Thermal behaviour of acidic salts of mixed tetravalent metals

The results of investigations on intercalated crystalline zirconium phosphate are described in the literature. The behaviour of crystalline phosphates containing both zirconium and titanium metal ions has not been investigated previously. Within these investigations, the thermal behaviour of such materials has been studied in the temperature interval 25–1000 °C by simultaneous recording of TG, DTG and DTA curves. The results are presented in this paper.

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Zusammenfassung Ergebnisse über Untersuchungen an in Schichten eingelagerten kristallinen Zirkoniumphosphat sind in der Literatur beschrieben. Das Verhalten kristalliner Phosphate, die sowohl Zirkoniumals auch Titanmetallionen enthalten, wurde bis jetzt nicht untersucht. Als Teil dieser Untersuchungen wurde das thermische Verhalten solcher Materialien im Temperaturbereich 25–1000 °C durch simultanes Registrieren der TG-, DTG- und DTA-Kurven näher bestimmt, dessen Ergebnisse hier dargelegt werden.

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. , . , , 25–1000°. .

     

The use of temperature to simplify formose sugar composition

Form ose reaction, the Ca(OH)₂ catalyzed condensation of HCHO to a complex mixture of sugars, does not lose its autocatalytic nature at 98°C. The induction period is 15 sec, and then, at 18% total HCHO conversion, there was a period of approximately 3 sec duration in which the reaction had produced C₆ sugars at 84.3 wt.% selectivity. Glucose amounted to 90% of those sugars, and no branched sugars were detected. Conversion was complete within 3 min. The simple nature of the product was lost at lower temperatures or higher conversions.

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— HCHO, Ca(OH)₂, 98°C. 15 , 38%- HCHO 3 , C₆ 84,3 . %. 90%, . 3- . .

     

Zum Verhalten von Olefinen,konjugierten Dienen und Steroidolefinen gegenüber Pb(OCOCF3)4

The reaction of Pb(OCOCF₃)₄ with several olefines and conjugated dienes is reported. The oxidation of styrene, stilbene and 1.4-dihydro-1.4-methanonaphthalene leads to phenylacetaldehyde (1), benzaldehyde (2) and benzophenone (3), and to 1.2.3.4-tetrahydro-1.4-methanonaphthalene-(2S,9R+2R,9S)-diol-bis-trifluoroacetate (8) respectively. Of the conjugated dienes, 1.3-cyclohexadiene yieldscis-2-cyclohexene-1.4-diol bis-trifluoroacetate (4), cyclopentadiene yieldscis-2-cyclopentene-1.4-diolbis-trifluoroacetate (5) andtrans-2-cyclopentene-1.4-diol-bis-trifluoroacetate (6) andE,E-2.4-hexadiene yields the isomers of 3-hexene-2.5-diol bis trifluoroacetate (7). Oxidation of unsaturated steroids such as 2-cholestene, 2-androsten-17-one, 4-cholestene, androsta-4.9(11)-diene-3.17-dione and 3-acetoxy-5-cholestene results in cholestane-2,3-diol diacetate (9), 2,3-diacetoxyandrostan-17-one (10) and 1-acetoxy-2-androsten-17-one (11), in coprostane-4,5-diol-4-trifluoroacetate (12) or coprostane 4,5-diol-4-acetate (12a), 4-cholestanone (13), in 12-trifluoroacetoxyandrosta-4,9(11)-diene-3.17-dione (14), and in cholestane-3,5,6-triol-3-acetate-6-trifluoracetate.

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Mit 1 Abbildung     

Interaction of super-finely dispersed Al powders with water

Interaction of super-finely dispersed Al powders (SFDP) with water is characterized by the presence of a considerable section on the kinetic curves, where the conversion rate is maximum and its degree is as high as =0.5–0.7. It is suggested that the essential factor accounting for the conversion kinetics and the phase composition of its products is the self-heating of Al particles.

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() , , () 0,5–0,7. , .

     

Some comments on Prigogine's theories

Objections are raised against the theories of the Brussels group because they greatly exaggerate claims for the theory, neglect other relevant theories of themodynamics and overemphasize the role of the Poisson distribution. A necessary and sufficient condition will be given for (not necessary linear) simple birth-and-death processes to have a Poissonian stationary distribution.

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, .. =ye , . ( ) --, .

     

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 . .

     

Platinum-palladium catalysts in hydrogenation of methylbenzenes

Hydrogenation of benzene, toluene, o,m and p-xylene over Pt, Pd and Pt–Pd/Al₂O₃ catalysts has been studied. Experimental data show that when Pd is added to Pt catalysts, a decrease in activity and changes in selectivity occur. This is explained by the formation of electron-deficient and electrorich metallic species.

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, , -, - - Pt, Pd Pt–Pd/Al₂O₃. , Pd Pt . .

     

Catalytic incineration of n-hexane on Pt/Al2O3

The catalytic incineration of n-hexane over a Pt/Al₂O₃ catalyst has been studied using a fixed bed reaction. The reaction was carried out in dry air between 250 and 350 °C and at 1 atm pressure. The concentration of n-hexane was between 25 and 300 ppm. The reaction was found to be zero order in n-hexane concentration and the activation energy was found to be 21 kcal/mol. The zero order kinetics can be explained by a surface redox cycle known as Mars-van Krevelen mechanism in which the oxidation of surface Pt is the rate-controlling step.

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- Pt/Al₂O₃ . , 250–350°C 1 . - 25–300 .. - –21 /. , — , , , Pt.

     

A method to study reaction kinetics over finely-dispersed catalysts in stationary and non-stationary conditions

The application of a small-volume gradientless flow reactor with a vibrofluidized catalyst bed, mass-spectrometric analysis of the reaction products and a membrane turbulizer for alternate purging of the reactor filters by the reaction mixture permits to study the kinetics of complex catalytic reactions over catalysts with 50–100m grains in both stationary and nonstationary conditions.

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, - 50–100 .

     

Decomposition of cumene hydroperoxide in the presence of metal 1,2-dithiolate complexes

Metal 1,2-dithiolate complexes were studied as catalysts for decomposition of cumene hydroperoxide. Reaction proceeds by a two-stage process and the first stage, corresponding to destruction of the metal complex, is influenced by the type of metal and substituents on the dithiolate ligand. On average, almost two sulfur atoms in each metal chelate are oxidized to SO₂ or SO₃, which decompose the main part of hydroperoxide.

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1,2- . : . SO₂ SO₃, .

     

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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- . , , - .

     

An application of thermogravimetry to quantitative studies of feldspar alteration in soils

Thermogravimetry is a fast, accurate and highly sensitive method for the quantitative determination of halloysite, kaolinite and gibbsite in 10 mg altered feldspar grains from lateritic saprolite materials. A wide range in composition occurs between grains, and is evidence of the existence of various geochemical microenvironments within lateritic saprolite. Variations in dehydroxylation temperature of gibbsite and halloysite/kaolinite between the altered feldspar grains are an analytical artefact. The dehydroxylation temperature of gibbsite and halloysite/kaolinite increased from 242 °C to 302 °C and 454 °C to 491 °C respectively with the increase in the concentration of these minerals in the altered feldspar grains.

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Zusammenfassung Die Thermogravimetrie ist eine schnelle, genaue und hochempfindliche Methode zur quantitativen Bestimmung von Halloysit, Kaolinit und Gibbsit in Feldspatkörnern von lateritischen Saproplit-Materialien. Die Zusammensetzung der Körner schwankt in weiten Grenzen, was auf die Existenz von verschiedenen geochemischen Mikroumgebungen innerhalb des lateritischen Saprolits hinweist. Unterschiede in der Dehydroxylierungstemperatur von Gibbsit und Halloysit/Kaolinit haben sich als Artifakte herausgestellt. Die Dehydroxylierungstemperatur von Gibbsit bzw. Halloysit/Kaolinit stieg mit zunehmender Konzentration dieser Minerale in den Feldspatkörnern von 242 auf 302 °C bzw. von 454 auf 491 °C.

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, , 10 - . . /, , . / , , 242 302° 454° 491° .

     

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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, - . . .

     

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 .

     

Applied chemical thermodynamics and kinetics on pharmaceutical compounds

The important role of thermoanalytical methods in the field of pharmaceutical and galenic research is outlined. The thermodynamic stability of polymorphic forms of a substance is discussed.

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Zusammenfassung Es wird die wichtige Rolle thermoanalytischer Methoden auf dem Gebiet der pharmazeutischen und galenischen Forschung betont und die thermodynamische Stabilität polymorpher Formen von Substanzen besprochen.

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. .

     

IR and thermal studies on lithium oxomolybdenum(VI) oxalate

A new molybdenum(VI) complex, Li₂[Mo₂O₆(C₂O₄)] · 2 H₂O (LMO), was prepared and characterized by chemical analysis and IR spectral studies. Its thermal decomposition was studied by using TG and DTA techniques. LMO loses its two moles of water between 75 and 170° to give the anhydrous product, which decomposes in three stages between 240 and 380°. The first two stages occur in the temperature ranges 240–280° and 280–305°, to give intermediates with the tentative compositions Li₆[Mo₆O₁₉(C₂O₄)₂] and Li₆[Mo₆O₂₀(C₂O₄)], respectively. In the third stage, which extends up to 380°, Li₆[Mo₆O₂₀(C₂O₄)] decomposes to give the end-product, Li₂Mo₂O₇.

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Zusammenfassung Ein neuer Molybdän(VI)-Komplex der Formel Li₂[Mo₂O₆(C₂O₄)] · 2 H₂O (LMO) wurde dargestellt und durch chemische Analyse und IR-spektroskopisch charakterisiert. Die thermische Zersetzung dieses Komplexes wurde mittels TG und DTA untersucht. LMO verliert die zwei Wassermoleküle zwischen 75 und 170° unter Bildung des wasserfreien Produktes, das zwischen 240 und 380° in drei Stufen zersetzt wird. Die in den Temperaturbereich von 240–280° und 280–305° verlaufenden ersten zwei Reaktionsschritte ergeben Intermediäre der tentativen Zusammensetzung Li₆[Mo₆O₁₉(C₂O₄)₂] bzw. Li₆[Mo₆O₂₀(C₂O₄)]. In dem sich bis 380° erstreckenden dritten Reaktionsschritt wird Li₆[Mo₆O₂₀(C₂O₄)] unter Bildung des Endproduktes Li₂Mo₂O₇ zersetzt.

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Li₂[MO₂O₆(C₂O₄] · 2 ₂ . . - 70–170° , , 240–380°. 240–280° 280–305° - Li₆[Mo₆O₁₉(C₂O₄)₂] Li₆[Mo₆O₂₀(C₂O₄)]. - 380° Li₂Mo₂O₇.

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The authors are grateful to Prof. S. N. Tandon, Head of the Chemistry Department, for providing the research facilities.     

Application of the vapor phase supporting (VPS) method for preparing SnO2/SiO2 catalysts

Supported SnO₂/SiO₂ catalysts have been prepared by the reaction of the surface hydroxy groups of silica gel and gas phase tin chloride (PS method). The catalytic properties have been examined in the reaction of 2-propanol to show the effect of VPS cycles on the amount and nature of the active sites.

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SnO₂/SiO₂ . 2- VPS .

     

Mechanism of action of sulfur-containing complexes in oxidation processes

A mechanism of the inhibiting action of Cu(II), Ni(II), Pb(II), Zn bis(N, N-dialkyldithiocarbamates) and Cu(II) bis (-thiopicolineanilides) in the AIBN initiated oxidation of ethylbenzene, styrene and nonene-1 is proposed. Inhibition is due to the deactivation of free radicals upon interaction with the chelate active center consisting of a metal with coordinated ligand atoms. As supported by the experimental data, the reaction occurs by an electron transfer mechanism.

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-(N,N-) Cu(II), Ni(II), Pb(II), Zn -(-) Cu(II) , -1. . . .

     

Formation and creeping of the crystalline phase wavefront within the bed of vanadium sulfuric acid catalyst

Kinetics of the reduction of sulfur dioxide by methane in the presence of molecular oxygen at 732–831°C have been obtained.

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732–831°C.

     

Thermoanalytical study of the solid state reaction between hydrated ZnO and Fe2O3

The hydrated oxides which are formed by the addition of ammonium bi-carbonate to a solution of Zn(NO₃)₂ and Fe(NO₃)₃, and drying the precipitates at 110° are zinc hydroxy carbonate(I) and iron(III) oxide gel(II), respectively. A new, derived derivative thermogravimetric curve along with conventional DTA and DTG methods have been used to study the reaction between (I) and (II) in two components system.A mixture of (I) and (II) subjected to grinding yields about 16% zinc ferrite precursor. In a sample prepared by coprecipitation from the mixed nitrate solution and drying at 110°, nearly 70% precursor is formed. The formation of zinc ferrite spinel reported to take place at low temperature in such cases appears to be related with the formation of the precursor, and reactivity and phase transformation temperature in Fe₂O₃.

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Zusammenfassung Die durch Zugabe von Ammoniumbicarbonat zu einer Lösung von Zn(NO₃)₂ und Fe(NO₃)₃ und Trocknung des Niederschlags bei 110° gebildeten hydratisierten Oxide sind Zinkhydroxycarbonat (I) bzw. Eisen(III)oxidgel (II). Eine neue derivierte derivative thermogravimetrische Kurve wurde gemeinsam mit den konventionellen DTA und DTG Methoden zum Studium der Reaktion zwischen (I) und (II) in Zweikomponentensystemen eingesetzt.Das Gemisch von (I) und (II) ergibt beim Mahlen etwa 16% Zinkferrit »Prekursor«. In einer durch Mitfällung der gemischten Nitrate und Trocknung bei 110° erhaltenen Probe wurde fast 70 % »Prekursor« gebildet. Die Bildung von Zinkferritspinell, über dessen Entstehung in solchen Fällen bei niedrigen Temperaturen berichtet wird, scheint mit der Bildung des »Prekursors« verbunden zu sein, sowie mit der Reaktivität und der Phasenübergangstemperatur in Fe₂O₃.

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Résumé Les oxydes hydratés formés lors de l'addition du bicarbonate d'ammonium à une solution de Zn(NO₃)₂ et de Fe(NO₃)₂ suivie du séchage du précipité à 110°, sont l'hydroxy-carbonate de zinc(I) et le gel de l'oxyde de fer(III) (II). On a utilisé une nouvelle technique de thermogravimétrie en dérivation, ainsi que les méthodes d'ATD et TGD conventionnelles, pour étudier la réaction entre (I) et (II) dans le système à deux composants.Un mélange de (I) et de (II), soumis au broyage, donne environ 16 p.c. de ferrite de zinc «précurseur», tandis qu'un échantillon préparé par coprécipitation à partir de la solution des nitrates mixtes et séchage à 110°, en donne environ 70 p.c.La formation du spinelle de ferrite de zinc décrite comme ayant lieu, dans des cas similaires, à des températures faibles, paraît être en rapport avec la formation du «précurseur» ainsi qu'avec la réactivité et la température de la transformation de phase de Fe₂O₃.

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Zn(NO₃)₂ Fe(NO₃)₃, , 110°, , , (I) (II). , , I II . I II, , 16% , . , 110°, 70% , . « » , Fe₂O₃.