Kinetics of CO2 formation in thermal destruction of brown coals

The previously suggested approach to the problem of kinetic system identification /1/ was used for the system of independent first order reactions. The analysis of the curves of CO₂ formation in thermal destruction of brown coal indicates that both structure and model parameters of real processs can be identified in terms of the continuity concepts.

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(I) ë . CO₂ , , .

     

Investigation of Pd?Pb/Al2O3 catalysts by temperature-programmed reduction

Temperature-programmed reduction has been used to characterize, a series of Pd–Pb/Al₂O₃ catalysts. Oxidation and thermal decomposition of bimetallic Pb–Pb/Al₂O₃ catalysts in a stream of argon leads to segregation of individual oxides. Reduction of PdO–PbO/Al₂O₃ occurs at the same temperature as that found for PdO/Al₂O₃ and PbO/Al₂O₃. TPR measurement after isothermal reduction at 823 K and reoxidation point to bimetallic interaction between palladium and lead atoms only for small percentages of palladium.

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- () Pd–Pb/Al₂O₃. PdO–Pb/Al₂O₃ . PdO–PbO/Al₂O₃ PdO/Al₂O₃ PbO/Al₂O₃. - 823 — .

     

51V NMR studies of systems V2O5-KHSO4 and V2O5?K2SO4

Systems V₂O₅–KHSO₄ and V₂O₅–K₂SO₄ have been studied by the⁵¹V NMR method. The first system demonstrates the same states of vanadium as the previously studied V₂O₅–K₂S₂O₇, in this system a compound with an equimolar ratio of components has been found. In V₂O₅–K₂SO₄ the state of vanadium differs from the above systems and the formation of a compound with V/K=4 is observed.

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⁵¹V KHSO₄–V₂O₅ K₂SO₄–V₂O₅. , K₂S₂O₇–V₂O₅, . K₂SO₄–V₂O₅ V/K4.

     

Studies of the reactions of Br(2P3/2) and Br(2P1/2) with SiH4

Photobromination of SiH₄ under uv-irradiation at various wavelengths has been studied. Rate constants for the elementary reactions Br(²P_3/2)+SiH₄HBr+SiH₃ (k=3.2×10^–11 exp(–21.8±2.5)/RT, cm³/s) and Br^* (²P_1/2)+SiH₄HBr+SiH₃ (k^*=(3±1)×10^–13 cm³/s) have been determined in the temperature range from 300 to 415 K.

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- . Br(²P_3/2)+SiH₄HBr+SiH₃, k=3,2×10^–11 exp (–21,8±2,5)/RT ³/ Br^*(²P_1/2)+SiH₄HBr+SiH₃, k^*=(3±1)×10^{–13 3}/ 300–415 K.

     

Studies on the V2O5?TiO2 system, V. Equilibrium pressures

The oxygen equilibrium pressures from pure V₂O₅ and co-precipitated V₂O₅–TiO₂ system were measured in the range of 200–450 °C. The behavior of the equilibrium pressure with changes of temperature of the samples with and without TiO₂ is attributed to Ti⁴⁺ interaction with the V₂O₅ lattice.

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V₂O₅ - V₂O₅–TiO₂ 200–450°C. TiO₂ Ti⁺⁴ V₂O₅.

     

CO hydration over catalysts prepared via supporting Fe3(CO)12 and (NEt4)2[Fe2Mn(CO)12] on oxide supports

A comparison of the properties of iron-containing catalysts prepared through carbonyl clusters Fe₃(CO)₁₂ and (NEt₄)₂[Fe₂Mn(CO)₁₂] and iron and manganese nitrates in CO hydration indicates that the addition of Mn incorporated in (NEt₄)₂[Fe₂Mn(CO)₁₂] decreases the methane yield and increases the portion of higher hydrocarbons.

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, Fe(CO)₁₂ (NEt₄)₂[Fe₂Mn(CO)₁₂] , CO. Mn (NEt₄)₂[Fe₂Mn(CO)₁₂] .

     

1H,13C and17O NMR studies of cumene hydroperoxide coordination to Cr(AA)3

It has been established that the outer sphere coordination of cumene hydroperoxide to Cr(AA)₃ is due to both the formation of hydrogen bonds between hydroxyl proton and chelate oxygen atoms and the --interactions between the aromatic ring and chelate -system.

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, - Cr(III) , --- - .

     

Hysteresis of thermogravimetric curves of nickel catalysts for methane conversion in CH4+CO2 mixture

Characteristic peculiarities of the supercarbonization peak, i. e. the effect of carbon accumulation on the catalyst surface and its subsequent removal under heating in the CH₄+CO₂ mixture have been studied. Hysteresis of thermogravimetric curves in the heating/cooling cycle has been established.

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— . -.

     

Supported catalysts prepared using Ti(C7H11)4 for ethylene polymerization

Supported catalysts for ethylene polymerization were prepared by anchoring tetrakis(1-bicycloheptyl) titanium [Ti(C₇H₁₁)₄] on alumina. The influence of the dehydration temperature of the support and the conditions of catalyst activation on the catalytic properties was studied. At low content of Ti these catalysts were found to be highly active for ethylene polymerization with the formation of superhigh molecular weight polymers.

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(1-) [Ti(C₇H₁₁)₄] . , . , .

     

Structure of surface species in Mo/Al2O3 catalysts prepared through Mo(V) oxalate

EXAFS and RED structural studies of surface species of Mo/Al₂O₃ catalysts prepared through the anchoring of [Mo₂O₄(C₂O₄)₂(H₂O)]^2– anion to -Al₂O₃ have shown that these surface metal complexes preserve a binuclear structure of the Mo(V) oxalate framework fragment.

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EXAFS Mo/Al₂O₃, [Mo₂O₄(C₂O₄)₂(H₂O)₂]^2– -Al₂O₃. , (V).

     

Dispersity and reducibility of the molybdenum oxide phase in SiO2, SiO2?Al2O3 and γ-Al2O3 supported molybdena catalysts

XRD, isothermal and temperature-programmed reduction (TPR) experiments were carried out with SiO₂, SiO₂–Al₂O₃ and -Al₂O₃ supported catalysts. Molybdena is in a more disperse state on supports containing more alumina and it is more reducible on SiO₂–Al₂O₃ than on SiO₂ or -Al₂O₃. TPR curves were shown to reflect connections between reduction kinetics and dispersity.

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-, , SiO₂, SiO₂–Al₂O₃ -Al₂O₃. , , SiO₂–Al₂O₃ SiO₂ -Al₂O₃. .

     

ESR studies of spectral dependences and kinetics of O2 photoadsorption on SnO2

Oxygen photoadsorption on SnO₂ is shown to be accompanied by the formation of O ₂ ^– ion-radicals. Charge separation under irradiation and stabilization of photoinduced centers is mot effective in the presence of physically adsorbed O₂.

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, SnO₂ - O ₂ ^– . . O₂.

     

Kinetic studies of thiolane synthesis from tetrahydrofurane and H2S

Kinetic studies of tetrahydrofuran reaction with H₂S were carried out in a flow-circulation reactor. Presumably, the reaction takes place through dissociative chemisorption of reactants and the interaction of surface structures formed to produce thiolane and water. A kinetic equation that agrees with the suggested mechanism has been derived.

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- H₂S. , . , .

     

Oxygen diffusion in Me2O?V2O5 melts

The anodic and cathodic polarization of a platinum electrode in K₂O–V₂O₅ melt have been studied. The dissolved oxygen is shown to be ionized. Diffusion coefficients of oxygen in K₂O–V₂O₅ and Na₂O–V₂O₅ melts at various temperatures and K/V ratios are presented.

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K₂O–V₂O₅. , . K₂O–V₂O₅, Na₂O–V₂O₅ K/V.

     

Determination of the exposed surface area of V2O5 on a V2O5/Al2O3 catalyst

NH₃, NO and CO₂ were tested as adsorbates for selective determination of exposed surface area of V₂O₅ on a V₂O₅/Al₂O₃ catalyst. The most promising appears to be CO₂ which interacts with the support Al₂O₃ only.

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NH₃, NO CO₂ V₂O₅ V₂O₅/Al₂O₃. CO₂, Al₂O₃.

     

Reaction of ethylene with Os? anion radicals stabilized on ZnO surface

Interaction of O _s ^– anion radicals stabilized on ZnO surface with ethylene is shown to be accompanied by the formation of polymeric radicals that are stable in vacuum up to 160–180 K and destroyed in the presence of molecular O₂ even at 90 K.

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, - O _s ^– , ZnO, . 160–180 . O₂ 90 .

     

Influence of anchored cerium ions on the dispersity and activity of Pd/SiO2 catalysts

(Pd+Ce)/SiO₂ catalysts prepared by decomposition of organometallic complexes of Ce and Pd have higher activity, dispersity and selectivity in methanol synthesis than Pd/SiO₂ catalysts.

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, (Pd+Ce)/SiO₂ , Ce Pd, Pd/SiO₂.

     

On the dehydration enthalpies of some beta-aluminas

The energetics of the dehydration reaction of single crystal (Na, Na 50%-Li, Li) and ceramic Na beta-aluminas have been studied.From the dependence of the dehydration enthalpy values on the water content it has been deduced that lattice water can be bound in two different ways i.e. by ion-dipole interactions with conducting cations and by hydrogen bonds with spinel block oxygens. As expected, the first one gives binding energies depending on the nature of the monovalent cation (H=84.5 and 59.4 kJ/mol H₂O for Li and Na beta-alumina respectively). In contrast, the enthalpy change associated with the second one is identical for the three beta-aluminas (H=15.1 kJ/mol H₂O). The ceramic Na beta-alumina undergoes a surface reaction too (with CO₂) leading to the formation of carbonates and bicarbonates.

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Zusammenfassung Die Energetik der Dehydratisierungsreaktion von Einkristallen von Na-, Na (50%)/Li- und Li- sowie von Na--Aluminiumoxid wurde untersucht. Aus der Abhängigkeit der Dehydratisierungsenthalpie vom Wassergehalt ergibt sich, daß Wasser auf zwei verschiedene Weisen gebunden ist, nämlich durch Ion-Dipol-Wechselwirkung mit leitenden Kationen und durch Wasserstoffbrückenbindungen mit Sauerstoffatomen. Wie zu erwarten war werden für die ersteren von der Natur der einwertigen Kationen abhängige Bindungsenergien (H=84.1 kJ/Mol H₂O bzw. 59.4 kJ/Mol H₂O für Li- bzw. Na--Alumina) erhalten. Die auf die zweite Wechselwirkung zurückzuführenden Enthalpieänderung ist dagegen für die drei-Aluminiumoxide identisch (H=15.1 kJ/Mol H₂O). Das keramische Na--Aluminiumoxid zeigt auch eine Oberflächenreaktion mit CO₂, die zur Bildung von Carbonaten und Bicarbonaten führt.

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(Na, Na 50%-Li, Li)- -- . , - . , Li — Na-- , , 84.5 59.4 / ₂. , - 15.1 / ₂. Na- , .

     

Reactivity of coordinated O2? towards. One-electron oxidants

Ion-radical complexes Ti(IV) (O ₂ ^– ) are unreactive towards most oxidants except Ce(IV) and Cr₂O ₇ ^2– . The one-electron redox potential for the O_{2 coord.}/O _{2 coord.} ^– couple lies between 1 and 1.6 V.

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- O ₂ ^– Ti(IV) , Ce(IV) Cr₂ O ₇ ^2– . - O_{2 .}/O ₂ ^– . 1 1,6 .

     

Some spectroscopic and freezing point depression measurements on the homogeneous hydrogenation catalyst CoH3(PPh3)3

NMR, EPR and freezing point depression (FPD) experiments were performed on solutions of the homogeneous hydrogenation catalyst CoH₃(PPh₃)₃. The results of these measurements show that the compound has a dynamic structure on the NMR time scale at room temperature and that it is slightly dissociated into bisphosphine species and free phosphine. FPD and¹H-NMR measurements indicate that one Et₂O molecule is present per catalyst molecule.

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, () CoH₃(PPh₃)₃. , , . H¹- , Et₂O.