CO hydrogenation on a highly loaded Rh/TiO2 catalyst and the influence of strong metal-support interaction

The CO hydrogenation on a highly loaded (25 wt.%) Rh/TiO₂ catalyst was investigated after reduction at 573 K and 723 K. Chemisorption measurements show that the Rt/TiO₂ ratio is in the SMSI state after the high temperature reduction. The catalytic activity is significantly lower in the SMSI state than after reduction at low temperature. The selectivity of CO hydrogenation is changed in the SMSI state to higher hydrocarbons

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CO Rh/TiO₂ (25 .%) 573 723 . , Rh/TiO₂ . , , .

     

Complexes of acid amides with polar aprotic solvents. II. Thermal analysis of the complexes of bis(N-phenyl)-pyromellitic acid amide with dimethylformamide,dimethylacetamide, N-methylpyrrolidone and dimethylsulfoxide

The synthesis of solid complexes of bis(N-phenyl)-pyromellitic acid amide (PMA) with aprotic solvents (dimethylformamide, dimethylacetamide,N-methylpyrrolidone and dimethylsulfoxide) and their thermal analysis (evolved gas analysis using mass spectroscopy, and thermogravimetry) is described. In all cases, the composition of the complexes was found to be 1PMA: 2 solvent. The activation energy of the decomposition process of the complexes was determined from TG data. The values found were between 40 and 80 kJ/mol.

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Zusammenfassung Es wird die Synthese der festen Komplexe von Bis(N-phenyl)-pyro-mellithsäureamid (PMA) mit aprotischen Lösungsmitteln (Dimethylformamid, Dimethylacetamid, N-Methylpyrrolidon und Dimethylsulfoxid) und deren thermische Analyse (massenspektrometrische Analyse der gebildeten Gase und Thermogravimetrie) beschreiben. In allen untersuchten Komplexen betrug das Zahlenverhältnis von PMA- zu Lösungsmittelmolekülen 21. Die für die Zersetzung der Komplexe aufzubringenden Aktivierungsenergien wurden aus TG-Daten bestimmt. Die ermittelten Werte lagen zwischen 40 und 80 kJ·mol^–1.

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- (MTA) () -(N-)-- () ( , , N- , ). , []₁: [Sol]₂. , 40–80 /.

     

Determination of the kinetic parameters of polyvinylchloride

Kinetic equations proposed in the literature for thermal decomposition reactions may be approximated at low conversions by the relation: ^b=Dp(x). This equation reveals three kinds of behaviour under isothermal conditions, as evidenced in the thermal dehydrochlorination of Polyvinylchloride. The kinetic parameters were determined with a computing program and its performances were tested. The calculation method was applied to some Polyvinylchloride macromodels.

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Zusammenfassung In der Literatur vorgeschlagene kinetische Gleichungen für thermische Zersetzungsreaktionen können bei niedrigen Konversionen mit der Gleichung ^b=Dp(x) genähert werden. Diese Gleichung offenbart unter isothermen Bedingungen drei Verhaltensweisen, wie an der thermischen Dehydrochlorierung von Polyvinylchlorid bewiesen wird. Die kinetischen Parameter wurden mittels eines Computerprogrammes ermittelt und ihre Leistungsfähigkeit überprüft. Das Rechenverfahren wurden an einigen Polyvinylchloridmakromodellen getestet.

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, , ^b =Dp(x). , . , . .

     

Decomposition of hydrogen molybdenum bronze, H0.30MoO3, upon increasing temperature in various gases

When H_0.30MoO₃ was heated at increasing temperature in H₂, N₂, H₂O, and in vacuum, the total weight loss just corresponded to the weight of 0.15 H₂O in H_0.30MoO₃. On the other hand, when the bronze was heated in CH₃OH vapor, one of the lattice oxygens was removed and the bronze was partly reduced to MoO₂.

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H_0,30MoO₃ H₂, N₂, H₂O , 0,15H₂O H_0,30MoO₃. , CH₃OH, MoO₂.

     

Etude,par atd,du diagramme d'etat de l'arsenic et mesure de son enthalpie de fusion aux conditions du point triple

Résumé L'ATD de l'arsenic placé dans des ampoules à volume mort non nul montre deux types de courbes selon la valeur du rapportV/m entreV, volume interne de l'ampoule etm, masse d'échantillon.La répartition des domaines de phases, dans le planT — V/m, est décrite. Elle permet de déterminer le volume spécifique de la vapeur d'arsenic au point triple. Le résultat obtenu (7.90 mm³ · mg^–1) s'accorde avec le fait que la vapeur d'arsenic est alors constituée de molécules tétraatomiques. Les courbes d'ATD obtenues permettent enfin une estimation de l'enthalpie de fusion de l'arsenic au point triple. La valeur obtenue (24.2 kJ · mol^–1) est en bon accord avec les résultats décrits dans la littérature.

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For DTA studies, arsenic samples are placed in silica ampoules which are evacuated and sealed. Since the arsenic sample does not fill the whole inner volume of the ampoule, theV/m ratio (whereV is the inner volume andm is the weight of the sample) can be varied. Depending on theV/m value, two kinds of curves are obtained. The distribution of phase regions in theT vs.V/m space is described. This distribution makes it possible to determine the specific volume of arsenic vapor at the triple point. The result obtained (7.90 mm³ mg^–1) is consistent with As₄ molecules in the vapor phase. From the DTA curves obtained, the heat of fusion of arsenic is estimated. The result (24.2 kJ mol^–1) is consistent with the values reported in the literature.

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Zusammenfassung DTA-Untersuchungen von Arsenik in Ampullen mit einem von Null verschiedenem Totvolumen, weisen je nach Verhältnis des inneren VolumensV der Ampulle und der Massem der Probe,V/m, zwei Typen von Kurven auf.Die Verteilung der Phasenbereiche in der FunktionT-V/m wird beschrieben. Sie gestattet die Bestimmung des spezifischen Volumens des Arsenikdampfes am Tripelpunkt. Das erhaltene Ergebnis (7.90 mm³ · mg^–1) stimmt mit der Existenz von As₄-Molekülen in der Dampfphase überein.Aus den erhaltenen DTA-Kurven wurde die der Schmelzenthalpie von Arsenik abgeschätzt. Der erhaltene Wert (24.2 kJ · mol^–1) ist in guter Übereinstimmung mit den in der Literatur veröffentlichten Ergebnissen.

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, , , . , V/m, V- , «» — . V/m . – V/m. . — 7.90 ³ · ^–1 — , As₄ · Ha - , 24.2 . ^–1. .

     

Ethylene hydroformylation over a nafion-supported rhodium catalyst

Ethylene hydroformylation over a Nafion-supported rhodium catalyst has been studied under atmospheric pressure in the temperature range of 100–135 °C, using the transient response method.

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, , 100–135°C, .

     

Kinetics of hydrogenation of cyclohexene on a sulfided Ni?W/Al2O3 catalyst

Kinetics of hydrogenation of cyclohexene on a sulfided Ni–W/Al₂O₃ catalyst has been studied with a flow microreactor under normal atmospheric pressure. The reaction rate is found to be zero and first order with respect to cyclohexene and hydrogen partial pressures, respectively, in the temperature range 250–350°C.

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Ni–W/Al₂O₃ . , , 250–350°C.

     

Kinetic studies of Pt/Al2O3 catalyst pellets with nonuniform activity

Catalysts with nonuniform distribution of the catalytically active component (Pt) over their porous support (Al₂O₃) have been studied. A nonuniform activity distribution changes not only the reaction rate but also the kinetics can be different on these catalysts.

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(Pt) (Al₂O₃). , , .

     

Modifying action of carbon dioxide in catalytic oxidation of ethylene on silver

Carbon dioxide exerts a strong inhibitory effect on oxygen adsorption and complete oxidation of ethylene on silver but has little effect on the rate of ethylene oxidation to ethylene oxide.

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.

     

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

The pressure dependence of the unimolecular rate constants for the thermal decomposition of 2-methyloxetane and 3-methyloxetane has been studied. The average energy transferred downward in gas-gas collision was determined by the application of RRKM theory and a stepladder model of energy transfer.

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2- 3-. , - , .