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1.
    
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The amount of oxygen chemisorbed on molybdena-alumina catalysts at room temperature has been determined by a pulse chromatographic technique. The variation of molybdenum dispersity with its concentration and the calcination temperature is discussed.
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2.
The problem of predicting the activity of oxide and carbonate catalysts for some reactions of petrochemical synthesis (vapor phase conversion of carboxylic acids, catalytic oxidation of asphaltic tar to bitumen) according to the established dependence of thermal stability variations of intermediates on the formation enthalpy of metal oxides or standard ele.trode potentials is discussed.
, ( , ) .
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3.
Two phase diagrams of the L-citrulline-water system were obtained by using DTA on samples held in sealed glass ampoules. The first one exhibits only the anhydrous solid-liquid-vapour equilibrium, while the second one shows the peritectic decomposition reaction of L-citrulline dihydrate at 61. Tammann's curve does not reveal a maximum point for the dihydrate composition; this point is located in the water-rich part of the diagram. This must be related to the action of a non-negligible vapour pressure. A monotropic polymorphism of L-citrulline is expected. The second diagram is an isochoric (V/m=8 cm3 g–1) section of theT-V/m-x diagram, which involves the presence of a vapour phase.
Zusammenfassung Zwei Phasendiagramme des L-Citrullin-Wasser-Systems wurden durch DTA von in Glasampullen eingeschmolzenen Proben erhalten. Das erste bezieht sich nur auf das Gleichgewicht zwischen wasserfreiem Festkörper, Flüssigkeit und Dampf, wÄhrend das zweite die peritektische Zersetzungsreaktion von L-Citrullin-Dihydrat bei 61 wiedergibt. Die Tammann-Kurve zeigt kein Maximum bei der dem Dihydrat entsprechenden Zusammensetzung; dieser Punkt befindet sich im wasserreichen Teil des Diagramms. Dies mu\ der Wirkung eines nicht zu vernachlÄssigenden Dampfdruckes zugeschrieben werden. Ein monotroper Polymorphismus von L-Citrullin ist zu erwarten. Das zweite Diagramm ist ein isochorer (V/m=8 cm3 · g–1) Abschnitt des eine Dampfphase involvierendenT-V/m-x-Diagramms.

L-- , . ——, — L- 61. , , . . L-. (V/m=8 3 –1) T–V/m–x, .
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4.
Oxidation rates and k2/k6 ratios are given for some acids from propionic to lauric. The k2/k6 ratio is shown to be influenced by the electrostatic effect of the solvent. A linear dependence between the isodielectric values of k2/k6 and the number of methylene groups in the acid molecules is described.
k2/k6 . k2/k6 k2/k6 .
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5.
    
CO Pd- . W=f(CO.2), . . .
In terms of the ideal adsorbed layer model it appeared possible to predict some critical effects in the catalytic CO oxidation on a Pd-containing catalyst and to predict and experimentally reproduce the relation W=f(CO2) characterized by the clock-counterwise hysterests. Previously these critical effects in the region of high pressures have not been described. In the same region self-oscillations of the reaction rate have been predicted and reproduced.
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6.
Bromocomplex forming metal ions (Tl3+, Hg2+) alter considerably the parameters of chemical oscillations in bromate oscillators. Even at 10–5 M metal ion concentration the period of the oscillation is doubled or tripled; at 10–4 M the oscillation is quenched. At high (10–2 M) Tl3+ concentration, high frequency, strongly damped oscillations occur although [Br]eq is below 10–10 M. By the addition of Tl3+ we could determine the amount of Br formed in a single autocatalytic step, which we found to be about 10–4 M.
(Tl3+, Hg2+), , . 10–5 M , ; 10–4 M . Tl3+ (10–2 M) , [Br]eq 10–10 M. Tl3+ Br, , 10–4 M.
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7.
Zirconia is well known as a promising support for active metallic centers but it is also by itself an interesting catalyst for reactions involving hydrogen in particular. This paper describes the catalytic properties of ZrO2-obtained in the form of an aerogel-, towards butene-1-isomerization and/or its hydrogenation at low temperature. Activation at 430°C in vacuum led to the best results in cis-trans isomerization in the temperature range of 80–200°C. It is shown that at temperatures 150°C a carbanion mechanism is operating while at higher temperatures the thermodynamic selectivity is attained. Selective poisoning experiments by NH3 or CO2 were carried out in order to identify the catalytic sites for the isomerization of n-butene.
, , . ZrO2, , / -1 . 430°C - 80–200°C. , 150°C , . NH3 CO2 -.
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8.
In accordance with structural data and numerical analysis of relaxation curves, a detailed scheme for the reaction of o-xylene oxidation is suggested.
-.
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9.
Sodium perborate was used for oxidation of bromide ions at pH 3.64. The reaction was conducted by potentiometric measurements. The orders with respect to perborate and bromide ions were found to be unity in each reagent and a plausible mechanism was postulated. The effect of temperature was studied in the range of 20–40 °C and the Arrhenius parameters were evaluated.
pH=3,64. . , . 20–40 °C, .
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10.
It has been established that copper oxide promotes the catalytic activity of iron-chromia catalyst in the water gas shift reaction due to the formation of catalytically active aggregates. However, due to their gradual recrystallization and sintering into larger copper particles, the promoting effect sharply decreases.
, , . , .
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11.
By using the interacting bonds method (IBM), it has been established that for the chloride Ziegler systems (TiCl4+AlR3) for polymerization the formation of Ti 2 7+ and Ti 2 6+ pairs is a thermodynamically favorable process.
(TiCl4+AlR3) () , Ti 2 7+ Ti 2 6+ .
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12.
Vanadyl -and -polyphosphates in vapor phase oxidation of 2-methylpyridine show comparable activity and selectivity to the formation of pyridine-2-carboxaldehyde as traditional vanadium-molybdeum oxide catalysts. A redox mechanism for the reaction of 2-methylpyridine oxidation on vanadyl polyphosphates is suggested with interaction between 2-methylpyridine and oxygen of the catalyst lattice as the rate-determining step.
- - 2- -- . - 2- . - 2- .
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13.
Zusammenfassung Eine Methode zur Differentialspektrophotometrie durch Modulation eines Monochromators wird beschrieben. Der Monochromator oscilliert mit variabler Bandbreite zwischen 1 und ( 1+). Wenn ( 1+) die Wellenlänge des Absorptionsmaximums ist, erscheint am Photo multiplierausgang einer Sinuswelle, deren Amplitude der Extinktions differenz zwischen 1 und ( 1+) proportional ist. Die Schaltung zur ultralinearen Messung dieser Amplitude ist angegeben und ihre Anwendung mit dem Zweistrahlphotometer Rapidspektroskop gezeigt. Die Empfindlichkeit wird durch die Kombination um den Faktor 10 bis 100 gesteigert. Der Rauschpegel ist bei der Monochromator-Modulationstechnik etwa 10–4 E.Das Differentialspektrum stellt die erste Ableitung eines Spektrums dar und gestattet die genauere Lokalisation von Schultern in steilen Flanken eines Spektrums. Die Kombination der beschriebenen Methode mit der Technik des Rapidspektroskops erlaubt es, dasselbe mit gleichem Erfolg wie ein Dual-Wavelength-Gerät einzusetzen.
Summary A method for differential spectrophotometry by modulation of a single monochromator is described. A single monochromator oscillates with variable bandwidth between 1 and ( 1+ ). If ( 1 + ) is the wavelength at maximal optical density, the photomultiplier output gives a sinus-wave, the amplitude of which is proportional to the optical density difference between 1 and ( 1+). The circuit for ultralinear measurement of this amplitude is described and details of its application with the split-beam spectrophotometer Rapidspektroskop are given. The sensitivity of the entire assembly is increased by a factor of between ten and one hundred. The noise level of the monochromator-modulated technique is about 10–4 optical density units. The differential spectrum represents the first derivative of a spectrum and allows one to determine more exactly the location of shoulders in the slope of a spectrum.The combination of the described method with the techniques of the Rapid spektroskop thus provides facilities which equal those of a dual-wavelength apparatus.
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14.
The catalytic incineration of n-hexane over a Pt/Al2O3 catalyst has been studied using a fixed bed reaction. The reaction was carried out in dry air between 250 and 350 °C and at 1 atm pressure. The concentration of n-hexane was between 25 and 300 ppm. The reaction was found to be zero order in n-hexane concentration and the activation energy was found to be 21 kcal/mol. The zero order kinetics can be explained by a surface redox cycle known as Mars-van Krevelen mechanism in which the oxidation of surface Pt is the rate-controlling step.
- Pt/Al2O3 . , 250–350°C 1 . - 25–300 .. - –21 /. , — , , , Pt.
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15.
    
The results of a study of the temperature dependence of the SSCCs of the hydroxyl protons in the PMR spectra of 5-O-trityluridine indicate the existence of an intramolecular bond between the 2-keto oxygen of the base and the 2-hydroxyl in deuterochloroform. Under these conditions, stabilization of the 3-endo (N) conformation of the ribose ring is observed. The existence of the influence of the temperature on the population of the 3-hydroxyl rotamers shows the formation of a hydrogen bond between OH-3 and O-2. In polar solvents free rotation of the hydroxy groups is observed.All-Union Scientific-Research Institute of Applied Biochemistry, Olaine. Translated from Khimiya Prirodnykh Soedinenii, No. 3, pp. 358–362, May–June, 1981.  相似文献   

16.
The heat of formation of some copper clusters in a MgO lattice has been calculated by the interacting bonds method.
MgO.
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17.
Kinetics of p-xylene oxidation in an aqueous system catalyzed by cobalt oxide have been studied at 140 °C under oxygen. The reaction is second order in p-xylene and first order in cobalt oxide concentration. The rate constant and product distribution are very close to those found for homogeneous catalytic reactions. Based on these findings, a reaction scheme describing the influence of oxide catalyst is formulated. - , , 140° C . - . , . , .  相似文献   

18.
Mass-spectrometric data for the products of temperature-programmed reaction of methane with Re- and Pt-containing Al2O3 contacts show that the active sites for methane conversion to benzene over these systems are formed during high-temperature contact of these systems with methane.
- Re, Pt- , , , .
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19.
The influence of oscillations in the feed concentration on the selectivity of a catalytic process has been studied for parallel reactions. The selectivity increase in periodic operations depends on both the type of kinetic functions and the non-steady-state properties of the catalysts.
. , .
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20.
The contribution of thermal methods of analysis to the study of the structure and reactivity of vanadium-phosphorus oxides is examined. In particular, data are reported on the solid-state reaction VOHPO4·1/2H2O(VO)2P2O7+2 H2O for VOHPO4·1/2H2O prepared in different ways, on the redox properties of oxidation and reduction of vanadium for catalysts prepared with different PV atomic ratios in the range 0.9–1.3, and on the surface properties determined by TPD of catalysts with different PV ratios. The relationship between these properties and the catalytic properties in the selective oxidation ofn-butane and but-1-ene is discussed.
Zusammenfassung Der Beitrag thermischer Analysenmethoden zur Untersuchung der Struktur und Reaktivität von Vanadin-Phosphor-Oxiden wird erörtert. Insbesondere werden sich auf die Festkörperreaktion 2VOHPO4.1/2H2O(VO)2P2O7+2H2O für auf verschiedene Weise dargestelltes VOHPO4.1/2H2O, auf die Redox-Eigenschaften von Vanadin in Katalysatoren mit P/V-Atomverhältnissen im Bereich 0.9–1.3 und auf durch TPD bestimmte Oberflächeneigenschaften von Katalysatoren mit unterschiedlichen P/V-Verhältnissen beziehende Angaben gemacht. Zusammenhänge zwischen diesen Eigenschaften und den katalytischen Eigenschaften bei der selektiven Oxydation von n-Butan und N-Buten werden diskutiert.

- . , VOHPO4 · 1/2H2O, VOHPO4 · 1/2H2O(VO)2P2O7 + 2H2O, - PV 0,91,3. - 1-.
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