Studies of the interaction of 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) with imidazole in acetonitrile

The reaction of DDQ with imidazole in acetonitrile is a two-step process. The formation of an anion radical is followed by slow substitution of Cl atoms to form diaminobenzoquinone. Kinetics of the second step is reported. . - Cl CN- . .     

Abnormally high fractal dimension of silica surfaces measured by adsorption of aliphatic alcohols

Factors leading to abnormally high fractal dimension D of silica surfaces measured by adsorption of aliphatic alcohols have been analyzed. , D .     

TPD of ammonia from H-ZSM-5 zeolites deactivated during coupled methanol hydrocarbon cracking (CMHC)

The deactivation of H-ZSM-5 zeolite samples during coupled methanol/hydrocarbon cracking (CMHC) with n-butane as feed has been investigated in two different reaction modes (with intermediate regeneration and without regeneration). TPDA was used to characterize strong Brönsted acidity of fresh, regenerated and steamed H-ZSM-5 zeolite. The prevention of dealumination by blocking the acid centers with carbonaceous products could be proved, but the conversion rate of n-butane and the olefin selectivity declined drastically with increasing coking rate. H-ZSM-5 - / - - ( -). , - H-ZSM-5. - , , - - .     

Alkylation of p-substituted phenols by heteropoly acids

Liquid-phase alkylation of p-tert-butylphenol (TBP) and p-cresol by olefins and benzyl chloride in the presence of solid heteropoly acids (HPA) H₃PW₁₂O₄₀ and 25% H₃PW₁₂O₄₀/SiO₂ at 100–150°C provides high yields of mono- and disubstituted products. HPAs are more active than H₂SO₄, easily separated from the reaction mixture and can be used repeatedly. -- () - () H₃PW₁₂O₄₀ 25% H₃PW₁₂O₄₀/SiO₂ 100–150°C - - . , H₂SO₄, - - .     

Studies of the effect of strong metal-support interaction (SMSI) over model catalyst Rh/TiO2

The effect of strong metal-support interaction (SMSI) has been studied over Rh/TiO₂ as a model catalyst. Adsorbability variations during SMSI state generation have been found to be due to the production of Rh–Ti alloy. - Rh/TiO₂. , SMSI Rh–Ti.     

Kinetics of C2H4 polymerization on reduced V2O5/Al2O3 catalyst

Kinetic study of C₂H₄ polymerization on reduced V₂O₅/Al₂O₃ catalysts revealed that the rate equation can be expressed as V=k exp (-Y) K_aP_E/(1+K_aP_E) in the temperature range of –20 to 70°C. The deactivation constant, , was found to have a close relation with the yield and molecular weight of the polymer. C₂H₄ V₂O₅/Al₂O₃ –20 +70°C : V_p=k·exp(-Y_p)·K_aP_e/(1+K_aP_e). .     

Kinetics and mechanism of the ligand substitution reaction of aquodiethylenetriaminepentaacetatoruthenate (III) in aqueous solution

The kinetics of ligand substitution reactions of [Ru(H₂dtpa) (H₂O)] (2) (H₂dtpa=diprotonated diethylenetriaminepentaacetic acid) were studied as a function of ligand (L) concentration, pH (2.5–8.0) and temperature (30–45 °C) at 0.2 M ionic strength. The equilibrium constants for the formation of mixed ligand complex [Ru^III(dtpa) (L)] (L=2-mercaptopyrimidine, cysteine) and the distribution of various species in solution in the pH range of 2.5–8.0 were computed from potentiometric results. [Ru(H₂dtpa) (H₂O)] ( H₂dtpa= ) , pH (2,5–8,0) (30–45°C) 0,2 M. [Ru^III(dtpa) (L)] ( L=2-, ) pH=2,5–8,0.     

On the mechanism of water dissociation on the surface of Al2O3. Quantum-chemical calculations

Quantum-chemical calculations of clusters modelling adsorption complexes on the -Al₂O₃ surface have been used to evaluate two points of view on the mechanism of surface dissociation of water molecules on this oxide. The calculations show that this process involves interaction of water molecules with basic surface oxygen atoms rather than with Lewis acid sites.- , -Al₂O₃, H₂O . , .     

Kinetics and deuterium isotope effects of proton transfer reactions of di (4-nitrophenyl) methane with alkoxide bases in appropriate alcohols

The second-order rate constants, activation parameters and primary deuterium isotope effects are reported for the proton-transfer reactions from di (4-nitrophenyl)-methane to sodium ethoxide, iso-propoxide and t-butoxide in appropriate alcohols. The mechanism for the reaction is discussed. , -(4-) , - . .     

Salt effects in the reaction between IrCl62? and MnEDTA2?

The oxidation of MnEDTA^2–. (EDTA=ethylenediaminetetra-acetate) by hexachloroiridate(IV) has been studied in concentrated electrolyte solutions at 298 K. The estimation of the activity coefficients of the species from the Stokes-Robinson hydration theory indicates that the observed salt effects have their origin in a greater destabilization of the initial state with respect to the transition state when increasing salt concentration. MnEDTA^2– (EDTA= ) (IV) . -, , .     

Oscillatory reactions of sakhalin oil oxidation

After light irradiation of oil films on water surface the autoxidation process has been found to be of nonsteady auto-oscillatory character, which can be observed in rate oscillations of O₂ absorption. Also recorded have been intensity oscillations of the EPR signal from the radical counter added into an oil sample. Complex dynamics of autoxidation can be due to an autocatalytic process involving the participation of peroxides accumulated in oil during photooxidation., , , , O₂. , , . , , .     

Kinetics and mechanism of hydrazine oxidation by oxygenated Co2(L-his)4O2 complex

The kinetics of Co₂ (L-his)₄O₂ reduction by hydrazine in aqueous solution has been studied and the rate constants, the energy and entropy of activation have been determined.

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, , Co₂ (L-)₄O₂ .

     

Vapor phase oxidation of methylpyridines on zeolite catalysts

It has been established that zeolites containing Pd and Cu ions catalyze the vapor phase oxidation of methylpyridines. In oxidation of 2-methylpyridine on PdCuNa-mordenite at 375 °C the yield of 2-pyridinecarbaldehyde is 40 % of its theoretical values.

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, , Pd Cu, . 2- PdCuNa- 2- 375°C 40% .

     

Formation and thermal decomposition of silicon oxynitride compounds. Part III

The formation of a previously unknown compound with stoichiometry Li₆SiN₂O₂ was found during studies on the reactivity of Li₂SiN₂ with Li₂O, of SiO₂ with Li₃N and of Li₃SiNO₂ with Li₃N.

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Zusammenfassung Die Bildung einer bisher unbekannten Verbindung der Stöchiometrie Li₆SiN₂O₂ wurde bei Untersuchungen der Reaktivität von Li₂SiN₂ mit LiO, von SiO₂ mit Li₃N und von Li₃SiNO₂ mit Li₃N beobachtet.

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Li₆SiN₂O₂ Li₂SiN₂ , , Li₃SiNO₂ .

     

Stochastic approach to explosive phenomena: Master equation description of the Semenov model

Stochastic model of an exothermal chemical reaction with Newtonian heat exchange is proposed. The birth and death master equation based on the simplified discrete mechanism of heat transfer is presented. . , .