very sensitively on the heat treatment conditions which affect the relative magnitude of the EC in the mesophases.Study of these dependences revealed a memory effect. An explanation is given for this phenomenon.

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Zusammenfassung Die Änderungen der elektrischen Leitfähigkeit (EC) von Fettsäure-Thalium(I)-Salzen mit flüssig-kristallinen Phasen wurden als Funktion der Temperatur untersucht. Es wurde festgestellt, daß den Phasenübergängen scharfe EC-Sprünge entsprechen. Die EC der flüssig-kristallinen Phase hängt nicht nur von der Temperatur, dem Molekulargewicht und der Geometrie der Meßzelle ab, sondern auch — in sehr empfindlicher Weise — Phasen bestimmen.Die Untersuchung dieser Zusammenhänge führte zur Beobachtung eines »Memorieeffektes« Eine Erklärung dieser Erscheinung wird gegeben.

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Résumé On a étudié les variations de la conductibilité électrique (EC) des sels de thallium(I) des acides gras possédant des phases cristallines liquides, en fonction de la température. On a établi que les variations brusques d'EC correspondent aux transitions de phases. L'EC des phases cristallines liquides dépend non seulement de la température, de la masse molaire et de la géométrie de la cellule de mesure, mais aussi, et d'une manière très sensible, des conditions du traitement thermique qui affectent l'amplitude relative de l'EC dans les mésophases.Un «effet de mémoire» a été observé lors de l'étude de ces phénomènes, dont on donne une explication.

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(I) , , . , . - , , , . « ». .

     

Chelated amines as ligands in olefin hydrogenation catalysts

Activities of catalysts obtained in the reaction of [MCl(C₈H₁₄)₂]₂, (M=Rh, Ir) with amines NH₂(CH₂)_nNH₂, (N=2–5), (CH₃)₂NC₂H₄(CH₃)₂ and 1.8=diaminonaphthalene have been examined. The most efficient catalyst was obtained with 1.3-diaminopropane.

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, [MCl(C₈H₁₄)₂]₂. (M=Rh, Ir) NH₂(CH₂)_nNH₂, (n=2–5). (CH₃)₂NC₂H₄(CH₃)₂ 1,8-. , 1,3-.

     

Non-isothermal crystallisation kinetics of nucleated poly(ethylene terephthalate)

Crystallisation of poly(ethylene terephthalate) in dependence on different crystallisation promotors has been studied by non-isothermal DTA runs with several heating and cooling rates. Using an evaluation method, proposed by Kissinger, activation parameters have been evaluated for crystallisation from the amorphous state and from the melt. Calculated rate constants and half time values of crystallisation, respectively, are in good agreement with crystallisation behaviour of different samples observed under technical conditions.

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Zusammenfassung Die Kristallisation von Polyethylenterephthalat in Abhängigkeit von verschiedenen Kristallisationspromotoren wurde durch nicht-isotherme DTA bei verschiedenen Aufheiz- und Abkühlgeschwindigkeiten gemessen. Unter Verwendung einer auf Kissinger zurückgehenden Auswertemethode wurden Aktivierungsparameter für die Kristallisation aus dem amorphen Zustand bzw. aus der Schmelze ermittelt. Die berechneten Geschwindigkeitskonstanten und Halbwertszeiten der Kristallisation zeigen gute übereinstimmung mit dem Kristallisationsverhalten verschiedener Proben unter technischen Bedingungen.

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. , . .

     

Reaction scheme in the non-isothermal decomposition of (C6H5NH3)4Mo8O26 · 2 H2O

The thermogravimetric decomposition of anilinum octamolybdate has been studied under non-isothermal conditions to elucidate the chemical reactions taking place in the first step of decomposition of the anhydrous compound.The decomposition products were analyzed by gas-liquid chromatography, gas chromatography-mass spectrometry (GC/MS), infrared spectroscopy and X-ray powder diffraction.The main decomposition product of aniline turned out to be indole, which is different from the major product in the isothermal decomposition at the same temperature, i.e. N-ethyl-aniline.A dehydrocyclization reaction is suggested as the rate-dependent process. This is probably due to the catalytic effect of the octamolybdate anion.

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Zusammenfassung Die thermische Zersetzung von Anilinoctamolybdat wurde unter nicht-isothermen Bedingungen thermogravimetrisch untersucht, um die im ersten Zersetzungsschritt der wasserfreien Verbindung verlaufenden chemischen Reaktionen aufzuklären. Die Zersetzungsprodukte wurden mittels Gas-Flüssigkeits-Chromatographie, Gaschromatographie-Massenspektrometrie (GC/MS), Infrarotspektroskopie und Röntgendiffraktometrie analysiert. Als Hauptprodukt der Zersetzung von Anilin wurde Indol gefunden, während bei isothermer Zersetzung bei gleicher Temperatur vorwiegend N-Äthylanilin entsteht. Es wird angenommen, daß beim nicht-isothermen Prozeß eine wahrscheinlich durch das Octamolybdat katalysierte Dehydrocyclisierungsreaktion verläuft.

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, . - , -- , . , -N- . , , -.

     

Toluene disproportionation and coke formation over fluorided alumina and hydrogen-mordenite

Toluene transformation was investigated on a fluorided alumina and a protonic mordenite under hydrogen (0.8, 12 bar) and under nitrogen (12 bar). Hydrogen pressure considerably improves the catalytic stability of H-mordenite by inhibiting the formation of coke. Moreover, hydrogen eliminates part of the coke deposited by reaction under nitrogen, and regenerates the activity of the mordenite. On the contrary, hydrogen has no effect in the case of fluorided alumina. The particular behavior of the mordenite is attributed to its very strong acidity.

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(0,8, 12 ) (12 ). -, . , , , . , - . .