Various dynamic behavior of Ag+-induced oscillations in uncatalyzed bromate oscillators

Silver ion induces the uncatalyzed bromate oscillators /aromatics-bromate-acid/on a variety of dynamic behavior, including high frequency and complex oscillations. The behavior of a reacting system depends on the chemical composition of the armatics, the time of addition of Ag⁺, and the concentration of Ag⁺. The chemistry underlying the phenomena is discussed.

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(--) , . , Ag⁺ Ag⁺. .

     

Differential scanning calorimetry of spin-oriented polyester yarn

Polyester yarn spun over a range of wind-up speeds has been characterized using differential scanning calorimetry. Samples prohibited from shrinking during the thermal analysis show slightly smaller heats of fusion and crystallization and reduced cold crystallization temperatures than samples that are free-to-shrink, particularly in the intermediate wind-up speed region. One critical observation made is that the cold crystallization temperature reaches a minimum at some relatively low overall molecular orientation (n 0.020) and fails to decrease further. A likely explanation is that crystallization continuously removes polymer from the melt in the spinline in regions where the local orientation reaches some critically high value.

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Zusammenfassung Mit verschiedenen Aufspulgeschwindigkeiten gesponnenes Polyestergarn wurde durch DSC charackterisiert. Die während der tyermischen Analyse am Schrumpfen gehinderten Proben zeigen, besonders bei mittleren Aufspulgeschwindigkeiten, eine etwas geringere Schmelz- und Kristallisationswärme und niedrigere kalte Kristallisationstemperaturen als Proben, die ungehindert schrumpfen konnten. Die kalte Kristallisationstemperatur erreicht bei enier relativ niedrigen Gesamtmolekularorientierung (n 0.020) ein Minimum und nimmt nicht weiter ab. Wahrscheinlich ist, dass durch die Kristallisation das Polymer in den Bereichen, in denen die lokale Orientierung einen kritischen Wert erreicht, kontinuierlich aus der Schmelze entfernt wird.

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, , . , - , , , , , , . , (n0.020) . , , .

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The author appreciates the input provided by Dr. R. M. Mininni and the help of Dr. W. E. Bessey in fiber spinning and Ms. E. Fernekess in thermal analysis. The author is grateful to Celanese Corporation for allowing publication of this work.     

Selective synthesis of lower olefins by catalytic conversion of methanol

C₂C₄ olefins were synthesized from methanol on modified ZSM-34 type zeolite catalyst at 400°C. Methanol vapor of 12 vol.% was converted completely under flow conditions at 800 h^–1 space velocity, and in molar selectivity 42.9% C₂H₄, 33.4% C₃H₆, and 3.3% C₄H₈ were produced.

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C₂C₄ ZSM-34 400°C. 12 .%-, 800 h–1 : C₂H₄-42,9%, C₃H₆-33,4% C₄H₈-3,3%.

     

Effect of inorganic salts on the process of competitive hydrogenation of 2-methyl-3-butene-2-ol and 2-phenylpropene on a platinum catalyst

The effect of inorganic salts (NaNO₃, NaCl, Na₂SO₄, NaHCO₃ and Na₃PO₄) on the selectivity of competitive hydrogenation of 2-methyl-3-butene-2-ol and 2-phenylpropene at 20 °C and atmospheric pressure on a 5%Pt/act. C catalyst in methanol solution was investigated. The dependence of the selectivity and of the initial rate of hydrogenation of the given equimolar mixture on the amount of sodium phosphate used in the modification of the platinum catalyst was measured.

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(NaNO₃, NaCl, Na₂SO₄, NaHCO₃, Na₃PO₄) 2--3--2- 2- 20 °C 5% Pt . Na₃PO₄ .

     

Selective hydrogenation of carbon monoxide to light olefins catalyzed by supported potassium tetracarbonylhydridoferrate

In the Fischer-Tropsch synthesis, potassium tetracarbonylhydridoferrate, KHFe (CO)₄, supported on HY-zeolite or silica gel exhibited high selectivity to light olefins without following the Schulz-Flory distribution.

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, KHFe(CO)₄, HY —, — .

     

Oxidation of divalent manganese by peroxodiphosphate in acetate buffers. A kinetic study

Bivalent manganese in oxidized to the tervalent state in 4.0–5.3 pH (acetate buffers) when treated with an excess of peroxodiphosphate (PDP). Kinetic evidence for the formation of a 11 complex between manganese(II) and PDP was obtained. The reaction exhibits first order dependence on [Mn(II)] and fractional order dependence on [PDP]. The reaction is markedly inhibited by H⁺ ions. A plausible mechanism consistent with the observed data is proposed.

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pH=4,0–5,3 (). (II) 11. [Mn(II)] []. H⁺ . , .

     

Peculiarities of formation of ZnO and CuO-based solid solutions

Low-temperature (623 K) treatment of hydroxocarbonate compounds of copper-zinc and copper-zinc-aluminium leads to the formation of phases with CuO and ZnO structures, which are solid solutions of the promoter ions. The formation of solid solutions is attributed to structural distortions (uniform or local) in the oxide lattice due to the incomplete removal of OH^– and CO ₃ ^2– groups at low temperatures.

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, (623 ) - -- CuO ZnO, . , ( ) - OH ₃ ^–– - .

     

Method to affect catalytic properties of low-temperature transition metal oxides

A method to affect the catalytic properties of low-temperature oxide catalysts by their synthesis through hydroxide compounds of the required composition and structure is suggested.

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.

     

Solid aluminiumalkyl-based isomerization catalysts. Surface acidity and catalytic activity

Isomerization catalysts with high activity and selectivity were prepared by chemical anchoring of aluminiumethyldichloride on the surface of inorganic oxides. Surface acidity was studied by calorimetric and IR spectroscopy methods, and was found to correspond well with catalytic activity for m-xylene isomerization.

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. . , -.

     

Interrelation of addition reactions of hexachlorocyclopentadiene and bromine to N-arylimides of endo-and exo-bicyclo[2,2,1]hept-5-ene-2,3-dicarboxylic acids

A comparative analysis of the relative reactivities of N-arylimides of endo-and exobicyclo[2,2,1]hept-5-ene-2,3-dicarboxylic acids for the addition reactions of hexachlorocyclopentadiene and bromine has been carried out. According to different correlations the transition states of these two processes are shown to be similar.

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N- - - [2,2,1] -5--2,3- . .

     

Effect of the medium on the oxidation of aliphatic monocarboxylic acids

Oxidation rates and k₂/k₆ ratios are given for some acids from propionic to lauric. The k₂/k₆ ratio is shown to be influenced by the electrostatic effect of the solvent. A linear dependence between the isodielectric values of k₂/k₆ and the number of methylene groups in the acid molecules is described.

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k₂/k₆ . k₂/k₆ k₂/k₆ .

     

Pure pseudoboehmite from sodium aluminate

The influence of the Na₂O/Al₂O₃ mole ratio in sodium aluminate, the pH and the temperature of precipitation upon physicochemical properties of pseudoboehmite obtained from sodium aluminate has been studied. A mole ratio of 11 and low pH are favorable for the preparation of pure alumina.

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Na₂O/Al₂O₃ , pH , . , Na₂ O/Al₂O₃=1 , pH, .

     

Changes in the acid-strength distribution and the catalytic selectivity of H,Na?MOR

Acidities of synthetic H,Na–MOR samples decationized to different degrees have been characterized by differential adsorption heat distribution of ammonia. A fairly good correlation has been found between the number of acid sites of different strengths and the catalytic activity as well as the selectivity for xylene isomerization and disproportionation. The results are correlated with the mechanism of these reactions.

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H,Na–MOR, , - . , . .

     

Phase equilibria in the Tl2Te-Ag2Te system

The phase diagram for the Tl₂Te-Ag₂Te system has been established by thermal analysis and X-ray diffraction methods. The results obtained are compared with the data of other authors. Examples are given of using the disadvantages of thermal analysis for the correct interpretation of experimental data.

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Zusammenfassung Das Phasendiagramm von Tl₂Te-Ag₂Te wurde durch thermische Analyse und röntgendiffraktometrie ermittelt. Die erhaltenen Ergebnisse werden mit denen anderer Autoren verglichen. Beispiele werden angeführt, wie die Nachteile der thermischen Analyse zur korrekten Interpretation der experimentellen Daten benutzt werden können.

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Tl₂Te-Ag₂Te. . .

     

A new method for measuring the induction period of the oxidation of polymers

A simple method independent of oxygen absorption measurements was developed for estimating the induction period of the oxidation of polymers. The principle of this method is the estimation of the time in which a sample oxidized at constant temperature exhibits a temperature rise as a consequence of the exothermal effect of the oxidation reaction. The temperature rise is measured as the temperature difference between the sample and a reference material. Results of measurements of induction periods of the oxidation of polymeric substrates inhibited by various antioxidants, obtained both from oxygen absorption measurements and by the new method, are discussed.

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Zusammenfassung Eine von der Sauerstoffabsorption unabhängige Methode wurde zur Messung der Induktionsperiode der Oxydation von Polymeren entwickelt. Sie beruht auf Bestimmung der Zeit, die von einer isothermisch oxydierten Probe erforderlich ist, um einen durch den exothermischen Effekt der Oxydation hervorgerufenen Temperaturanstieg zu zeigen. Der Temperaturanstieg wird als eine Temperaturdifferenz zwischen Probe und Referenzstoff gemessen. Die Ergebnisse von Bestimmungen der durch verschiedene Antioxydanten inhibierten Induktionsperioden von Polymersubstraten durch Sauerstoffabsorption und durch die neue Methode werden besprochen.

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Résumé On développe une méthode simple et indépendante de la mesure de l'absorption de l'oxygène pour estimer la période d'induction au cours de l'oxydation des polymères. Le principe repose sur l'évaluation du temps pendant lequel un échantillon traité en conditions isothermes manifeste une élévation de température par suite de l'effet exothermique dû à l'oxidation. On mesure l'élévation de température sous forme d'une signal différentiel entre l'échantillon et une substance de référence. On discute les résultats des mesures des périodes d'induction des substrats polymères traités par divers antioxydants, en opérant à l'aide de la nouvelle méthode et par absorption d'oxygène.

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, . , , , . « ». , , , .

     

Tracer study of complete oxidation complexes in the oxidative dehydrogenation of butylene

A tracer technique using divinyl-¹⁴C was used to determine the butylene and divinyl contents in the surface complexes of complete oxidation during the oxidative dehydrogenation of butylenes over Bi–Mo, Fe–Sb and Fe₂O₃ catalysts. The rate of decomposition of the surface complexes was found to be independent of their relative butylene and divinyl content.

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–C¹⁴ Bi–Mo, Fe–Sb Fe₂O₃ ., .

     

Activation of magnesia by hydrogen spillover

Magnesia aerogel activated by hydrogen spillover at 430 °C or at 200 °C becomes a catalyst for the hydrogenation of ethylene. This catalytic activity, observed already at 50 °C, is further enhanced by a treatment in oxygen at 430 °C.

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, 430 200°C, . 50°C 430°C.

     

Comportement thermique des benzènesulfonates de lithium,sodium et potassium

Résumé Le comportement thermique des benzènesulfonates de lithium, sodium et potassium a été étudié par TG et ATD à l'air et sous atmosphère d'azote.Dans la zone de stabilité des sels anhydres, nous avons mis en évidence des transformations réversibles (changements de phase cristalline) dont certaines ont fait l'objet de mesures calorimétriques.L'étude des résidus solides de la décomposition a montré une proportion importante de sulfates dans les produits obtenus dans l'air, alors que sous azote, il s'agissait surtout de sulfures. Les sulfites ne se présentent qu'en très faible quantité dans les deux cas.

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The thermal behaviour of benzènesulphonates of lithium, sodium and potassium has been investigated by TG and DTA in air and in an atmosphere of nitrogen.We have shown in the stability interval of the anhydrous salts reversible transformations (phase transitions), some of which were quantitatively studied by calorimetry.The radiocristallographic study of the solid residues has shown an important proportion of sulphates in the residues in air and of sulphides in an inert atmosphere. The sulphites were found in very small quantity in both cases.

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Zusammenfassung Das thermische Verhalten der Benzolsulfonate von Lithium, Natrium und Kalium wurde durch TG und DTA in Luft und in Stickstoff untersucht.Im Stabilitätsbereich der wasserfreien Salze wurden reversible Umwandlungen (Phasenübergänge) nachgewiesen, von denen einige quantitativ durch Kalorimetrie untersucht wurden.Das radiokristallographische Studium der festen Rückstände zeigte, daß in Luft ein bedeutender Anteil der Rückstände aus Sulfaten und in inerter Atmosphäre aus Sulfiden besteht. Sulfite wurden in beiden Fällen in sehr geringen Mengen gefunden.

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, . , , ( ), . , , - . .

     

Specific changes in the activity of titanium carbides with various Ti/C ratios in propylene hydrogenation

According to X ray emission spectra, the established regularity in the activity change for titanium carbides with various Ti/C ratios is attributed to the filling degree of the t_2g states of titanium atoms determining the metallicity of chemical bonds of the compounds.

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Ti/C t_2g , .

     

Calorimetry for thermokinetic determinations

The possibilities of using direct calorimetric measurements for the determination of kinetic parameters of processes are discussed in terms of the choice of an appropriate method of reproduction of the course of changes in the heat power generated in time, i.e. thermokinetics. Such methods are presented and it is concluded that many of these methods permit reproduction of the thermokinetics in the same way as if the experimental thermal curve were obtained in a calorimetric system characterized by a time constant 100–200 times as large as that for the thermal inertia of this calorimetric system.

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Zusammenfassung Die Möglichkeiten zur Benutzung direkter kalorimetrischer Messungen zur Bestimmung kinetischer Parameter von Prozessen werden hinsichtlich der Wahl geeigneter Methoden zur Reproduzierung des Verlaufs der Änderungen der Wärmekraft mit der Zeit, d.h. zur Reproduzierung der Thermokinetik diskutiert. Solche Methoden werden angeführt und es wird die Schlussfolgerung gezogen, dass viele dieser Methoden die Reproduzierung der Thermokinetik auf gleiche Weise wie in den Fällen erlauben, in denen die thermische Kurve mit einem kalorimetrischen System erhalten wird, dessen Zeitkonstante um 100–200mal grösser als die des diskutierten Systems ist.

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. . . , , , 100–200 .

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Presented at the 2nd Czechoslovak Conference on Calorimetry, Liblice, Czechoslovakia, 1982.