Thermodynamics of solvation and association in solutions of fluorosiloxane rubber and polychloroprene in organic liquids

The enthalpy of dissolution and concentration dependences of the enthalpy of dilution of solutions of fluorosiloxane rubber and polychloroprene in different organic liquids are determined by means of isothermal microcalorimetry. It is established that the processes of polychloroprene dissolution are accompanied by exothermic effects, while those of fluorosiloxane rubber are accompanied by endothermic effects. The calorimetric data are analyzed using the UNIQUAC model to calculate the model parameters associated with the local concentrations of components in the solution that characterize solvation and association. It is shown that the local distribution of the solvent molecules in the polychloroprene solution differed only slightly from the average over the volume, while the process of solvent association predominated in the solution of fluorosiloxane rubber.     

Reinforced nickel and nickel-platinum catalysts for performing the thermally coupled reactions of methane steam reforming and hydrogen oxidation

The formation of composite nickel and nickel-platinum catalysts reinforced with steel gauze was studied. The catalysts were prepared by sintering powdered nickel metal and a supported nickel catalyst (GIAP-3 or NIAP-18) with a chromium oxide additive in the case of nickel-containing composite catalysts or by sintering powdered nickel, aluminum, and a supported platinum catalyst in the case of catalysts containing nickel-platinum. With the use of electron microscopy, mercury porosimetry, and X-ray electron probe microanalysis, it was found that a metal matrix, in the pores of which supported catalyst particles were distributed, was formed in the composite catalysts. The reinforced nickel catalysts prepared were active in the reaction of methane steam reforming, and the catalysts containing nickel-platinum were active in the reaction of hydrogen oxidation. An increase in the activity of reinforced nickel catalysts in the course of the reaction was found. It is believed that the increase of the activity was due to the reduction of nickel oxide from an inactive difficult-to-reduce oxide film containing nickel and chromium oxides under the action of the reaction atmosphere.     

2,2-Dialkoxyoxetanes

Conclusions 2,2-Dialkoxy-4-trihalomethyloxetanes are formed under mild conditions without irradiation from 1,1-dialkoxyethylenes and trihaloacetaldehydes; the reaction probably proceeds via a mechanism with cyclic electron transfer.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 668–670, March, 1972.     

Model of adsorption on graphene

A simple M-shaped model has been proposed for the density of states of the π bands of the graphene. The model has been used to derive the expression for the local density of states on the adsorbed atom and to calculate the corresponding occupation numbers for different model parameters. Additional simplifications have made it possible to represent the band contribution n _b to the total occupation number of the adatom n _a in the analytical form. The contributions of local states n _l to n _a = n _b + n _l have been calculated for different parameters. The charge has been numerically evaluated for the case of adsorption of alkali metal atoms on the graphene. The results obtained have been verified using the model of a surface diatomic molecule calculated by the Harrison bond-orbital method. The verification has demonstrated that the charges calculated in terms of radically different models are in good agreement.