Equilibria and heats of ion exchange in the system of mordenite-alkali and alkaline earth cations

A concurrent absorption analytical study of the ion exchange equilibria and direct microcalorimetric measurement of the heat of ion exchange absorption of K⁺ and Ca²⁺ cations for the sodium forms of two mordenites (NaM) obtained from naturally occurring samples rich in Na⁺ and Ca²⁺ cations has been carried out for the first time. The free energies and entropies of exchange have been calculated. It was shown that the free energy of exchange in the K⁺-NaM system is determined by the enthalpy, whereas in the Ca²⁺-NaM system it is determined by the entropy of solvation. The measured thermodynamic characteristics of exchange were analyzed taking into account the preferred localization of sorption for the cations in the structure. A memory effect in natural mordenites has been established for extra-skeletal K⁺ and Ca²⁺ cations, in the presence of which these zeolites crystallized in nature. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 42, No. 5, pp. 312–317, September–October, 2006.     

The role of electrolyte concentration in the decomposition of water and generation of electrons under conditions of anodic microdischarges

The dependence of the yield of water decomposition (from the measured yield of formation of hydrogen peroxide and yield of scavenging of OH radicals by isopropanol), as well as the yield of electron scavenging by a solute (nitrobenzene), on the concentration of aqueous electrolyte (sodium tetraborate and ammonium tetraborate) solutions under the action of anodic microdischarges was determined. Nonmonotonic functions were found, which exhibited maximums at 0.03 and 0.1 M concentrations for water decomposition and electrons, respectively. The results were explained by an increase in the fraction of anionic current through the discharge plasma-liquid cathode interface as the electrolyte concentration was increased.Translated from Khimiya Vysokikh Energii, Vol. 39, No. 2, 2005, pp. 140–142.Original Russian Text Copyright © 2005 by Polyakov, Badalyan, Bakhturova.This revised version was published online in April 2005 with a corrected cover date.     

NMR study of antipyrine adducts with lanthanide shift reagents. Molecular structure of 2,3-dimethyl -1-phenyl- 5-ethoxypyrazole

The complex formation of antipyrine with LSR in CCl₄ is studied. Recommendations for producing the limiting lanthanide induced shifts characteristic of the 11 complex are given and the geometry of the complex formed is determined. Results of an x-ray structure study of the adduct which is formed upon reaction of antipyrine and the ethyl ester of benzenesulfonic acid are presented.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 191–196, February, 1989.     

Thiophene hydrodesulfurization activity of MoS2/Al2O3 catalysts prepared via exfoliation. The effect of cobalt

In contrast to the bulk MoS₂, the structure of the active phase of the catalyst prepared via exfoliation is shown to exhibit a number of distortions, which form a superstructure of the type of the charge density waves with a quasi-period of 30 ?. Due to such distortions, the ions of cobalt firmly chemisorb on the basal plane of MoS₂ occupying, along the perimeter of the MoS₂ clusters, the regions with a lower energy of the Mo-S interaction. A synergetic increase in the catalyst activity due to the introduction of cobalt was observed up to the atomic ratios of Co/(Co+Mo) = 0.33, which is possible for the nanoparticles of MoS₂ with a diameter 200 ?, only if cobalt adsorbs on the basal plane. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effect of the chemical nature and length of spacer arms on the covalent grafting of fluorinated molecular probes at the surface of poly(ethylene terephthalate) membrane

A series of fluorinated molecular probes were synthesized that are characterized by spacer arms of various lengths and polarities. Previous molecules ( 1 , 2a , 2b , 2c , 3a , 3b ) were covalently fixed on the surface of poly(ethylene terephthalate) (PET) membranes via activated hydroxyl chain endings. X‐ray photoelectron microscopic analysis of the grafted samples allowed us to quantify the PET surface reactivity; the results were within 40–50 pmol/cm² of fixed probes, independent of the length and hydrophilicity of the spacer arms. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 770–781, 2002; DOI 10.1002/pola.10156     

Water vapor adsorption and microporous structure of carbon adsorbents. 17. Analysis of experimental isotherms for water vapor adsorption

Water vapor adsorption for various activated carbons with narrow and wide micropore volume distributions and mesopore surface areas between 40 and 300 m²/g have been investigated. For all the isotherms the point of inflection was determined, which can be taken as the point characterizing the formation of a water adsorption layer on the pore wall surface of carbon adsorbents. To do this the adsorption and desorption branches of the isotherms were approximated according to Weibull's distribution. A good correlation was obtained between values for the water monolayer capacity, calculated from the porous structure parameters of the carbons, and the adsorption values corresponding to the isotherm inflection pointsa _inf. For the group of carbons studied the values of relative pressure at the inflection point of the isotherms fell within the range 0.5–0.72.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 31–34, January, 1991.     

Submanifolds of differentiable manifolds provided with differential-geometric structures. I

The geometry of submanifolds of manifolds with (f)-structures, f-structures, and almost complex structures is presented.Translated from Itogi Nauki i Tekhniki, Seriya Problemy Geometrii, Vol. 11, pp. 3–64, 1980.