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2011, №2

pp. 4-26

Articles

Key words: statistical physics, theory of non-ideal systems, local fluctuations, critical and supercritical states of fluid

The equations for large-scale local fluctuations in fluids — from ideal gas to non-compressible liquids, including near-critical and supercritical (SC) states — are obtained from the first principles. The contemporary notions concerning the critical state are verified and described substantially more accurately. It is demonstrated that in compressible fluids the local density fluctuation is accompanied by non-thermodynamic fluctuations of collective velocity and fluid temperature. The features of the development of such fluctuations near the critical point determine a distinctive behavior of the fluid in critical and SC states.

2011, №2

pp. 27-34

Articles

Allylic Substitution in Supercritical Carbon Dioxide Medium Catalyzed by Palladium Complexes with Phosphite-type Ligands

S.E. Lyubimov, T.A. Verbitskaya, E.A. Rastorguev, P.V. Petrovskii, V.N. Kalinin, V.A. Davankov.

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Key words: supercritical carbon dioxide, allylic substitution, palladium complexes, phosphites, regioselectivity

Allylic amination and alkylation catalyzed by Pd complexes is carried out in supercritical carbon dioxide (SC-СO2) using phosphite-type ligands. It is shown that Pd-catalysts dissolved in SC-СO2 provide a high regioselectivity and thus present a useful approach to the synthesis of allylamines.

2011, №2

pp. 35-48

Articles

Key words: theory of absolute rates of reactions, non-ideal reaction systems, relaxation of environment, molecular theory

The analysis of the equations for rates of elementary reactions in non-ideal systems demonstrates that traditional notion of the existence of chemical potential of the activated complex in dense phases contradicts real times of molecular and procedure of statistical averaging of molecular distributions. The expressions connecting rate constants of elementary chemical reactions obtained at atmospheric pressure and in supercritical conditions are derived.

2011, №2

pp. 49-64

Articles

Key words: supercritical fluids, photochromism, spirocompounds, polar polymers, matrix immobilization, photoluminescence

It is shown that supercritical fluid (SCF) impregnation of polymers containing polar diphenilol and halogen groups (polyoxycarbonate, polytetrafluoroethylene, polyvinylchloride) by spirocompounds leads to conformational changes with the stabilization of merocianine form of photochroms. It is demonstrated also that previously observed effect of the formation of long-living form B of spiroantrooxazine molecules immobilized in polycarbonate matrix is also typical for other similar systems. In this work such effect is observed for a number of spirocompounds incorporated into polar polymer matrixes using the SCF impregnation method. Colored forms of spirocompounds immobilized in halogen-containing matrixes have an intense fluorescence.

2011, №2

pp. 65-73

Articles

Key words: supercritical state, high-purity polystyrene, thermal polymerization

The possibility and conditions of frontal (thermal) polymerization of styrene in the conditions of the transition of its mixture with carbon dioxide into supercritical state is studied. The experimental procedure is developed and parameters (temperature and pressure) of such transition at different styrene-to-СO2 ratios are determined. The numerical study of a mathematical model of thermal polymerization of styrene in a tubular reactor is performed. The distributions of temperatures and concentrations along the reactor corresponding to the transition of the styrene — carbon dioxide mixture to the supercritical state are calculated.

2011, №2

pp. 74-82

Articles

Key words: supercritical carbon dioxide, quantum dots, methylmetacrylate, styrene, copolymers, polymer nanocomposites

A new method of synthesis of dispersed fluorescent polymer composites based on dispersion copolymerization of methylmetacrylate and styrene in the presence of quantum dots CdSe/CdS in supercritical carbon dioxide is suggested. A one-step scheme of the formation of fine particles of polymethylmetacrylate/polystyrene/CdSe/CdS composite is carried out and factors controlling their photoluminescent features and photochemical stability at long-term exposition under intense UV and sunlight irradiation on air are investigated.

2011, №2

pp. 83-91

Articles

Effect of Treatment in Supercritical Carbon Dioxide on Composition and Structure of Tea Leafs and Cellulose

F.N. Shamsetdinov, L.Yu. Yarullin, F.M. Gumerov, F.R. Gabitov, Z.I. Zaripov, A.B. Remizov, I.M. Kolyadko, V.G. Nikitin, A.K. Fakhreev, D.I. Kamalova.

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Key words: green Chinese tea, supercritical carbon dioxide, tea leafs, cellulose, elemental composition, structure

The effect of preliminary treatment in supercritical carbon dioxide (SC-СO2) on the elemental composition of tea leafs is studied. FT-IR absorption spectroscopy is employed to study the effect on the structure of green Chinese tea leafs and cellulose.

2011, №2

pp. 92-113

Articles

Key words: sub- and supercritical water-salt equilibria, critical phenomena, heterogenization of homogeneous SC fluids, hydrothermal salt solubility, ternary phase diagrams

Experimental studies of high temperature phase equilibria in the system BaCl2—NaCl—H2O determine the conditions when the homogeneous supercritical (SC) fluid, spreading from the binary subsystem BaCl2—H2O of type 2, transforms into the heterogeneous equilibria. These data also show that liquid-gas equilibria in ternary mixture can be continuously transformed into the immiscibility equilibria in the SC conditions. The comparison of the obtained experimental results with available data for the system K2SO4—KCl—H2O suggests that ternary systems with one volatile component formed by binary subsystems of type 2 with immiscibility and of type 1 without immiscibility have phase diagrams of the same type.