Coupling of thermometric titrimetry and constant-current coulometry: Study and applications

Two systems involving the coupling of thermometric and coulometry are presented. In the first assembly, the two electrodes were in the same compartment. Bromocoulometry was used to test the possibilities of this coupling in the sequential titration of a vitamin C+ aspirin mixture about (10^–4 M) and the determination of enthalpy changes. In a second coupling system, the anodic and cathodic compartments were separated by a sintered-glass disc of porosity 3. The conditions for obtaining an electrochemical cell which is also a good calorimeter are discussed. Examples of applications are given, such as analytical measurements, the study of an electrochemically catalysed reaction and of the thermal effects of electrode reactions.

---

Zusammenfassung Zwei Systeme werden beschrieben, die eine Kombination von thermometrischer Titrimetrie und Coulometrie darstellen. Bei der ersten Vorrichtung sind die Elektroden im gleichen Raum Untergebracht. Die Bromocoulometric wurde zur Testung der durch diese Kombination für die aufeinanderfolgende Titration von Vitamin C/Aspirin Gemischen (ungefähr 10^–4 M) und für die Bestimmung der Enthalpieänderungen gebotenen Möglichkeiten angewandt. In einem zweiten kombinierten System waren Anoden- und Kathodenraum durch ein Sinterglasfilter der Porosität 3 voneinander getrennt. Es werden die Bedingungen diskutiert, die notwendig sind, um eine elektrochemische Zelle zu erhalten, die zugleich auch ein gutes Kalorimeter ist. Anwendungsbeispiele sind angegeben, wie analytische Messungen und elektrochemische Untersuchungen katalysierter Reaktionen oder thermischer Effekte von Elektrodenreaktionen.

---

, . . — 10^–4 M . — N^o3. , . , , .

     

Kinetic analysis of temperature-programmed desorption of hydrogen after reduction of a NiNaY zeolite

From the kinetic analysis of TPD curves it can be calculated that hydrogen desorption after reduction at lower temperatures can be described by a rate equation of first order, while reduction at higher temperatures provides a second order equation interpreted by a change of the rate-determining step of the complex desorption process.

---

, , , 2- . , .

     

Investigation of thermal decomposition of hydrated aluminium oxide

The composition of a hydrated aluminium oxide was determined and the course of its thermal decomposition was investigated. The stages of the dissociation were established and all the solid and gaseous intermediates of the decomposition were identified. A correlation was observed between the peak temperatures for boehmite and the particle size and degree of crystallinity.

---

Zusammenfassung Die Zusammensetzung eines hydratisierten Aluminiumoxids wurde bestimmt und der Verlauf der thermischen Zersetzung dieses Oxids untersucht. Die Dissoziationsstufen wurden ermittelt und alle gasförmigen und festen Zwischenprodukte der Zersetzung identifiziert. Es wurde eine Korrelation zwischen den Peak-Temperaturen für Böhmit und der Partikelgrö\e und dem Kristallisationsgrad beobachtet.

---

. . , .

     

A gradientless airtight glass reactor with a detachable catalyst chamber

A gradientless airtight glass reactor supplied with a detachable chamber for the catalyst has been developed. It is designed for investigations on the kinetics of heterogeneous catalytic processes and the determination of catalytic activities at atmospheric and reduced pressures by the flow-circulation and quasi-static techniques.

---

. - . , .

     

Investigation of the chemisorption of propylene on zinc oxide by temperature-programmed desorption

The interactions of propylene with zinc oxide have been studied by temperature-programmed desorption (TPD) under experimental conditions free of inter- or intraparticle limitations or readsorption phenomena.The results indicate that propylene is adsorbed on two types of active sites, and the Arrhenius parameters for the corresponding desorption processes have been calculated; moreover, on the basis of these results, important hypotheses can be made regarding the reaction mechanisms of the total oxidation and the dehydroaromatization of propylene on zinc oxide.The experiments confirm that thermal methods can be successfully used in the interesting and important field of heterogeneous catalysis.

---

Zusammenfassung Die Wechselwirkungen von Propylen mit Zinkoxid wurden durch temperaturprogrammierte Desorption (TPD) unter Versuchsbedingungen frei von inter- oder intrapartikulären Begrenzungen oder Readsorptionserscheinungen untersucht.Die Ergebnisse zeigen, daß Propylen an zwei Typen von aktiven Stellen adsorbiert wird. Die Arrhenius-Parameter für die entsprechenden Desorptionsprozesse wurden berechnet. Aufgrund dieser Ergebnisse können wichtige Hypothesen bezüglich des Reaktionsmechanismus der totalen Oxidation und der Dehydroaromatisierung von Propylen an Zinkoxid aufgestellt werden.Die Versuche bestätigen, daß thermische Methoden auf dem interessanten und wichtigen Gebiet der heterogenen Katalyse mit Erfolg eingesetzt werden können.

---

- , . , . . , . , .

     

Bauxites as hydrotreatment catalysts

The effects of calcination temperature on structural and textural characteristics of two Greek bauxites were examined by different physicochemical techniques. Although the above minerals exhibited lower activity than a commercial CoMo/Al₂O₃ catalyst, they were evaluated as possible hydrotreating catalysts.

---

. , CoMo/Al₂O₃, , .

     

Performance of a cobalt oxide catalyst in the oxidation of NH3 to NO

The cause for a fall in the conversion of NH₃ to NO within 73 hours from 97% to 78% with a cobalt oxide catalyst was investigated. Results show that sintering, change in valence and cation distribution in Co₃O₄ contribute to the decrease in activity. Incorporation of ThO₂ and K₂O improves the performance of the catalyst.

---

NH₃ NO 73 97% 78%. , , Co₃O₄. ThO₂ K₂O NH₃ NO.

     

The influence of CSH phase nuclei on Ca3SiO4Cl2 hydration

The influence of CSH phase nuclei on calcium chlorosilicate hydration has been studied by means of calorimetry, QXRD, DTA and TG methods.

---

Zusammenfassung Mittels kalorimetrischen, QXRD-, DTA- und TG-Verfahren wurde der Einfluß von CSH Phasenkörpern auf die Hydratierung von Kalziumchlorosilikat untersucht.

---

, , .

---

---

C=CaO, S=SiO₂, H=H₂O     

Thermodynamic limitations in searching for regions of optimal performance of complex chemical reactions (exemplified by conversion of hydrocarbons)

An algorithm of searching for optimal nonequilibrium reaction mixture compositions accounting for thermodynamic limitations is suggested. It is exemplified by the analysis of a steam conversion of hydrocarbons.

---

, . .

     

A study of the thermal decompositions of orthotelluric acid,urea and the orthotelluric acid adduct with urea

A new type of deposit has been observed on the inside inner surface at glass exhibition cases for textiles. By thermogravimetric methods the main part of the coating has been shown to consist of wool fibers. The origin is the textile itself, and the fibers have been transported due to an electrostatic charge induced by polishing from the outside. Such damage can be avoided by grounding the boxes.

---

Zusammenfassung Ein neuer Typ von Ablagerungen an der Innenseite von Ausstellungsvitrinen für Textilien wurde beobachtet. Durch thermogravimetrische Methoden konnte gezeigt werden, dass der Hauptteil der Ablagerung aus Wollfasern besteht. Diese stammen von den Textilien selbst und gelangen infolge der durch Polieren der Aussenseite induzierten elektrostatischen Ladung an die Scheiben. Solche Schäden können durch Erdung der Vitrinen vermieden werden.

---

. , . , , . .

     

Thermal decomposition of 5-Nitro-2-Furaldehyde Semicarbazone

Nitrofurazone, 5-nitro-2-furaldehydesemicarbazone, pharmaceutical compound, has been synthesized and its thermal behaviour studied by DTA, DSC and TG. The resulting thermoanalytical curves, showing that the maximum change in mass occurred at 516.5 K, with a 67% weight loss, are in good correlation with the enthalpy of the decomposition reaction, 326.93 kJ mol^–1. On the basis of the results, it is possible to establish the mechanism of the thermal decomposition and to acquire information on the stability of the analyzed organic compound, 5-nitro-2-furaldehydesemicarbazone.

---

Zusammenfassung Das Arzneimittel Nitrofurazon (5-Nitro-2-furaldehyd-Semicarbazon) wurde synthetisiert und dessen thermisches Verhalten mittels DTA, DSC und TG untersucht. Die erhaltenen thermoanalytischen Kurven, die einen Gewichtsverlust von 67 Gew.-% mit maximaler Geschwindigkeit der Gewichtsabnahme bei 516,5 K zeigen, sind in guter Übereinstimmung mit der Enthalpie der Zersetzungsreaktion von 326,93 kJ·mol^–1. Aus den Versuchsergebnissen können der Mechanismus der thermischen Zersetzung abgeleitet und Informationen über die Stabilität von 5-Nitro-2-furaldehyd-Semicarbazon erhalten werden.

---

, — 5-. , (67%) 516,5 , , 326,93 ·^–1. .

     

Ligand exchange between bis-acetylacetonato cobalt (II) and organotin compounds SnR2Cl2 (R=Ph, Et), I. NMR identification of exchange products in the Co(AA)2?SnPh2Cl2 system

NMR studies of the interaction between bis-acetylacetonato Co(II) and organotin compound SnPh₂Cl₂ (Ph=C₆H₅ ^–) in chloroform solutions with pyridine additive have revealed ligand exchange between the initial components to form Co(II) and Sn(IV) complexes with different numbers of ligands.

---

Co(II) SnPh₂Cl₂ (Ph=C₆H₅ ^–). , Co(II) Sn(IV) .

     

Comparison of the sulfurization of CoMoK/Al2O3 catalyst with H2S and CS2

Only H₂S consumption and H₂O formation was found in the sulfurization of CoMoK/Al₂O₃ water gas shift catalyst with H₂S/H₂, but CO₂ was formed first, then CH₄, H₂O and H₂S appeared in the later part of TPS with CS₂/H₂. Carbon deposition on the catalyst during the sulfurization with CS₂/H₂ caused a lower activity than the catalyst sulfurized with H₂S but could be removed in the run of WGS reaction.

---

, CoMoK/Al₂O₃, H₂S/H₂ H₂S H₂O, CS₂/H₂ CO₂ CH₄, H₂O H₂S. CS₂/H₂ H₂S, , .

     

AlPO4?ZrO2 catalysts, II. Synthesis, textural properties and crystal structure of systems obtained in ethylene oxide

The effects of surface dehydration on textural properties, crystallinity and the structure of AlPO₄–ZrO₂ (weight ratio AlPO₄/ZrO₂=3) systems precipitated with ethylene oxide have been studied by N₂ adsorption and XRD measurements. The increase in calcination temperature in the range 773–1273 K decreases the textural parameters as a consequence of AlPO₄ crystallization to the tridymite form.

---

, AlPO₄–ZrO₂ ( AlPO₄/ZrO₂=3), , N₂ - . 773 1273 , AlPO₄ .

     

Effect of reduction temperature on the dehydrocyclizing activity of pure chromia and chromia containing K2O and CaO

The dehydrocyclization of n-heptane at 520–550°C over pure chromia and chromia with added CaO and K₂O (5 wt.% each) has been investigated. Introduction of an alkaline additive into Cr₂O₃ decreases markedly the yield of toluene. Raising of the reduction temperature of alkali-containing samples from 550 to 700°C results, in contrast to pure Cr₂O₃ and chromia-alumina systems, not in diminished, but in increased yields of toluene, the activity enhancement being particularly pronounced for the CaO-containing catalyst. These increased activities cannot be correlated either with variations in specific surface area or changes in the content of Cr⁶⁺ during subsequent oxidation, and presumably should be ascribed to more extensive catalyst reduction at higher temperatures.

---

- 520–550° CaO K₂O ( 5% .). Cr₂O₃ . 550° 700° , Cr₂O₃ , , , CaO. , , .

     

Redox processes in o-xylene oxidation over V?Ti oxide catalysts

It has been established that fast relaxations are due to catalytic conversion and slow ones are due to the formation of structures with decreasing activity and selectivity.

---

, , — , .

     

Variation of the surface potential of zinc oxide under illumination

Spectral and kinetic dependences of the decrease in the surface potential (SP) of ZnO under illumination and processes of SP relaxation in the dark have been studied. A significant contribution to the decrease of SP in the less-than-bandgap light absorption region is shown to be due to the photodissociation of specific surface bonds with the formation of localized Zn _s ⁺ and O _s ^– .

---

() ZnO . , Zn _s ⁺ O _s ^– .

     

Reactivity of polychloroalkyl radicals in the cotelomerization of ethylene and 1-hexene with carbon tetrachloride

The kinetics of cotelomerization of ethylene and 1-hexene with carbon tetrachloride has been studied. Chain transfer and cotelomerization constants have been calculated for several polychloroalkyl radicals.

---

I- 303–398 . .

     

Preparation and properties of supported vanadium-phosphorus catalysts studied by chemical analysis and ESR

The preparation of vanadium-phosphorus catalysts is described, showing the considerable influence of phosphorus on the concentration of V⁴⁺ ions. The oxidation properties were studied by chemical analysis and electron spin resonance. Moreover, ESR spectra show a strong influence of moisture on the structure of the catalysts.

---

- , V⁺⁴. , . , , .

     

Kinetics of reaction between 1,3-butadiene and p-benzoquinone

Kinetics of Diels-Alder reaction between 1,3-butadiene and p-benzoquinone in benzene and glacial acetic acid as a catalyst has been studied. Influence of reactant and catalyst concentrations on the rate has been established. Kinetic equation has been derived to describe experimental data.

---

- 1,3- 1,4- - . , .