Reaction routes for hydrogenation of acetylene-ethylene mixtures using a double labelling method

Hydrogenation of C₂H₂:C₂H₄ mixtures using a double labelling method has been studied. Both in the presence and absence of ethylene the rate of acetylene hydrogenation on its partial pressure proceeds through a maximum and the rate is higher when ethylene is added. Using¹⁴C–C₂H₂ it was demonstrated that at low acetylene partial pressures the main route of acetylene hydrogenation was the formation of ethane and C₄ hydrocarbons. Using¹⁴C–C₂H₄ it was also shown that at certain acetylene partial pressures the formation of ethane from ethylene completely ceased. Different surface species are suggested and a reaction mechanism is proposed.

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C₂H₂:C₂H₄, . , , . C¹⁴–C₂H₂, , C₄. C¹⁴–C₂H₄, , . .

     

Catalysis of thiophene hydrogenolysis by bimetallic sulfide catalysts of different compositions

The activity of sulfide catalysts M_I/SiO₂, M_I/WS₂, (M_I,W)/SiO₂ and (Ni,M_II)/SiO₂ (M_I is a first row transition metal, and M_II=Nb, Mo, W or Re) in the thiophene hydrogenolysis reaction has been studied. Activities of mono- and bimetallic catalysts are found to change in the same manner depending upon the nature of M_I. The formation of a sulfide bimetallic species (SBMS) is suggested.

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M_I/SiO₂, M_I/WS₂, (M_I,W)/SiO₂ (Ni, M_II)/SiO₂, M_I — , M_II–Nb, Mo, W, Re. - M_I. .

     

Thermal decompositions of Y,La and light lanthanide thiodiglycolates

The conditions of thermal decomposition of the thiodiglycolates of Y, La and light lanthanides from Ce to Gd have been studied. On heating, these complexes decompose in various ways. Hydrated thiodiglycolates of La,Ce(III), Pr(III) and Gd lose crystallization water in one step, while those of Y, Nd, Sm and Eu(III) do so in two steps. The anhydrous complexes subsequently decompose in several steps to the oxysulfates Ln₂O_3–x((SO₄)_x.

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Zusammenfassung Bedingungen der thermischen Zersetzung der Thiodiglycolate von Y, La und den leichten Lanthaniden von Ce bis Gd wurden untersucht. Beim Erhitzen zersetzen sich diese Komplexe auf verschiedene Weise. Hydratisierte Thiodiglycolate von La, Ce(III), Pr(III) und Gd verlieren das Kristallwasser in einem Schritt, die von Y, Nd, Sm, und Eu(III) dagegen in zwei Schritten. Die wasserfreien Komplexe zersetzen sich in mehreren Schritten zu den Oxysulfaten Ln₂O_3–x(SO₄)_x.

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. . . , , , , , . Ln₂O_3–x(SO₄)_x.

     

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.

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( ) , -. 1,7–4,0 , .

     

Catalytic ammoxidation of coal

Ammoxidation of coal on oxide catalyts has shown the possibility of hydrocyanic acid formation at sufficiently low temperatures.

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. .

     

A stochastic analysis of catalyst deactivation in presence of external transfer limitations

The paper analyzes the simplest case of concentration independent deactivation of a catalyst surface in the presence of external transport limitations and accounts for the variations around the mean value of the activity of the catalysts leading to a stochastic formulation. The results reveal interesting features which would not be evident from the conventional deterministic analysis.

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- , , . , .

     

Correlation between acid strength (Ho) and ammonia desorption temperature for aluminas and silica-aluminas

Correlation between the temperature at which a base is desorbed and the acid strength (H_o) of the sites set free by it, was looked for. Ammonia was employed as base. A linear correlation of the type H_o=+/T (K) is valid with and constants, dependent on the adsorbate and the adsorbent.

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(H_o) , . H_o=+/T (K), .

     

Chiral recognition of enantiomeric peptides in water at 25° by calorimetry

The heats of dilution in water of binary and ternary solutions of the two enantiomeric forms ofN-acetylalanineamide have been measured at 25°. The excess enthalpies, expressed as virial expansion series, permit evaluation of the pairwise self and cross enthalpic coefficients. As for the chiral forms of some monosaccharides, the cross coefficient for the interaction between theD andL forms ofN-acetylalanineamide is slightly but significantly different from the corresponding self coefficient. A weak, water-mediated chiral recognition can be assumed to exist between pairs of amide molecules.

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Zusammenfassung Die Verdünnungswärmen von binären und ternären wässrigen Lösungen der zwei enantiomeren Formen von N-Acetylalaninamid wurden bei 25 °C gemessen. Die in einer Virialexpansionsreihe entwickelten Überschußenthalpien ermöglichen die Berechnung der self und cross Enthalpiekoeffizientenpaare. Was die optisch aktiven Formen einiger Monosaccharide anbetrifft, so ist der cross Koeffizient für die Wechselwirkung zwischen der D- und L-Form von N-Acetylalaninamid etwas, aber signifikant verschieden von dem entsprechenden self Koeffizienten. Es kann angenommen werden, daß Paare von Amidmolekülen eine schwache, durch Wasser vermittelte Unterscheidungsfähigkeit hinsichtlich der optischen Aktivität zeigen.

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25° - N-. . L- N- , , , . .

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This work was carried out with the financial support from the italian C. N. R. (Rome) and from the Ministry of Public Education.     

Oxidative dehydrogenation (OXD) of n-butane I. Activity of natural quartz II. Kinetic and catalytic activity of nickel oxides

The oxidative dehydrogenation of n-butane on nickel oxide catalysts and on natural quartz, used as catalysts diluent, were studied. It is assumed that oxygen ions from the oxide lattice participate in the initial step of the reaction.

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- , . , .

     

Investigation of the effects of diethylene glycol on the hydration of C3S and C3A pastes

The effects of diethylene glycol on the hydration characteristics of tricalcium silicate and tricalcium aluminate pastes were studied. Diethylene glycol acts as a retarder in the hydration of C₃S, and as an accelerator in the hydration of C₃A. The amount of Ca(OH)₂ found in pastes of C₃S treated with diethylene glycol was lower, the induction period increased and the formation of hydrates was retarded. For C₃A pastes, hydration in the presence of diethylene glycol accelerated the formation of the hexagonal aluminate hydrates and promoted the conversion to the cubic form.

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Zusammenfassung Der Einfluss von Diethylenglykol auf die Hydratation von Tricalciumsilicat- (C₃S) und Tricalciumaluminat- (C₃A) -Pasten wurde untersucht. Diethylenglykol verzögert die Hydratation des C₃S und beschleunigt die des C₃A.In C₃S-Proben, die mit Diethylenglykol hydratisiert wurden, ist der Gehalt an Ca(OH)₂ geringer, die Induktionsperiode länger und die Bildung von Hydraten verzögert. In C₃A-Pasten wird in Gegenwart von Diethylenglykol die Bildung des hexagonalen Calciumaluminathydrats beschleunigt und seine Umwandlung in die kubische Form begünstigt.

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. , . , , , , , . .

     

Synthesis and structure of (pyridine) bis(acetylacetonato) (1-methyl-1-phenylethylperoxo) cobalt (III)

Synthesis and structure of (pyridine) bis(acetylacetonato) (1-methyl-1-phenylethylperoxo) cobalt(III) complex are described.

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() () (III).

     

Formation of allyl radicals in the adsorption of propylene on zinc oxide

It has been found by the ESR technique that the adsorption of propylene on zinc oxide leads to the formation of a -allyl radical. It is suggested that the radical species of the surface allyl compound on this catalyst is responsible for its high selectivity in the dehydroaromatization of propylene to benzene.

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, - . , .

     

Comparative testing of the flammability of upholstery textiles

Flash ignition temperatures of upholstery textiles were measured with a modified derivatograph, and the TG, DTG, DTA and T curves were also recorded. The results obtained with the newly-developed system were compared with those of the ASTM D 1929 test procedure and with the simultaneously recorded thermal analysis curves.

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Zusammenfassung Der Flammpunkt von Upholstery-Textilien wurde mittels eines modifizierten Derivatographen gemessen. TG-, DTG-, DTA- und T-Kurven wurden registriert. Die mit diesem neuentwickelten System erhaltenen Ergebnisse wurden mit den nach dem ASTM D 1929 Testverfahren erhaltenen und mit den simultan registrierten thermoanalytischen Kurven verglichen.

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, -, -, - -. , ASTM 1929 .

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Paper presented at the World Conference on Thermal Analysis, Madeira (Portugal), 1986.     

Effect of preparation conditions on the properties of carbon-supported nickel catalysts

Carbon-supported Ni catalysts were prepared from nickel nitrate or chloride. Characterization was carried out by H₂ and CO chemisorption, XRD and TEM. Catalysts were further tested in the hydrogenolysis of n-butane.

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, , . H₂ CO, ., -.

     

Cracking of cumene on vanadium doped silica-alumina

The influence of small admixtures of vanadium on the activity of a silica-alumina catalyst in cumene cracking has been investigated. A correlation has been established between the catalytic and acidic properties of the vanadium doped catalyst.

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. .

     

Effect of orbital-rotational coupling on the rate of ion-dipole capture at extremely low temperatures

The rate of the ion-dipole capture at very low temperatures or energies has been examined using the Statistical Adiabatic Channel model.

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- .

     

IR spectroscopic studies of adiponitrile and ammonia adsorption over Ti?Sb?O catalyst

Rate constants for the aminolysis of o-(2,4-dinitrophenyl) cyclopentanone oxime with several primary alkylamines, C₂H₅NH₂–C₆H₁₃NH₂ and one secondary arylamine, purrolidine, in 11 water-acetonitrile are reported. With primary amines, base catalysis is absent, while with pyrrolidine saturation catalysis has been observed. Reduction in size of nonconjugated oxime moiety (leaving group), drastically decreases the rates. Thermodynamic parameters for these reactions have also been calculated.

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O-(2,4-) (C₂H₅NH₂–C₆H₁₃NH₂) , , : =11. , . ( ) . .

     

Kinetic consequences of displacement adsorption in heterogeneous catalysis

Kinetic analysis of the simple reaction scheme of the heterogeneously catalyzed reaction AB has been made for the classical Langmuir adsorption and the Ipateev displacement adsorption. It has been shown that the only kinetic consequence of displacement adsorption is the different physical meaning of the parameters of the rate equation. Its form remains the same for both adsorption modes. This conclusion seems to be general also for other reaction schemes.

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AB . , . . .

     

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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.

     

Kinetics and mechanism of homogeneous catalytic oxidation of pyrocatechol in aqueous solutions containing Cu(II) and histidine

Kinetic studies of pyrocatechol oxidation by oxygen in weakly acidic aqueous solutions containing pyrocatechol, Cu(II) ions and histidine, indicate that the reaction involves mixed copper-pyrocatechol histidine complexes. The proposed mechanism of the process agrees with the kinetic relationships obtained.

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, , Cu(II) . , . , -.