Use of theory of multimolecular adsorption at heterogenous surfaces to describe the adsorption of hydrocarbon on polymeric sorbents

Theoretical and Experimental Chemistry -     

Some problems in adsorption and calorimetric studies of the steps of catalytic processes

Principal side factors as well as technical and procedural peculiarities capable of distorting the results of measurements of adsorbed and desorbed amounts, of falsifying the nature of the processes proceeding in the systems under study, and of promoting artifacts in calorimetric and other studies of gas chemisorption on powders are considered. Modified techniques and procedures allowing the elimination of sources of side phenomena and artifacts and freeing traditional glass static adsorption apparatuses and experimental procedures from undesirable factors and peculiarities are proposed. Some available chemisorption and calorimetric data representing artifacts and also some data that are not artifacts but,due to imperfections of chemisorption techniques, show up as artifacts are presented and discussed. Several applications of the improved techniques and procedures to calorimetric and adsorption studies of the steps of catalytic processes proceeding on the basis of natural gas and of products of its processing are presented and discussed.     

Influence of medium acidity upon the luminescence properties of 2,5-diphenyl-1,3,4-oxadiazole and 2,5-diphenyl-1,3-oxazole

The luminescence properties of 2,5-diphenyl-1,3,4-oxadiazole and 2,5-diphenyl-1,3-oxazole in aqueous solutions of sulfuric acid (pH 7 to H_o − 10) were studied. The spectral parameters are essentially acidity dependent, which is due to the acid-base equilibria of these heterocycles both in the ground and in the first excited singlet states. The difference between these two compounds is governed by their dissimilar solvation. The basicity constants of 2,5-diphenyl-1,3,4-oxadiazole in the S₀ state (pK_BH+ = − 2.49) and 2,5-diphenyl-1,3-oxazole in the S₀ and S₁ states (pK_BH+ = −1.93, pK_BH+^* = 1.95) were experimentally obtained. The enthalpies of formation, electron charge density, and geometry of the bases and corresponding conjugate acids in the S₀ and S₁ states were calculated by the MNDO method.     

Kinetic studies of Pt/Al2O3 catalyst pellets with nonuniform activity

Catalysts with nonuniform distribution of the catalytically active component (Pt) over their porous support (Al₂O₃) have been studied. A nonuniform activity distribution changes not only the reaction rate but also the kinetics can be different on these catalysts.

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(Pt) (Al₂O₃). , , .

     

Tetrazoles. 11. Acidities of tetrazolylacetic acids

The acidities of two series of substituted 1- and 2-tetrazolylacetic acids, as well as some 1- and 2-substituted 5-tetrazolylacetic acids, in water and 50% ethanol were investigated. All of the investigated compounds are stronger acids than acetic acid and are comparable to haloacetic acids. The induction constants (_I) of the 1-, 2-, and 5-tetrazolyl groups (0.65, 0.62, and 0.41, respectively) were calculated from data on the acidities of tetrazolylacetic acids.See [1] for communication 10.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 264–266, February, 1982.     

Polynuclear branched tetrazole systems. 3. Acidity of α,ω-ditetrazol-5-ylalkanes

α,ω-Ditetrazol-5-ylalkanes with 1 to 5 methylene groups in the alkyl fragment display the properties of dibasic heterocyclic NH acids with pK_a values lying in the range 3.4–6.1. The pK_a values of these compounds are in a linear dependence on the values of the dielectric permeability of the medium, on the chemical shifts of the signals of the endocyclic carbon atom, and of the carbon atom of the α-methylene group in the ¹³C NMR spectra. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 535–541, April. 2006.     

Effect of ultrasonic treatment on the mobility of short dislocations in Si crystals

The effect of ultrasonic treatment on the mobility of short surface dislocations in Si crystals is investigated. It is found that ultrasonic treatment of Si crystals changes the velocity of dislocations under a permanent mechanical load. The nature of variation of dislocation velocity is determined by the sign of external stresses acting on the sample: compressive forces decrease while tensile forces increase the velocity of dislocations. After ultrasonic treatment of the samples, a decrease in the activation energy for dislocation motion and the enhancement of the electroplastic effect are observed. A possible mechanism of the observed effects is considered.     

Protolytic equilibria in tetrazoles

Published data on protolytic equilibria involving tetrazole hetero ring are summarized. The information is systematized according to the types of protolytic equilibria.     

Exponential estimate for the law of the iterated logarithm in banach space

Obninsk Institute of Atomic Energy. Translated from Matematicheskie Zametki, Vol. 56, No. 5, pp. 98–107, November, 1994.