Electronic reflectance spectra of palladium-on-alumina catalysts

The electronic reflectance spectra of palladium-on-alumina catalysts prepared by various procedures from different precursor compounds are discussed. Information is obtained about the chemical state of palladium in the individual steps of preparation.

---

-, , -. , .

     

Study of hydroisomerization of n-hexane on natural mordenite catalyst

A mordenite-containing rock sample from the Tokaj Mountains (Hungary) and its various forms modified by chemical treatment have been tested for catalytic properties during isomerization of n-hexane. Addition of Pt to the catalyst leads to a sharp decrease in the rate of cracking and in the rate of deactivation and this results in a catalyst of high selectivity for hexane isomers.

---

(), , , , -. Pt , .

     

Influence of the crystallite size of platinum of the course of hydrogenolysis of ethane and propane over Pt/Al2O3 catalysts

The effect of the degree of platinum crystallite size on the reaction rate, selectivity and activation energy of ethane and propane hydrogenolysis has been studied in the range of platinum crystallite size of 1.7–4.0 nm. In the same range of Pt crystallite size, the activation energy of both processes shows a clear minimum. The decrease in Pt crystallite size bellow 3.0 nm brings about rapid changes in the selectivity of propane hydrogenolysis.

---

( ) , -. 1,7–4,0 , .

     

Electronic state of the active site of A V?P?O/SiO2 catalyst in oxidation of chlorine-containing hydrocarbons

V⁴⁺ ions in slightly associated states are supposed to play the role of V–P–O/SiO₂ active sites. V⁴⁺ ions are reduced to V³⁺ during deactivation of the V–P–O/SiO₂ catalyst.

---

V–P–O/SiO₂ V⁴⁺ . V–P–O/SiO₂ V⁴⁺ V³⁺.

     

Properties of double chlorides in the systems ACl/NdCl3 (ANa-Cs)

The pseudobinary systems ACl/NdCl₃ (A=Na-Cs) were reinvestigated by means of DTA. The following double chlorides were found primarily detected compounds are underlined):Na ₃Nd₅Cl₁₈; K₃NdCl₆, K₂NdCl₅,KNd ₂Cl₇;Rb ₃NdCl₆, Rb₂NdCl₅,RbNd ₂Cl₇; Cs₃NdCl₆,Cs ₂NdCl₅,CsNd ₂Cl₇.With a galvanic cell for solid electrolytes the thermodynamic functions of formation from ACl and NdCl₃ together with the free enthalpies of synproportionation from the compounds adjacent in the phase diagrams were measured. They revealed, that only the compounds A₂NdCl₅ are stable at ambient temperature. All other compounds are existing by a gain of entropy only at higher temperatures.The crystal structures of the compounds were determined by X-ray analysis on powders: the compounds are isotypic with the analogous double chlorides of La and Ce (A₃NdCl₆: high-temperature-modification = elpasolite-type; at room-temperature = metastable K₃MoCl₆-type; A₂NdCl₅=K₂PrCl₅-type; ANd₂Cl₇=-KEr₂F₇-type; Na₃Nd₅Cl₁₈=Na₃La₅Cl₁₈-type). Magnetic susceptibilities in the range from 80 to 300 K were measured with a Gouy-balance.

---

Zusammenfassung Die pseudobinären Systeme ACl/NdCl₃ (A=Na-Cs) wurden mittels DTA neu untersucht. Folgende Doppelchloride wurden gefunden (erstmalig beschriebene Verbindungen sind unterstrichen):Na ₃Nd₅Cl₁₈; K₃NdCl₆, K₂NdCl₅,KNd ₂Cl₇;Rb ₃NdCl₆, Rb₂NdCl₅,RbNd ₂Cl₇; Cs₃NdCl₆,Cs ₂NdCl₅,CsNd ₂Cl₇.Mit einer galvanischen Zelle für feste Elektrolyte wurden die thermodynamischen Funktionen für die Bildung aus ACl und NdCl₃ sowie die freien Enthalpien für die Synproportionierung aus den im Zustandsdiagramm benachbarten Verbindungen gemessen. Es zeigte sich, daß nur die Verbindungen A₂NdCl₅ bei Normaltemperaturen stabil sind. Alle anderen Verbindungen existieren aufgrund von Entropiegewinnen nur bei höheren Temperaturen. Anhand von Röntgen-Pulveraufnahmen wurden die Kristallstrukturen ermittelt. Die Verbindungen sind isotyp zu den entsprechenden Doppelchloriden des Lanthans und Cers (A₃NdCl₆: Hochtemperaturmodifikationen = Elpasolith-Typ; bei Normaltemperatur metastabil im K₃MoCl₆-Typ; A₂NdCl₅=K₂PrCl₅-Typ; ANd₂Cl₇=-KEr₂F₇-Typ; Na₃Nd₅Cl₁₈=Na₃La₅Cl₁₈-Typ). Mit einer Gouy-Waage wurden die magnetischen Suszeptibilitäten im Temperaturbereich 80–300 K gemessen.

---

ACl/NdCl₃, =NaCs. , : Na₃Nd₅Cl₁₈, K₃NdCl₆, K₂NdCl₅, KNd₂Cl₇, Rb₃NdCl₆, Rb₂NdCl₅, RbNd₂Cl₇, Cs₃NdCl₆, Cs₂NdCl₅, CsNd₂Cl₇. , . , A₂NdCl₅. . . , . A₃NdCl₆ , — K₃l₆. A₂NdCl₅ — K₂rl₅, ANd₂Cl₇ — -KEr₂F₇, Na₃Nd₅Cl₁₈- Na₃La₅Cl₁₈. 80–300 .

---

---

This work was supported by the Deutsche Forschungsgemeinschaft and the Fonds der Chemischen Industrie.     

Temperature programmed desorption of NH3 and H2O from NH4NaX and CoNH4NaX zeolites

A study has been made of temperature programmed desorption (TPD) of NH₃ and H₂O from samples of NH₄X and CoNH₄X zeolites of various degree of exchange. NH₃ TPD peaks could be explained by interaction of NH₃ with different Brönsted and Lewis acidic centers. Moreover a water peak at high temperatures allowed interpretations of the dehydroxylation, and by reason of the characteristic desorption temperatures a particular state of the Co²⁺ ions in the CoNH₄X zeolites is postulated.

---

- () NH₃ H₂O NH₄X CoNH₄X . NH₃ NH₃ =qs . . Co²⁺ CoNH₄X.

     

The interconversion of orthorhombic chromium oxy-hydroxide and chromium dioxide

The thermal behaviour of CrOOH and CrO₂ in different atmospheres has been studied by means of DTA, TG and X-ray diffraction. The easy interconversion between the two substances at one atmosphere pressure is explained on the basis of the results obtained.

---

Zusammenfassung Es wurde das thermische Verhalten von CrOOH und CrO₂ in verschiedenen Atmosphären mit Hilfe der Differentialthermoanalyse, Thermogravimetrie und Röntgendiffraktion untersucht und auf Grund der Ergebnisse die leichte Umwandlung wischen den zwei Verbindungen unter 1 Atm. Druck erklärt.

---

Résumé Étude du comportement thermique de CrOOH et de CrO₂ dans différentes atmosphères, par ATD, TG et diffraction de rayons X. Interprétation de l'interconversion légère entre les deux substances sous une pression d'une atmosphère.

---

lO₂ , -. , .

---

---

Thanks are due to Prof. Dr. S. C. Bevan of Brunei University and to Dr. E. Hockings of RCA (USA) for valuable discussions, and also to the D.G.E.S.I. (Spain) for a grant (to M.A.A.F.).     

Catalytic properties of nitrides in ammonia synthesis

Ammonia synthesis on nitrides CeN, UN_1.70 and iron catalyst CA-1 has been examined at pressures of up to 100 bar. Reaction kinetics is described by the Temkin-Pyzhev equation. Activation energy for all samples is similar and equals about 200 kJ/mol. Specific catalytic activity of nitrides is lower than that of the iron catalyst by a factor of 3–4 for uranium and 10 for cerium.

---

100 CeN, UN_{1, 70} CA-1. -. 200 /. : 3–4 10 .

     

Structure of some components of the roots of Prangos ferulacea

Summary From a methanolic extract of the roots ofPrangos ferulacea (L) Lindl., growing in the Nakhichevan ASSR, in addition to the compounds found previously, another six substances (I–VI) have been isolated, of which (I) and (VI) have been identified as, respectively, meransin hydrate monoacetate, found for the first time in nature, and umbelliferone: and in the study of a crystalline mixture obtained from the resin of the roots of the plant under investigation collected in Armenia, two coumarins — (VII) and (VIII) — have been isolated.On the basis of a study of IR, NMR, and mass spectra and chemical properties, the structures of the six new cumarin derivatives (II–V, VII, and VIII) have been established. Compound (II) has the structure of 8-(3-methylbutenyloxy)furo-2,3:7,6-coumarin and has been called feruliden; (III) is 7-hydroxy-8-(3-hydroxy-2-senecioyloxyisopentyl) coumarin and has been called ferudiol; (IV) is 7-hydroxy-8-(3-methoxy-2-senecioyloxyisopentyl) coumarin; (V) is 5-[1-(2,3-dihydroxy-3-methylbutyroyloxy)-1-methylethyl]-4,5-dihydrofuro-2,3:7,6-coumarin and has been called lindiol; (VII) is 8-(2-hydroxy-3-methylbut-3-enyloxy)-7-methoxycoumarin and has been called ferudenol; (VIII) is 7-methoxy-8-(3-methyl-2-oxobut-3-enyl)coumarin and has been called prangone.Leningrad Sanitary-Hygenic Medical Institute. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 568–574, September–October, 1974.     

Reaction of vinyl radicals with propylene in the gas phase

The reaction of vinyl radicals with propylene and propyl radicals was investigated in the gas phase. The radicals were produced by mercury sensitized decomposition of molecular hydrogen followed by addition of hydrogen atoms to propylene and acetylene. Vinyl radical adds to propylene effectively while hydrogen atom abstraction does not occur.

---

. , , . , , .

     

Kinetics and mechanism of the permanganate oxidation of trans-crotonic acid

The kinetics and intermediates of the permanganate oxidation of trans-crotonic acid have been investigated in the pH range of 0.5–5.0 using the stoppedflow technique. The formation of manganese(III) as a short-lived intermediate has been established. The reaction is first order with respect to both MnO ₄ ^– and crotonic acid (crotonate). The resolved rate constants at 25°C are 730 and 410 M^–1 sec^–1 for the acid and the anion, respectively. The reaction mechanism is discussed.

---

pH=0,5–5,0, . (III) . MnO ₄ ^– , (). 25°C 730 410 M^{–1 –1} , . .

     

Investigations of solid phase transitions of low molecular organic compounds by differential scanning calorimetry

For the purpose of finding temperature standards for DTA at the temperature below 150°, some solid transitions of low molecular organic compounds were measured by differential scanning calorimetry. Among fourteen materials, we have concluded to select transitions for hexachloroethane (71°) and hexamethylbenzene (110°) as candidates for such standards.

---

Zusammenfassung Zur Temperaturnormung unter 150° die DTA Methode wurden verschiedene organische Verbindungen von niedrigem Molekulargewicht und geeigneten Umwandlungen in fester Phase durch Differential Scanning Kalorimetrie geprüft. Von 14 verschiedenen Substanzen wurden Hexachloräthan (71°) und Hexamethylbenzol (110°) zum gesuchten Zweck geeignet gefunden.

---

Résumé Pour le but de trouver des étalons de température au-dessous de 150°C pour l'ATD, on a examiné les transitions en phase solide de différents composés organiques de bas poids moléculaire à l'aide d'un analyseur enthalpique différentiel. Sur les 14 échantillons étudiés, on propose l'hexachloroéthane (71°) et l'hexaméthylbenzène (110°) comme étalons.

---

150° . , 14 (71°) (110°), .

---

---

The authors wish to thank Dr. H. G. McAdie of the Ontario Research Foundation, Canada, for his kind suggestions on this work.     

Determination of the surface acidity of solid catalysts

A novel method has been developed for determining the surface acidity of white, as well as deeply colored porous solids. The method, which was tested on Al₂O₃, SiO₂–MgO–Al₂O₃ and Fe₂O₃ catalysts, is based on the adsorption of pyridine or benzylamine on acidic sites and subsequent displacement of the adsorbed bases by n-butylamine. A linear correlation was found between the concentration of acidic sites on Al₂O₃ and Fe₂O₃ catalysts and their activity in the dehydration oftert-butyl alcohol.

---

, . , Al₂O₃, SiO₂–MgO–Al₂O₃ Fe₂O₃, -. Al₂O₃ Fe₂O₃ - .

     

Effect of solvent on photochemically induced olefin metathesis by tungstenhexacarbonyl

Effect of solvents on photochemically induced metathesis of pentene-2 by W(CO)₆ has been investigated. Structure of the catalyst and a reaction mechanism are proposed.

---

-2 W(CO)₆. .

     

Thermal conductivities of polytetrafluoroethylene and polychlorotrifluoroethylene between 4.2 and 20 K

The thermal conductivities of bulk technical samples of polytetrafluoroethylene and polychlorotrifluoroethylene were measured in the temperature range 4.2–20 K by application of the steady-state method. An interpretation of the thermal conductivity data in terms of the available theoretical and empirical models is presented.

---

Zusammenfassung Die thermischen Leitfähigkeiten technischer Einzelproben von Polytetrafluoräthylen und Polychlortrifluoräthylen wurden im Temperaturbereich von 4.2 bis 20 K durch Einsatz der Festkörper-Methode gemessen. Eine Deutung der thermischen Leitfähigkeitsangaben wird anhand der zur Verfügung stehenden theoretischen und empirischen Modelle gegeben.

---

4.2–20 . .

---

---

This work was done in the International Laboratory of High Magnetic Fields and Low Temperatures, Wrocaw, Poland.     

Materials testing by Dynamic mechanical analysis

Applications of the new 980 Dynamic mechanical analyser (DMA) to the study of thermoplastic polymers, thermosetting polymers and metal glasses have been discussed in this paper. This instrument has also been used to study impact modified thermoplastics [2] elastomers [3] and metals. DMA is one of the thermo-analytical thechniques available to the research or quality control chemist for evaluating the mechanical properties of materials. With the introduction of the 980 it is anticipated that the disadvantages due to long operation time and complexity inherent in older instrumentation will no longer hold back progress towards the full realisation of the technique.

---

Zusammenfassung Der Einsatz des neuen 980 Dynamic Mechanical Analysers zur Untersuchung thermoplastischer und auf Hitzeeinwirkung fest werdender Polymere, sowie Metallgläser, wird in dieser Veröffentlichung beschrieben. Dieses Instrument wurde auch zur Untersuchung von durch Stoss modifizierten thermoplastischen Stoffen [2], Elastomeren [3] und Metallen verwendet. Die dynamische mechanische Analyse ist eine der für den Forschungsoder Kontrollchemiker bei der Bewertung der mechanischen Eigenschaften der Stoffe nützlichsten zur Verfügung stehenden thermoanalytischen Techniken. Die Einführung des Modells 980 gestattet die Folgerung, daß die bei den früheren Instrumenten als Nachteil verzeichnete lange Arbeitsdauer und Komplexität nunmehr dem Fortschritt in Richtung vollständiger Realisierung dieser Technik nicht mehr im Wege stehen werden.

---

Résumé L'application du nouvel analyseur mécanique 980 à l'étude des polymères thermoplastiques, des polymères thermodurcissables et des verres métalliques est discutée. L'instrument a également été utilisé pour l'étude des thermoplastiques traités par percussion [2], des élastotnères [3] et des métaux. L'analyse mécanique dynamique est l'une des techniques d'analyse thermique les plus utiles pour évaluer les propriétés mécaniques des matériaux, aussi bien en recherche que pour les opérations de contrôle de qualité. Avec l'introduction du modèle 980, il est prévisible que les inconvénients des instruments précédents, dus à la durée et à la complexité des opérations, n'entraveront pas le développement de cette technique.

---

980 , . , , . , . 980 , , , , .

     

Hydrogen and oxygen effect on homoexchange rate of ethylene over highly dispersed silver catalysts

Promoting effects of hydrogen and oxygen on the homoexchange rate of ethylene over highly dispersed silver catalysts has been established. On bulk silver no homoexchange is observed under the same conditions.

---

. .

     

The thermometric and enthalpimetric determination of organic compounds

Two main parameters determine the methods for the assay of organic compounds in industrial systems; these are the rates of reaction of the molecular organic and often non-aqueous systems which differ from those in ionic and aqueous systems, and secondly, the fact that in most organic systems an organic functional group is required to be determined by a general method applicable to the functional group in a variety of chemical environments. In pharmaceutical products it is desired to determine the functional groups without prior separation from excipients of various kinds and to obtain rapid assays, often with precision much lower than those normally required in inorganic systems. These methods are discussed with examples taken from the foodstuff industry, the pharmaceutical industry, etc.

---

: , . , - , . . , . , , .

---

---

Partly presented at the II. Seminar Thermometric Analysis, Budapest, September 2–7, 1980.     

Collisional energy transfer in the decomposition of 2-methyloxetane and 3-methyloxetane, II. Gas/wall collisions

The variable encounter method has been applied for the study of gas/wall vibrational energy transfer in the thermal decomposition of 2-methyloxetane and 3-methyloxetane. The average probability of reaction per collision was deduced from the data and was compared with stochastic calculations based on gaussian and exponential energy transfer probability models. The gaussian model fits the experimental data best. Using this model, the average down step energies were 2600 and 2690 cm^–1 for 2-methyloxetane and 3-methyloxetane, respectively, at 750 K, and they decreased with increasing temperature.

---

/ 2- 3-. , . . , 2600 2690 ^–1 750 K 2- 3-, . .

     

On the mechanism of propylene epoxidation catalyzed by molybdenum naphthenate

The mechanism of the catalytic epoxidation of propylene with -phenylethyl hydroperoxide has been investigated. The epoxidation step is a molecular interaction between propylene and a complex formed from hydroperoxide and catalyst, while part of side products is formed in free radical reactions. This mechanism is valid for the kinetics of both epoxidation and catalytic decomposition of hydroperoxide.

---

. — . . .