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In situ measurement of volatile organic compounds in groundwater by methods coupled to the cone penetrometer

Description: The objective of this investigation is to interface an in situ, on-line sparging system with a cone penetrometer to provide direct analysis of volatile organic compounds (VOCS) in groundwater by on-site analysis. Transfer line materials (15 m {times} 0.160--0.216 cm ID) composed of stainless steel, nickel, aluminum and Teflon{reg_sign}PFA, PTFE, and FEP were evaluated for their ability to quantitatively transfer chloroform, 1,1,1-trichloroethane, carbon tetrachloride, tetrachloroethylene, n-hexane, benzene, toluene, and o-xylene in the gas phase. The water content of the gas stream had an insignificant effect on the quantitative transfer of VOCs through Teflon{reg_sign} tubing but was critical to quantitative transfer of the compounds through metal tubing, particularly for nickel. Transfer efficiencies for all 7 analytes in moist gas streams through stainless steel tubing were greater than 95%. Toluene, tetrachloroethylene, and o-xylene were transferred with 93, 81 and 80% efficiency, respectively when drawn through Teflon{reg_sign}PFA tubing at 25 C. The sorption of these VOCs by Teflon{reg_sign} tubing was reversible and their transfer efficiencies improved to 94% when the tubing was flushed with 16 equivalent volumes of air. In general, the retention of the VOCs by Teflon{reg_sign} increased with decreasing aqueous solubility of the analyte. The efficiency at which VOCs were sparged from aqueous standards in Teflon{reg_sign}PFA, Type 304 stainless steel, and glass vessels were similar.
Date: March 1, 1995
Creator: Doskey, P.V.; Aldstadt, J.H.; Kuo, J.M.; Costanza, M.S. & Erickson, M.D.
Partner: UNT Libraries Government Documents Department

A comparison of the costs of treating wastes from a radio analytical laboratory

Description: The Radiological and Environmental Sciences Laboratory (RESL) is a government-owned, government-operated facility at the Idaho National Engineering Laboratory (INEL). RESL`s traditional strengths are in precise radionuclide analysis and dosimetry measurements. RESL generates small quantities of various types of waste. This study identified potential waste management options for a solvent extraction process waste stream and the cost differences resulting from either process changes, improved technology usage, or material substitutions or changes at RESL. Where possible, this report identifies changes that have resulted or may result in waste reduction and cost savings. DOE P2 directs the lab to review processes, evaluate waste practices, and estimate potential reductions in waste volumes and waste management costs. This study focused on selected processes, but the processes are illustrative of potential waste volume reductions and cost minimizations that may be achieved elsewhere at the INEL and throughout the DOE complex. In analyzing a waste disposal process, the authors allocated component costs to functional categories. These categories included the following: (1) operational costs, included waste generation and collection into a storage area; (2) administrative costs, including worker training, routine inspections, and reporting; and (3) disposal costs, including preparing the waste for shipment and disposing of it.
Date: April 1, 1996
Creator: Moore, R. & Pole, S.B.
Partner: UNT Libraries Government Documents Department

Preflame zone structure and main features of fuel conversion in atmospheric pressure premixed laminar hydrocarbon flames

Description: This report describes the structure study of the premixed hydrocarbon-oxidizer Bunsen flames burning at the atmospheric pressure and also the ones with some inhibitors added. Studies were performed on hexane, propane, methane, acetylene, and hexene flames.
Date: August 25, 1995
Creator: Ksandopulo, G.I.
Partner: UNT Libraries Government Documents Department

Autoignition chemistry of the hexane isomers: An experimental and kinetic modeling study

Description: Autoignition of the five distinct isomers of hexane is studied experimentally under motored engine conditions and computationally using a detailed chemical kinetic reaction mechanism. Computed and experimental results are compared and used to help understand the chemical factors leading to engine knock in spark-ignited engines and the molecular structure factors contributing to octane rating for hydrocarbon fuels. The kinetic model reproduces observed variations in critical compression ratio with fuel structure, and it also provides intermediate and final product species concentrations in very dose agreement with observed results. In addition, the computed results provide insights into the kinetic origins of fuel octane sensitive.
Date: June 1, 1995
Creator: Curran, H.J.; Gaffuri, P.; Pitz, W.J.; Westbrook, C.K. & Leppard, W.R.
Partner: UNT Libraries Government Documents Department

Solvent usage and recycling potential in a research and development setting

Description: Argonne National Laboratory utilizes thousands of gallons of chemicals each year. Laboratory wastes can be broadly characterized as coming from three focus areas: (1) restoration and decommissioning associated wastes generate larger quantities of waste on a one-time basis. The wastes may be non-hazardous to highly toxic and the quantities are variable. (2) Laboratory operations generate approximately 50% of all waste disposed. Operational waste can be characterized as less hazardous, reasonably consistent in nature, generally in larger quantities. (3) the final waste stream is small quantities of many different materials coming from many different waste streams. This waste stream is at the center of ANL`s pollution prevention program. The research areas have implemented many pollution prevention techniques. Solvent substitution has been effective in reducing hazardous cleaning wastes, scintillation cocktail wastes, and other chlorinated wastes. Micro chemistry is effective at minimizing certain chemical process wastes, developing new analytical chemistry procedures has reduced and eliminated other waste forms. New instrumentation has provided first level reductions in many waste streams. Despite these new techniques solvent usage remains the largest research related waste stream. The present solvents are generated from instruments such as electrophoresis and high pressure liquid chromatographs (HPLC), solvent extractions, biological staining and cleaning practices. ANL recognizes the significant role recycling this waste stream is in Pollution Prevention Program implementation. ANL initiated a study to quantify solvent usage, characterization of the waste solvent, and match the purity requirements exploring all opportunities to substitute and recycle.
Date: July 1, 1996
Creator: Vivio, F.; Thuot, J.R. & Peters, R.W.
Partner: UNT Libraries Government Documents Department

Refining of fossil resin flotation concentrate from Western coal. Ninth quarterly report, January 1--March 31, 1995

Description: Heptane showed a consistently higher extraction than hexane even through heptane contains only one more methylene group in its molecular structure. However economic factors must also be considered in the overall evaluation of the process. In this regard a simple economic evaluation was carried out taking into consideration the operating costs for the resin concentrate refining process. First of all, the price of industrial grade heptane is about the same as hexane. Because the process operates in a recycle mode, the initial cost would be about the same for both solvents. But in order to obtain the final resin product, the extracted resin has to be recovered from solution using evaporation techniques, which consume energy. Due to the significant difference in boiling points between the two solvents, approximately 25--35% more energy will be required for resin recovery by evaporation if heptane is used as the solvent for extraction. This represents a very significant increase of the operating cost. Secondly, based on bench scale tests the same yield can be achieved with hexane if the average residence time is increased. Such an increase in retention time only increases the capital cost by a small amount. It appears then from an economic perspective that hexane is the most appropriate solvent.
Date: March 31, 1995
Creator: Jensen, G.F. & Miller, J.D.
Partner: UNT Libraries Government Documents Department

Vapor space characterization of waste tank 241-TY-103: Results from samples collected on 4/11/95

Description: This report describes inorganic and organic analyses results from samples obtained from the headspace of the Hanford waste storage Tank 241-TY-103 (referred to as Tank TY-103). The results described here were obtained to support safety and toxicological evaluations. A summary of the results for inorganic and organic analytes is listed in Table 1. Detailed descriptions of the results appear in the text. Quantitative results were obtained for the inorganic compounds ammonia (NH{sub 3}), nitrogen dioxide (NO{sub 2}), nitric oxide (NO), and water (H{sub 2}O). Sampling for hydrogen cyanide (HCN) and sulfur oxides (SO{sub x}) was not requested. In addition, quantitative results were obtained for the 39 TO-14 compounds plus an additional 14 analytes. Of these, 16 were observed above the 5-ppbv reporting cutoff. Sixteen tentatively identified compounds (TICs) were observed above the reporting cutoff of (ca.) 10 ppbv and are reported with concentrations that are semiquantitative estimates based on internal-standard response factors. The 10 organic analytes with the highest estimated concentrations are listed in Table 1 and account for approximately 95% of the total organic components in Tank TY-103. Two permanent gases, carbon dioxide (CO{sub 2}) and nitrous oxide (N{sub 2}O), were also detected.
Date: October 1, 1995
Creator: Ligotke, M.W.; Clauss, T.W. & Pool, K.H.
Partner: UNT Libraries Government Documents Department

HYBRID SULFUR RECOVERY PROCESS FOR NATURAL GAS UPGRADING

Description: This first quarter report of 2002 describes progress on a project funded by the U.S. Department of Energy (DOE) to test a hybrid sulfur recovery process for natural gas upgrading. The process concept represents a low cost option for direct treatment of natural gas streams to remove H{sub 2}S in quantities equivalent to 0.2-25 metric tons (LT) of sulfur per day. This process is projected to have lower capital and operating costs than the competing technologies, amine/aqueous iron liquid redox and amine/Claus/tail gas treating, and have a smaller plant footprint, making it well suited to both on-shore and offshore applications. CrystaSulf{sup SM} (service mark of CrystaTech, Inc.) is a new nonaqueous sulfur recovery process that removes hydrogen sulfide (H{sub 2}S) from gas streams and converts it into elemental sulfur. CrystaSulf features high sulfur recovery similar to aqueous-iron liquid redox sulfur recovery processes, but differs from the aqueous processes in that CrystaSulf controls the location where elemental sulfur particles are formed. In the hybrid process, approximately 1/3 of the total H{sub 2}S in the natural gas is first oxidized to SO{sub 2} at low temperatures over a heterogeneous catalyst. Low temperature oxidation is done so that the H{sub 2}S can be oxidized in the presence of methane and other hydrocarbons without oxidation of the hydrocarbons. The project involves the development of a catalyst using laboratory/bench-scale catalyst testing, and then demonstration of the catalyst at CrystaTech's pilot plant in west Texas. In a previous reporting period tests were done to determine the effect of hydrocarbons such as n-hexane on catalyst performance with and without H{sub 2}S present. The experiments showed that hexane oxidation is suppressed when H{sub 2}S is present. Hexane represents the most reactive of the C1 to C6 series of alkanes. Since hexane exhibits low reactivity under H{sub 2}S oxidation ...
Date: April 1, 2002
Creator: Srinivas, Girish; Gebhard, Steven C. & DeBerry, David W.
Partner: UNT Libraries Government Documents Department

Recovery of semi-volatile organic compounds during sample preparation: Compilation for characterization of airborne particulate matter

Description: Semi-volatile compounds present special analytical challenges not met by conventional methods for analysis of ambient particulate matter (PM). Accurate quantification of PM-associated organic compounds requires validation of the laboratory procedures for recovery over a wide volatility and polarity range. To meet these challenges, solutions of n-alkanes (nC{sub 12} to nC{sub 40}) and polycyclic aromatic hydrocarbons PAHs (naphthalene to benzo[ghi]perylene) were reduced in volume from a solvent mixture (equal volumes of hexane, dichloromethane and methanol), to examine recovery after reduction in volume. When the extract solution volume reached 0.5 mL the solvent was entirely methanol, and the recovery averaged 60% for n-alkanes nC{sub 12} to nC{sub 25} and PAHs from naphthalene to chrysene. Recovery of higher MW compounds decreased with MW, because of their insolubility in methanol. When the walls of the flasks were washed with 1 mL of equal parts hexane and dichloromethane (to reconstruct the original solvent composition), the recovery of nC{sub 18} and higher MW compounds increased dramatically, up to 100% for nC{sub 22}-nC{sub 32} and then slowly decreasing with MW due to insolubility. To examine recovery during extraction of the components of the High Capacity Integrated Gas and Particle Sampler, the same standards were used to spike its denuders and filters. For XAD-4 coated denuders and filters, normalized recovery was > 95% after two extractions. Recovery from spiked quartz filters matched the recovery from the coated surfaces for alkanes nC{sub 18} and larger, and for fluoranthene and larger PAHs. Lower MW compounds evaporated from the quartz filter with the spiking solvent. This careful approach allowed quantification of organics by correcting for volatility- and solubility-related sample preparation losses. This method is illustrated for an ambient sample collected with this sampler during the Texas Air Quality Study 2000.
Date: May 1, 2002
Creator: Swartz, Erick; Stockburger, Leonard & Gundel, Lara
Partner: UNT Libraries Government Documents Department

A study of competitive adsorption of organic molecules onto mineral oxides using DRIFTS

Description: Analysis of DRIFTS spectra was used for a quantitative study of competitive adsorption of myristic and salicylic acids onto kaolinite or {gamma}-alumina. Peaks unique to the ring or the chain were selected and single molecule studies used as calibration. Samples were exposed to hexane solution containing equal molecular quantities of each acid. The surface loading of salicylic acid was not influenced by the presence of myristic acid on either mineral but the maximum loading of myristic acid was decreased (46-50%) by salicylic acid. Displacement of myristic acid from {gamma}-alumina, but not kaolinite, was observed when excess salicylic acid remained in solution. A 25% increase in the maximum loading was observed for kaolinite, but not for{gamma}-alumina. On {gamma}-alumina, after a loading of 1 molecule per nm{sup 2}, increased exposure resulted in salicylic acid adsorption only, this value is approximately the same for salicylic acid adsorption from aqueous solution or for water washed hexane treated samples. Thus a set of sites for adsorption of either acid is indicated together with other energetically less favorable sites, which can be occupied by salicylic, but not by myristic, acid.
Date: February 1, 2010
Creator: Joan E. Thomas, Michael J. Kelley
Partner: UNT Libraries Government Documents Department

Pentan isomers compound flame front structure

Description: The fuels (hexane, pentane, diethyl ether) and conditions investigated in this study are relevant to engine knock in spark- ignition engines. A review is provided of the field of low temperature hydrocarbon oxidation. Studies were made of radical and stable intermediate distribution in the front of cool flames: Maximum concentrations of H atoms and peroxy radicals were observed in the luminous zone of the cool flame front. Peroxy radicals appear before the luminous zone at 430 K due to diffusion. H atoms were found in cool flames of butane and hexane. H atoms diffuses from the luminous zone to the side of the fresh mixture, and they penetrate into the fresh mixture to a small depth. Extension of action sphear of peroxy radicals in the fresh mixture is much greater than that of H atoms due to their small activity and high concentrations.
Date: August 13, 1995
Creator: Mansurov, Z. A.; Mironenko, A. W.; Bodikov, D. U. & Rachmetkaliev, K. N.
Partner: UNT Libraries Government Documents Department

Microwave processing improvements for methane conversion to ethylene

Description: This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The project`s objective was to investigate microwave enhanced catalysis. Published work by others had demonstrated improved selectivity in microwave-driven catalytic conversion of 2-methylpentane to its isomers. We reproduced their experiment, discovering that there is no improvement in selectivity using microwaves. The selectivity at a given conversion was the same for both microwave heated and conventionally heated catalyst beds. Meetings with the authors of the previously published work led to the conjecture that their catalyst was not being prepared properly, leading to anomalously low selectivity for their conventional heating runs. An optical temperature diagnostic suitable for use on a microwave applicator was developed and characterized in this project. This pyrometer can measure the temperature of small scale features on the catalyst bed, and it has a fast response that can follow the rapid heating often encountered in a microwave processing system. The behavior of the microwave applicator system was studied, and theoretical models were developed to yield insight about the stability and control of the system.
Date: August 1, 1997
Creator: Stringfield, R.; Ott, K.; Nelson, E.; Anderson, G.; Chen, Dye-Zone; Dyer, T. et al.
Partner: UNT Libraries Government Documents Department

Potential VOC Deflagrations in a Vented TRU Drum

Description: The objective of the analysis is to examine the potential for lid ejection from a vented transuranic (TRU) waste drum due to pressure buildup caused by the deflagration of hydrogen and volatile organic compounds (VOCs) inside the drum. In this analysis, the AICC pressure for a stoichiometric mixture of VOCs is calculated and then compared against the experimental peak pressure of stoichiometric combustion of propane and hexane in a combustion chamber. The experimental peak pressures of propane and hexane are about 12 percent lower than the calculated AICC pressure. Additional losses in the drum are calculated due to venting of the gases, drum bulging, waste compaction, and heat losses from the presence of waste in the drum. After accounting for these losses, the final pressures are compared to the minimum observed pressure that ejects the lid from a TRU drum. The ejection pressure of 105 psig is derived from data that was recorded for a series of tests where hydrogen-air mixtures were ignited inside sealed TRU drums. Since the calculated pressures are below the minimum lid ejection pressure, none of the VOCs and the hydrogen (up to 4 percent) mixtures present in the TRU waste drum is expected to cause lid ejection if ignited. The analysis of potential VOC deflagrations in a vented TRU drum can be applied across the DOE-Complex since TRU waste is stored in drums throughout the complex.
Date: April 7, 2005
Creator: Mukesh, GUPTA
Partner: UNT Libraries Government Documents Department

Solution Effects on Cesium Complexation with Calixarene - Crown Ethers from Liquid to Supercritical Fluids

Description: Supercritical fluid CO2 is an alternative solvent for extraction of metals. The solubility parameter of supercritical CO2 varies with density resembling that of liquid hexane at moderate pressures in the supercritical region to those of chlorinated solvents at very high pressures. By changing density of supercritical CO2, the solvation environment of a metal chelate system can vary continuously and resembles over a wide range of solvents. Thus, supercritical CO2 provides a unique system for studying solvation effects on metal chelation. This project is designed to investigate the solvation effects on cesium complexation with macrocyclic compounds including crown ethers and calixarene-crown ethers in CO2 from liquid to supercritical region at high pressures. A powerful spectroscopic technique for studying cesium chelation is nuclear magnetic resonance (NMR). Cesium has only one isotope, 133Cs, with a nuclear spin I = 7/2. Popov et al. used NMR to study cesium complexation with crown ethers and cryptand.
Date: June 1, 1999
Creator: Wai, Chien M. & Yonker,Clem
Partner: UNT Libraries Government Documents Department

Sensing liquid properties with shear-mode resonator sensors

Description: Liquid properties are measured from the changes they induce in the resonant frequency and damping of thicknessshear mode quartz resonators. A smooth-surfaced resonator viscously entrains the contacting fluid and responds to the density-viscosity product. Separation of density and viscosity is accomplished using two devices: one with a smooth surface and one with a corrugated surface that traps fluid. By observing the difference in stored and dissipated energies in the contacting fluid, its non-Newtonian characteristics can also be determined.
Date: June 1, 1995
Creator: Martin, S.J.; Cernosek, R.W. & Spates, J.J.
Partner: UNT Libraries Government Documents Department

SEPARATION OF FISCHER-TROPSCH WAX FROM CATALYST BY SUPERCRITICAL EXTRACTION

Description: The objective of this research project is 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}, will be extracted with a hydrocarbon solvent that has a critical temperature near the operating temperature of the SBC reactor, i.e., 200-300 C. Initial work is being performed using n-hexane as the solvent. The success of the project depends on two factors. First, the supercritical solvent must be able to dissolve the F-T wax; furthermore, this must be accomplished at conditions that do not entrain the solid catalyst. Second, the extraction must be controlled so as not to favor the removal of the low molecular weight wax compounds. That is, a constant carbon-number distribution in the wax slurry must be maintained at steady-state column operation. Three major tasks are being undertaken to evaluate our proposed SCF extraction process. Task 1: Equilibrium solubility measurements for model F-T wax components in supercritical fluids at conditions representative of those in a SBC reactor. Task 2: Thermodynamic modeling of the measured VLE data for extending our results to real wax systems. Task 3: Process design studies of our proposed process. Additional details of the task structure are given.
Date: July 31, 1998
Creator: THIES, MARK C. & JOYCE, PATRICK C.
Partner: UNT Libraries Government Documents Department

Final Technical Report: Effects of Impurities on Fuel Cell Performance and Durability

Description: The main objectives of this project were to investigate the effect of a series of potential impurities on fuel cell operation and on the particular components of the fuel cell MEA, to propose (where possible) mechanism(s) by which these impurities affected fuel cell performance, and to suggest strategies for minimizing these impurity effects. The negative effect on Pt/C was to decrease hydrogen surface coverage and hydrogen activation at fuel cell conditions. The negative effect on Nafion components was to decrease proton conductivity, primarily by replacing/reacting with the protons on the Bronsted acid sites of the Nafion. Even though already well known as fuel cell poisons, the effects of CO and NH3 were studied in great detail early on in the project in order to develop methodology for evaluating poisoning effects in general, to help establish reproducibility of results among a number of laboratories in the U.S. investigating impurity effects, and to help establish lower limit standards for impurities during hydrogen production for fuel cell utilization. New methodologies developed included (1) a means to measure hydrogen surface concentration on the Pt catalyst (HDSAP) before and after exposure to impurities, (2) a way to predict conductivity of a Nafion membranes exposed to impurities using a characteristic acid catalyzed reaction (methanol esterification of acetic acid), and, more importantly, (3) application of the latter technique to predict conductivity on Nafion in the catalyst layer of the MEA. H2-D2 exchange was found to be suitable for predicting hydrogen activation of Pt catalysts. The Nafion (ca. 30 wt%) on the Pt/C catalyst resides primarily on the external surface of the C support where it blocks significant numbers of micropores, but only partially blocks the pore openings of the meso- and macro-pores wherein lie the small Pt particles (crystallites). For this reason, even with 30 wt% Nafion ...
Date: November 11, 2011
Creator: Goodwin, James G., Jr.; Colon-Mercado, Hector; Hongsirikarn, Kitiya & Zhang, Jack Z.
Partner: UNT Libraries Government Documents Department

Fischer-Tropsch synthesis in supercritical fluids. Final report

Description: The objective of this study was to investigate Fischer-Tropsch Synthesis (FTS) in the supercritical phase employing a commercial precipitated iron catalysts. As the supercritical fluid the authors used propane and n-hexane. The catalyst had a nominal composition of 100 Fe/5 Cu/4.2 K/25 SiO{sub 2} on mass basis and was used in a fixed bed reactor under both normal (conventional) and supercritical conditions. Experimental data were obtained at different temperatures (235 C, 250 C, and 260 C) and synthesis gas feed compositions (H{sub 2}/CO molar feed ratio of 0.67, 1.0 and 2.0) in both modes of operation under steady state conditions. The authors compared the performance of the precipitated iron catalyst in the supercritical phase, with the data obtained in gas phase (fixed bed reactor) and slurry phase (STS reactor). Comparisons were made in terms of bulk catalyst activity and various aspects of product selectivity (e.g. lumped hydrocarbon distribution and olefin content as a function of carbon number). In order to gain better understanding of the role of intraparticle mass transfer during FTS under conventional or supercritical conditions, the authors have measured diffusivities of representative hydrocarbon products in supercritical fluids, as well as their effective diffusion rates into the pores of catalyst at the reaction conditions. They constructed a Taylor dispersion apparatus to measure diffusion coefficients of hydrocarbon products of FTS in sub and supercritical ethane, propane, and hexane. In addition, they developed a tracer response technique to measure the effective diffusivities in the catalyst pores at the same conditions. Based on these results they have developed an equation for prediction of diffusion in supercritical fluids, which is based on the rough hard sphere theory.
Date: December 31, 1998
Creator: Akgerman, A. & Bukur, D.B.
Partner: UNT Libraries Government Documents Department

Separation of Fischer-Tropsch Wax from Catalyst by Supercritical Extraction

Description: The proposed process of using supercritical fluid extraction in conjunction with the Fischer-Tropsch slurry bubble column reactor has been examined using the ASPEN Plus simulator by the research group at North Carolina State University. Qualitative results have been obtained for varying the following process parameters: solvent-to-wax ratio, solvent type (pentane or hexane), extraction temperature and pressure, and recovery unit temperature and pressure. The region of retrograde behavior was determined for pentane and hexane. Initial results show hexane to be the superior solvent; compared to pentane, hexane requires lower quantities of solvent makeup (the amount of solvent which needs to be added to account for solvent that cannot be recycled), and also results in a lower average molecular weight of slurry in the reactor. Studies indicate that increasing the extraction temperature, extraction pressure, recovery temperature, or solvent to wax ratio decreases the amount solvent makeup required. Decreasing the recovery pressure was found to decrease the makeup flowrate.
Date: January 31, 1997
Creator: Joyce, P.C. & Thies, M.C.
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

Separation of Fischer-Tropsch wax from catalyst using supercritical fluid extraction. Quarterly technical progress report, April 1, 1996--June 30, 1996

Description: The objective of this research project is to evaluate the potential of SCF extraction for separating the catalyst slurry of a Fischer- Tropsch (F-T) slurry bubble column (SBC) reactor into two fractions: (1) a catalyst-free wax containing less than 10 ppm particulate matter and (2) a concentrated catalyst slurry that is ready for recycle or regeneration. The wax will be extracted with a hydrocarbon solvent that has a critical temperature near the operating temperature of the SBC reactor, i.e., 200-300{degrees}C. Initial work is being performed using n-hexane as the solvent. The success of the project depends on two major factors. First, the supercritical solvent must be able to dissolve the F-T wax; furthermore, this must be accomplished without entraining the solid catalyst. Second, the extraction must be controlled so as not to favor the removal of the low molecular weight wax compounds, i.e., a constant carbon-number distribution of the alkanes in the wax slurry must be maintained at steady-state column operation. To implement our objectives, the following task structure is being implemented: Task 1 equilibrium solubility measurements; Task 2 thermodynamic modeling; and Task 3 process design studies. Progress reports are presented for each task.
Date: November 1, 1996
Creator: Joyce, P.C. & Thies, M.C.
Partner: UNT Libraries Government Documents Department

Catalytic steam gasification of carbon

Description: Unsupported carbide powders with high specific surface area, namely {alpha}-WC (35 m{sup 2}/g, hexagonal), {beta}-WC{sub 0.61} (100 m{sup 2}/g, cubic face centered) and {beta}-WC{sub 0.5} (15 m{sup 2}/g, hexagonal) have been prepared. The key element in this preparation is the successful removal of surface polymeric carbon by careful gasification to methane by means of dihydrogen. These tungsten carbide powders have been used in catalytic reactions of oxidation of H{sub 2} and hydrogenolysis of alkanes, such as butane, hexane, and neopentane.
Date: December 31, 1990
Creator: Boudart, M.
Partner: UNT Libraries Government Documents Department

Separation of Fischer-Tropsch wax from catalyst using supercritical fluid extraction. Quarterly technical progress report, 1 January 1996--31 March 1996

Description: The objective of this research project is to evaluate the potential of supercritical fluid extraction for separating the catalyst slurry of a Fischer-Tropsch (F-T) slurry bubble column (SBC) reactor into two fractions: (1) a catalyst-free wax containing less than 10 ppm particulate matter and (2) a concentrated catalyst slurry that is ready for recycle or regeneration. The wax will be extracted with a hydrocarbon solvent that has a critical temperature near the operating temperature of the SBC reactor, i.e., 200--300 {degrees}C. Initial work is being performed using n-hexane as the solvent. The success of the project depends on two major factors. First, the supercritical solvent must be able to dissolve the F-T wax; furthermore, this must be accomplished without entraining the solid catalyst. Second, the extraction must be controlled so as not to favor the removal of the low molecular weight wax compounds, i.e., a constant carbon-number distribution of the alkanes in the wax slurry must be maintained at steady-state column operation. During this quarter work focused on task 1b, experimental measurement of selected model systems. Vapor-liquid equilibrium experiments for the n- hexane/squalane system, which we initiated in the previous quarter, were continued and results are discussed in this report.
Date: September 1, 1996
Creator: Joyce, P.C. & Thies, M.C.
Partner: UNT Libraries Government Documents Department