The maximum kinetic mechanism and rate constants in the H2?O2 system

The maximum (in a combinatorial sense) kinetic mechanism of hydrogen oxidation is defined and the rate constants of all elementary steps are given. The possible error limit is given for each elementary step.

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( ) . .

     

Formation of O2? ion-radicals on reduced anatase. Influence of adsorbed CO on the stabilization of O2?

ESR studies of O₂ adsorption on reduced anatase have been performed. The amount of O ₂ ^– species is determined by adsorbed surface oxygen and their parameters are changed by CO adsorption.

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O₂ . , O ₂ ^– , CO.

     

Studies on thermal decomposition of rare earth element complexes with glycolic acid

The rare earth complexes with glycolic acid were prepared as crystalline solids with general formula [Ln(CH₂OHCOO)₃H₂O]·nH₂O, wheren=0 for La-Gd andn=2 for Y and Tb-Lu. During heating the monohydrates of La and Pr-Gd decomposed in two steps to Ln₂O₃ and Pr₆O₁₁, with intermediate formation of Ln₂O₂CO₃; monohydrated Ce(III) glycolate decomposed directly to CeO₂. The trihydrated glycolates of Y and Tb-Lu first lost two water molecules and the monohydrated complexes then decomposed to Ln₂O₃ and Tb₄O₇ through Ln₂O₂CO₃.

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Zusammenfassung Komplexe der Seltenerden mit Glykolsäure wurden in Form von kristallinen Substanzen mit der allgemeinen Formel [Ln(CH₂OHCOO)₃·H₂O]·nH₂O mitn=0 für La-Gd undn=2 für Y und Tb-Lu dargestellt. Die Monohydrate von La und Pr-Gd zersetzen sich beim Erhitzen in zwei Stufen über die Zwischenstufe Ln₂O₂CO₃ in Ln₂O₃ und Pr₆O₁₁. Das Monohydrat von Ce(III) glykolat zerfiel direkt in CeO₂. Die Trihydrate der Glykolate von Y und Tb-Lu gaben zunächst zwei Moleküle Wasser ab und die so entstandenen Monohydratkomplexe zersetzen sich dann über Ln₂O₂CO₃ in Ln₂O₃ bzw. Tb₄O₇.

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[Ln(CH₂OHCOO)₃·₂]·n₂, =0 La-Gd =2 Tb-Lu. Pr-Gd Ln₂O₃ r₆₁₁ Ln₂O₂CO₃. ₂. Tb-Lu , Ln₂O₃ b₄₇ Ln₂O₂CO₃.

     

Calorimetric models

The basis of the determination of mathematical models of calorimetic systems is presented. Examples of applications of these models are given for the elaboration of a classification of calorimetric systems; the analysis of the course of heat effects in calorimeters; the analysis of dynamic properties: and the analysis of total heat effects and thermokinetics. Special attention is paid to the application of the multi-body method for the construction of mathematical models of calorimetic systems.

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Zusammenfassung Die Grundlage zur Ableitung mathematischer Modelle von kalorimetrischen Systemen wird vorgestellt. Für diese Modelle werden folgende Anwendungsbeispiele ausgeführt: Fortgeschrittene Klassifizierung kalorimetrischer Systeme, Analyse des Verlaufs von Wärmeeffekten in Kalorimetern, Analyse der dynamischen Eigenschaften, Analyse der vollständigen Wärmeeffekte, Thermokinetik. Besondere Aufmerksamkeit gilt der Anwendung der Vielkörpermethode zur Aufstellung eines mathematischen Modells für kalorimetrische Systeme.

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. , , , . .

     

Effect of acid treatment on the properties of an activated carbon

The enhancement of the activity of a carbon treated with HF is due to the drastic diminution of its inorganic impurities, which produces an increase of the surface area of the carbon, a stronger Pt-C interaction and a higher Pt dispersity.

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, HF, , , Pt-C Pt.

     

Temperature-programmed reduction of bimetallic Ir?Fe/Al2O3 catalysts

Investigations on the temperature-programmed reduction of 3% Ir–Fe/Al₂O₃ catalysts after their oxidation at different temperatures T_ox have been carried out. A substantial promoting effect of iridium on the reducibility of iron has been observed for all the investigated catalysts, at T_ox applied.

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- 3% Ir–Fe/Al₂O₃ (T_ox). T_ox.

     

Oxidation of carbon monoxide on the (001) plane of ruthenium

The Ru(001) plane is shown to possess high but variable activity in the reaction of CO oxidation. A drop of activity is attributed to the transformation of surface oxygen into the unreactive state.

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, (001) Ru , . .

     

Dissociative adsorption of propene on chromium molybdate

TPD studies of the interaction of propene with oxidized chromium molybdate have revealed that propene is reversibly chemisorbed on the Cr(MoO₄)₃ surface. The kinetic order of propene desorption is close to 2, which indicates a dissociative character of adsorption. It permits to suggest the presence of a -allyl complex of propene on the surface.

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. , . , . - .

     

Photoinduced oxygen adsorption of AgBr crystals at 77 K

Photoinduced adsorption (PIA) of oxygen molecules on AgBr films at 77 K has been experimentally observed and investigated. Lifetimes of PIA centers and desorption activation energies of O₂ molecules have been determined. The process is suggested to compete with the ionic step of AgBr photolysis.

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- () - AgBr 77 K. - O₂. , , - AgBr.

     

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, ., -.

     

Kinetics of ion-exchange of transition metals on tin(IV) arseno-silicate cation exchanger

Exchange kinetics of some transition metal ions on tin(IV) arsenosilicate has been studied at various temperatures under particle diffusion controlled conditions. Various useful kinetic parameters such as self-diffusion coefficient (D_o), energy of activation (E_a) and entropy of activation (S^*) have been calculated and compared with other similar materials.

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(IV) . , (D_O), (E_a) (S^*), .

     

Effect of acetylenic carbinol structure on hydrogenation selectivity

Quantum-chemical calculations of dimethylethynylcarbinol (DMEC) and dimethylvinylcarbinol molecules by CNDO/2 and MINDO-3 method indicate that a double bond is more reactive than a triple, which hinders the selective hydrogenation process. Dehydrolinalool and DMEC hydrogenation selectivity has been studied.

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() /2 /3; . , , , .

     

Effect of water on the desorption of carbon dioxide from the surface of alumina

Based on investigations of temperature-programmed desorption of CO₂ from -Al₂O₃ surface, three forms of CO₂ adsorption differing considerably in quantitative contributions and temperature ranges of desorption have been distinguished. A significant inhibiting influence of water on CO₂ adsorption has been observed. Water adsorption results in gradual blocking of high and medium-energy adsorptive centers of CO₂ on -Al₂O₃.

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- CO₂ -Al₂O₃ CO₂, . CO₂. CO₂ Al₂O₃ .

     

Determination of the strength of aprotic acidic centers on catalyst surfaces from the IR spectra of adsorbed carbon monoxide

Correlations between the adsorption heats of carbon monoxide on aprotic acidic centers and the v _CO values in IR spectra have been studied. In the case of aprotic centers formed by cations of non-transition metals, v _CO is shown to be linearly dependent on the adsorption heat.

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v _CO . , , , v _CO .

     

Influence of Zr, Ge, B and Co additives on the activity of Pt/Al2O3 catalysts for dehydrocyclization

IR studies of the effect of Zr, Ge, B and Co additives on the activity of the Pt/Al₂O₃ catalyst for dehydrocyclization have revealed their promoting action on both oxidation and reduction of platinum. Benzene yield depends on the degree of platinum reduction promoted by boron, whereas with increasing platinum oxidation, the cracking product yield decreases.

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, , . , . . . .

     

Influence of thermal treatment and rehydration of Al2O3 on the amount of Al3+ ions migrating into HCl solution

The amount of Al³⁺ ions migrating into HCl solution from unit surface of Al₂O₃ grows with increasing oxide calcination temperature up to 1123 K, remains unchanged up to 1373 K and then, after the formation of -Al₂O₃, rises sharply. Preliminary rehydration of the surface - and -Al₂O₃ relatively decreases their amount.

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Al³⁺, Al₂O₃, 1123 1373 , -Al₂O₃ . - -Al₂O₃ , .

     

Poly(vinylpyridine) complexes of palladium as hydrogenation catalysts. Effect of polymeric ligand structure

The title complexes exhibit high catalytic activity, selectivity and stability in hydrogenation of allyl alcohol. The structure of a polymeric ligand (i.e. the position of the nitrogen atom in the pyridine ring) affects catalyst activity. According to the hydrogenation rates of allyl alcohol, the complexes studied are arranged in the sequence: P4VP-Pd>P2VP-Pd>P2M5VP-Pd.

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, - - . ( ) . : 4->2-Pd>25-.

     

A mechanistic study of cycloaddition of carbon dioxide to propyne over supported Rh4 and Fex Rhy carbonyl cluster derived catalysts

CO₂ undergoes cycloaddition to propyne on a cationic rhodium site with the assistance of O^2–/OH^– of support or iron oxide over Rh₄ and Fex Rhy carbonyl clusterderived catalysts.¹³CO₁₂ labeling and FTIR studies suggest that monodentate carbonate formed on the catalyst surface is most likely a key species to offer an active CO₂ to be converted into a carbonyl intermediate prior to the product 4,6-dimethyl-2-pyrone.

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CO₂ O^2–/OH Rh₄ Fex Rhy. ¹³CO₂ , CO₂ , 4,6--2-.

     

Temperature-programmed reduction and oxidation of bimetallic Pd?Ni/Al2O3 catalysts

Temperature-programmed reduction and oxidation of bimetallic catalysts Pd–Ni/Al₂O₃ seem to indicate phase segregation of palladium and nickel oxides and alloying of palladium and nickel in the process of reduction of oxidized catalysts.

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- Pd–Ni/Al₂O₃ , .

     

Influence of water vapor on propylene oxidation on VMo catalyst

The dependence of reaction rates for acetone and acetic acid formation on the concentration of water vapor is determined on the basis of the participation of surface hydroxy groups and Brönsted acid centers of the catalyst.

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