Heterogeneous-homogeneous decomposition of HNO3

In contrast to ZSM zeolites impregnated with V⁵⁺ salts, catalysts prepared by adding V³⁺ salts during zeolite synthesis exhibited (even when transformed into cristobalite by oxidative activation) higher selectivity to furane in the oxidation of butadiene. Non-oxidative activation preserved the zeolitic structure and increased both the total activity and the selectivity to furane.

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ZSM, V⁵⁺, V³⁺ ( ) . , , .

     

Effect of catalyst surface modification on pentachlorobutene-1 oxidation to dichloromaleic anhydride

Modification of V–P–O catalyst surface by reaction products changes the reaction course and increases its catalytic activity in pentachlorobutene-1 oxidation to dichloromaleic anhydride.

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V–P–O . -1 .

     

Large deviations of sums of independent random variables from the domain of attraction of a stable law

The paper continues the author's previous paper and deals with the case where the existence of the exponential moment of the distribution under consideration is not assumed. Bibliography: 11 titles. Translated fromZapiski Nauchnykh Seminarov POMI, Vol. 228, 1996, pp. 262–283.     

The sorption of molybdenum by polymeric chelate-forming sorbents with the o-hydroxy?1-Azo-1′?o′-hydroxy functional group

The sorption of molybdenum by synthesized polymeric chelate-forming sorbents (PCSs) based on hydroxypolystyrene and a structural fragment with o-〈1-azo-1′〉o′-hydroxybenzene was studied. A mechanism of the sorption of molybdenum(VI) was suggested and substantiated. Qualitative correlations between the most important physicochemical parameters of the sorbent, sorption process, and sorbate (chelate) were established and described. The correlations can be used to quantitatively predict the physicochemical parameters of sorbents and their chelates for the purposes of synthesis, the use of PCSs for the concentration and isolation of elements, and physicochemical studies.     

Uniqueness and absolute continuity of weak solutions for parabolic SPDE's

The paper presents necessary and sufficient conditions for the absolute continuity of measures generated by infinite-dimensional martingale problems. This result is applied to the study of the existence and uniqueness of weak solutions to nonlinear parabolic SPDE's. The paper also addresses the problem of stochastic integration with respect to a martingale in a quasi-complete locally convex topological vector space.This work was partially supported by NSF Grant # DMS-9002997 and ONR Grant # N00014-91-J-1526.     

Hydrocarbon specificity in the selective catalytic reduction of NOx over Cu-ZSM-5 and Co-ZSM-5 catalysts

Transformation of surface nitrates under CH₄ (CH₄+O₂) was found to ensure steady-state activity of Co-ZSM-5 in the selective catalytic reduction of nitrogen oxides by methane (CH₄-SCR). For Cu-ZSM-5, such species are mainly converted into NO. Relaxation of the coordination sphere due to oxygen and NO adsorption, stability of C,N-containing intermediates and activation routes of hydrocarbons (methane, propane) were analyzed as factors determining catalytic properties of Cu and Co cations.     

Synthesis of gasoline from syngas via dimethyl ether

Zeolite H-TsVM has been loaded with palladium by different methods. The properties of the resulting catalysts in gasoline synthesis from syngas via dimethyl ether depend on the way in which palladium was introduced. The catalysts have been characterized by ammonia temperature-programmed desorption (TPD), temperature-programmed reaction with hydrogen, and X-ray photoelectron spectroscopy. According to ammonia TPD data, use of a palladium ammine complex instead of palladium chloride reduces the concentration of strong acid sites and raises the concentration of medium-strength acid sites, thereby reducing the yield of C1–C4 hydrocarbons and increasing the yield of gasoline hydrocarbons. At T = 340°C, P = 100 atm, and GHSV = 2000 h^?1, the dimethyl ether conversion is 98–99%, the gasoline selectivity is >60%, the isoparaffin content of the product is ～61%, and the arene content is not higher than 29%.     

Laws of selective CO oxidation over a Ru/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> catalyst in the surface ignition regime: II. Transition states

The kinetics of selective CO oxidation (or individual CO or H₂ oxidation) over ruthenium catalysts are considerably as affected by the heat released by the reaction and specifics of the interaction of ruthenium with feed oxygen. In a reactor with reduced heat removal (a quartz reactor) under loads of ∼701 g_Cat⁻¹ h⁻¹ and reagent percentages of ∼1 vol % CO, ∼1 vol % O₂, ∼60 vol % H₂, and N₂ to the balance, the reaction can be carried out in the catalyst surface ignition regime. When catalyst temperatures are below ∼200°C, feed oxygen deactivates metallic ruthenium, the degree of deactivation being a function of temperature and treatment time. Accordingly, depending on the parameters of the experiment and the properties of the ruthenium catalyst, various scenarios of the behavior of the catalyst in selective CO oxidation are realized, including both steady and transition states: in a non-isothermal regime, a slow deactivation of the catalyst accompanied by a travel of the reaction zone through the catalyst bed along the reagent flow; activation of the catalyst; or the oscillation regime. The results of this study demonstrate that, for a strongly exothermic reaction (selective CO oxidation, or CO, or H₂ oxidation) occurring inside the catalyst bed, the specifics of the entrance of the reaction into the surface ignition regime and the effects of feed components on the catalyst activity should be taken into account.