Eight alcohols in their supercritical states were used individually to treat crude bio-oil and pine wood chips. All supercritical alcohols studied, with the exception of tertbutanol, exhibited the ability to decrease the oxygen content, acid value and/or remove unstable compounds from the crude bio-oil. For supercritical 1-butanol, its use for upgrading of crude bio-oil resulted in a product with much lower oxygen content, lower acid value and fewer unstable compounds. Two CoMo catalysts were examined for their impact on the bio-oil upgrading process with supercritical alcohol. Their influence on the oxygen content, acid value and concentrations of unstable compounds in the processed bio-oil was examined. The basic CoMo/MgO catalyst was demonstrated to effectively eliminate acid content from the bio-oil, regardless of the alcohol employed. Compared with crude bio-oil produced by fast pyrolysis of pine wood lumber, the liquid products produced from supercritical alcohol treatment of pine wood chips possessed one or more of the desirable characteristics: lower acid value, lower oxygen content and fewer unstable compounds. Generally, supercritical butanol isomers produced liquid fuels with lower oxygen content. However, the bulky structure of branched alcohol isomers (secondary and tertiary alcohols) appeared to hinder the degradation of pine wood chips. The CoMo/MgO catalyst exhibited the ability to decrease the acid value, but not to decrease the oxygen content in the liquid product. Wood chip size, wood chip/methanol mass ratios, temperatures, pressures and reaction time were examined in this work. However, the influence of these variables on liquid yield from supercritical methanol treatment of pine wood chips was not substantial.

No description available.

Efficient use of renewable feedstocks for production of chemicals and intermediates is necessary to reduce dependence upon petroleum. A large portion of these chemicals could be produced using lipids from renewable feedstocks such as vegetable oils, animal fats, and bacterial lipids. For example, many lipid sources contain unsaturated fatty acids, which can be oxidized to form a variety of products such as diacids and epoxides. These chemicals are used to formulate herbicides, detergents, plasticizers, lubricants, paints, and other useful products. One of the most common unsaturated fatty acids is oleic acid, and it can be oxidized with an ozone/oxygen mixture to produce azelaic acid and pelargonic acid. Since the ozone/oxygen mixture is a gas and oleic acid is a liquid under reaction conditions, mass transfer limitations exist. However, a reduction of the mass-transfer limitations can be achieved if the reactants coexist in a single phase. When supercritical carbon dioxide (SC-CO2) is used as the reaction medium, it is possible for both oleic acid and the ozone/oxygen mixture to both exist in the same phase at the same time. Use of supercritical carbon dioxide also provides the possibility of product fractionation, depending upon the solubility of the products in SC-CO2. The overall goal of this research was to determine if any advantages could be realized by conducting the oleic acid oxidation in a supercritical fluid medium. First, the solubility of azelaic acid and pelargonic acid in supercritical carbon dioxide was determined over a range of temperatures and pressures. Pelargonic acid was found to have a significantly higher solubility than azelaic acid, which indicated the potential for product separation with supercritical carbon dioxide. Second, the impact of the solvent medium on reaction kinetics and product formation was determined using two oxidizers: ozone and potassium permanganate. Due to experimental limitations, no reaction was observed in the case of ozone in supercritical carbon dioxide. However, oxidation of oleic acid with potassium permanganate in supercritical carbon dioxide resulted in higher oleic acid conversion and increased yields of azelaic acid and pelargonic acid compared to the oxidation without SC-CO2.

No description available.

The rise in anthropogenic carbon dioxide in the atmosphere has caused the pursuit of adequate methods to alleviate the resulting strain on the world's ecosystem. A promising strategy is the geological sequestration of carbon dioxide, in which carbon dioxide emitted from large point sources is injected underground for storage. Under storage, carbon dioxide trapped as a carbonate mineral may be stable for geological time periods. Experiments were conducted to test the potential of ferric-bearing minerals to sequester carbon as a ferrous carbonate mineral (siderite). The formation of siderite requires the reduction of ferric ions which may be achieved by the co-injection of H2S or SO2 contaminants with CO2. Both ferrihydrite and hematite nanoparticles were exposed to an aqueous Na2S solution in the presence of supercritical CO2 (scCO2) and were analyzed in situ by attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR). In situ ATR-FTIR indicated that the formation of siderite occurred on the order of minutes for ferrihydrite and hematite nanoparticles. Particles were analyzed post-reaction with X-ray diffraction (XRD) and electron microscopy. XRD results indicated that ferrihydrite reacted completely to form siderite and elemental sulfur after 24 h at 100 °C, while hematite only partially reacted to form siderite and pyrite after 24 h at 70 °C. Additionally, hematite nanoparticles were exposed to H2S and scCO2 in a series of batch reactions, and the reaction products were determined by XRD as a function of CO2 and H2S partial pressures, alkalinity, salinity, time, and temperature. / Chemistry

The use of supercritical carbon dioxide (scCO₂) as a processing aid to help exfoliate nano-clays and improve their dispersion during melt blending in polymer matrices has been reported in the literature. One of the best processes in terms of improving the degree of nano-clay dispersion and composite mechanical properties was developed in our laboratory. This process allows the clay to be in direct contact with scCO₂ and expanding the clay-CO₂ mixture via rapid depressurization into a two-stage screw extruder to mix with the polymer pellets. However, composites with clay loading higher than 6.6 wt % were not reported. In addition, the scCO₂ aided processing method has not been applied to carbon nanotube (CNT) based composites. This dissertation initially focused on applying the scCO₂ aided processing technique to the field of CNT expansion and CNT/polymer composite preparation. The relationship with the expanded CNT morphology and the experimental conditions of the expansion procedure (including pressures, temperatures, exposure time, and depressurization rates) was studied. Microscopy results showed improved CNT dispersion in the polymer matrix and more uniform networks formed with the use of scCO₂, which indicated that CO₂ expanded CNTs are easier to disperse into the polymer matrix during the blending procedure. The CNT/ poly(phenylsulfone) (PPSF) composites prepared with scCO₂ aided method provided continuous improvements in Young's modulus up to the addition of 7 wt % CNTs. However, the Young's modulus of the composite prepared by means of conventional direct melt blending failed to increase beyond the addition of 1 wt % CNT. The second part of this work is concerned with the development of a semi-continuous process using scCO₂ to process polymer-clay composites with clay loading higher than 6.6 wt % (i.e. 10 wt %). Two major modifications are involved in the new procedure: exfoliating the nano-clay directly into the hopper filled with pellets followed by processing the composite immediately and sequentially mixing the clay into the melt. Transmission electron microscopy (TEM) and wide angle X-ray diffraction (WAXD) results show that this modified procedure help to reduce the clay collapse when processing the composites with high clay loadings. Surface modified montmorillonite (MMT) nano-clay/polypropylene (PP) composite at 10 wt % nano-clay with improved clay dispersion was obtained with increased modulus and tensile strength of 63 % and 16%, respectively, compared to the pure PP matrix. Additional mechanical property improvements for nano-clay based composites are then obtained with the use of high crystallinity polypropylene (HCPP) and polypropylene grafted with maleic anhydride (PP-g-MA). HCPP has higher crystallinity and stiffness than conventional PP and, therefore, composites made from HCPP have better mechanical properties to start with. PP-g-MA has polar groups grafted on the PP chains that promote the intercalation of PP with clay. By using the newly developed procedure, the HCPP nanocomposite at 10 wt % of nano-clay has a Young's modulus as high as 3.236 GPa, and the modulus of the 10% MMT/PP-g-MA sample is found to be 2.595 GPa, both higher than that of the composite prepared by the direct blending method and that of a composite based on a conventional PP matrix. / Ph. D.

The high flow rate that results as fluid decompresses through the restrictor is arguably the single greatest problem with supercritical fluid extraction techniques. As a result of these high flow rates, solvent trapping is not efficient in many cases, and the more complicated sorbent trapping technique must be used. In addition, loss of the collection solvent may occur during the process making it difficult to work with small volumes, which are desirable from the standpoint of sensitivity, cost, and environmental concerns. Similarly, these high decompressed flows have made it difficult to directly interface supercritical fluid extraction methods with separation techniques. This is unfortunate as supercritical extractions are ideal for on-line coupling in other respects, such as the fact that the fluid becomes gaseous upon depressurization and that supercritical fluids generally extract less contaminant material. In this thesis we have shown that, by elevating the post-restrictor pressure, the decompressed flow rate can be reduced, and these problems can be minimized, considerably. Off-line trapping becomes much simpler when working at elevated pressures as the need for sorbent trapping is virtually eliminated and solvent trapping may be conducted with much less difficulty. Elevated post-restrictor pressures were found to be very beneficial for on-line work as well. SFE/GC was carried out with complete transfer of the extraction effluent to a capillary GC column, which has not previously been demonstrated. Likewise the use of an open-tubular column interface, maintained at moderately elevated pressures, allowed SFE/HPLC to be conducted with quantitative analyte transfer, even in the presence of 10% modifier. In all cases - but especially for the on-line methods - more practical extraction parameters were possible, including extraction vessel volume, extraction flow rate, and dynamic extraction time. Another benefit of elevating the post-restrictor pressure is that higher extraction flow rates will generally be possible. The benefits of this were not evaluated in the research presented here, however, the effect that the extraction flow rate can have on extraction time is considered, from a theoretical standpoint, in Chapter five. / Ph. D.

Flow 1H dynamic nuclear polarization (DNP) experiments of small probe molecules (i.e. chloroform and benzene) were conducted in normal liquids (i.e. neat benzene, deuterated benzene, chloroform) and supercritical fluid CO₂. Initial data collected on the 14N NMR line width of acetonitrile in normal liquids and SF CO₂ resulted in a 2-6 factor increase in the molecular motion of the molecule in the SF--the result of which corresponds to the expected factor increase in DNP signal enhancements in the low viscosity fluid. Observed DNP signal enhancements were 2-5 times greater in the supercritical fluid versus the normal liquids in both the solid-liquid intermolecular transfer (SLIT) and liquid-liquid intermolecular transfer (LLIT) experiments. Significant changes in the electron spin-spin (T1S) and spin-lattice (T2S) relaxation times of the nitroxide radical TEMPO in neat benzene, deuterated benzene, and SF CO₂ were noted; the T1ST2S product (calculated from DNP saturation plots) of the LLIT DNP data were compared. Due to the high pressures and elevated temperatures necessary for optimum flow DNP with SF CO₂ (e.g. P = 2310 psi, T = 313 K), high pressure flow cells were developed (and, also, adapted to a commercially available probe in the NMR regime) using PEEK (polyetheretherketone) material. / Ph. D.

Alkylphenol ethoxylates (APEOs), alcohol ethoxylates (AEOs), and alcohol propoxylates (APOs) are non-ionic surfactants used in daily care products and detergents. They are formed as an oligomeric series with a varying distribution, which determines their commercial application. The goal of the research performed was the development of sample characterization methods for non-ionic surfactants utilizing supercritical fluid chromatography (SFC) under mild instrument operating conditions. The aryl group present in APEOs allowed ultraviolet (UV) detection, with an equal molar response for oligomers, allowing average molar oligomer values to be calculated. APEOs were separated by ethoxylate unit via SFC-UV as well as normal phase HPLC-UV employing packed columns. Stationary phase and column length were varied in the SFC setup to produce the most favorable separation conditions. Fractions from SFC runs of APEOs were collected and analyzed by flow injection analysis electrospray ionization mass spectrometry (FIA-ESI-MS) to identify fraction composition. SFC provided shorter retention times with similar resolution as HPLC for separation of APEOs and consumed a smaller amount of organic solvent. AEOs and APOs lack functionality capable of absorbing UV light outside the UV cut-off of normal organic solvents. SFC was able to separate AEOs and APOs derivatized as trimethylsilyl ethers (TMS) with pure CO2 with detection at 195 nm. The instrumental conditions, however, needed for separation necessitated high temperature and high CO2 pressure. Derivatization of alcohol polyether samples with an UV absorbing agent was achieved with phenylated disilazane-chlorosilane mixtures forming phenylsilylethers detected at 215 nm. Use of an organic solvent-modified CO2 mobile phase afforded lower pressure and temperature conditions for oligomer separation. The use of polar embedded alkyl phases combined with use of organic modified CO2 produced good resolution between oligomers. Better peak shape and shorter retention times were realized with methanol-modified CO2 than acetonitrile-modified CO2. Peak assignments were made via SFC coupled with ESI-MS detection in the positive ion mode. SFC-UV and SFC-ESI-MS data were jointly used for calculation of average molar oligomer values. Proton nuclear magnetic resonance (1H-NMR) analysis of non-derivatized samples was performed to determine average molar oligomer values and was used for comparison with values calculated from SFC-UV data. / Ph. D.

Supercritical fluids (SF)s have several physicochemical properties that can often make them superior to conventional liquid solvents. These characteristics include relatively high densities, low viscosities, zero surface tension and high diffusivities. This unique combination of properties allows them to have solvating strengths that can approach those of pure liquids while maintaining many of the advantageous transport qualities of gases. In the past decade SFs have seen increased use as solvents for both extraction (SFE) and chromatography (SFC). A particularly exciting area of applications has been in the field of polymeric materials. Since polymers are not discrete molecules, but, rather broad distributions of very similar compounds (oligomers), they can pose interesting challenges for the separation chemist. SFs are uniquely suited to meet these challenges. The goal of the work done in this laboratory over the past few years has been to use SFs to extract and characterize both oligomers and additives from polymeric materials. A method for the post-polymerization fractionation of a low molecular weight, high density polyethylene wax using analytical scale SFE equipment was developed. Supercritical CO₂ was used to separate very narrow molecular weight distributions (MWD)s from the polyethylene feedstock. The resulting MWDs were characterized by SFC and high temperature gel permeation chromatography (GPC) and found to have polydispersities and molecular weights much lower than the parent wax. Supercritical propane was used to fractionate higher MWDs from the feedstock, however its greater solvating strength for the polyethylene oligomers resulted in larger polydispersities. A dual pump SFE system was used to deliver a dynamic mixture of propane in CO₂. The resulting fractions were very similar to those achieved by pure CO₂, but the recoveries were much higher. Increasing the temperature appeared to have both a kinetic and thermodynamic contribution to oligomer extraction. Supercritical CO₂ was also used to extract additives from an insoluble polymeric nitrocellulose (NC). The primary stabilizer additive (diphenylamine) and its nitrated derivatives were extracted from the propellant. The SF extracted stabilizer profile was characterized using liquid chromatography (LC), gas chromatography (GC) and SFC. SFC was shown to provide separations of propellant additives that were superior to the existing LC method while maintaining lower temperatures than GC. Extracts from propellants stored at elevated surveillance temperatures contained more highly nitrated stabilizer derivatives. However, some question was raised as to the actual validity of elevated temperature programs for propellant screening due to potential differences in reaction mechanisms. A LC-thermospray mass spectrometry (MS) interface was modified for use wtih packed column SFC. The system was used as a chemical ionization (CI) source for the high CO₂ flow rates emanating from packed columns. Methane was used as a reagent gas (RG) for positive chemical ionization (PCI). The resulting CO₂ + CH₄ mixed RG was studied at CO₂ pump pressures typical of SFC pressure programming. The background ions varied widely with CO₂ partial pressure and source temperature, however, spectra of a propellant test mixture were relatively unaffected by changing RG. The system was also used to perform negative CI (NCI) using the mobile phase CO₂ as a RG. This method was found to be very useful for nitrated derivatives of diphenylamine. SFC-CH₄-PCI-MS confirmed the intact elution of thermally labile N-nitroso compounds thought to exist in propellants. SFC-CI-MS, both NCI and PCI, was used to characterize the SF extracts of polymeric nitrocellulose and was demonstrated to have potential for the analysis of a wide range of compounds found in the propellant industry. SFC-CH₄-PCI was also determined to be compatible with methanol modified mobile phases. The mobile phases in this case were delivered from premixed cylinders. However, severe limitations regarding the reliability of premixed mobile phases in SFC were shown to exist. / Ph. D.