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Analysis of the radical hydrogen transfer pathway for cleaving strong bonds in coal

Description: Hydrogen transfer processes involving radical intermediates are of key importance in the liquefaction of coal. While the primary function of donor solvents is to transfer H{lg_bullet} to coal-derived radicals that form when weak bonds are cleaved thermolytically, growing evidence suggests that the donor solvent can play a role in promoting cleavage of strong {alpha}-bonds. McMillen and Malhotra have explained the results in terms of a single-step mechanism referred to as radical H-transfer (RHT). Mechanistic kinetic models have been used to suggest the importance of RHT pathways in anthracene- and pyrene-based solvent systems. However, we question the reliability of these approaches because little experimental data exists to support the 16.5 kcal/mol intrinsic barriers they assume for RHT reactions. Unambiguous evidence for RHT is very difficult to obtain experimentally because at the temperatures required to activate the RHT reaction, a suite of multistep reactions can occur, which yield the same products, i.e. H-elimination from hydroaryl radicals followed by ipso addition. For this reason, we have sought to gain insight to barrier heights for RHT from theory. This paper reports our use of Marcus theory in combination with ab initio and semiempirical molecular orbital methods to show how the intrinsic barriers for RHT reactions depend on structural and thermodynamic properties of the reacting partners. In addition, reactions thought to be mediated by RHT are reexamined using mechanistic kinetic modeling (MKM) to determine the extent to which these reactions can be explained by conventional pathways.
Date: September 1, 1993
Creator: Autrey, S. T.; Camaioni, D. M.; Ferris, K. F. & Franz, J. A.
Partner: UNT Libraries Government Documents Department

Applied research and evaluation of process concepts for liquefaction and gasification of western coals. Final report

Description: Fourteen sections, including five subsections, of the final report covering work done between June 1, 1975 to July 31, 1980 on research programs in coal gasification and liquefaction have been entered individually into EDB and ERA. (LTN)
Date: September 1, 1980
Creator: Wiser, W. H.
Partner: UNT Libraries Government Documents Department

Binding of hydrocarbons and other extremely weak ligands to transition metal complexes that coordinate hydrogen: Investigation of cis-interactions and delocalized bonding involving sigma bonds

Description: This is the final report of a three-year Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). At the forefront of chemistry are efforts to catalytically transform the inert C-H bonds in alkanes to more useful products using metal compounds. The goal is to observe binding and cleavage of alkane C-H bonds on metals or to use related silane Si-H bonding as models, analogous to the discovery of hydrogen (H{sub 2}) binding to metals. Studies of these unique sigma complexes (M{hor_ellipsis}H-Y; Y{double_bond}H, Si, C) will aid in developing new catalysts or technologies relevant to DOE interest, e.g., new methods for tritium isotope separation. Several transition metals (Mo, W, Mn, and Pt) were found to reversibly bind and cleave H{sub 2}, silanes, and halocarbons. The first metal-SiH{sub 4} complexes, thus serving as a model for methane reactions. A second goal is to study the dynamics and energetics of H-Y bonds on metals by neutron scattering, and evidence for interactions between bound H-Y and nearby H atoms on metal complexes has been found.
Date: July 1, 1997
Creator: Kubas, G.J.; Eckert, J. & Luo, X.L.
Partner: UNT Libraries Government Documents Department

Catalytic conversion of polycyclic aromatic hydrocarbons: Mechanistic investigations of hydrogen transfer from an iron-based catalyst to alkylarenes

Description: Results of our model compound studies suggest that free radical hydrogen transfer pathways from the catalyst to the alkylarene are responsible for the scission of strong carbon-carbon bonds. There are two requisites for the observed selective bond scission. First is the stability of the ipso adduct precursor leading to displacement, the more stable the adduct the more probable bond scission. This explains why benzyl radical displacement > phenoxy radical displacement in benzyldiphenyl ether and explains why PhCH{sub 2}CH{sub 2}PhCH{sub 2} radical > naphthylmethyl radical from NMBB. Second, given equal ipso adduct precursor stabilities, e.g. methyldiphenylmethane, the stability of the departing radical determines the selectivity. this explains benzyl radical > methyl radical in the methylated diphenylmethanes and explains why {alpha}-hydroxyphenethyl radical > methyl radical in 1,2-ditolylethanol. We have assumed little physical interaction between the molecules and the catalytic surface and have been able to satisfactorily explain most of the observed selectivity. However, for NMBB we expect a higher selectivity for -A- bond scission relative to -B- bond scission, given the ca. 6 kcal/mol difference between the radical adduct formed by the hydrogen atom addition to 1-methylnaphthalene and p-xylene. It is possible that physical properties play a role in lowering the selectivity in -B- bond scission. Also, catalysts prepared by other methods may contain different activity sites and operate by different mechanisms.
Date: August 1, 1995
Creator: Autrey, T.; Linehan, J.C.; Camaioni, D.M.; Powers, T.R.; McMillan, E.F. & Franz, J.A.
Partner: UNT Libraries Government Documents Department

Chemical structures and reactivities of coal as an organic natural product

Description: Some chemical reactions involved in coal liquefaction have been studied using carbon 14 labelled compounds and nuclear magnetic resonance. On the basis of these studies it is concluded that the role of tetralin during coal conversion is (1) to act as a dispersion vehicle; (2) to supply hydrogen radicals, when needed, to trap coal radicals, and (3) in a very minor way to undergo intermolecular reaction with the coal through making and breaking of C--C (and possibly other) bonds. As a result of other experiments it is concluded that to the methods previously employed for breaking bonds in coal molecules and thereby lowering their molecular weights, must now be added the use of solvated-electrons for breaking -CH/sub 2/--CH/sub 2/- linkages. A possible mechanism for the cleavage of bibenzyl (used as a model compound for coal) is given. (LTN)
Date: January 1, 1979
Creator: Collins, C J; Hombach, H P; Benjamin, B M; Roark, W H; Maxwell, B & Raaen, V F
Partner: UNT Libraries Government Documents Department

Chemistry and catalysis in supercritical media

Description: This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The aim of this research is to explore the potential of supercritical fluids as reaction media for stoichiometric and catalytic chemical transformations in an effort to develop new, environmentally-friendly methods for chemical synthesis or processing. This approach offers the possibility of opening up substantially different chemical pathways, increasing selectivity while enhancing reaction rates, facilitating downstream separations and mitigating the need for hazardous solvents. The authors describe investigations into a number of catalytic processes for which carbon dioxide represents a viable solvent replacement. In several cases they have observed significant enhancements in selectivity and/or reactivity relative to conventional organic solvents. They have investigated the following catalytic processes: (a) selective oxidation including dihydroxylation and epoxidation, (b) asymmetric hydrogenation and hydrogen transfer reduction, (c) Lewis acid catalyzed acylation and alkylation, and (c) coupling of amines with carbon dioxide to make isocyanates.
Date: July 1, 1997
Creator: Tumas, W.; Morgenstern, D. & Feng, S.
Partner: UNT Libraries Government Documents Department

Chemistry and morphology of coal liquefaction. Annual report, October 1, 1979-September 30, 1980

Description: The present annual report summarizes quarterly reports and includes work performed during the last quarter of fiscal 1980. The first year of this project has just been completed and much of the time and effort has been concentrated on equipment building, assembling, testing, and on staffing. This, of course, has been more true in the areas of work with spectroscopic and high pressure equipment than in organic chemical reactions. More experimental results are therefore reported in the areas of hydrogen transfer mechanisms and catalysis and organo-metallic chemistry. A few of the significant results in these and other areas are the evidence for catalysis in hydrogen transfer from tetralin; a novel and possibly very important new synthesis of alkyl aromatics from benzene, carbon monoxide, and hydrogen; the study of coals in the transmission electron microscope identifying coal macerals, minerals and metals, and leading to the possibility of observing location of and catalytic influences on pyrolysis and hydrogenation at elevated temperatures; the finding that scales formed on deactivated cobalt-molybdena-alumina-hydrogenation catalysts contain not only metals from the liquid feedstocks, but also molybdenum sulfide which must derive from migration from the catalyst interior to and beyond the surface. Insights gained in mechanisms of pyrolysis, hydrogenation, hydrogen transfer, and indirect liquefaction of coal promise to lead to improving technology by defining problem areas and showing routes to by-pass problems.
Date: September 1, 1980
Creator: Heinemann, H.
Partner: UNT Libraries Government Documents Department

Chemistry of coal model compounds: cleavage of aliphatic bridges between aromatic nuclei catalyzed by Lewis acids. [M. S. thesis]

Description: The condensed polynuclear aromatic clusters of coal are believed to be linked principally by straight-chain aliphatic bridges varying from 0 to 4 carbon atoms in length and the cleavage of these linkages is expected to be an important step in the coal liquefaction process. This study focuses on the means by which Lewis acid catalysts, specifically AlCl/sub 3/ and ZnCl/sub 2/, promote the cleavage of these linkages. To facilitate product identification and interpretation of reaction mechanisms, organic compounds which model the aliphatic bridges were used on substrates. All experiments were performed in a magnetically stirred autoclave under either an H/sub 2/ or N/sub 2/ atmosphere at elevated pressure to determine the role of H/sub 2/. Reaction temperatures ranging from 200 to 350/sup 0/C were used to avoid the complication of pyrolysis reactions. Reaction products were identified with the aid of gas chromatography/mass spectrometry, and quantitative product yields were determined by gas chromatography. Experiments with AlCl/sub 3/ and the substrates containing two phenyl rings linked by 0 to 4 carbon atoms showed that AlCl/sub 3/ catalyzed cleavage of all the aliphatic bridges. ZnCl/sub 2/ was totally inactive in cleaving the alkyl bridges in these compounds. Substitution of a phenyl group by a hydroxyphenyl or a naphthyl group in the model compounds promoted the cleavage of aliphatic linkages in the presence of AlCl/sub 3/. In contrast to reactions with the diphenylalkanes, ZnCl/sub 2/ was also found to catalyze the cleavage of these compounds. Plausible reaction mechanisms are proposed which explain the experimental results. The role of gaseous H/sub 2/ in these mechanisms was also investigated.
Date: April 1, 1978
Creator: Taylor, N.D.
Partner: UNT Libraries Government Documents Department

Coal-derived promoters for the liquefaction of Illinois coal

Description: The objective of this program is to investigate the use of liquids derived from coal either by mild gasification or supercritical extraction (SCE) to promote direct liquefaction of Illinois coal. Some organic sulfur-, nitrogen-, and oxygen-containing compounds have been found to enhance liquefaction reactions. The use of Illinois coal to produce liquid fractions rich in these types of compounds could increase the rates of liquefaction reactions, thus improving the process economics. An integrated process combining direct liquefaction with mild gasification or SCE of coal is being developed by IGT. The approach taken in this two-year program is to use recently developed molecular probe techniques to assess the reactivity of three coal-derived liquids with respect to (A) hydrogen transfer rate, (B) carbon-carbon bond cleavage rate, (C) free radical flux, and (D) hydrocracking activity. Sample liquids from Illinois Basin Coal IBC-106 are prepared by three methods: mild gasification in an isothermal free-fall reactor (IFFR), steam treatment followed by mild gasification in a fixed-bed reactor (ST/FBR), and SCE using toluene in a batch autoclave. During the first year of the program, the IFFR and ST/FBR coal liquids were produced and characterized, and the IFFR liquid was assessed by the four molecular-probe methods. During the first quarter of the second year, reactivity testing and data analysis on the ST/FBR coal liquid was completed. For the ST/FBR liquid, hydrogen transfer rate showed a mean increase of 7%, C-C bond cleavage selectivity increased by 27%, free radical flux increased 101%, and data indicated a 227% increase in hydrocracking activity. 12 refs., 5 figs., 7 tabs.
Date: January 1, 1991
Creator: Carty, R.H.
Partner: UNT Libraries Government Documents Department

Coal-derived promoters for the liquefaction of Illinois coal. Final technical report, September 1, 1991--August 31, 1992

Description: The objective of this program was to investigate the use of liquids derived from coal either by mild gasification or supercritical extraction (SCE) to promote direct liquefaction of Illinois coal. In this two-year program recently developed molecular probe techniques were used to assess the activity of three coal-derived liquids with respect to accelerating (A) hydrogen transfer, (B) carbon-carbon bond cleavage, (C) free radical flux, and (D) hydrocracking activity. Three sample liquids were prepared from IBC-106 coal by: mild gasification in an isothermal free-fall reactor (IFFR), steam treatment/mild gasification in a fixed-bed reactor (ST/FBR), and SCE using toluene. For comparison, tests were also performed on a Wilsonville recycle solvent (RS) and on benzyl phenyl sulfide (BPS), a ``benchmark`` promoter. Sample/blank pairs were tested at 400--425{degrees}C in laboratory microreactors, and effectiveness was based on the increase in extent of a key reaction for each sample containing coal liquid, compared to its blank. In general, the IFFR liquid was the most effective liquid for promoting hydrogen transfer (+21%) and free radical flux (+107%), while the SCE liquid was the most effective promoter of C-C bond cleavage selectivity (+119%) and hydrocracking (+359%). The ST/FBR liquid was slightly less effective than the IFFR liquid in all categories. BPS was used primarily to validate the adequacy of the methods.
Date: December 31, 1992
Creator: Carty, R. H. & Knight, R. A.
Partner: UNT Libraries Government Documents Department

Coal-derived promoters for the liquefaction of Illinois coal. Technical report, September 1, 1991--November 30, 1991

Description: The objective of this program is to investigate the use of liquids derived from coal either by mild gasification or supercritical extraction (SCE) to promote direct liquefaction of Illinois coal. Some organic sulfur-, nitrogen-, and oxygen-containing compounds have been found to enhance liquefaction reactions. The use of Illinois coal to produce liquid fractions rich in these types of compounds could increase the rates of liquefaction reactions, thus improving the process economics. An integrated process combining direct liquefaction with mild gasification or SCE of coal is being developed by IGT. The approach taken in this two-year program is to use recently developed molecular probe techniques to assess the reactivity of three coal-derived liquids with respect to (A) hydrogen transfer rate, (B) carbon-carbon bond cleavage rate, (C) free radical flux, and (D) hydrocracking activity. Sample liquids from Illinois Basin Coal IBC-106 are prepared by three methods: mild gasification in an isothermal free-fall reactor (IFFR), steam treatment followed by mild gasification in a fixed-bed reactor (ST/FBR), and SCE using toluene in a batch autoclave. During the first year of the program, the IFFR and ST/FBR coal liquids were produced and characterized, and the IFFR liquid was assessed by the four molecular-probe methods. During the first quarter of the second year, reactivity testing and data analysis on the ST/FBR coal liquid was completed. For the ST/FBR liquid, hydrogen transfer rate showed a mean increase of 7%, C-C bond cleavage selectivity increased by 27%, free radical flux increased 101%, and data indicated a 227% increase in hydrocracking activity. 12 refs., 5 figs., 7 tabs.
Date: December 31, 1991
Creator: Carty, R. H.
Partner: UNT Libraries Government Documents Department

Coprocessing through fundamental and mechanistic studies in hydrogen transfer and catalysis. Quarterly report, December 27, 1991--March 27, 1992

Description: The research conducted this quarter evaluated hydrogen transfer from resids reduced using the Birch reduction method and their corresponding parent resid to an aromatic acceptor, anthracene (ANT). The reactions involved thermal and catalytic reactions using sulfur introduced as thiophenol. This catalyst has been shown by Rudnick to affect the hydrogen transfer from cycloalkane to aromatics/or coal. The purpose of this current study was to evaluate the efficacy of hydrogen transfer from the hydrogen-enriched reduced resid to an aromatic species and to compare that to the hydrogen transfer from the original resid. The analyses performed to evaluate hydrogen transfer were the determination of product slates from the hydrogenation of ANT and the fractionation of the resid into solubility fractions after reaction with ANT. The amount of coal conversion to THF solubles was higher in the coprocessing reactions with the reduced resids compared to the reactions with the corresponding untreated resid. The reduction of the resids by the Birch method increased the hydrogen donating ability of the resid to the same level as that obtained with the introduction of isotetralin (ISO) to the original resid. The ISO was introduced at a level of 0.5 wt % donable hydrogen. Both the original resids and the resids reduced by the Birch method were reacted in the presence of an aromatic species, anthracene (ANT). These reactions were performed under both nitrogen and hydrogen atmospheres at a pressure of 1250 psig introduced at ambient temperature. The reactions were performed both thermally and catalytically at 380{degree}C for 30 minutes. The catalyst used was thiophenol which is the same catalyst as has been used in the previously reported model compound studies involving hydrogen transfer from cycloalkanes to aromatics.
Date: December 31, 1992
Creator: Curtis, C. W.
Partner: UNT Libraries Government Documents Department

Coprocessing through fundamental and mechanistic studies in hydrogen transfer and catalysis. Quarterly report, March 28, 1992--June 30, 1992

Description: Hydrogen transfer from naphthenes to aromatics, coal, resid, and coal plus resid has been investigated at 430{degree}C in a N{sub 2} atmosphere. The reaction of perhydropyrene (PHP) with anthracene (ANT) resulted in the formation of pyrene (PYR) and dihydroanthracene. The weight percents of the products formed varied according to the initial ratio of ANT/PHP with a minimum appearing at a 2:1 weight ratio. Increased reaction times and high ANT/PHP ratios also yielded tetrahydroanthracene (THA). Reactions of Illinois No. 6 coal from the Argonne Premium Coal Sample Bank with PHP, ANT, and PYR resulted in higher coal conversion with PHP and lower with ANT and PYR. Reactions of PHP with resid resulted in less retrogressive reactions occurring in the resid than with either PYR or ANT. Apparent hydrogen transfer from coal or resid to ANT and PYR was observed. Combining PHP with ANT or PYR with coal, resid or coal plus resid yielded higher conversions and less retrogressive reactions. Hydrogen transfer occurred from PHP to ANT or PYR and to the coal and resid as evinced by the increased conversion.
Date: December 31, 1992
Creator: Curtis, C. W.
Partner: UNT Libraries Government Documents Department

Coprocessing through fundamental and mechanistic studies in hydrogen transfer and catalysis. Quarterly report, September 26, 1991--December 26, 1991

Description: The research conducted during this quarter evaluated hydrogen transfer from hydroaromatics and cyclic olefins to aromatics under thermal and catalytic conditions. The reactions under study involved thermal reactions of a cyclic olefin, isotetralin (ISO), with aromatics, anthracene (ANT) and pyrene (PYR). These reactions completed a set of experiments with hydrogen-rich species and aromatics previously reported that included cycloalkanes of perhydropyrene (PHP) and perhydroanthracene (PHA), hydroaromatic donors, tetralin (TET) and dihydroanthracene (DHA), cyclic olefins, hexahydroanthracene (HHA) and ISO, and aromatics, PYR and ANT. Catalytic reactions performed this quarter used a sulfur catalyst that had been shown by Rudnick to affect the hydrogen transfer from cycloalkanes to aromatics and/or coal. Rudnick investigated the dehydrogenation of alicyclic compounds converting them to the corresponding aromatic compounds in a process in which the alicyclic compounds served as hydrogen donors. Thiophenol and thiol were effective catalysts and helped promote the conversion of alicyclic compounds to aromatic compounds. The research performed in our laboratory focused on evaluating the effect of a sulfur catalyst on the transfer of hydrogen from cycloalkanes like perhydropyrene (PHP) to aromatics like anthracene under catalytic conditions. The catalyst used in this study was sulfur generated from thiophenol present at a concentration level of 2000 ppm of sulfur. The reactions were performed under two temperature conditions, 380 and 440{degrees}C; both thermal and catalytic reactions were performed for comparison. In addition, the individual cycloalkane and aromatic compounds were reacted under these conditions so that a direct comparison of the effect of temperature and of catalyst on the reaction products formed could be made.
Date: December 31, 1991
Creator: Curtis, C. W.
Partner: UNT Libraries Government Documents Department

Development of laser-ion beam photodissociation methods. Progress report, December 1991--November 1994

Description: This project emphasizes the development of laser mass spectrometry methods for fundamental and applied studies of gas-phase processes. The current studies are focussed on the photochemistry and photophysics of peptides and other biological molecules. Matrix-assisted laser desorption ionization (MALDI) is used to produce ions that are subsequently subjected to photoexcitation and dissociation. MALDI is still very much in the developmental stages, thus a significant portion of this research focusses on fundamental studies of the MALDI ion formation/energy transfer process. The authors view is that excited state H+-transfer reactions play an important role in MALDI, consequently a significant portion of their research activities are focussed on such studies. Fundamental studies of the role of the matrix in MALDI are an integral part of this project. A new MALDI experiment, MALDI of aerosol particles generated from solutions, has been demonstrated and new developmental research in this area is planned. The authors are also actively pursuing a research program on gas-phase H+-transfer processes that mimic the MALDI process. In addition, they are developing photodissociation experiments, based on tandem time-of-flight mass spectrometers, for structural characterization of complex organic molecules. The photodissociation studies use MALDI as the ionization method. These research areas involve the development of new instrumentation, new instrument methodologies, and data processing.
Date: June 1, 1994
Creator: Russell, D. H.
Partner: UNT Libraries Government Documents Department

Development of Novel Electrode Materials for the Electrocatalysis of Oxygen-Transfer and Hydrogen-Transfer Reactions

Description: Throughout this thesis, the fundamental aspects involved in the electrocatalysis of anodic O-transfer reactions and cathodic H-transfer reactions have been studied. The investigation into anodic O-transfer reactions at undoped and Fe(III)[doped MnO{sub 2} films] revealed that MnO{sub 2} film electrodes prepared by a cycling voltammetry deposition show improved response for DMSO oxidation at the film electrodes vs. the Au substrate. Doping of the MnO{sub 2} films with Fe(III) further enhanced electrode activity. Reasons for this increase are believed to involve the adsorption of DMSO by the Fe(III) sites. The investigation into anodic O-transfer reactions at undoped and Fe(III)-doped RuO{sub 2} films showed that the Fe(III)-doped RuO{sub 2}-film electrodes are applicable for anodic detection of sulfur compounds. The Fe(III) sites in the Fe-RuO{sub 2} films are speculated to act as adsorption sites for the sulfur species while the Ru(IV) sites function for anodic discharge of H{sub 2}O to generate the adsorbed OH species. The investigation into cathodic H-transfer reactions, specifically nitrate reduction, at various pure metals and their alloys demonstrated that the incorporation of metals into alloy materials can create a material that exhibits bifunctional properties for the various steps involved in the overall nitrate reduction reaction. The Sb{sub 10}Sn{sub 20}Ti{sub 70}, Cu{sub 63}Ni{sub 37} and Cu{sub 25}Ni{sub 75} alloy electrodes exhibited improved activity for nitrate reduction as compared to their pure component metals. The Cu{sub 63}Ni{sub 37} alloy displayed the highest activity for nitrate reduction. The final investigation was a detailed study of the electrocatalytic activity of cathodic H-transfer reactions (nitrate reduction) at various compositions of Cu-Ni alloy electrodes. Voltammetric response for NO{sub 3}{sup -} at the Cu-Ni alloy electrode is superior to the response at the pure Cu and Ni electrodes. This is explained on the basis of the synergism of the two different metal sites at these binary ...
Date: August 27, 2002
Creator: Simpson, Brett Kimball
Partner: UNT Libraries Government Documents Department

Diosmacycloalkanes as models for the formation of hydrocarbons from surface methylenes

Description: We are making progress on our investigation of the mechanism of olefin exchange with Os{sub 2}(C{sub 2}H{sub 4})(CO){sub 8}. We are probing this system by kinetic study of the reaction of Os{sub 2}(C{sub 2}H{sub 4})(CO){sub 8} with butyl acrylate (BA) under various pressures of ethylene.
Date: May 1, 1992
Creator: Norton, J.R.
Partner: UNT Libraries Government Documents Department

Diosmacycloalkanes as models for the formation of hydrocarbons from surface methylenes. Progress report, November 1, 1991--October 31, 1992

Description: We are making progress on our investigation of the mechanism of olefin exchange with Os{sub 2}(C{sub 2}H{sub 4})(CO){sub 8}. We are probing this system by kinetic study of the reaction of Os{sub 2}(C{sub 2}H{sub 4})(CO){sub 8} with butyl acrylate (BA) under various pressures of ethylene.
Date: May 1, 1992
Creator: Norton, J. R.
Partner: UNT Libraries Government Documents Department

DOE Laboratory Catalysis Research Symposium - Abstracts

Description: The conference consisted of two sessions with the following subtopics: (1) Heterogeneous Session: Novel Catalytic Materials; Photocatalysis; Novel Processing Conditions; Metals and Sulfides; Nuclear Magnetic Resonance; Metal Oxides and Partial Oxidation; Electrocatalysis; and Automotive Catalysis. (2) Homogeneous Catalysis: H-Transfer and Alkane Functionalization; Biocatalysis; Oxidation and Photocatalysis; and Novel Medical, Methods, and Catalyzed Reactions.
Date: February 1, 1999
Creator: Dunham, T.
Partner: UNT Libraries Government Documents Department

The effect of selective absorption on coal conversion. [2-t-butyltetralin]

Description: Scope of work: (1) Importance of hydrogen donors in the coal, prepare highly pure 2-t-butyltetralin. Study the conversion of Argonne coals in tetralin and 2-t-butyltetralin and compare the following: conversion to soluble products, product molecular weight distributions, and product structure. Hydrogen donated by both solvents will be measured by gas chromatography and the same technique will be used to establish the amount of dealkylation of 2-t-butyltetralin. Reactions will be run at several temperatures for varying times. (2) Selective recycle solvent absorption. Argonne coals will be exposed to recycle solvents at several elevated temperatures and the non-absorbed portion of the solvent will be separated by filtration. The composition of the whole oil and non-absorbed portion will be analyzed spectroscopically and chromatographically and compared to determine the composition of the recycle oil dissolved in the coal. 6 figs., 1 tab.
Date: July 1, 1991
Creator: Larsen, J.W. & Lazarov, L.
Partner: UNT Libraries Government Documents Department

The effect of selective solvent absorption on coal conversion. Final technical report

Description: Using a pair of different recycle oils from Wilsonville and {sup 1}H NMR, {sup 13}C NMR, gel permeation (GPC) chromatography, high pressure liquid chromatography (HPLC), and elemental analysis, no significant differences were observed between the composition of the recycle oil and that portion of the oil not absorbed by the coal. For these complex mixtures, coals are not selective absorbants. Since most of the heteroatoms responsible for most of the specific interactions have been removed by hydrogenolyses, this is perhaps not surprising. To address the issue of the role of hydrogen bond donors in the reused as hydrogen donor coal, tetralin and 2-t-butyltetralin were used as hydrogen donor solvents. This work is reported in detail in Section 2. The basic idea is that the presence of the t-butyl group on the aromatic ring will hinder or block diffusion of the hydrogen donor into the coal resulting in lower conversions and less hydrogen transferred with 2-t-butyltetralin than with tetralin. Observed was identical amounts of hydrogen transfer and nearly identical conversions to pyridine solubles for both hydrogen donors. Diffusion of hydrogen donors into the coal does not seem to play a significant role in coal conversion. Finally, in Section 3 is discussed the unfavorable impact on conversion of the structural rearrangements which occur when Illinois No. 6 coal is swollen with a solvent. We believe this rearrangement results in a more strongly associated solid leading to the diminution of coal reactions. Hydrogen donor diffusion does not seem to be a major factor in coal conversion while the structural rearrangement does. Both areas warrant further exploration.
Date: November 1, 1993
Creator: Larsen, J. W.
Partner: UNT Libraries Government Documents Department

Effect of tetralin on polymer degradation in solution. [Quarterly report, January--March 1995]

Description: The effect of a hydrogen-donor solvent (tetralin) on the thermal degradation of poly(styrene-allyl alcohol) in solution was investigated in a steady-state tubular flow reactor at 1000 psig (6.8 MPa), at various tetralin concentrations (0--50%), polymer concentrations (1--4 g/L), and temperatures (130--200 C). The molecular weight distributions of the effluent at each condition were examined as a function of residence time by gel permeation chromatography. In the presence of tetralin, the polymer degrades by deploymerization to specific low molecular weight compounds and by random chain scission. No reaction was observed in the solvent 1-butanol in the absence of tetralin. The experimental data were interpreted with a rate expression first-order in polymer concentration based on continuous mixture kinetics, and rate coefficients were determined for the specific and random degradation processes. Activation energies were in the range of 5--10 kcal/mol for specific degradation and 33 kcal/mol for the random degradation process. A plot of rate coefficients versus tetralin concentration indicates a first-order rate at low tetralin concentrations and a zero-order dependence at high tetralin concentrations.
Date: April 26, 1995
Creator: Madras, G.; Smith, J.M. & McCoy, B.J.
Partner: UNT Libraries Government Documents Department

Effect of tetralin on the degradation of polymer in solution

Description: The effect of a hydrogen-donor solvent tetralin on thermal degradation of poly(styrene-allyl alcohol) in liquid solution was investigated in a steady-state tubular flow reactor at 1000 psig at various tetralin concentrations, polymer concentrations, and temperatures. The experimental data were interpreted with continuous- mixture kinetics, and rate coefficients determined for the specific and random degradation processes.
Date: December 31, 1995
Creator: Madras, G.; Smith, J.M. & McCoy, B.J.
Partner: UNT Libraries Government Documents Department