Synthesis gas reactions on Pd-catalysts

Reactions of synthesis gas (CO/H₂) have been followed on a number of Pd-metal and Pd-alloy catalysts. Formation of methanol is sensitive to the choice of the carrier, but as the literature (and some of the data presented) is indicating, it is not proportional to the Pd-metal surface area. Alloying with Ag does not suppress methane formation substantially. It has been inferred from these results that methane is formed, at least partially, from an oxygen containing intermediate and that Pd ions play a role in the formation of these intermediates.

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, -, CO/H₂, Pd . , , ( ), Pd. . , , - , , , Pd.

     

Kinetics of molecular exchange in CF3COOH complexes with proton acceptors

The kinetics of hydrogen bond dissociation and formation in solution has been studied by a lineshape analysis of the¹H NMR signals of the proton donor (CF₃COOH) and proton acceptor (DMF) between –100 and –170°C. It has been found that proton exchange is much slower than molecular exchange and it does not affect the lineshape. A stepwise mechanism has been confirmed.

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( ) () — –100°–170°C. , . .

     

Thermische Zersetzung der [Pd(NH3)4]-Form von Mordenit

Zusammenfassung Die Zersetzung der Palladium-tetrammin-Form von Mordenit in inerter und oxdlativer Atmosphäre wird mittels TG, DTA und automatischer Titration des freigesetzten Ammoniaks untersucht. In N₂-Atmosphäre erfolgt bei 590 K eine Redoxreaktion under Bildung von Pd und NH₄-Mordenit als feste Reaktionsprodukte. Bei höheren Temperaturen erfolgt dann die bekannte Deammonisierung und Dehydroxylierung des NH₄-Mordenits.In O₂-Atmosphäre entstehenzum Teil über wasser- bzw. hydroxylgruppenhaltige Intermediäre—PdO und H-Mordenit als feste Reaktionsprodukte, die unter H₂O-Bildung zu Pd-Mordenit weiterreagieren. Beim Gitterzusammenbruch (1130–1210 K) entsteht metallisches Pd und eine äquivalente Menge an Sauerstoff.

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The decomposition of [Pd(NH₃)]₄-mordenite in inert and oxidizing atmospheres was studied by TG/DTA and titration of the evolved ammonia. In nitrogen, a redox reaction proceeds at 600 K, resulting in Pd- and NH₄-mordenite as solid reaction products. At higher temperatures, the usual deammonization and dehydroxylation of NH₄-mordenite take place. In oxygen, PdO and H-mordenite are formed as solid reaction products, partly via intermediates containing hydroxyl groups and water. PdO is involved in the dehydroxylation of H-mordenite at higher temperatures, which results in the formation of the Pd-form and water. Lattice collapse at 1130–1210 K involves the formation of metallic Pd and the evolution of an equivalent amount of oxygen.

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, [d(N₃)]₄- . - 600 -. . , , . - - . 1130–1210 .

     

Thermal decomposition of tetraamineplatinum(II) chloride by simultaneous TG/DTG/DTA/MS and direct insertion probe mass spectrometry

Simultaneous thermogravimetry (TG), derivative thermogravimetry (DTG), differential thermal analysis (DTA), and evolved gas analysis (EGA) by mass spectrometry (MS) have been used to determine the decomposition path for tetraamineplatinum(II) chloride and cis- and trans-diamineplatinum(II) chloride. Unequivocal identification of the evolved gases was done by direct insertion probe mass spectrometry.The thermal decomposition of (NH₃)₄PtCl₂ occurred in two steps. The first was endothermic loss of two moles of ammonia producing a mixture of cis- and trans-diaamineplatinum(II) chloride. The second step was decomposition of the diamine complex to metallic Pt and N₂, HCl, and NH₄Cl. Reduction of Pt(II) to metallic Pt was coupled with oxidation of ammonia to molecular nitrogen and protons.

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Zusammenfassung Simultane Thermogravimetrie (TG), derivative Thermogravimetrie (DTG), Differentialthermoanalyse (DTA) und Analyse der entwickelten Gase (EGA) durch Massenspektrometrie (MS) wurden zur Bestimmung des Reaktionsverlaufs bei Zersetzung von Tetraminplatin(II)-chlorid sowie cis- und trans-Diaminplatin(II)-chlorid herangezogen. Die eindeutige Identifizierung der entwickelten Gase erfolgte durch Massenspektrometrie mit direkter Probeneinführung. Die thermische Zersetzung von (NH₃)₄PtCl₂ erfolgt in zwei Schritten. Der erste ist die endotherme Abspaltung von zwei Mol Ammoniak unter Bildung eines Gemisches von cis- und trans-Diamin-platin(II)-chlorid. Der zweite Schritt ist die Zersetzung des Diaminkomplexes zu metallischem Pt, H₂, HCl und NH₄Cl. Die Reduktion von Pt(II) zu metallischem Pt ist mit der Oxydation von Ammoniak zu molekularem Stickstoff und Protonen gekoppelt.

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-, -, -, - - (II) - (II) . (II). -. (NH₃)₄PtCl₂ . - -(NHN₃)₂PtCl₂. , , . .

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The technical assistance of G. J. Dechert is gratefully acknowledged.     

Theoretical models of calorimetric systems

In the present paper the dynamic properties of nonisothermal-nonadiabatic calorimeters have been analysed. In these calorimeters the thermal effect produced is partly accumulated in the calorimetric vessel, and partly transmitted to the shield with constant temperature. The generalized equation of the heat balance and the equation of the dynamics have been given for this type of calorimeter. The dependence between the course of the thermal effectQ in timet as a function of the temperature changes of the calorimeter has been presented. DependencesQ(t)=f[(t)] for a calorimeter with different domain configurations distinguished in it, and with different mutual locations of heat sources and temperature sensor have been given. Practical application of the considerations presented has been given.

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Zusammenfassung Die Eigenschaften der sog. nicht-isotherm-nicht-adiabatischen Kalorimeter werden analysiert. In diesen Kalorimetern wird der ausgelöste thermische Effekt teils im Kalorimetergefäß gespeichert und teils dem Konstanttemperaturschild übertragen. Die verallgemeinerte Gleichung des Wärmegleichgewichts und die Gleichung der Dynamik werden für diesen Kalorimetertyp mitgeteilt. Die Abhängigkeit zwischen dem Verlaufe des thermischen EffektesQ in der Zeitt als Funktion der Temperaturänderungen des Kalorimeters werden ebenfalls mitgeteilt. Die AbhängigkeitenQ(t)=f[(t)] werden für ein Kalorimeter mit verschiedenen Bereichskonfigurationen, verschiedenen gegenseitigen Störungen der Wärmequelle und des Temperatursensors angegeben. Es wird auch die praktische Anwendung der beschriebenen Anordnungen gezeigt.

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Résumé Les propriétés dynamiques des calorimètres appelés non-isothermes/non-adiabatiques sont examinées dans cet article. Dans ces calorimètres, l'effet thermique étudié est, en partie, accumulée dans la cellule calorimétrique et, en partie, transmis à la gaine à température constante. On donne l'équation générale du bilan thermique et l'équation de la thermocinetique pour ce type de calorimètre. L'évolution de l'effet thermiqueQ pendant le tempst est exprimée en fonction des variations de température du calorimètre en tempst. Les relationsQ(t)=f[(t)] sont données pour un calorimètre avec différentes configurations et différentes altérations mutuelles des sources de chaleur et des détecteurs de température. On donne également une application pratique des considérations présentées.

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- . , . . Q t . Q(t)=f[(t)] . .

     

Kinetics of oxidation of water by Mn(IV) sulfate in acid media

Kinetics of the Mn(IV)Mn(III) transition in the oxidation of watet to O₂ was investigated at 60–100°C in 6–15 M H₂SO₄. The reaction is approximately 2-nd order in Mn(IV) concentration in the process of oxidation and 1-st order in initial Mn(IV) concentration. The kinetics is interpreted by the existence of dimeric forms Mn(IV)·Mn(IV), Mn(IV)·Mn(III) and Mn(III)·Mn(III). The suggested mechanism includes O₂ formation directly in the coordination sphere of the Mn(IV)·Mn(IV) dimer in a polyelectronic process.

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Mn (IV)»Mn (III) O₂ 60–100°C 6–15 M H₂SO₄. Mn (IV) I- Mn (IV). [Mn (IV)]₂; [Mn(III)]₂ Mn(IV)·Mn (III). , [Mn (IV)]₂

     

Adsorption properties of membrane catalysts

A method for adsorption measurements on catalysts with small surface areas has been devised. The adsorption of argon has been examined on membrane catalysts made from Pd–Ni and Pd–Ru alloys before and after catalytic experiments. A sharp change of the adsorption properties and an increase in the surface areas of catalysts after reactions have been observed.

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. Pd–Ni Pd–Ru . - .

     

Conversion of toluene on NiNaY and CeNaY zeolites

Ce–Y and Ni–Y zeolites were studied in the toluen conversion reaction before and after poisoning the acid centers by Na⁺ ions. It has been found that both Ce–Y and Ni–Y zeolites were active in the disproportionation of toluene at elevated pressures, which occur on strong Brönsted acid centers. The poisoning of the acid centers in Ni–Y zeolite led to the appearance of the activity of metallic Ni and complete change in the selectivity.

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Ce- Ni- Na⁺. , , . Ni- .

     

Comparative kinetic and thermodynamic study on the chlorination of V2O5 with CCl4, COCl2 and Cl2

The chlorination kinetics of pure vanadia was studied via isothermal thermogravimetric measurements, with CCl₄, CoCl₂ and Cl₂ as chlorinating agents. At temperatures where chemical control was predominant, apparent activation energies of 77, 48 and 126 kJ: mol^–1 were obtained for chlorination by CCl₄, COCl₄ and Cl₂, respectively. For interpretation of the conversion vs. time curves in the whole conversion range, a non-uniform particle size distribution was assumed, where the reacting solid phase was considered to be composed of thin plates of different thicknesses. With this model, a fairly good correspondence was obtained between the measured and calculated kinetic curves. Selected thermodynamic calculation data on the V₂O₅ + CCl₄, V₂O₅ + COCl₂ and V₂O₅ + Cl₂ systems are presented.

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Zusammenfassung Mittels isothermen Thermogravimetriemessungen wurde die Kinetik der Chlorierung von reinem Vanadiumoxid mit CCl₄, COCl₂ und Cl₂ als Chlorierungsmittel untersucht. Bei Temperaturen mit vorherrschender chemischer Kontrolle wurde für die Chlorierung mit CCl₄, COCl₂ bzw. Cl₂ Bruttoaktivierungsenergien von 77, 48 bzw. 126 kJ/mol erhalten. Zur Interpretation der Konversion-Zeit-Diagramme im gesamten Conversionsbereich wurde eine nichteinheitliche Teilchengrösseverteilung angenommen, namentlich den Bestand der reagierenden Festphase aus dünnen Plättchen unterschiedlicher Dicke. Mit diesem Modell konnte eine recht gute Übereinstimmung zwischen errechneten und ermittelten kinetischen Kurven erhalten werden. Einige thermodynamische Rechenbeispiele für die Systeme V₂O₅ + CCl₄, V₂O₅ + COCl₂ und V₂O₅+Cl₂ wurden gegeben.

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, l₄, l₂ l₂. , l₄, l₂ l₂, 77, 48 126 ·^–1. — , . , . - . V₂O₅+CCl₄, V₂O₅+COCl₂ V₂O₅+Cl₂.

     

Identifiability classes in reaction kinetics

Some difficulties of eliciting reliable rate constants from experimental data are considered. Different classes of ill-posed estimation problems are given and demonstrated by simple examples.

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. .

     

Comportement thermique complexe du propionate de magnesium dihydrate

Résumé Un sel nouveau, le propionate de magnésium dihydraté, est préparé. Il cristallise dans le système monoclinique. Son étude par TG et ATD montre un comportement thermique assez complexe en trois étapes: déshydratation conduisant au sel anhydre amorphe aux rayons X, cristallisation du sel anhydre dont 25 % environ se transforment simultanément en sel basique [4Mg(C₂H₅CO₂)₂,MgO], enfin fusion et décomposition du mélange sel neutresel basique avec formation d'oxyde MgO bien cristallisé. Au cours de la décomposition, il y a dégagement de diéthylcétone, mis en évidence par chromatographie.

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A new salt, magnesium propionate dihydrate, has been prepared. It crystallizes in the monoclinic system. TG and DTA study shows rather complex thermal behaviour in three stages: dehydration leading to an anhydrous salt amorphous to X-rays; crystallization of the anhydrous salt, about 25% of which simultaneously transforms into the basic salt [4Mg(C₂H₅CO₂)₂,MgO]; fusion and decomposition of the neutral salt + basic salt mixture to a well-crystalline MgO residue. During the decomposition, gas-chromatography reveals evolution of diethyl ketone.

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Zusammenfassung Ein neues Salz, das Magnesiumpropionat-Dihydrat, wurde hergestellt. Es kristallisiert im monoklinen System. Seine Untersuchung durch TG und DTA ergibt ein ziemlich komplexes thermisches Verhalten in drei Stufen: eine Dehydratierung, welche — wie durch Röntgenbeugung nachweisbar — zum amorphen Anhydro-Salz führt, die Kristallisation des Anhydro-Salzes, wovon etwa 25% gleichzeitig in das basische Salz übergehen [4Mg(C₂H-,CO₂)₂,MgO] und schließlich das Schmelzen und die Zersetzung des Gemisches aus neutralem Salz und basischem Salz unter Bildung von gut kristallisiertem MgO. Das im Verlauf der Zersetzung freigesetzte Diäthylketon wurde chromatographisch nachgewiesen.

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, . , : , , , 25% [4Mg(C₂H₅CO₂)₂, MgO] , . , .

     

Possibility of thermal analysis of different types of bonding of water in minerals

Various types of water bonding were studied. e.g. water bound by occlusion, by adsorption, by capillary condensation, by chemisorption and as a solid solution, zeolitic water, interlayer water, crystal water and structural water bound in form of hydroxil groups. The differentiation of these various types of bonding is rather difficult, for on heating water is evolved at various temperatures and in rather wide temperature domains which overlap to different extents. Efforts were made to improve the detection by applying the quasi-isothermal quasi-isobaric measuring technique.

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Zusammenfassung Es wurden verschiedene Bindungstypen von Wasser untersucht. Wasser kann unter anderem durch Einschlüsse, Adsorption. Kapillarkondensation, Chemisorption und in Form von Mischkristallen, zeolitisch, schichteingebettetem und Kristallwasser sowie als OH-Form gebunden sein. Die Untersuchung dieser zahlreichen Bindungstypen ist äußerst schwierig, da die Wasserabgabe bei verschiedenen Temperaturen geschieht und die ziemlich breiten Temperaturintervalle mehr oder weniger überlappen. Mittels quasiisothermen und quasiisobaren Meßtechniken wurde versucht, die Möglichkeit der Bestimmung zu verbessern.

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. , , , , , , , . , , . , .

     

Synthesis of benzothiophenes in gas phase from aromatic hydrocarbons and carbon disulfide

A way of synthesis of benzothiophenes, in the gas phase, employing a monosubstituted aromatic compound, carbon disulfide as sulfur source and a Kearby type aluminium orthophosphate as catalyst, has been studied. The best yields in benzothiophene (53%) were reached when vinylbenzene was employed, in a very selective reaction.

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, , , , . (53%) .

     

Gradient systems are cross-catalytic

If the kinetic differential equation of a chemical mechanism is a gradient system, the mechanism is essentially cross-catalytic. Consequently, rather few conservative (in the Horn-Jackson sense) mechanisms have a kinetic differential equation of the gradient type. Relations with thermodynamics are only briefly mentioned.

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, , , . ( -) . .

     

Catalytic deamination on solid surfaces part 2.-Deamination of dicyclohexylamine on aluminium oxide

Deamination of dicyclohexylamine gives the same final products as those obtained from the respective primary amine on a similar surface. A theoretical rate equation derived permits the calculation of various rate constants from the experimental data. It is concluded that one of the intermediates formed from the two amines must be identical.

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, . . , , , .

     

Aromatization of propylene and butadiene over MoO3?SiO2 and WO3?SiO2 catalysts

The activity of various MoO₃–SiO₂ and WO₃–SiO₂ catalysts for the aromatization of propylene and butadiene has been investigated. The results obtained show a comparatively high aromatization activity of the catalysts for propylene to benzene and toluene. The direct conversion of butadiene to ethylbenzene, using WO₃ on acid treated silica, is considered to be an alternative reaction pathway to the known metathesis step to ethylene and benzene.

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MoO₃–SiO₂ WO₃–SiO₂ . . , WO₃ .

     

Calculation of recombination rate constants in (H2?O2) system

Rate constants of the three-body recombination for the elementary three-molecule stages in hydrogen oxydation have been calculated.

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, .

     

Kinetics of the catalytic transformation of isobutene into methacrylonitrile with NO on supported nickel oxide aerogel

Kinetic studies of the nitroxidation of isobutene by NO show that the reaction follows a redox mechanism in the temperature range of 300–400°C. This mechanism implies an interaction between dehydrogenated isobutene -allyl radical and atomic nitrogen due to the decomposition of NO by the reduced catalyst, which is then reoxidized.

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NO , 300–400°C. - , NO , .