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A 2-D Self-Consistent DSMC Model for Chemically Reacting Low Pressure Plasma Reactors

Description: This paper will focus on the methodology of using a 2D plasma Direct Simulation Monte Carlo technique to simulate the species transport in an inductively coupled, low pressure, chemically reacting plasma system. The pressure in these systems is typically less than 20 mtorr with plasma densities of approximately 10{sup 17} {number_sign}/m{sup 3} and an ionization level of only 0.1%. This low ionization level tightly couples the neutral, ion, and electron chemistries and interactions in a system where the flow is subsonic. We present our strategy and compare simulation results to experimental data for Cl{sub 2} in a Gaseous Electronics Conference (GEC) reference cell modified with an inductive coil.
Date: June 17, 1999
Creator: Bartel, Timothy J.; Economou, Demetre & Johannes, Justine E.
Partner: UNT Libraries Government Documents Department

100 Area groundwater biodenitrification bench-scale treatability study procedures

Description: This document describes the methodologies and procedures for conducting the bench-scale biodenitrification treatability tests at Pacific Northwest Laboratory{sup a} (PNL). Biodenitrification is the biological conversion of nitrate and nitrite to gaseous nitrogen. The tests will use statistically designed batch studies to determine if biodenitrification can reduce residual nitrate concentrations to 45 mg/L, the current maximum contaminant level (MCL). These tests will be carried out in anaerobic flasks with a carbon source added to demonstrate nitrate removal. At the pilot scale, an incremental amount of additional carbon will be required to remove the small amount of oxygen present in the incoming groundwater. These tests will be conducted under the guidance of Westinghouse Hanford Company (WHC) and the 100-HR-3 Groundwater Treatability Test Plan (DOE/RL-92-73) and the Treatability Study Program Plan (DOE/RL-92-48) using groundwater from 100-HR-3. In addition to the procedures, requirements for safety, quality assurance, reporting, and schedule are given. Appendices include analytical procedures, a Quality Assurance Project Plan, a Health and Safety Plan, and Applicable Material Data Safety Sheets. The procedures contained herein are designed specifically for the 100-HR-3 Groundwater Treatability Test Plan, and while the author believes that the methods described herein are scientifically valid, the procedures should not be construed or mistaken to be generally applicable to any other treatability study.
Date: May 1, 1993
Creator: Peyton, B. M. & Martin, K. R.
Partner: UNT Libraries Government Documents Department

2007 Inorganic Reaction Mechanisms Gordon Research Conference-February 18-23

Description: This conference focuses on kinetic, mechanistic, and thermodynamic studies of reactions that play a role in fields as diverse as catalysis, energy, bioinorganic chemistry, green chemistry, organometallics, and activation of small molecules (oxygen, nitrogen, carbon monoxide, carbon dioxide, alkanes). Participants from universities, industry, and national laboratories present results and engage in discussions of pathways, intermediates, and outcome of various reactions of inorganic, organic, coordination, organometallic, and biological species. This knowledge is essential for rational development and design of novel reactions, compounds, and catalysts.
Date: January 1, 2008
Creator: Gray, Andreja Bakac Nancy Ryan
Partner: UNT Libraries Government Documents Department

Ab initio studies of transition-metal dihydrogen chemistry

Description: Examples of transition metal complexes containing dihydrogen ligands are investigated using ab initio electronic structure calculations employing effective core potentials. Calculated geometrical structures and relative energies of various forms of WL/sub 5/(H/sub 2/) complexes (L = CO, PR/sub 3/) are reported, and the influence of the ligand on the relative stabilities of the dihydrogen and dihydride forms is studied. The possible intramolecular mechanisms for H/D scrambling are investigated in another d/sup 6/ complex, Cr(CO)/sub 4/(H/sub 2/)/sub 2/, where various polyhydride intermediates are possible. 8 refs., 6 figs., 1 tab.
Date: January 1, 1988
Creator: Kober, E. M. & Hay, P. J.
Partner: UNT Libraries Government Documents Department

Abiotic Degradation Rates for Carbon Tetrachloride: and Chloroform: Progress in FY 2008

Description: This is a letter report summarizing work performed in FY2008 to determine the rates of carbon tetrachloride hydrolysis at temperatures close to actual groundwater temperatures. The report describes the project, the methodology, and the results obtained since the project's inception in FY2006. Measurements of hydrolysis rates in homogeneous solution have been completed for temperaturs of 70 C through 40 C, with additional data available at 30 C and 20 C. These results show no difference between the rates in deionized H2O and in filter-sterilized Hanford-Site groundwater. Moreover, the rates measured are 2-3 times slower than predicted from the open literature. Measurements of rates involving sterile suspensions of Hanford-Site sediment in Hanford-Site groundwater, however, show faster hydrolysis at temperatures below 40 C. Extrapolation of the current data available suggests a six-fold increase in rate would be expected at groundwater temperature of 16 C due to the presence of the sediment. This result translates into a 78-year half-life, rather than the 470-680 year half-life that would be predicted from rate determinations in homogeneous solution. The hydrolysis rate data at 20 C, in contrast to those at higher temperatures, are preliminary and have low statistical power. While significant (p < 0.05) differences between the heterogeneous and homogeneous systems are seen at 30 C, the results at 20 C are not statistically significant at this level due to limited data and the very slow nature of the reaction. More time is needed to collect data at these low temperatures to improve the statistical power of our observation. Given the critical need for hydrolysis rate data at temperatures relevant to groundwater systems, we have three recommendations for future work. First, we recommend a continuation of the sampling and analysis of the remaining long-term sealed-ampule experiments described in this report. These are primarily 20 C and ...
Date: October 31, 2008
Creator: Amonette, James E.; Jeffers, Peter M.; Qafoku, Odeta; Russell, Colleen K.; Wietsma, Thomas W. & Truex, Michael J.
Partner: UNT Libraries Government Documents Department

Abiotic Degradation Rates for Carbon Tetrachloride and Chloroform: Progress in FY 2010

Description: This report documents the progress made through FY 2010 on a project initiated in FY 2006 to help address uncertainties related to the rates of hydrolysis in groundwater at the Hanford Site for carbon tetrachloride (CT) and chloroform (CF). The study also explores the possible effects of contact with minerals and sediment (i.e., heterogeneous hydrolysis) on these rates. The research was initiated to decrease the uncertainties in abiotic degradation rates of CT and chloroform CF associated with temperature and possible heterogeneous effects. After 2 years of data collection, the first evidence for heterogeneous effects was identified for hydrolysis of CT, and preliminary evidence for the effects of different mineral types on CF hydrolysis rates also was reported. The CT data showed no difference among mineral types, whereas significant differences were seen in the CF results, perhaps due to the fact that CF hydrolyzes by both neutral and base-catalyzed mechanisms whereas CT follows only the neutral hydrolysis path. In this report, we review the project objectives, organization, and technical approaches taken, update the status and results of the hydrolysis-rate experiments after 4 years of experimentation (i.e., through FY 2010), and provide a brief discussion of how these results add to scientific understanding of the behavior of the CT/CF plume at the Hanford Site.
Date: December 8, 2010
Creator: Amonette, James E.; Jeffers, Peter M.; Qafoku, Odeta; Russell, Colleen K.; Humphrys, Daniel R.; Wietsma, Thomas W. et al.
Partner: UNT Libraries Government Documents Department

Abiotic immobilization/detoxification of recalcitrant organics

Description: In contrast to many remedial techniques that simply transfer hazardous wastes from one part of the environment to another (e.g., off-site landfilling), in situ restoration may offer a safe and cost-effective solution through transformation (to less hazardous products) or destruction of recalcitrant organics. Currently, the US Environmental Protection Agency and US Department of Energy are encouraging research that addresses the development of innovative alternatives for hazardous-waste control. One such alternative is biotic and abiotic immobilization and detoxification of polynuclear aromatic hydrocarbons (PNAs) as associated with the soil humification process. This paper discusses (1) the possibility of using abiotic catalysis (with manganese dioxide) to polymerize organic substances; (2) aspects associated with the thermodynamics and kinetics of the process, and (3) a simple model upon which analyses may be based. 36 refs., 7 figs., 3 tabs.
Date: November 1, 1990
Creator: Whelan, G. & Sims, R. C.
Partner: UNT Libraries Government Documents Department

Accelerated glass reaction under PCT conditions

Description: Static leach tests similar to PCT (Product Consistency Test) were performed for up to 2 years to assess long-term reaction behavior of high-level nuclear waste glasses similar to those at Defense Waste Processing Facility. These tests show the reaction rate to decrease with the reaction time from an initially high rate to a low rate, but then to accelerate to a higher rate after reaction times of about 1 year, depending on glass surface area/leachant volume ratio used. Solution concentrations of soluble glass components increase as the reaction is accelerated, while release of other glass components into solution is controlled by secondary phases. Net result is that transformation of glass to stable phases is accelerated while the solution becomes enriched in soluble components not effectively contained in secondary phases. Rate becomes linear in time after the acceleration and may be similar to the initial forward rate. A current model of glass reaction predicts that the glass reaction will be accelerated upon the formation of secondary phases which lower the silicic acid solution concentration. These tests show total Si concentration to increase upon reaction acceleration, however, which may be due to the slightly higher pH attained with the acceleration. The sudden change in the reaction rate is likely due to secondary phase formation. 17 refs, 2 tabs, 3 figs.
Date: December 31, 1992
Creator: Ebert, W. L.; Bates, J. K.; Buck, E. C. & Bradley, C. R.
Partner: UNT Libraries Government Documents Department

Accelerated glass reaction under PCT conditions

Description: Static leach tests similar to PCT (Product Consistency Test) were performed for up to 2 years to assess long-term reaction behavior of high-level nuclear waste glasses similar to those at Defense Waste Processing Facility. These tests show the reaction rate to decrease with the reaction time from an initially high rate to a low rate, but then to accelerate to a higher rate after reaction times of about 1 year, depending on glass surface area/leachant volume ratio used. Solution concentrations of soluble glass components increase as the reaction is accelerated, while release of other glass components into solution is controlled by secondary phases. Net result is that transformation of glass to stable phases is accelerated while the solution becomes enriched in soluble components not effectively contained in secondary phases. Rate becomes linear in time after the acceleration and may be similar to the initial forward rate. A current model of glass reaction predicts that the glass reaction will be accelerated upon the formation of secondary phases which lower the silicic acid solution concentration. These tests show total Si concentration to increase upon reaction acceleration, however, which may be due to the slightly higher pH attained with the acceleration. The sudden change in the reaction rate is likely due to secondary phase formation. 17 refs, 2 tabs, 3 figs.
Date: January 1, 1992
Creator: Ebert, W.L.; Bates, J.K.; Buck, E.C. & Bradley, C.R.
Partner: UNT Libraries Government Documents Department

Acetic acid production from marine algae. Progress report No. 2, September 30--December 31, 1977

Description: Preliminary results on the production of acetic acid from marine algae by anaerobic fermentation indicate that the rate is quite fast. First order rate constants of 0.77 day/sup -1/ were observed. This rate constant gives a half-life of less than one day. In other words, with a properly designed product removal system a five day retention time would yield 98% of theoretical conversion. Determination of the theoretical conversion of marine algae to acetic acid is the subject of much experimentation. The production of one acetic acid molecule (or equivalent in higher organic acids) for each three carbon atoms in the substrate has been achieved; but it is possible that with a mixed culture more than one acetic acid molecule may be produced for each three carbons in the substrate. Work is continuing to improve the yield of acetic acid from marine algae. Marine algae have been found to be rather low in carbon, but the carbon appears to be readily available for fermentation. It, therefore, lends itself to the production of higher value chemicals in relatively expensive equipment, where the rapid conversion rate is particularly cost effective. Fixed packed bed fermenters appear to be desirable for the production of liquid products which are inhibitory to the fermentation from coarse substrates. The inhibitory products may be removed from the fermentation by extraction during recirculation. This technique lends itself to either conventional processing or low capital processing of substrates which require long retention times.
Date: January 1, 1977
Partner: UNT Libraries Government Documents Department

Acid-Base Behavior in Hydrothermal Processing of Wastes - Final Report

Description: A major obstacle to development of hydrothermal oxidation technology has been a lack of scientific knowledge of chemistry in hydrothermal solution above 350 C, particularly acid-base behavior, and transport phenomena, which is needed to understand corrosion, metal-ion complexation, and salt precipitation and recovery. Our objective has been to provide this knowledge with in situ UV-visible spectroscopic measurements and fully molecular computer simulation. Our recent development of relatively stable organic UV-visible pH indicators for supercritical water oxidation offers the opportunity to characterize buffers and to monitor acid-base titrations. These results have important implications for understanding reaction pathways and yields for decomposition of wastes in supercritical water.
Date: December 1, 2000
Creator: Johnston, K. & Rossky, P.
Partner: UNT Libraries Government Documents Department

Actinide Phosphonate Complexes in Aqueous Solutions

Description: Complexes formed by actinides with carboxylic acids, polycarboxylic acids, and aminopolycarboxylic acids play a central role in both the basic and process chemistry of the actinides. Recent studies of f-element complexes with phosphonic acid ligands indicate that new ligands incorporating doubly ionizable phosphonate groups (-PO{sub 3}H{sub 2}) have many properties which are unique chemically, and promise more efficient separation processes for waste cleanup and environmental restoration. Simple diphosphonate ligands form much stronger complexes than isostructural carboxylates, often exhibiting higher solubility as well. In this manuscript recent studies of the thermodynamics and kinetics of f-element complexation by 1,1 and 1,2 diphosphonic acid ligands are described.
Date: October 1993
Creator: Nash, K. L.
Partner: UNT Libraries Government Documents Department

Active sites in char gasification: Final technical report

Description: Among the key variables in the design of gasifiers and combustors is the reactivity of the chars which must be gasified or combusted. Significant loss of unburned char is unacceptable in virtually any process; the provision of sufficient residence time for complete conversion is essential. A very wide range of reactivities are observed, depending upon the nature of the char in a process. The current work focuses on furthering the understanding of gasification reactivities of chars. It has been well established that the reactivity of char to gasification generally depends upon three principal factors: (1) the concentration of ''active sites'' in the char; (2) mass transfer within the char; and (3) the type and concentration of catalytic impurities in the char. The present study primarily addresses the first factor. The subject of this research is the origin, nature, and fate of active sites in chars derived from parent hydrocarbons with coal-like structure. The nature and number of the active sites and their reactivity towards oxygen are examined in ''model'' chars derived from phenol-formaldehyde type resins. How the active sites are lost by the process of thermal annealing during heat treatment of chars are studied, and actual rate for the annealing process is derived. Since intrinsic char reactivities are of primary interest in the present study, a fair amount of attention was given to the model char synthesis and handling so that the effect of catalytic impurities and oxygen-containing functional groups in the chemical structure of the material were minimized, if not completely eliminated. The project would not be considered complete without comparing characteristic features of synthetic chars with kinetic behavior exhibited by natural chars, including coal chars.
Date: September 1, 1987
Creator: Wojtowicz, M.; Lilly, W.D.; Perkins, M.T.; Hradil, G.; Calo, J.M. & Suuberg, E.M.
Partner: UNT Libraries Government Documents Department

Activity testing of fine-particle size, iron catalysts for coal liquefaction

Description: The use of fine-particle size (< 40 nm) unsupported catalysts in direct coal liquefaction may result in improved economics due to possible enhanced yields of desired products, the potential for decreasing reaction severity, and the possibility of using less catalyst. Sandia has developed a standard testing procedure for evaluating and comparing the fine-particle catalysts. The test procedure uses phenanthrene as the reaction solvent, the DECS-17 Blind Canyon Coal, and a statistical experimental design to enable evaluation of the catalysts over ranges of temperature (350 to 400{degrees}C), time (20 to 60 minutes), and catalyst loading (0 to 1 wt % on a dmmf coal basis). Product analyses include tetrahydrofuran (THF) conversion, heptane conversion, solvent recovery, and gas analyses. Phenanthrene as the solvent in the testing procedure yielded significant differences between thermal and catalytic reactions, whereas using a good hydrogen donor such as 9,10-dihydrophenanthrene (DHP) showed no catalytic effects.
Date: October 1, 1993
Creator: Stohl, F. V.; Diegert, K. V. & Gugliotta, T. P.
Partner: UNT Libraries Government Documents Department

Adaptation of U(IV) reductant to Savannah River Plant Purex processes

Description: Partitioning of uranium and plutonium in the Purex process requires the reduction of the extracted Pu(IV) to the less extractable Pu(III). This valence adjustment at SRP has historically been performed by the addition of ferrous ion, which eventually constitutes a major component of high-level waste solids requiring costly permanent disposal. Uranous nitrate, U(IV), is a kinetically fast reductant which may be substituted for Fe(II) without contributing to waste solids. This report documents U(IV) flowsheet development in the miniature mixer-settler equipment at SRL and provides an insight into the mechanisms responsible for the successful direct substitution of U(IV) for Fe(II) in 1B bank extractant. U(IV) will be the reductant of choice when its fast reduction kinetics are required in centrifugal-contactor-based processing. The flowsheets investigated here should transfer to such equipment with minimal modifications.
Date: April 1, 1986
Creator: Orebaugh, E.G.
Partner: UNT Libraries Government Documents Department

The addition of disilanes to cumulenes

Description: The syntheses of silicon-containing compounds and the studies of their rearrangements have been active research areas in the Barton research group. Previously, the addition of disilanes to acetylenes was studied in the group and an intramolecular 2S + 2A mechanism has been proposed. In this thesis, the work is focused on the addition of disilanes to cumulenes. The syntheses of the precursors are discussed and the possible mechanisms for their thermal, photochemical and catalytic rearrangements are proposed. Conjugated organic polymers have been studied in the group since 1985 because of their potential for exhibiting high electroconductivity, photoconductivity, strong non-linear optical response and intense fluorescence. In the second section of this dissertation, the synthesis and property studies of poly(phenylene vinylene) analogues are discussed.
Date: October 8, 1997
Creator: Chen, Y.
Partner: UNT Libraries Government Documents Department

Adiabatic calorimetry (RSST and VSP) tests with sodium acetate

Description: As requested in the subject reference, adiabatic calorimetry (RSST and VSP) tests have been performed with sodium acetate covering TOC concentrations from 3 to 7% with the following results: Exothermic activity noted around 200{degrees}C. Propagating reaction initiated at about 300{degrees}C. Required TOC concentration for propagation estimated at about 6 w% (dry mixture) or about 20 w% sodium acetate. Heat of reaction estimated to be 3.7 MJ per kg of sodium acetate (based on VSP test with 3 w% TOC and using a dry mixture specific heat of 1000 J kg{sup {minus}1} K{sup {minus}1}). Based upon the above results we estimate that a moisture content in excess of 14 w% would prevent a propagating reaction of a stoichiometric mixture of fuel and oxidizer ({approximately} 38 w% sodium acetate and {approximately}62 w% sodium nitrate). Assuming that the fuel can be treated as sodium acetate equivalent, and considering that the moisture content in the organic containing waste generally is believed to be in excess of 14 w%, it follows that the possibility of propagating reactions in the Hanford waste tanks can be ruled out.
Date: September 1, 1993
Creator: Kirch, N. W.
Partner: UNT Libraries Government Documents Department

Advanced direct liquefaction concepts for PETC generic units. [Mainly, the effect of preteatment of coal with carbon monoxide and steam]

Description: CAER/UK: Detail coal and starting solvents from Wilsonville were analyzed to develop the data necessary to conduct process studies in the CO Pretreatment and Catalyst Evaluation segment of this program. A comparison of the solvent separation analysis with the distillation/separation used at Wilsonville showed that the residual solvent components contained a large amount of residual pentane soluble products. The ashy resid contained 3% iron and 400 ppM molybdenum. Although the iron content in the distillate and deashed resid was much less, namely about 200 ppM., the molybdenum concentrations in these fractions were not significantly reduced over the concentration in the ashy resid, i.e., 200 ppM in each. The pretreatment of coal with CO/H{sub 2}O in the presence of NaOH and Na{sub 2}CO{sub 3} has been shown to give a product which is lower in oxygen content and higher in hydrogen content compared to the raw coal. The atomic H/C ratios of the H{sub 2}O-insolubles, THF insolubles and the PA+A fractions of the products-together with the hydrogen consumption data suggested that the raw coal has been substantially depolymerized and hydrogenated via the WGS reaction during the pretreatment process. The extensive amount of molecular reconstruction that has occurred in the solid product was evident from the ease of solubilization of the product into pyridine. The result of the pretreatment process is a product which is highly reactive under hydroliquefaction conditions at 400{degrees}C. Reaction rates seem to be much faster than the raw coal, especially at shorter reaction times, providing the opportunity for major reductions in plant vessel sizes, and preliminary data has led us to believe that better efficiency in hydrogen utilization is achieved.
Date: August 1, 1992
Partner: UNT Libraries Government Documents Department

Advanced direct liquefaction concepts for PETC generic units. Quarterly technical progress report, April 1992--June 1992

Description: CAER/UK: Detail coal and starting solvents from Wilsonville were analyzed to develop the data necessary to conduct process studies in the CO Pretreatment and Catalyst Evaluation segment of this program. A comparison of the solvent separation analysis with the distillation/separation used at Wilsonville showed that the residual solvent components contained a large amount of residual pentane soluble products. The ashy resid contained 3% iron and 400 ppM molybdenum. Although the iron content in the distillate and deashed resid was much less, namely about 200 ppM., the molybdenum concentrations in these fractions were not significantly reduced over the concentration in the ashy resid, i.e., 200 ppM in each. The pretreatment of coal with CO/H{sub 2}O in the presence of NaOH and Na{sub 2}CO{sub 3} has been shown to give a product which is lower in oxygen content and higher in hydrogen content compared to the raw coal. The atomic H/C ratios of the H{sub 2}O-insolubles, THF insolubles and the PA+A fractions of the products-together with the hydrogen consumption data suggested that the raw coal has been substantially depolymerized and hydrogenated via the WGS reaction during the pretreatment process. The extensive amount of molecular reconstruction that has occurred in the solid product was evident from the ease of solubilization of the product into pyridine. The result of the pretreatment process is a product which is highly reactive under hydroliquefaction conditions at 400{degrees}C. Reaction rates seem to be much faster than the raw coal, especially at shorter reaction times, providing the opportunity for major reductions in plant vessel sizes, and preliminary data has led us to believe that better efficiency in hydrogen utilization is achieved.
Date: August 1, 1992
Partner: UNT Libraries Government Documents Department

Advanced direct liquefaction concepts for PETC generic units. Quarterly technical progress report, October 1992--December 1992

Description: The reactivity of the THF insoluble fraction of the ashy resid component of Wilsonville recycle oil (WRO) during liquefaction of Black Thunder coal in tetralin was determined at 415{degrees}C and 60 minutes. The liquefaction runs were made by combining this material with Black Thunder coal at the same ratio used in the WRO coal runs. THF conversion and product distribution from liquefaction in tetralin in the presence of the THF insoluble fraction of the ashy resid were similar to results from liquefaction in WRO. THF conversion was greater than loot with an oil yield that was somewhat higher than in WRO. Differences in HC gas yield and H{sub 2} consumption were slight, while conversion and product distribution from liquefaction of Black Thunder coal in tetralin or in the WRO distillate were quite different. In both these solvents the 85--86% THF conversions were less than for runs in which the THF insoluble fraction of the ashy resid was present. This establishes that the THF insoluble fraction of the ashy resid is the reactive fraction of the WRO.
Date: February 1, 1993
Partner: UNT Libraries Government Documents Department

Advanced Experimental Analysis of Controls on Microbial Fe(III) Oxide Reduction - Final Report - 09/16/1996 - 03/16/2001

Description: Considering the broad influence that microbial Fe(III) oxide reduction can have on subsurface metal/organic contaminant biogeochemistry, understanding the mechanisms that control this process is critical for predicting the behavior and fate of these contaminants in anaerobic subsurface environments. Knowledge of the factors that influence the rates of growth and activity of Fe(III) oxide-reducing bacteria is critical for predicting (i.e., modeling) the long-term influence of these organisms on the fate of contaminants in the subsurface, and for effectively utilizing Fe(III) oxide reduction and associated geochemical affects for the purpose of subsurface metal/organic contamination bioremediation. This research project will refine existing models for microbiological and geochemical controls on Fe(III) oxide reduction, using laboratory reactor systems that mimic, to varying degrees, the physical and chemical conditions of the subsurface. Novel experimental methods for studying the kinetics of microbial Fe(III) oxide reduction and measuring growth rates of Fe(III) oxide-reducing bacteria will be developed. These new methodologies will be directly applicable to studies on subsurface contaminant transformations directly coupled to or influenced by microbial Fe(III) oxide reduction.
Date: March 16, 2001
Creator: Roden, Eric E.
Partner: UNT Libraries Government Documents Department

Advanced sulfur control concepts in hot gas desulfurization technology. Quarterly report, April 1--June 30, 1996

Description: Experimental effort during the past quarter was restricted to the fixed-bed reactor. Effort during April was devoted to the sulfidation and regeneration of cerium oxide. Sulfidation tests were plagued by over-sulfidation, i.e., the quantity of H{sub 2}S removed from the gas phase exceeded the stoichiometric amount associated with the conversion of CeO{sub 2} to Ce{sub 2}O{sub 2}S. This was initially attributed to the formation of Ce{sub 2}S{sub 3} which was found to be thermodynamically possible in the highly reducing feed gas. However, the addition of steam to the feed gas to prevent Ce{sub 2}S{sub 3} formation did not eliminate the over-sulfidation problem. Later tests indicated that the apparent over-sulfidation was due to reaction between H{sub 2}S and the walls of the reaction vessel. Apparently the alonizing treatment to passivate the reactor walls was either ineffective at the reaction conditions or had deteriorated with use to the point that protection was no longer viable. Limited Ce{sub 2}O{sub 2}S regeneration results, although very qualitative, were quite favorable. In one regeneration test in an O{sub 2}-N{sub 2} atmosphere, no SO{sub 2} or H{sub 2}S were detected by the chromatograph in the regeneration product. Significant amounts of total sulfur were detected, and the test had to be terminated prematurely when elemental sulfur caused the product line leading to the chromatograph to plug. Experimental tests during May and June examined the regeneration of FeS as a function of temperature, gas feed composition, and gas flow rate. Complete regeneration was achieved with as much as 75% of the sulfur liberated in elemental form. Low regeneration temperature and large ratios of H{sub 2}O to O{sub 2} in the feed gas promote the formation of elemental sulfur. A number of changes in the reactor system were made during the quarter, including improvements to the sulfur condenser and filters ...
Date: May 1, 1997
Partner: UNT Libraries Government Documents Department

Advanced thermally stable jet fuels. Technical progress report, April 1993--June 1993

Description: The Penn State program in advanced thermally stable coal-based jet fuels has five broad objectives: (1) development of mechanisms of degradation and solids formation; (2) quantitative measurement of growth of sub-micrometer and micrometer-sized particles suspended in fuels during thermal stressing; (3) characterization of carbonaceous deposits by various instrumental and microscopic methods; (4) elucidation of the role of additives in retarding the formation of carbonaceous solids; and (5) assessment of the potential of production of high yields of cycloalkanes by direct liquefaction of coal. Some of our accomplishments and findings are: The product distribution and reaction mechanisms for pyrolysis of alkylcyclohexanes at 450{degree}C have been investigated in detail. In this report we present results of pyrolysis of cyclohexane and a variety of alkylcyclohexanes in nitrogen atmospheres, along with pseudo-first order rate constants, and possible reaction mechanisms for the origin of major pyrolysis products are presented. Addition of PX-21 activated carbon effectively stops the formation of carbonaceous solids on reactor walls during thermal stressing of JPTS. A review of physical and chemical interactions in supercritical fluids has been completed. Work has begun on thermal stability studies of a second generation of fuel additives, 1,2,3,4-tetrahydro-l-naphthol, 9,10-phenanthrenediol, phthalan, and 1,2-benzenedimethanol, and with careful selection of the feedstock, it is possible to achieve 85--95% conversion of coal to liquids, with 40--50% of the dichloromethane-soluble products being naphthalenes. (Further hydrogenation of the naphthalenes should produce the desired highly stable decalins.)
Date: October 1, 1993
Creator: Schobert, H. H.; Eser, S. & Song, C.
Partner: UNT Libraries Government Documents Department