Selective hydrogenation of cyclopentadiene in the liquid phase on palladium catalysts

The catalytic hydrogenation of cyclopentadiene to cyclopentene was investigated under atmospheric pressure and 20°C in liquid phase with palladium carrier catalysts. The reaction was carried out in methanol and toluene in the presence of n-octylcatechol as a polymerization inhibitor. Using 0.56% Pd/Al₂ O₃, a 100% selectivity of the hydrogenation of cyclopentadiene to cyclopentene was achieved in toluene. In methanol, the selectivity of hydrogenation was lower and a partial polymerization of cyclopentadiene took place.

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20° C Pd- . -. 0,56% Pd/Al₂ O₃ 100%. , .

     

Specificity of states of Cu2+ ions in ZSM zeolites due to the cooperative Jahn-Teller effect

Crystalline silicate of ZSM zeolite structure was synthesized via hydrothermal crystallization at large contents of copper. ESR spectra of Cu²⁺ ions stabilized in this system are determined by the specific ordering due to the cooperative Jahn-Teller effect of Cu²⁺ ions with the d_x ²–y² ground state.

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423° ZSM . Cu(II), , - Cu²⁺ cdx²–y²— .

     

Determination of hydroxyl groups and/or water on the surface of oxide catalysts by a pulse chromatographic method

A pulse chromatographic method based on the reaction of gaseous dimethylzinc tetrahydrofura nate was developed for the determination of surface hydroxyl groups and/or adsorbed water in solid porous materials. The procedure is rapid and gives results comparable to other methods. Some heterogeneous catalysts and supports have been analyzed.

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, , / , . , . .

     

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 and mechanism of the oxidation of methyl phenyl sulfoxide by peroxodiphosphate

The kinetics of the oxidation of methyl phenyl sulfoxide (MPSO) by potassium peroxodiphosphate (PP) in 50% aqueous acetic acid obeys the rate law.-d[PP]_T/dt=k[PP] [MPSO] at constant [H⁺]. The active species in the oxidation has been found to be H₃P₂O ₈ ^– . The kinetic results have been explained by a polar mechanism.

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() () 50%- (./.) -d[]^T/dt=k·[]·[] [H^*]. H₃P₂O ₈ ^– . .

     

Discrimination of the kinetic model of overlapping solid-state reactions from non-isothermal data

A method has been developed that allows the deconvolution of up to 15 overlapping solidstate reactions without previous assumptions. Both the kinetic parameters and the reaction mechanisms fitted by the unit reactions can be determined from a series of non-isothermal experiments carried out at different heating rates.

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Zusammenfassung Es wurde eine methode zur Dekonvolution von bis zu 15 einander überlappenden Festphasenreaktionen entwickelt, die keinerlei vorherige Annahmen notwendig macht. Mittels einer Reihe nichtisothermer Experimente mit unterschiedlichen Aufheizgeschwindigkeiten können sowohl die kinetischen Parameter als auch der Reaktionsmechanismus der Teilreaktionen bestimmt werden.

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, 15. .

     

Stopped-flow study of the oxidation of ascorbic acid by the oxo-bridged trinuclear ruthenium complex [(NH3)5RuORu(NH3)4 ORu(NH3)5]7+

The kinetics of the oxidation of ascorbic acid by [(NH₃)₅RuORu(NH₃)₄ORu(NH₃)₅]⁷⁺ has been studied by the stopped-flow method. The activation parameters have been calculated and a possible mechanism is suggested.

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[(NH₃)₅RuORu(NH₃)₄ORu·(NH₃)₅]⁷⁺ . .

     

A differential scanning calorimetric study of some phenol derivatives

Differential scanning calorimetry has been applied to derive the fusion enthalpies and entropies of series of mono and dimethylphenols, mono and dichlorophenols, and mono and dinitrophenols.

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Zusammenfassung DSC wurde verwendet zur Ermittlung der Schmelzenthalpie und Entropie der Reihen von Mono- und Dimethylphenolen, Mono- und Dichlorphenolen, Mono- und Dinitrophenolen.

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- , - , - .

     

Ethylene hydrogenation in electrochemical cell with solid proton-conducting electrolyte

The effect of electrochemical H⁺ pumping on the hydrogenation rate of ethylene on Ni electrode catalysts in a solid proton-conducting electrolyte cell has been studied.

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Ni — .

     

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.

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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.

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, . . — 10^–4 M . — N^o3. , . , , .

     

Spectroscopic studies of the state of Cu2+ ions in Cu?Zn?Al oxide catalysts

ESR and electronic spectroscopy have reveled that in low-temperature ZnO the copper ions form Cu–O–Cu type cluster structures with highly covalent bonds and strong exchange interaction between the ions. The nearer environment of the Cu²⁺ ions is an octahedron with distortion towards square planar coordination.

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, ZnO Cu–O–Cu . Cu²⁺- , .

     

On the state of Re in the Pt/Re reforming catalysts

Both Pt/Al₂O₃ and (Pt+Re)/Al₂O₃ industrial catalysts contain, after reduction (at 450 °C) ions, extractable by acetylacetone. However, a substantial part of Re is reduced.

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Pt/Al₂O₃ (Pt+Re)/Al₂O₃ ( 450 °C) , . , .

     

A Thermal study of the precipitates formed in ammonia neutralization of acidic solutions of dissolved phlogopite

The precipitates containing mainly iron, aluminium and magnesium hydroxides, obtained from phlogopite dissolved in nitric acid by means of the neutralization procedure with ammonia, have been investigated by thermal analysis (TG, DTG and DTA). According to the present study, which is part of a larger investigation into the chemical utilization of Finnish mica minerals, the formation of solid solutions between iron and aluminium hydroxides in silt increases with an increasing neutralization temperature. Nitrogen exists mainly in the form of nitrate in silts, and magnesium forms mixed hydroxides with aluminium, which causes a separation between the iron hydroxide and magnesium aluminium hydroxide phases.

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Zusammenfassung Die von in Salpetersäure gelöstem Phlogopit durch Neutralisierung mit Ammoniak erhaltenen, hauptsächlich Eisen-, Aluminium- und Magnesiumhydroxid enthaltenden Niederschläge wurden thermoanalytisch (TG, DTG und DTA) untersucht. In der vorliegenden Arbeit, die Teil einer grossangelegten Untersuchung zur chemischen Nutzung finnischer Glimmermineralien ist, wird gezeigt, dass die Bildung fester Lösungen von Eisen- und Aluminiumhydroxiden in Schluff mit zunehmender Neutralisationstemperatur ansteigt. Stickstoff kommt in Schluff hauptsächlich in Form von Nitraten vor, und Magnesium bildet Mischhydroxide mit Aluminium, was eine Trennung der Eisenhydroxidphase von der Magnesium-Aluminium-Hydroxidphase bewirkt.

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

     

Liquid phase CO+H2 reactions in presence of ruthenium catalysts

Several effects on the hydrogenation of carbon monoxide in propanol in presence of ruthenium catalysts are examined. The homologation reaction is not observed, only propyl formate and propyl acetate are produced with any ruthenium catalyst. The pH-value is an important parameter: in acid media, the yield of propyl formate is noticeably increased indicating different catalytic active species. The addition of cesium salts is also benefitial for formate formation. This is not the case when water is associated with propanol as solvent. Finally, no ethylene glycol is detected. The process is found to be homogeneous and methanol seems to be the precursor of methyl formate.

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

     

Thermal decompositions of complexes of metal ions with riboflavin

Two kinds of complexes of riboflavin with Zn(II), Co(II), Cu(II), Fe(III), Mg(II) and Ca(II) were synthesized, having metal: ligand molar ratios of 11 and 21. When heated, these complexes first lose water. Their thermal degradation in static air atmosphere starts at temperatures higher than, equal to, or lower than that observed for free riboflavin degradation. The rates and stages of pyrolysis were related to the structures of the complexes.

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Zusammenfassung Es wurden zwei verschiedenartige Komplexe von Riboflavin mit Zn(II), Co(II), Cu(II), Fe(III), Mg(II) und Ca(II) mit einem molaren Metall-Ligandenverhältnis von 11 und 21 dargestellt. Beim Erhitzen geben diese Komplexe zuerst Wasser ab. Ihre thermische Zersetzung beginnt in unbewegter Luftathmosphäre bei einer Temperatur, die entweder mit der für die Zersetzung freien Riboflavins übereinstimmt, größer oder kleiner als diese ist. Die Abschnitte und Geschwindigkeit der Pyrolyse werden mittels der Struktur der Komplexe erläutert.

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, , , : 11 21. . , . .

     

Kinetic simulation of oxidative dehydrogenation of n-butenes over SnO2?Sb2O4 catalysts

A previously suggested reaction mechanism was utilized to evaluate a kinetic model for the oxidation of n-butenes over ShSb=31 mixed oxide catalyst. With this model, kinetic curves measured at 673 K were simulated, illustrating the changes of amounts of undetectable surface components, too.

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- SnSb=31 . , 673 K, .

     

Kinetics and mechanism of oxidation of triphenylphosphine by hydrogen peroxide

Kinetics of oxidation of triphenylphosphine (TPP) by hydrogen peroside has been investigated in 95 vol. % aqueous ethanol. The reaction is first-order each in TPP and hydrogen peroxide. A mechanism involving a bimolecular nucleophilic displacement of TPP on the peroxide molecule in the rate-determining step is proposed.

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() 95 .% . , H₂O₂. , , , H₂O₂ .

     

Inhibition by phase transfer catalysts

While phase transfer catalysts have generally a positive effect on substitution of halides by rhodanide ion in two-phase reaction systems changing the structure of alkyl halide from primary to tert.-alkyl groups, catalysis reverses into inhibition. The assumption that this is due to the change in reaction mechanism from S_N2 to S_N1 was proved on hydrolysis of triphenylmethyl chloride in a two-phase system, where the inhibitory effect of phase transfer catalysts is even more pronounced.

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, , , , . , S_N2 S_N1, , .

     

Dehydrogenation of cyclohexane and chemisorption of H2 and O2 on supported Pt?Pb and Pt?Sn catalysts

With increasing amounts of Pb or Sn the weak adsorption of hydrogen decreases, the adsorption of oxygen increases and the activity in the dehydrogenation of cyclohexane decreases. A correlation could be found between the amount of weakly adsorbed hydrogen and the dehydrogenation activity.

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. . .

     

Distribution of components in the rare earth ammonia synthesis catalysts and effect of additives

The distribution of components in the HG-1 ammonia catalyst promoted by rare earth oxide (successfully developed by the authors) was analyzed by electron microprobe photography. The results enable us to explain the effect of additives upon the activity as well as the remarkably high lifetime of catalyst.

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HG-1, ( ) , . , .