100 Matching Results

Search Results

Advanced search parameters have been applied.

Task 2 -- Extraction and analysis of pollutant organics from contaminated solids using off-line supercritical fluid extraction (SFE) and on-line SFE-infrared spectroscopy. Semi-annual report, April 1--September 30, 1997

Description: The work for this task was canceled as of February 1997. At that time, Suprex Corporation, the commercial partner, was purchased by a competitor (ISCO of Lincoln, Nebraska). ISCO had no plans to continue the development of the interface which the EERC and Suprex were developing since ISCO had recently developed a similar product based on a window (rather than a fiber optic) interface. The EERC is currently waiting for approval from the US Department of Energy to close out this task.
Date: December 31, 1997
Creator: Hawthorne, S.B.
Partner: UNT Libraries Government Documents Department

Supercritical fluids: Reactions, materials and applications

Description: A number of important processes utilizing supercritical fluids have been either implemented or are emerging for extractions, separations and a wide range of cleaning applications. Supercritical fluids can be reasonable solvents yet share many of the advantages of gases including miscibility with other gases (i.e. hydrogen and oxygen), low viscosities and high diffusivities. Carbon dioxide has the further advantages of being nontoxic, nonflammable, inexpensive and currently unregulated. The use of compressed gases, either as liquids or supercritical fluids, as reaction media offers the opportunity to replace conventional hazardous solvents and also to optimize and potentially control the effect of solvent on chemical and material processing. The last several years has seen a significant growth in advances in chemical synthesis, catalytic transformations and materials synthesis and processing. The authors report on results from an exploratory program at Los Alamos National Laboratory aimed at investigating the use of dense phase fluids, particularly carbon dioxide, as reaction media for homogeneous, heterogeneous and phase-separable catalytic reactions in an effort to develop new, environmentally-friendly methods for chemical synthesis and processing. This approach offers the possibility of opening up substantially different chemical pathways, increasing selectivity at higher reaction rates, facilitating downstream separations and mitigating the need for hazardous solvents. Developing and understanding chemical and catalytic transformations in carbon dioxide could lead to greener chemistry at three levels: (1) Solvent replacement; (2) Better chemistry (e.g. higher reactivity, selectivity, less energy consumption); and (3) New chemistry (e.g. novel separations, use of COP{sub 2} as a C-1 source).
Date: April 9, 1999
Creator: Tumas, W.; Jacobson, G.B.; Josephsohn, N.S. & Brown, G.H.
Partner: UNT Libraries Government Documents Department

A rapid supercritical extraction process for the production of silica aerogels

Description: Silica aerogels are a special class of porous materials in which both the pore size and interconnected particle size have nanometer dimensions. This structure imparts unique optical, thermal, acoustic, and electrical properties to these materials. Transmission electron microscopy and small angle x-ray scattering show that this nanostructure is sensitive to variations in processing conditions that influence crosslinking chemistry and growth processes prior to gelation. Recently, Lawrence Livermore National Laboratory (LLNL) has demonstrated that a Rapid Supercritical Extraction (RSCE) process can be used to prepare near-net shape silica aerogels in hours rather than days. Preliminary data from RSCE silica aerogels show that they have improved mechanical properties and slightly lower surface areas than their conventionally dried counterparts, while not compromising their optical and thermal performance.
Date: April 1, 1996
Creator: Poco, J.F.; Coronado, P.R.; Pekala, R.W. & Hrubesh, L.W.
Partner: UNT Libraries Government Documents Department

Supercritical Fluid Reactions for Coal Processing

Description: Exciting opportunities exist for the application of supercritical fluid (SCF) reactions for the pre-treatment of coal. Utilizing reactants which resemble the organic nitrogen containing components of coal, we developed a method to tailor chemical reactions in supercritical fluid solvents for the specific application of coal denitrogenation. The tautomeric equilibrium of a Schiff base was chosen as one model system and was investigated in supercritical ethane and cosolvent modified supercritical ethane. The Diels-Alder reaction of anthracene and 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD) was selected as a second model system, and it was investigated in supercritical carbon dioxide.
Date: November 1, 1997
Creator: Eckert, Charles A.
Partner: UNT Libraries Government Documents Department

Supercritical Fluid Reactions for Coal Processing

Description: Exciting opportunities exist for the application of supercritical fluid (SCF) reactions for the pre-treatment of coal. Utilizing reactants which resemble the organic nitrogen containing components of coal, we propose to develop a method to tailor chemical reactions in supercritical fluid solvents for the specific application of coal denitrogenation. The Diels´┐ŻAlder reaction of anthracene and 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD) was chosen as the model system and was investigated in supercritical carbon dioxide. Kinetic data have been previously collected for pure CO2 at 40C and pressures between the critical pressure of CO2 (73.8 bar) and 216 bar. These data support the theory of local density enhancements suggested in the literature. Data taken at 50C and pressures ranging from 70 bar to 195 bar are currently reported; they do not exhibit the molecular clustering evident closer to the critical temperature. The data taken at 40C are now being used to construct mathematical forms which can model these pressure-induced kinetic changes. One promising avenue of investigation involves treating the supercritical medium as a dense gas, which allows a kinetic model based on high reference pressure fugacity coefficients to be derived.
Date: July 1997
Creator: Eckert, Charles A.
Partner: UNT Libraries Government Documents Department

Technical design issues for a field-portable supercritical fluid extractor

Description: Supercritical fluid extraction is gaining acceptance as an alternative sample preparation method for trace organic analysis. The development of SFE instrumentation optimized for field use requires taking several technical design issues including size and weight requirements, user-friendly operation, and technical performance capabilities into consideration. Parameters associated with a prototype SFE instrument under development for potential use in conducting on-site inspections of the Chemical Weapons Convention and its preliminary technical and operational performance are described.
Date: January 1, 1995
Creator: Wright, B. W.; Zemanian, T. S.; Robins, W. H. & Wright, C. W.
Partner: UNT Libraries Government Documents Department

Data Quality Objectives for Moisture Measurement in Stabilized Special Nuclear Material

Description: Data Quality Objectives methodology is applied to Loss-on-Ignition (LOI) moisture content testing for stabilized nuclear materials. This work was performed by Pacific Northwest National Laboratory in support of the Plutonium Finishing Plant (PFP) / Fluor Hanford, Inc. Historical results on LOI test results for two material types, oxide and sludge, are used to estimate within container variability. This variability estimate is then used in formulating the two recommended acceptance criteria for containers of material. The criteria which follow are proposed to replace the current criterion, which requires recycle if either of two container LOI measurements exceed 0.5 wt%, the DOE Standard 3013-99 threshold value. 1. The 95% upper confidence limit (UCL) for the true mean underlying moisture content in the container material should be less than 0.5 wt%. 2. The difference between the two LOI measurements per container should not exceed their expected 95th percentile relative to the estimated variability. Containers not meeting the first criterion, or those that generate in any negative LOI result, require material recycle. Containers not meeting the second criteria require review of the measurement results, potentially leading to resampling and retesting. Data from Los Alamos National Laboratory studies on moisture testing are obtained and analyzed. The performance of Supercritical Fluid Extraction (SFE), which will soon be implemented at the PFP, is described for several material types. This information will be used to establish initial acceptance criteria when SFE comes on line.
Date: June 1, 2000
Creator: Weier, Dennis R.; Pulsipher, Brent A. & Silvers, Kurt L.
Partner: UNT Libraries Government Documents Department

Supercritical fluid reactions for coal processing. Quarterly progress report, October 1, 1996--December 31, 1996

Description: Exciting opportunities exist for the application of supercritical fluid (SCF) reactions for the pre-treatment of coal. Utilizing reactants which resemble the organic nitrogen containing components of coal, we propose to develop a method to tailor chemical reactions in supercritical fluid solvents for the specific application of coal denitrogenation. The Diels - Alder reaction of anthracene and 4-phenyl-1,2,4-triazoline-3,5-dione (PTAD) was chosen as the model system and was investigated in supercritical carbon dioxide. During this quarter, measurement of the density dependence of the kinetic rate constant for PTAD and anthracene in supercritical solvents was continued. Having completed studies of rates versus density in pure CO{sub 2} at 40C, attention was focused on CO{sub 2}/Cosolvent mixtures. Experiments were performed using binary mixtures of CO{sub 2} and either chloroform or acetone as cosolvent. Cosolvent concentrations were varied between 0.00826 mol/L and 0.0826 mol/L. The cosolvents produced no significant change in the rate constant over that of pure CO{sub 2} at these concentrations.
Date: September 1, 1994
Creator: Eckert, C.A.
Partner: UNT Libraries Government Documents Department

Task 4.4 - development of supercritical fluid extraction methods for the quantitation of sulfur forms in coal

Description: Development of advanced fuel forms depends on having reliable quantitative methods for their analysis. Determination of the true chemical forms of sulfur in coal is necessary to develop more effective methods to reduce sulfur content. Past work at the Energy & Environmental Research Center (EERC) indicates that sulfur chemistry has broad implications in combustion, gasification, pyrolysis, liquefaction, and coal-cleaning processes. Current analytical methods are inadequate for accurately measuring sulfur forms in coal. This task was concerned with developing methods to quantitate and identify major sulfur forms in coal based on direct measurement (as opposed to present techniques based on indirect measurement and difference values). The focus was on the forms that were least understood and for which the analytical methods have been the poorest, i.e., organic and elemental sulfur. Improved measurement techniques for sulfatic and pyritic sulfur also need to be developed. A secondary goal was to understand the interconversion of sulfur forms in coal during thermal processing. EERC has developed the first reliable analytical method for extracting and quantitating elemental sulfur from coal (1). This method has demonstrated that elemental sulfur can account for very little or as much as one-third of the so-called organic sulfur fraction. This method has disproved the generally accepted idea that elemental sulfur is associated with the organic fraction. A paper reporting the results obtained on this subject entitled {open_quote}Determination of Elemental Sulfur in Coal by Supercritical Fluid Extraction and Gas Chromatography with Atomic Emission Detection{close_quote} was published in Fuel (A).
Date: April 1, 1995
Creator: Timpe, R.C.
Partner: UNT Libraries Government Documents Department

SEPARATION OF FISCHER-TROPSCH WAX FROM CATALYST BY SUPERCRITICAL EXTRACTION

Description: The objective of this research project was to evaluate the potential of supercritical fluid (SCF) extraction for the recovery and fractionation of the wax product from the slurry bubble column (SBC) reactor of the Fischer-Tropsch (F-T) process. The wax, comprised mostly of branched and linear alkanes with a broad molecular weight distribution up to C{sub 100}, is to be extracted with a hydrocarbon solvent that has a critical temperature near the operating temperature of the SBC reactor, i.e., 200-300 C. Aspen Plus{trademark} was used to perform process simulation studies on the proposed extraction process, with Redlich-Kwong-Soave (RKS) being used for the thermodynamic property model. In summary, we have made comprehensive VLE measurements for short alkane + long alkane systems over a wide range of pressures and temperatures, dramatically increasing the amount of high-quality data available for these simple, yet highly relevant systems. In addition, our work has demonstrated that, surprisingly, no current thermodynamic model can adequately predict VLE behavior for these systems. Thus, process simulations (such as those for our proposed SCF extraction process) that incorporate these systems can currently only give results that are qualitative at best. Although significant progress has been made in the past decade, more experimental and theoretical work remain to be done before the phase equilibria of asymmetric alkane mixtures can be predicted with confidence.
Date: March 31, 1999
Creator: Joyce, Patrick C. & Thies, Mark C.
Partner: UNT Libraries Government Documents Department

FUNDAMENTAL KINETICS OF SUPERCRITICAL COAL LIQUEFACTION: EFFECT OF CATALYSTS AND HYDROGEN-DONOR SOLVENTS

Description: This report outlines a distribution kinetics approach to macromolecular reactions that has been applied to several processes. The objective was to develop an understanding of high-temperature, dense-phase thermolytic processes for complex macromolecular systems, such as coal. Experiments and theory are described for chemical models that simulate depolymerization of coal. The approach has been exceptionally successful for the model macromolecular systems. Development of a novel chemical reaction engineering analysis, based on distribution kinetics, was a major accomplishment of the current research.
Date: August 1, 1998
Creator: McCoy, Benjamin J. & Smith, J.M.
Partner: UNT Libraries Government Documents Department

Task 5.4 -- Stable and supercritical chars. Semi-annual report, January 1--June 30, 1995

Description: The use of chars and carbons as absorbents and catalyst supports could be expanded if their stability to reactive gases were improved. The purpose of this task is to develop methods for applying surface coatings of boron carbide, silicon carbide, and titanium carbide on the char. Formation of these composites will increase stability and improve structural strength and, consequently, resistance to abrasion. The first objective of this task is to develop methods for coating low-rank coal (LRC) chars and carbons by chemical vapor deposition (CVD) to produce high surface area composites that are inert to reactive atmospheres. The proposed coating layers will be formed from elements known to form extremely hard and stable carbide materials. The second objective is to determine the feasibility of using supercritical extraction to prepare an activated carbon with a very high surface area. During this report period supercritical solvent extraction was investigated as a means of producing very large microporous structures in chars. Wyodak subbituminous coal, Gascoyne lignite, and Velva lignite were used for the supercritical extractions.
Date: December 31, 1995
Creator: Olson, E.S. & Sharma, R.K.
Partner: UNT Libraries Government Documents Department

Transparent monolithic metal ion containing nanophase aerogels

Description: The formation of monolithic and transparent transition metal containing aerogels has been achieved through cooperative interactions of high molecular weight functionalized carbohydrates and silica precursors, which strongly influence the kinetics of gelation. After initial gelation, subsequent modification of the ligating character of the system, coordination of the group VIII metal ions, and supercritical extraction afford the aerogels. The structures at the nanophase level have been probed by photon and electron transmission and neutron scattering techniques to help elucidate the basis for structural integrity together with the small entity sizes that permit transparency in the visible range. They also help with understanding the chemical reactivities of the metal-containing sites in these very high surface area materials. These results are discussed in connection with new reaction studies.
Date: December 1, 1999
Creator: Risen, W. M., Jr.; Hu, X.; Ji, S. & Littrell, K.
Partner: UNT Libraries Government Documents Department

Hanford/Rocky Flats collaboration on development of supercritical carbon dioxide extraction to treat mixed waste

Description: Proposals for demonstration work under the Department of Energy`s Mixed Waste Focus Area, during the 1996 through 1997 fiscal years included two applications of supercritical carbon dioxide to mixed waste pretreatment. These proposals included task RF15MW58 of Rocky Flats and task RL46MW59 of Hanford. Analysis of compatibilities in wastes and work scopes yielded an expectation of substantial collaboration between sites whereby Hanford waste streams may undergo demonstration testing at Rocky Flats, thereby eliminating the need for test facilities at Hanford. This form of collaboration is premised the continued deployment at Rocky Flats and the capability for Hanford samples to be treated at Rocky Flats. The recent creation of a thermal treatment contract for a facility near Hanford may alleviate the need to conduct organic extraction upon Rocky Flats wastes by providing a cost effective thermal treatment alternative, however, some waste streams at Hanford will continue to require organic extraction. Final site waste stream treatment locations are not within the scope of this document.
Date: November 1, 1995
Creator: Hendrickson, D.W.; Biyani, R.K.; Brown, C.M. & Teter, W.L.
Partner: UNT Libraries Government Documents Department

Oil, grease, and solvent removal from solid waste using supercritical carbon dioxide

Description: Supercritical carbon dioxide extraction is being explored as a waste minimization technique for separating oils, greases, and solvents from solid waste. The contaminants are dissolved into the supercritical fluid and precipitated out upon depressurization. The carbon dioxide solvent can then be recycled for continued use. Definitions of the temperature, pressure, flowrate, and potential co-solvents are required to establish the optimum conditions for hazardous contaminant removal. Excellent extractive capability for common manufacturing oils, greases, and solvents has been observed in both supercritical and liquid carbon dioxide.
Date: August 1, 1995
Creator: Smith, H.M.; Olson, R.B.; Adkins, C.L.J. & Russick, E.M.
Partner: UNT Libraries Government Documents Department

Solvent reorganization energies measured by an electron transfer reaction in supercritical ethane.

Description: The intermolecular electron transfer reaction between a biphenyl anion and pyrene in supercritical ethane was studied using pulse radiolysis. Second-order electron transfer rates were found to be of the order of 10{sup 11} M{sup {minus}1} s{sup {minus}1}. The rate constants appear to be approximately constant over the pressure range 55-133 bar. Two possibilities are discussed that could explain the present results: solvent clustering; or a dependence of the solvent reorganization energy on pressure. Reorganization energies E{sub r} of non-polar supercritical ethane were estimated from the observed rate constant using the modified Marcus equation. E{sub r} may be larger than normally expected for non-polar solvents because of density fluctuations.
Date: April 14, 1997
Creator: Feng, W.; Jonah, C. D.; Sawamura, S. & Takahashi, K.
Partner: UNT Libraries Government Documents Department

Development and design of a high pressure carbon dioxide system for the separation of hazardous contaminants from non-hazardous debris

Description: Under the Department of Energy (DOE)/United States Air Force (USAF) Memorandum of Understanding, a system is being designed that will use high pressure carbon dioxide for the separation of oils, greases, and solvents from non-hazardous solid waste. The contaminants are dissolved into the high pressure carbon dioxide and precipitated out upon depressurization. The carbon dioxide solvent can then be recycled for continued use. Excellent extraction capability for common manufacturing oils, greases, and solvents has been measured. It has been observed that extraction performance follows the dilution model if a constant flow system is used. The solvents tested are extremely soluble and have been extracted to 100% under both liquid and mild supercritical carbon dioxide conditions. These data are being used to design a 200 liter extraction system.
Date: July 1, 1995
Creator: Adkins, C. L. J.; Russick, E. M.; Smith, H. M. & Olson, R. B.
Partner: UNT Libraries Government Documents Department

Structural evolution in carbon aerogels as a function of precursor material and pyrolysis temperature

Description: Several organic reactions that proceed through a sol-gel transition have been identified at LLNL. The most-studied reaction involves the aqueous polycondensation of resorcinol (1,3-dihydroxybenzene) with formaldehyde. Recently, we have shown that phenol can be added to this polymerization as a comonomer. The resultant crosslinked gels are supercritically dried from carbon dioxide ({Tc}=31{degrees}C, P{sub c}=7.4 MPa) to give resorcinol-phenol-formaldehyde (RPF) aerogels. Because RPF aerogels are composed of a highly crosslinked aromatic polymer, they can be pyrolyzed in an inert atmosphere to form vitreous carbon monoliths. The resultant aerogels are black in color and no longer transparent, yet they retain the high porosity (40--98 %), ultrafine cell/pore size (< 50 nm), high surface area (600--800 m{sup 2}/g), and interconnected particle ({approximately}10 nm) morphology of their organic precursors. In this study, we examine the acoustic and mechanical properties of these materials as a function of precursor material and pyrolysis temperature.
Date: April 1, 1996
Creator: Gross, J.; Alviso, C.T.; Neilsen, J.K. & Pekala, R.W.
Partner: UNT Libraries Government Documents Department

Separation of Fischer-Tropsch wax from catalyst by supercritical extraction. Quarterly progress report, October 1, 1996--December 31, 1996

Description: One of the major objectives of this research project is to predict the phase behavior of model wax compounds in dense supercritical fluids such as hexane. Because initial results with the SAFT equation have been less promising than expected, the group at North Carolina State University has focused their recent attention on cubic equations of state, in particular the Peng-Robinson and Soave-Redlich-Kwong versions. The focus of this work has been on developing correlations that can be used to predict binary interaction parameters (i.e., k{sub ij}s) for a given binary wax-solvent system. As a first step, k{sub ij}s were first calculated from experimental data on systems containing alkanes between nC{sub 4} and nC{sub 23} at temperatures between 25 and 357{degrees} C. Attempts were then made to correlate these parameters with specific pure component properties of the alkanes of interest. Reasonably good agreement between experimental and predicted k{sub ij}s was found using a correlation that incorporates both temperature and the molecular size of the alkanes. As phase equilibrium data becomes available for higher molecular weight model wax compounds, the ability of the correlation to handle such systems will need to be tested. The phase equilibrium apparatus is currently undergoing modifications that will allow the system to run components that are solids at ambient temperatures. Some problems are still being resolved, as the heavy component tends to precipitate in the sample lines. Modifications have been made that should allow the system to operate reliably.
Date: January 1, 1997
Creator: Joyce, P.C. & Thies, M.C.
Partner: UNT Libraries Government Documents Department

A comparison of chilled DI water/ozone and CO{sub 2}-based supercritical fluids as replacements for photoresist-stripping solvents

Description: Part of the Hewlett Packard Components Group`s Product Stewardship program is the ongoing effort to investigate ways to eliminate or reduce as much as possible the use of chemical substances from manufacturing processes. Currently used techniques to remove hard-baked photoresists from semiconductor wafers require the use of inorganic chemicals or organic strippers and associated organic solvents. Environmental, health and safety, as well as cost considerations prompted the search for alternative, more environmentally-benign, and cost-effective solutions. Two promising, emerging technologies were selected for evaluation: the chilled DI water/ozone technique and supercritical fluids based on carbon dioxide (CO{sub 2}). Evaluating chilled DI water/ozone shows this process to be effective for positive photoresist removal, but may not be compatible with all metallization systems. Testing of a closed-loop CO{sub 2}-based supercritical CO{sub 2} Resist Remover, or SCORR, at Los Alamos, on behalf of Hewlett-packard, shows that this treatment process is effective in removing photoresists, and is fully compatible with commonly used metallization systems. In this paper, the authors present details on the testing programs conducted with both the chilled DI H{sub 2}O/ozone and SCORR treatment processes.
Date: October 1998
Creator: Rubin, J. B.; Davenhall, L. B.; Barton, J.; Taylor, C. M. V. & Tiefert, K.
Partner: UNT Libraries Government Documents Department

Transport of metal sulfides in supercritical carbon dioxide

Description: This report presents the results of studies of supercritical fluid extraction of selected organics and of transition metal sulfides using carbon dioxide with and without modifiers. For the metal sulfides, the modifiers water, aqueous EDTA, methanol, and methanolic 2,4-pentanedione (acetyl acetone) were added in amounts ranging from 1 to 10 wt% depending on the specific modifier used. Extraction efficiency was studied as a function of fluid composition and extraction temperature and pressure. The objective of the work was to investigate the scientific feasibility of using this type of extraction process for metallurgical or environmental applications. Theoretical modeling studies were performed in an attempt to develop predictive capabilities for both solubility calculations and extraction simulation. The experimental studies have established the scientific feasibility of extraction and transport of selected cations by these fluids. Depending on the metal and conditions, transport of up to 12% of the starting material has been observed; however, the observed extraction efficiencies for inorganics do not approach those typical for organics under similar conditions.
Date: May 1, 1996
Creator: Propp, W. A.; Carleson, T. E.; Wai, C. M. & Huang, S.
Partner: UNT Libraries Government Documents Department

SAXS and SANS studies of surfactants and reverse micelles in supercritical CO{sub 2}

Description: Surfactants promise to extend the applicability of supercritical CO{sub 2} (SC-CO{sub 2}) to processing of insoluble materials such as polymers and aqueous systems. In this short paper the authors summarize the techniques for studying surfactants and reverse micelles in SC-CO{sub 2} using SAXS and SANS; they will describe the scattering instruments and the pressure cells for conducting these studies; they will describe the types of measurement that yield the desired characterizations; they will describe the methods of data analysis and interpretation; and they will provide illustrative results from this laboratory. Industry seeks to replace common organic solvents now used in many reaction and separation processes; SC-CO{sub 2} is a potential solvent substitute widely favored by both government and industry. The currently available surfactants are limited in number and performance. In ongoing work the authors are coupling their SAXS and SANS scattering studies with complementary molecular simulations in efforts to understand, at a molecular level, what surfactant characteristics lead to improved performance. They hope that superior surfactants for use in SC-CO{sub 2} can be designed and synthesized based on this new level of understanding.
Date: March 1, 1997
Creator: Londono, J.D.; Dharmapurikar, R.S.; Wignall, G.D. & Cochran, H.D.
Partner: UNT Libraries Government Documents Department