Key words: микронизация, белки, лизоцим, трипсин, сверхкритические растворители, диоксид углерода
The main features of microparticle formation from protein substances (trypsin, lysozyme) using supercritical fluids (SAA technique) are studied. Optical and scanning electron microscopies are applied to study the morphology of the particles. The size distribution of the particles is studied using a cascade restrictor. The method of deposition of the obtained particles onto haemostatic material «Collachit-G» is developed.
Key words: суб- и сверхкритическая вода, алюмиsний, окисление, наночастицы
Oxidation of bulk aluminum samples by sub- and supercritical water leads to the formation of (AlOOH)n and (Al2O3)n nanoparticles. At uniform heating of reactants to 700 K, H2 evolution starts at 523 K. If supercritical water (665 K, 23.1 MPa) is injected into reactor containing aluminum sample, the time delay of oxidation is 140 s. The transmission electron microscopy study of oxidized aluminum samples shows that oxidation by supercritical water leads to the preferential formation of large (300÷400 nm) particles of α-Al<sub>2</sub>O<sub>3</sub>. Small (20÷50 nm) particles of γ-Al<sub>2</sub>O<sub>3</sub> with insignificant contents of AlOOH together with large particles of α-Al<sub>2</sub>O<sub>3</sub> are found when in aluminum is oxidized by water vapor in a programmed heating regime. The kinetic equations describing the rate of H<sub>2</sub> production during the reaction of water with aluminum are derived and mechanisms of nanostructuring are discussed.
Key words: термодинамика, равновесные флуктуации, кинетическая теория газов, химическая кинетика, скорость реакции, константа скорости
The contribution of local fluctuations to the rates of thermal chemical reactions is evaluated for the first time. In the framework of the «ideal gas» model the fluctuation supplement to the rate constant is proportional to the specific volume of the particles and can reach 1—10 % at densities not exceeding a 20-fold normal atmosphere density. This is the reason why the accounting of local fluctuations in chemical kinetics should be made before the accounting of specific volumes in the equation of state.
Key words: нанесенный катализатор «никель на кизельгуре», регенерация, сверхкритический диоксид углерода.
The nature of deactivating deposits forming on the supported «nickel on kiеselguhr» catalyst in the course of hydration of unsaturated compounds is analyzed. The possibility of regeneration of the catalyst using pure and polar additive (3 wt. % methanol) modified supercritical carbon dioxide (SC-CO<sub>2</sub>) is investigated at 70 and 150 °C in the pressure range 10÷30 MPa. The kinetic features of the catalyst regeneration with SC-CO<sub>2</sub> is studied.
Key words: делигнификация, сверхкритические флюиды, лигнин, пероксид водорода, окисление.
Transformation of functional groups of lignin in the course of low-temperature delignification by hydrogen peroxide in the medium of supercritical (SC) CO<sub>2</sub> during the preparation of pulp fiber semi-product was studied. Molecular-mass characteristics of lignins are affected by the oxidation. The analyses of functional groups demonstrate that both oxidation and substitution processes are taking place. Oxidation in SC-CO<sub>2</sub> leads to the formation of water- and alkali-soluble lignin species, while the degree of oxidation of the latter is mild or low due to a relatively low oxidant consumption.
Key words: изомеризация, <em>н</em>-алканы, цеолитные катализаторы
The skeletal isomerization of <em>n</em>-butane, <em>n</em>-hexane and <em>n</em>-heptane in the supercritical (SC) conditions is studied over H-forms of zeolites (mordenite, beta, ZSM-5) at 260÷450 °C and 80÷130 bars. The isomerization of <em>n</em>-hexane and <em>n</em>-heptane is accompanied by such side processes as oligomerization and cracking. Selectivity with respect to the formation of branched isomers of these hydrocarbons does not exceed 70 and 30 %, respectively. ZSM-5 is shown to be the most durable catalyst, however selectivity towards the formation of branched isomers does not exceed 30 % even at 260—280 °C; it decreases down to 3 % at 400—450 °C. The fraction of aromatization products in these conditions does not exceed 15 %. The effect of the addition of C6—C7 <em>n</em>-alkanes onto the isomerization of <em>n</em>-pentane over H-mordenite in SC conditions (260 °C, 120 bars) is studied. It is demonstrated that the gradual decrease of activity is due to the formation of higher hydrocarbons.
Key words: сверхкритическая флюидная импрегнация, галогенсодержащие полимеры, спироантрооксазин
Matrix isolation of photochromic spiroanthrooxazine (SAO) molecules in the films of halogen-containing polymers (polyvinylchloride (PVC) and tetrafluoroethylene-vinylidene-difluoride (TVD copolymer)) performed using a supercritical fluid impregnation leads to the stabilization of an excited (colored) B-state of SAO, which does not relax into the colorless ground A-state. Such a long-living excited state can exist in the isomeric form that is characterized by the absorption band at Xmax = 535 nm ( В<sub>535</sub>, in the TVD matrix), as well as in the «normal» B-state (Xmax > 610 nm) with a minor contribution of В<sub>535</sub>-form (in PVC).
Key words: побеги сосны, сверхкритическая флюидная экстракция, радиозащитные свойства, антиатерогенное и антиоксидантное действие
Radioprotective properties of preparation obtained from pine sprouts by supercritical carbon dioxide (SC-CO<sub>2</sub>) extraction are studied using the experimental red marrow form of radiation disease as a model. Experiments are carried out with non-linear white mice. The SC-CO<sub>2</sub> extract of pine sprouts is shown to display radioprotective activity. The preclinical trial of antiatherogenic and antioxidant activity of this extract are executed on male rates (Wistar line) in the conditions of experimental hyperlipidemia.
Key words: сверхкритическая флюидная экстракция, диоксид углерода, чеснок, экстракт, дисульфиды, биоциды
Garlic (<em>Allium sativum</em> L.) extracts were obtained using CO<sub>2</sub>-supercritical extraction. The extracts were separated into individual components by preparative HPLC and GC methods. Some of the isolated substances (allicin, diallyldisulfide, diallyltrisulfide) along with two synthetic analogs were tested as potential biocides using the following models: <em>Candida utilis, Bacillus cereus, Pseudomonas aurantiaca</em>, and <em>Escherichia coli</em>. Some of tested substances revealed high efficacy as biocides, in particular, against gram-negative cultures. The obtained results give evidence of good perspectives of sulfur-containing gar1ic components and their synthetic analogs as potential antimicrobial agents.
Key words: сверхкритическая вода, органические химикаты, глобальное фазовое поведение, коэффициент распределения веществ в смесях октанол — вода
Methods of computation and ranking of possible heterogeneous fluid equilibria in the systems «water — organic pollutant» are discussed in terms of modern notions about global phase diagrams of binary systems. The main classes of environmentally significant chemicals (such as polycyclic aromatic hydrocarbons, polychlorinated biphenyls, polychlorinated dibenzo-p-dioxins, furans, and selected pesticides) are studied. The binary interaction parameters k<sub>12</sub> for the one-fluid model of mixture were determined based on their revealed correlation with octanol — water partition coefficients K<sub><em>OW</em></sub>. Analytical expressions for the prediction of azeotropy in binary mixtures are suggested and the possibility of azeotropic behavior in aqueous solutions of several organic compounds is evaluated. The results of simulations of phase equilibria and critical curves for some mixtures of supercritical water with organic pollutants based directly on their molecular structure are presented.
Synthesis of Glycyrrhetinic Acid via Hydrolysis of Licorice Root Extract in Subcritical Water Medium
Key words: субкритическая вода, тритерпеновые гликозиды, глицирретиновая кислота, экстракт корня солодки, высокоэффективная жидкостная хроматография, спектроскопия ЯМР <sup>13</sup>С
A method for glycyrrhetinic acid (the aglycon of glycyrrhizic acid) synthesis via a sub-critical water hydrolysis of licorice root extract is developed. Its high efficiency in the comparison with a conventional hydrolysis is demonstrated. The high-performance liquid chromatography is used to prove the presence of glycyrrhetinic acid and to determine its concentration in the product. Using the <sup>13</sup>С NMR spectroscopy it is proved that glycyrrhetinic acid obtained in the sub-critical water medium has a β-configuration in theС<sub>18</sub> carbon atom environment.
Key words: сверхкритические флюиды, критические явления тройных систем, стабильные и метастабильные области расслаивания
Some features of phase equilibria in ternary systems with one volatile component and with a region of homogeneous supercritical fluid (SCF) in one of binary sub-systems (with two critical end-points <strong>p</strong> and <strong>Q</strong>) are analyzed. It is demonstrated that heterogenization of SCF that is spreading into a ternary system from the boundary binary sub-system of <strong>2d'</strong> type starts from monovariant critical phenomena in saturated solutions (liquid<sub>1</sub> = liquid<sub>2</sub> - solid) or (gas = liquid - solid), which pass through extremal parameters (temperature, composition) and form such special critical equilibria as double critical end-point (liquid<sub>1</sub> = liquid<sub>2</sub> - solid, gas = liquid - solid, liquid<sub>1</sub> = liquid<sub>2</sub> - gas) or double homogeneous points (liquid<sub>1</sub> = liquid<sub>2</sub> - solid о gas = liquid - solid). Ternary nonvariant points (liquid<sub>1</sub> = liquid<sub>2</sub> = gas, liquid<sub>1</sub> = liquid<sub>2</sub> - gas - solid and liquid<sub>1</sub> = gas - liquid<sub>2</sub> - solid) appear at the cross-sections of monovariant critical and non-critical curves.
Possible Mechanism of Oil Formation in the Flow of Supercritical Fluid Illustrated by Carbon Dioxide
Key words: сверхкритическая флюидная экстракция, образование нефти, механохимическое преобразование, органическое вещество, нефтяные углеводороды
The experiment on the supercritical (SC) CO<sub>2</sub> extraction of organic matter from rocks and soils showed that the SC fluid can dissolve, transfer and accumulate petroleumlike hydrocarbons, including relict ones. Based on the obtained results, it was hypothesized
that during the SC extraction the dissolution of organic substances is accompanied by their mechanochemical transformation in micropores and microcracks of solid matter. The resulting changes in composition, structure and distribution of individual hydrocarbons are similar to those, supposedly, taking place in petroleum-mother rocks. Thus, one can assume the possibility of rapid mechanochemical transformation of dispersed organic matter of sedimentary rocks in a flow of plutonic SC fluid, which, in turn, would allow one to re-consider the time scale of oil accumulation from millions to, possibly, hundreds of years.
Key words: сверхкритический диоксид углерода, β-дикетонаты европия, фторполимеры, фотолюминесценция, термочувствительность
Optical properties of the fluoracrilate based fluoropolymers doped with Eu(fod)<sub>3</sub>, Eu(fod)<sub>3</sub>phen and Eu(tta)<sub>3</sub> by supercritical fluid impregnation are studied. Effects of polymer matrix type on the efficiency supercritical fluid impregnation and optical properties of impregnated polymers are revealed. A comparative analysis of the quantum yield (&lambda<sub>exc</sub> = 300 and 380 nm) and thermosensitivity of Eu<sup>3+</sup> ions photoluminescence depending on the type of ligand and the chemical structure of polymers is performed. The effect of supercritical fluid extraction of photoinitiator residuals from doped fluoropolymer on their optical bleaching at wavelengths below 300 nm is established.
Key words: сверхкритический диоксид углерода, метилметакрилат, стирол, сополимеры, полимерные нанокомпозиты
We report about thin polymer particles synthesis based on radical co-polymerization of methylmetacrylate and styrol in supercritical СO<sub>2</sub> medium. We utilize supercritical СO<sub>2</sub> soluble polydimethylsiloxan metacrylate as a dispersion agent, which allow us to produce almost monosize particles. Co-polymer spherical powder, with typical sizes about 1 micron and molecular weight M<sub>w</sub> ~ 36000 has higher thermostability compare to similar M<sub>w</sub> polymethylmetacrylate. We have shown the possibility of mechanical and hydrophobic co-polymer properties controlled changes with varying of monomer charge ratio.
Key words: полимерный нанокомпозит, сверхкритическая флюидная импрегнация, нанокристаллический кремний, фотолюминесценция
With the use of supercritical carbon dioxide (SC-СO<sub>2</sub>) a process of matrix immobilization of photoluminescent silicon nanocrystals (nc-Si) in polytetrafluoroethylene microparticles (mp-PTFE) is implemented, which leads to the formation of photoluminescent nanocomposite mp-PTFE/nc-Si containing ~10<sup>3</sup> ÷10<sup>4</sup> of nc-Si in one PTFE particle (1—2 microns in size). This process is based on the effect of polymer swelling in SC-СO<sub>2</sub>, efficient transport of nanoparticles into internal free volume of polymer with SC-СO<sub>2</sub>, and shrinkage of nanocomposite after the release of СO<sub>2</sub> thus preventing their subsequent agglutination. Particles of nc-Si photoluminescent in the visible spectrum range were synthesized from silicon suboxide powder (SiO<sub>x</sub>, x ~ 1) heated at temperatures from 25 °C to 950 °C and next etched in concentrated hydrofluoric acid. The hydrosilylation procedure was used to attach 1-octadecene molecules to the surface of nc-Si. As a result, the photoluminescence intensity of nc-Si increased substantially. According to TEM images and small angle X-ray diffraction results, the maximum size of nc-Si particles did not exceed 5 nm and 7 nm respectively, and the core of these nanoparticles consisted of crystalline silicon. The structure and spectral properties of the initial nc-Si particles and synthesized photoluminescent nanocomposite mp-PTFE/nc-Si microparticles were studied.
Key words: сапропель, экстракция, докритический и сверхкритический диоксид углерода, аминокислоты, витамины, биологически активные вещества
The possibility of utilization of extraction with liquid and supercritical carbon dioxide for the isolation of biologically active substances from sapropels is demonstrated. The chemical composition of extracts is determined using a high performance liquid chromatography. The yield of total extract and efficiency of isolation of different components are varied with experimental conditions (temperature, pressure, extraction time).