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Analysis of yield and composition profile of Melissa officinalis (Lemon balm) extract obtained by two-step CO2 extraction at high pressure was analyzed. The first or essential oil fraction, collected at 10 MPa and 40 degrees C, contained mostly the high volatile and aromatic compounds. The second fraction was consenquently extracted at 30 MPa using different temperature: 25 degrees C (higher pressure than critical pressure but at temperature below the critical; HPCP-CO2), 40 degrees C or 100 degrees C (supercritical CO2; SC-CO2). Obtained yield of essential oil fraction was 0.45% at 10 MPa, while depending on applied extraction temperature (HPCP-CO2 or SC-CO2), the yields of the second fractions collected at 30 MPa varied from 0.44% to 0.94%. Within the study, the content of active substances in obtained extracts was analyzed, too. For comparison with CO2 extracts (HPCP or SC) the yield and characterization of essential oil obtained by hydrodistillation was accomplished, as well. A significant difference was noted not only between the essential oil isolated by hydrodistillation and SC-CO2 extraction (40 degrees C, 10 MPa) but also between total extracts obtained by HPCP-CO2 and SC-CO2 extraction. The pseudo kinetic model was applied to define SC-CO2 extraction of Lemon balm to describe the relation between the yield of extraction and CO2 consumption. Antioxidant activity of obtained extracts was determined by free radical scavenging capacity (RSC) and significant correlation of antioxidant capacity and composition profile between obtained extracts was observed.

Analysis of yield and composition profile of Melissa officinalis (Lemon balm) extract obtained by two-step CO2 extraction at high pressure was analyzed. The first or essential oil fraction, collected at 10 MPa and 40 degrees C, contained mostly the high volatile and aromatic compounds. The second fraction was consenquently extracted at 30 MPa using different temperature: 25 degrees C (higher pressure than critical pressure but at temperature below the critical; HPCP-CO2), 40 degrees C or 100 degrees C (supercritical CO2; SC-CO2). Obtained yield of essential oil fraction was 0.45% at 10 MPa, while depending on applied extraction temperature (HPCP-CO2 or SC-CO2), the yields of the second fractions collected at 30 MPa varied from 0.44% to 0.94%. Within the study, the content of active substances in obtained extracts was analyzed, too. For comparison with CO2 extracts (HPCP or SC) the yield and characterization of essential oil obtained by hydrodistillation was accomplished, as well. A significant difference was noted not only between the essential oil isolated by hydrodistillation and SC-CO2 extraction (40 degrees C, 10 MPa) but also between total extracts obtained by HPCP-CO2 and SC-CO2 extraction. The pseudo kinetic model was applied to define SC-CO2 extraction of Lemon balm to describe the relation between the yield of extraction and CO2 consumption. Antioxidant activity of obtained extracts was determined by free radical scavenging capacity (RSC) and significant correlation of antioxidant capacity and composition profile between obtained extracts was observed.

Yield and composition of curry flower (Helichrysum italicum) and sage leaves (Salvia officinalis) extract obtained by supercritical CO2 extraction (SFE) at 15 MPa and 40 degrees C were analyzed and compared to composition of curry flowers and sage essential oil isolated by hydrodistillation. Furthermore, the SFE performed using a mixture of curry flowers and sage plant and SFE of mixture of curry flowers and essential oil of sage were analyzed, too. It was shown that the average selectivity of monoterpenes and some individual sesquiterpenes and diterpenes present in pure sage or pure curry extract were significantly changed when mixture of these plants was used for SFE. The goal of SFE realized with mixture of curry flowers and sage essential oil was to explain effect of essential oil used as co-solvent changing the solubility of different compounds or characteristic group of terpenes in supercritical CO2. Increased extraction of heavier compounds from curry flower which is actually not present in pure essential oil of sage was also detected. The pseudo-kinetic model was proposed and corresponding parameters which define the rate of extraction were determined and compared to the parameters obtained according to Sovova's model usually used in literature for predicting yield of SFE from different plants.

Yield and composition of curry flower (Helichrysum italicum) and sage leaves (Salvia officinalis) extract obtained by supercritical CO2 extraction (SFE) at 15 MPa and 40 degrees C were analyzed and compared to composition of curry flowers and sage essential oil isolated by hydrodistillation. Furthermore, the SFE performed using a mixture of curry flowers and sage plant and SFE of mixture of curry flowers and essential oil of sage were analyzed, too. It was shown that the average selectivity of monoterpenes and some individual sesquiterpenes and diterpenes present in pure sage or pure curry extract were significantly changed when mixture of these plants was used for SFE. The goal of SFE realized with mixture of curry flowers and sage essential oil was to explain effect of essential oil used as co-solvent changing the solubility of different compounds or characteristic group of terpenes in supercritical CO2. Increased extraction of heavier compounds from curry flower which is actually not present in pure essential oil of sage was also detected. The pseudo-kinetic model was proposed and corresponding parameters which define the rate of extraction were determined and compared to the parameters obtained according to Sovova's model usually used in literature for predicting yield of SFE from different plants.

In this study, the synthesis of biodiesel or fatty acid methyl esters (FAME) from sunflower oil and methanol using CaO center dot ZnO catalyst was investigated. Catalyst was synthesized by ball milling of Ca(OH)(2) and ZnO powder mixture with the addition of water (BMH), as well as solely by ball milling of mentioned powders (BM) and subsequent calcination at 700 degrees C in air atmosphere. For comparison, the CaO center dot ZnO mixed oxide was also prepared using usual coprecipitation procedure (CP) followed by calcination at 700 degrees C of the formed calcium zinc hydroxide hydrate. The BMH, BM and CP catalysts were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), infrared spectroscopy (FTIR), particle size distribution measurement and scanning electron microscopy (SEM and SEM-EDS). In addition, specific surface area (BET), solubility in methanol at 60 degrees C and alkalinity (Hammett indicator method) were also determined. The activity of BMH, BM and CP catalysts for biodiesel synthesis were tested at 60 degrees C and 1 bar, using molar ratio of sunflower oil to methanol of 1:10 and with 2 wt% of catalyst based on oil weight.

In this study, the synthesis of biodiesel or fatty acid methyl esters (FAME) from sunflower oil and methanol using CaO center dot ZnO catalyst was investigated. Catalyst was synthesized by ball milling of Ca(OH)(2) and ZnO powder mixture with the addition of water (BMH), as well as solely by ball milling of mentioned powders (BM) and subsequent calcination at 700 degrees C in air atmosphere. For comparison, the CaO center dot ZnO mixed oxide was also prepared using usual coprecipitation procedure (CP) followed by calcination at 700 degrees C of the formed calcium zinc hydroxide hydrate. The BMH, BM and CP catalysts were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA), infrared spectroscopy (FTIR), particle size distribution measurement and scanning electron microscopy (SEM and SEM-EDS). In addition, specific surface area (BET), solubility in methanol at 60 degrees C and alkalinity (Hammett indicator method) were also determined. The activity of BMH, BM and CP catalysts for biodiesel synthesis were tested at 60 degrees C and 1 bar, using molar ratio of sunflower oil to methanol of 1:10 and with 2 wt% of catalyst based on oil weight.

The goal of present work was to investigate and explain kinetics and mass transfer phenomena occurring during the SFE from the mixture of two plants with different initial composition. The extractions from pure clove, oregano and thyme as well as from clove/oregano (C/O) and clove/thyme (C/T) mixtures with various initial compositions of plant material were carried out using supercritical CO2 at 10 MPa and 40 degrees C. The results indicated that presence of light compounds in supercritical CO2 originated from the oregano leaves or thyme at the beginning of extraction process increases the extraction rate of compounds from clove bud. Only small added amounts of oregano or thyme to clove bud (C/O - 90:10%, w/w; or C/T - 84:16%, w/w) in the starting plant mixture had the same effect resulted in the similar and the highest increase of the extraction rate and had negligible influence on total extraction yield compared to extract isolated from pure clove. Different mathematical models were used for simulation of experimental data which showed that the highest increase of the solubility of extractable compounds in supercritical CO2 as well as the highest mass transfer rate in the solid phase during extractions existed during extraction from C/O (90:10, w/w) and C/T (84:16, w/w) mixtures. Decrease of SC CO2 consumption or shorter time of extraction necessary for achieving desired extract yield in the case of SFE of the clove buds could be important for industrial-scale application.

The goal of present work was to investigate and explain kinetics and mass transfer phenomena occurring during the SFE from the mixture of two plants with different initial composition. The extractions from pure clove, oregano and thyme as well as from clove/oregano (C/O) and clove/thyme (C/T) mixtures with various initial compositions of plant material were carried out using supercritical CO2 at 10 MPa and 40 degrees C. The results indicated that presence of light compounds in supercritical CO2 originated from the oregano leaves or thyme at the beginning of extraction process increases the extraction rate of compounds from clove bud. Only small added amounts of oregano or thyme to clove bud (C/O - 90:10%, w/w; or C/T - 84:16%, w/w) in the starting plant mixture had the same effect resulted in the similar and the highest increase of the extraction rate and had negligible influence on total extraction yield compared to extract isolated from pure clove. Different mathematical models were used for simulation of experimental data which showed that the highest increase of the solubility of extractable compounds in supercritical CO2 as well as the highest mass transfer rate in the solid phase during extractions existed during extraction from C/O (90:10, w/w) and C/T (84:16, w/w) mixtures. Decrease of SC CO2 consumption or shorter time of extraction necessary for achieving desired extract yield in the case of SFE of the clove buds could be important for industrial-scale application.

Swelling of plant material belonging to several plant families and the influence of swelling on supercritical fluid extraction process were investigated in this study. While swelling of Lamiaceae family species as well as hop cones and pellets occurred during the exposure of plant material to supercritical carbon dioxide, swelling of valerian root and ginger rhizome happened after the decompression step. Optimal pretreatment of herbaceous matrix which will enable commencement of continuous extraction from already swollen plant material was defined on the basis of swelling test results. Experimental results were modeled and energy savings due to the optimal processing on the laboratory scale were calculated. Sorption of carbon dioxide into the hop pellet was measured and the diffusion coefficient in the solid phase was determined. Obtained results indicated that the effective diffusion coefficient in the hop pellet was increased by one order of magnitude due to swelling.

The analysis of phase equilibrium between methanol and glycerides during methyl esters of fatty acids (FAME or biodiesel) synthesis at high pressure and temperature is very important for describing the kinetic and process design. It was studied at pressure between 1.1 and 28.0 MPa and temperature from 150 to 270 degrees C. The transition of phases and composition of identified phases was calculated using RK-Aspen EOS and obtained values were also compared to experimentally determined data at subcritical condition (1.1-4.5 MPa and 150-210 degrees C). Results of experimental investigation, as well as performed simulation of some specified composition of reaction mixture, showed that system of triglycerides and methanol, at the beginning of reaction (at all analysed conditions except for supercritical state of mixture) is in equilibrium between two liquid phases. During the methanolysis of triglycerides, the phase's distribution was changed accordingly and it highly depends on actual composition of reaction mixture, temperature and pressure. Calculated and measured values indicated that distribution of methanol between the oil phase, the methyl esters, and the glycerol rich phase exists and depends of working condition. As a consequence of fact, that the methanolysis of triglycerides (oil) is mainly realized in the oil-rich phase, at the end of reaction, after all triglycerides are converted into FAME and glycerol, the oil phase disappears. Furthermore, according to the results of phase composition calculation, it was shown that from the beginning to the end of reaction one phase only exists, for methanolysis performed at 270 degrees C and 20.0 MPa.

Swelling of plant material belonging to several plant families and the influence of swelling on supercritical fluid extraction process were investigated in this study. While swelling of Lamiaceae family species as well as hop cones and pellets occurred during the exposure of plant material to supercritical carbon dioxide, swelling of valerian root and ginger rhizome happened after the decompression step. Optimal pretreatment of herbaceous matrix which will enable commencement of continuous extraction from already swollen plant material was defined on the basis of swelling test results. Experimental results were modeled and energy savings due to the optimal processing on the laboratory scale were calculated. Sorption of carbon dioxide into the hop pellet was measured and the diffusion coefficient in the solid phase was determined. Obtained results indicated that the effective diffusion coefficient in the hop pellet was increased by one order of magnitude due to swelling.

The analysis of phase equilibrium between methanol and glycerides during methyl esters of fatty acids (FAME or biodiesel) synthesis at high pressure and temperature is very important for describing the kinetic and process design. It was studied at pressure between 1.1 and 28.0 MPa and temperature from 150 to 270 degrees C. The transition of phases and composition of identified phases was calculated using RK-Aspen EOS and obtained values were also compared to experimentally determined data at subcritical condition (1.1-4.5 MPa and 150-210 degrees C). Results of experimental investigation, as well as performed simulation of some specified composition of reaction mixture, showed that system of triglycerides and methanol, at the beginning of reaction (at all analysed conditions except for supercritical state of mixture) is in equilibrium between two liquid phases. During the methanolysis of triglycerides, the phase's distribution was changed accordingly and it highly depends on actual composition of reaction mixture, temperature and pressure. Calculated and measured values indicated that distribution of methanol between the oil phase, the methyl esters, and the glycerol rich phase exists and depends of working condition. As a consequence of fact, that the methanolysis of triglycerides (oil) is mainly realized in the oil-rich phase, at the end of reaction, after all triglycerides are converted into FAME and glycerol, the oil phase disappears. Furthermore, according to the results of phase composition calculation, it was shown that from the beginning to the end of reaction one phase only exists, for methanolysis performed at 270 degrees C and 20.0 MPa.

The main goal of this study is analysis the existing and recently published data related to design of larger scale plant for biodiesel synthesis at supercritical conditions. Such analysis was focused on the problem of insufficiency of the previously in the literature published industrial plant design simulation. A continuous process flowsheet for biodiesel production from triglycerides under supercritical conditions of alcohol (SCA) was analyzed and influence of triglycerides degree of conversion on overall energy consumption in SCA was examined. A comparison between the homogenous alkali-catalyzed alcoholysis (HACA) and the supercritical methanolysis of triglyceride was made in order to point out the advantages and disadvantages of each of analyzed process. Furthermore, the usage of energy in each step and environmentally weak points of both process are discussed and the possible solutions for avoiding them are proposed.

The main goal of this study is analysis the existing and recently published data related to design of larger scale plant for biodiesel synthesis at supercritical conditions. Such analysis was focused on the problem of insufficiency of the previously in the literature published industrial plant design simulation. A continuous process flowsheet for biodiesel production from triglycerides under supercritical conditions of alcohol (SCA) was analyzed and influence of triglycerides degree of conversion on overall energy consumption in SCA was examined. A comparison between the homogenous alkali-catalyzed alcoholysis (HACA) and the supercritical methanolysis of triglyceride was made in order to point out the advantages and disadvantages of each of analyzed process. Furthermore, the usage of energy in each step and environmentally weak points of both process are discussed and the possible solutions for avoiding them are proposed.

St. John's Wort (Hypericum perforatum L.) was extracted with supercritical carbon dioxide (SC CO2) under 10, 15 and 20 MPa and at 313 and 323 K. The influence Of SC CO2 density (400-800 kg/m(3)) was examined with respect to extraction yield as well as to hyperforin and adhyperforin content, which was determined using a highly selective LC/MS/MS analytical method. A high concentration (up to 526 mg/g total extract) of two phloroglucinol derivatives was determined in this study showing that the absolute extracted amount of hyperforin and adhyperforin (mg per I g of dry plant) is almost constant not depending on total yield of extract, i.e. on density Of SC CO2. Determination of the rate of hyperforin and adhyperforin extraction at 313 K and 10 MPa showed that the maximal rates correspond to consumption of 7-8.5 9 Of CO2 per I g of dry St. John's Wort. Investigation of ultrasonic extraction of St. John's Wort followed after pre-treatment of plant material (323 K; 10 MPa; 2 h; without CO2 flow) indicated that obtained extract contains a higher amount (mg/g plant material) of two most important pharmacological active compounds of St. John's Wort, hyperforin and hypericin, than the extract obtained by ultrasonic extraction only.

This article reports the achievements of the micro-scale (secretory-structure-scale) mathematical modelling of essential oil isolation by supercritical carbon dioxide. Some new experimental and modelling results are presented. The improved model for the supercritical fluid extraction from the glandular trichomes (peltate glands) is introduced. According to the behavior of plant secretory structures during the extraction as well as according to the modelling results, plant material was classified according to the dominant resistance to mass transfer during the extraction process. External mass transfer was the rate limiting step in the extraction from plants with secretory ducts and secretory cavities of citrus family. In the case of extraction from secretory cells, internal diffusion was the rate limiting step. In the extraction from glandular trichomes, external mass transfer, as well as diffusion through the gland membrane influenced the process.

St. John's Wort (Hypericum perforatum L.) was extracted with supercritical carbon dioxide (SC CO2) under 10, 15 and 20 MPa and at 313 and 323 K. The influence Of SC CO2 density (400-800 kg/m(3)) was examined with respect to extraction yield as well as to hyperforin and adhyperforin content, which was determined using a highly selective LC/MS/MS analytical method. A high concentration (up to 526 mg/g total extract) of two phloroglucinol derivatives was determined in this study showing that the absolute extracted amount of hyperforin and adhyperforin (mg per I g of dry plant) is almost constant not depending on total yield of extract, i.e. on density Of SC CO2. Determination of the rate of hyperforin and adhyperforin extraction at 313 K and 10 MPa showed that the maximal rates correspond to consumption of 7-8.5 9 Of CO2 per I g of dry St. John's Wort. Investigation of ultrasonic extraction of St. John's Wort followed after pre-treatment of plant material (323 K; 10 MPa; 2 h; without CO2 flow) indicated that obtained extract contains a higher amount (mg/g plant material) of two most important pharmacological active compounds of St. John's Wort, hyperforin and hypericin, than the extract obtained by ultrasonic extraction only.

This article reports the achievements of the micro-scale (secretory-structure-scale) mathematical modelling of essential oil isolation by supercritical carbon dioxide. Some new experimental and modelling results are presented. The improved model for the supercritical fluid extraction from the glandular trichomes (peltate glands) is introduced. According to the behavior of plant secretory structures during the extraction as well as according to the modelling results, plant material was classified according to the dominant resistance to mass transfer during the extraction process. External mass transfer was the rate limiting step in the extraction from plants with secretory ducts and secretory cavities of citrus family. In the case of extraction from secretory cells, internal diffusion was the rate limiting step. In the extraction from glandular trichomes, external mass transfer, as well as diffusion through the gland membrane influenced the process.

In this study, the supercritical carbon dioxide extraction of essential oils from plants which contain secretory ducts as essential oil reservoirs was investigated and modelled. Supercritical carbon dioxide extraction of essential oils from Asteraceae family species, marigold and chamomile, indicated that particle size had no significant influence on the extraction rate in two outermost cases: fine milled plant material and plant material cut to particle length of 5 mm. This confirmed previously reported phenomenon that in some cases particle size had no influence on the rate of supercritical extraction process. In order to explain this behavior, the mathematical model which took into consideration the phenomena occurring on the secretory duct scale, was developed and applied to simulate experimental data of marigold and chamomile supercritical carbon dioxide extraction. Proposed model was also applied to the literature experimental data of fennel fruit supercritical fluid extraction where the same phenomenon had been observed. To obtain information regarding secretory structure, scanning electron microscopy investigation of the plant material was performed. Very good agreement of the model results and experimental data in the case of different plant species, extraction conditions and particle sizes, confirmed the basic hypothesis of the model.

In this study, the supercritical carbon dioxide extraction of essential oils from plants which contain secretory ducts as essential oil reservoirs was investigated and modelled. Supercritical carbon dioxide extraction of essential oils from Asteraceae family species, marigold and chamomile, indicated that particle size had no significant influence on the extraction rate in two outermost cases: fine milled plant material and plant material cut to particle length of 5 mm. This confirmed previously reported phenomenon that in some cases particle size had no influence on the rate of supercritical extraction process. In order to explain this behavior, the mathematical model which took into consideration the phenomena occurring on the secretory duct scale, was developed and applied to simulate experimental data of marigold and chamomile supercritical carbon dioxide extraction. Proposed model was also applied to the literature experimental data of fennel fruit supercritical fluid extraction where the same phenomenon had been observed. To obtain information regarding secretory structure, scanning electron microscopy investigation of the plant material was performed. Very good agreement of the model results and experimental data in the case of different plant species, extraction conditions and particle sizes, confirmed the basic hypothesis of the model.

Alumina/silica aerogel with zinc chloride alkylation catalyst, was obtained using one step sol-gel synthesis and subsequent drying with the supercritical carbon dioxide. The high density supercritical carbon dioxide drying conditions resulted in zinc chloride removal from the catalyst surface, surface area and pore volume increase and catalytic activity decrease. The low density supercritical carbon dioxide drying conditions, pore size distribution centred around 6 nm pore radius and high degree of mixed Al-O-Si bonds in the alumina/silica aerogel network, were found to increase the catalytic activity of the obtained aerogel catalysts.

Alumina/silica aerogel with zinc chloride alkylation catalyst, was obtained using one step sol-gel synthesis and subsequent drying with the supercritical carbon dioxide. The high density supercritical carbon dioxide drying conditions resulted in zinc chloride removal from the catalyst surface, surface area and pore volume increase and catalytic activity decrease. The low density supercritical carbon dioxide drying conditions, pore size distribution centred around 6 nm pore radius and high degree of mixed Al-O-Si bonds in the alumina/silica aerogel network, were found to increase the catalytic activity of the obtained aerogel catalysts.