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1.
“Thermodynamic and physical properties for high pressure process design”
Maša Knez Marevci, 2014, doktorska disertacija

Opis: The thesis is comprised of three main categories. The first part of dissertation covers investigations of phase equilibria of compounds from natural materials in conventional and also non conventional supercritical fluids. In details, the impact of pressure and/or temperature on the system behaviour (miscibility, solubility, phase inversion) is investigated, quantitative and qualitative analyses to evaluate and identify compounds contained after performing preliminary extraction experiments from different natural tissues are presented. The impact of operating parameters (pre-treatment of the raw material with SFE; different extraction solvents: propane, CO2, non conventional SCFs; different extraction temperatures and pressures) on extraction kinetics is observed. Following substances were taken into consideration: vanillins, caffeine, carnosoic acid extract and lecithin. Second part of dissertation covers studies of phase equilibria of the systems bio oil/gas, which is crucial in biorefinery process design. In this part of dissertation, which covers studies of phase equilibria of binary and ternary systems, the impact of pressure and/or temperature on the system behaviour (miscibility, solubility, phase inversion) for binary system bio oil/supercritical fluid (bio oil/CO2) and (bio oil/H2) was studied. Additionally, phase behaviour of ternary systems of (bio oil/diesel/CO2) and (bio oil/tail water/CO2) under the impact of pressure and/or temperature is observed. These data are of a high importance for bio refineries as an important part of necessary sustainable development. In recent years, studies on biodiesel synthesis have focused on development of process intensification technologies to resolve some of these issues. Fundamental data to design fractionation process of components of bio oil are crucial for an efficient hydrogenation process of bio oil. In the third part of dissertation observation of phase equilibria and determination of the parameters like diffusion coefficient, density and viscosity for the systems polymer/CO2 at elevated pressures is investigated. An overview of different methods applied to determine the parameters like diffusion coefficient, density and viscosity of the systems polymer (PEG)/CO2 at elevated pressures is offered. Observation of phase equilibria of the binary system PEG/CO2, determination of the impact of pressure and/or temperature on the system behaviour (miscibility, solubility, phase inversion), determination of thermodynamically and physically properties of the system with new applicative methods and finally, comparison of the results obtained by different methods is provided. The interfacial tension (IFT) at the (PEG)/CO2 interface has been determined by using an experimental technique developed to study the interfacial interactions of the liquids in equilibrium with gas in a glass-windowed equilibrium cell by the means of Capillary Rise (CR) method. Advantages and disadvantages of methods that were applied are exposed and discussed.
Ključne besede: phase equilibria, natural materials, conventional and non conventional supercritical fluids, extraction, bio oil, data for biorefinery process design, systems polymer (PEG)/CO2, diffusion coefficient, density, viscosity, surface tension, Capillary Rise (CR) method.
Objavljeno: 28.10.2014; Ogledov: 1844; Prenosov: 256
.pdf Celotno besedilo (4,46 MB)

2.
Phase equilibria in systems containing [alpha]-tocopherol and dense gas
Mojca Škerget, Petra Kotnik, Željko Knez, 2003, izvirni znanstveni članek

Opis: Solubility of ▫$alpha$▫-tocopherol in CO2 and propane was determined at temperatures 303, 313, 333 and 353 K and over a pressure range from 79 to 286 bar for CO2 and 16 to 112 bar for propane. A static-analytic method was applied. The solubility of ▫$alpha$▫-tocopherol in dense CO2 under the conditions investigated was in the range of 0.2-17.0 mg/g CO2. The maximal solubilities of ▫$alpha$▫-tocopherol in propane were approximately up to ten times higher than in CO2 and were in the range from 38.9 to 171.9 mg/g propane. Phase equilibrium data for Milk Thistle seed oil in supercritical CO2 were determined at temperatures 313, 333 and 353 K and pressures ranging from 100 to 300 bar. The oil was previously additionally vitaminized and contained 1.9 wt.% of ▫$alpha$▫-tocopherol and 1.7 wt.% of free fatty acids (FFA). The solubility of oil in CO2 was in the range from 1.3 to 17.9 mg/g CO2. The distribution coefficients of ▫$alpha$▫-tocopherol and FFA between light and heavy phase were determined on a solvent free basis. The obtained separation factors increased with temperature and pressure to approximately 160-200 bar and decreased with a further increase of pressure.
Ključne besede: chemical processing, supercritical fluids, phase equilibria, separation factors, vitamin E, CO2, dense gases
Objavljeno: 01.06.2012; Ogledov: 1329; Prenosov: 28
URL Povezava na celotno besedilo

3.
Phase equilibira of permethrin and dicofol with carbon dioxide
Petra Kotnik, Amra Perva-Uzunalić, Mojca Škerget, Željko Knez, 2005, izvirni znanstveni članek

Opis: The solubilities of pesticides (permethrin and dicofol) in CO2 were measured by a static-analytic method at pressures ranging from 10.0 MPa to 25.0 MPa andtemperatures of 293.2 K, 303.2 K, and 313.2 K. Due to the nonconventional shape of some solubility isotherms, solid-liquid transitions of pesticides under pressure of CO2 were determined using a modified capillary method. Sincethe solubilities depend on solvent density, the experimental binary solid-fluid equilibrium data were correlated as a function of solvent density by two different models.
Ključne besede: chemical processing, high pressure technology, CO2, pesticides, phase equilibria, solubility
Objavljeno: 01.06.2012; Ogledov: 1339; Prenosov: 27
URL Povezava na celotno besedilo

4.
Influence of the aromatic ring substituents on phase equilibria of vanilins in binary system with CO2
Mojca Škerget, Lucija Čretnik, Željko Knez, Maja Škrinjar, 2005, izvirni znanstveni članek

Opis: Solid-liquid phase transitions of vanillin, ethylvanillin, o-vanillin and o-ethylvanillin in presence of compressed CO2 were determined with the modified capillary method. Furthermore, the solubilities of the above mentioned vanillins in supercritical CO2 were measured at 313.2, 333.2 and 353.2 K and in the pressure range 8-30 MPa using a static-analytic method. The experimental equilibrium solubility data have been fitted to the Peng-Robinson equation in combination with two parameter van der Waals mixing rules and binary parameters were determined from the best fit. Results showed that the phase equilibria of vanillins in dense CO2 are influenced by the position of the hydroxyl group bound to the aromatic ring. Under the pressure of CO2 the melting point depression and also the solubility of both o-vanillins was higher than those of p-vanillins. Oppositely, the alchoxy group (methoxy or ethoxy) showed no significant influence on the solubility of vanillins.
Ključne besede: chemical processing, high pressure technology, CO2, phase equilibria, vanillin isomers, data, ring substituents
Objavljeno: 01.06.2012; Ogledov: 1570; Prenosov: 37
URL Povezava na celotno besedilo

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