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Supercritical fluid extraction of mogrosides from Siraitia grosvenoriiXia, Yan, 1971- January 2006 (has links)
No description available.
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Zr And Silicotungstic Acid Incorporated Silicate Structured Mesoporous Catalysts For Dimethyl Ether SynthesisOrman, Sultan 01 August 2011 (has links) (PDF)
Due to high consumption rates of petroleum derived fuels and environmental regulations, significant search has been initiated for the development of environmental friendly and efficient fuels, which were derived from more abundant feedstocks. Dimethyl ether (DME), as having a good combustion quality and high cetane number, is an efficient alternative for diesel fuel. With improved combustion quality, the emissions from DME used engines are greatly decreased. DME synthesis can be carried out via two different methods / methanol dehydration on acidic catalysis and syn-gas conversion on bifunctional catalysis.
In this study, the aim is to synthesize acidic catalysts using direct hydrothermal synthesis method for DME synthesis as using methanol as feed stock via dehydration and to characterize these materials.
The support of the synthesized materials comprises of MCM-41 structure and silicotungstic acid (STA) and metals (Zr / Ni / Cu) were incorporated into the MCM-41 structure during synthesis. Two different techniques were used to extract the surfactant (CTMABr) from catalyst matrix. First one is the conventional calcination technique (at 350° / C) and the second is supercritical fluid extraction (at various operating conditions) with methanol modified CO2. The effect of metal loading on extraction performance is analyzed through characterizations of Ni and Cu incorporated materials. In addition, The effect of operation parameters on catalyst properties are also investigated with performing extraction at different pressures for different durations. By changing the type of metal incorporated into the catalyst, the extraction performance is also monitored. The characterization results indicated that, SFE process is also a promising method for surfactant removal.
The activities of zirconium added catalysts are tested in methanol dehydration reaction towards DME. It is concluded that the conversion of methanol and selectivity of DME in presence of extracted samples are lower (maximum yield -0.54- obtained at 450° / C with sceSZ1) compared to the calcined materials (maximum yield -0.80- obtained at 300° / C with cSZ6). This result can also be foreseen by DRIFTS analysis of pyridine adsorbed samples. The acid sites of extracted materials are not as strong as in the calcined catalysts.
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Determination of organic pollutants in air and soil by supercritical fluid extraction, capillary electrophoresis, chromatographic and electrochemical methods /Long, Yinhua. January 2001 (has links)
Thesis (Ph. D.)--University of Hong Kong, 2001. / Includes bibliographical references.
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Extraction of bitumen from Athabasca oil sand slurry using supercritical carbon DioxideLa, Helen Unknown Date
No description available.
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Extraction of hydrocarbons from oil sand using supercritical carbon dioxidFang, Yi Unknown Date
No description available.
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Supercritical fluid extraction of mogrosides from Siraitia grosvenoriiXia, Yan, 1971- January 2006 (has links)
Mogrosides, the main active components in S. grosvenorii SWINGLE, are considered to be some 250 times sweeter than sucrose and to possess several medicinal attributes. Previous isolation processes used large quantities of toxic solvent that resulted in toxic residues of organic solvent in this high value food. Supercritical fluids fulfill the requirements of non-toxicity, recycle ability, and useful solvent characteristics. The work presented in this thesis is directed to the extraction of mogrosides from the powdered S. grosvenorii concentrate (SG) and the crude extract after resin treatment (MG) with sub critical water and supercritical CO2. / Because no source of mogroside V reference material is available commercially, the first objective of this research was to isolate mogroside V of sufficient purity that it could be crystallized. This objective was achieved by selecting suitable eluates from resin chromatography coupled with preparative thin layer chromatography (TLC). Crystalline white isolate was further characterized by 13C-NMR and by MS and determined to be mogroside V, which was suitable as a reference material for subsequent experiments. / The process variables for both sub critical water and supercritical carbon dioxide extraction were evaluated and optimized so that conclusions could be formulated regarding the relative merits of the two proposed extraction methods. The efficiency of extraction was determined spectrophotometrically based on the recovery of mogrosides from the starting material following the vanillin-HClO4 method. / When compared with Soxhlet solvent extraction, supercritical fluid extraction with either sub critical water or supercritical CO2 provided improved recoveries and consumed less organic solvent. In addition, the purity of the extracts differed greatly. For identical SG samples, sub critical water extraction was demonstrated to be more efficient (62.4% recovery) compared with 37.0% recovery by EtOH modified scCO2 extraction or 5.1% for Soxhlet extraction with hexane.
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Remediation of a soil contaminated with polyaromatic hydrocarbons (PAHs)Yuan, Tao, 1968- January 2006 (has links)
Sites contaminated with polyaromatic hydrocarbons (PAHs) pose serious health and safety risks to the surrounding environment due to their toxicity, persistence and accumulation in the environment. Because certain members of this class have been demonstrated to be both carcinogenic and mutagenic, PAHs are considered as environmental priority pollutants (US EPA). The studies in this thesis provide an efficient, economical and environmentally benign technique for the remediation of PAH contaminated soil/sediment by means of PAH mobilization with surfactant followed with a catalytic hydrogenation in supercritical carbon dioxide (scCO2). / Catalytic hydrogenation of naphthalene, acenaphthylene, ancenaphthene, anthracene, phenanthrene, chrysene and benzo[a]pyrene over alumina supported palladium (5% Pd0/gammaAl2O3) commercial catalyst were investigated in either a batch reaction mode or a continuous reaction system in H2-scCO2 (∼5% v/v). The hydrocarbon compounds were efficiently reduced to their corresponding fully saturated polycyclic hydrocarbon homologs with mild conditions of temperature (90°C) and pressure (60 psi H2 or 3000 psi H2-scCO2). The bacterial reverse mutation assay demonstrated that both the fully and partially hydrogenated products of chrysene and benzo[a]pyrene were devoid of mutagenic activity. / A laboratory study was conducted on the surfactant-assisted mobilization of PAH compounds combined with reagent regeneration and detoxification steps to generate innocuous products. Five minutes of ultrasonication of field contaminated soil with a 3% (w/v) surfactant suspension mobilized appreciable quantities of all PAH compounds. Formulating the Brij 98 surfactant in 0.1 M phosphate buffer (pH 8.0) mobilized the largest quantities of PAH compounds and the recovery of surfactant (>90%) but soil residues exceeded permissible maxima for five- and six-ring analytes. Five successive washes were required to reduce the residual fraction to permissible levels. The mobilized PAH compounds were then detoxified at line by catalytic hydrogenation in a 5% H2-scCO2 (v/v) atmosphere. / New palladium hydrogenation catalysts were fabricated in the laboratory with specific processes on various supports. The hydrogenation of phenanthrene and benzo[a]pyrene in a fixed bed micro reactor demonstrated that the catalyst that was fabricated from organosoluble precursor loaded on aluminum oxide (2.5% Pd0/gammaAl2O3) was four times more efficient than the commercial catalyst that was used for PAH hydrogenations.
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Extraction of bitumen from Athabasca oil sand slurry using supercritical carbon DioxideLa, Helen 06 1900 (has links)
Extraction of hydrocarbons from an Athabasca oil sand slurry were conducted using supercritical carbon dioxide (SC-CO2). The oil sand was slurried to a 1:1 ratio with water and experiments were conducted using a laboratory-scale batch supercritical fluid extraction (SFE) system. Preliminary tests revealed the importance of mixing rate on hydrocarbon yields. A 2^3 factorial experiment was then conducted to test the effect of temperature, pressure, and modifier (toluene) addition on hydrocarbon extraction yield. When toluene was absent, hydrocarbon extraction yields were greater at the high temperature (60°C); however, when toluene was present, the combination of low temperature (31°C) and high pressure (24.1MPa) provided greater extraction yields. The experiment that produced the highest cumulative hydrocarbon extraction yield was analyzed by GC-FID for product-quality. Two composite samples and one time series sample revealed a carbon distribution range of the extract centering on C25, corresponding to the light gas oil range as classified in petroleum fractions. / Environmental Science
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Extraction of hydrocarbons from oil sand using supercritical carbon dioxidFang, Yi 11 1900 (has links)
This study investigates the extraction of hydrocarbons from oil sand using supercritical carbon dioxide (SC CO2). Experiments were carried out on three different types of oil sands. After some preliminary experiments, the feasibility of extracting hydrocarbons from oil sands by SC CO2 was confirmed and three experimental factors (pressure, temperature and mixing rate) were identified for further study. A two to the three factorial design was used to determine the significance of each factor and the significance of the interaction of the factors on the extraction efficiency. The extraction efficiency was calculated from Dean-Stark extraction analysis and was compared to the extraction efficiency based on gravimetric analysis. The results show that the extraction efficiency increased with pressure at a constant temperature. The effect of temperature on extraction efficiency is complex. The highest extraction efficiency was obtained at the high pressure (24.1MPa), high temperature (60C) and a mixing rate of 250rpm. / Environmental Science
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Investigation of catalyzed hydrodechlorination reactions of organochlorines in supercritical carbon dioxide /Aikawa, Bio, January 1900 (has links)
Thesis (Ph. D.)--Carleton University, 2001. / Includes bibliographical references. Also available in electronic format on the Internet.
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