ACERC
Abstracts - 1986-1988 |
ACERC
Abstracts - 1986-1988 |
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Thrust Area 1: Fuel Structure and Reaction Mechanisms |
Huffman, G.P.; Huggins,
F.E.; Shah, N.; Bhattacharyya, D.; Pugmire, R.J.; Davis, B.H.; Lytle, F.W. and
Greegor, R.B.
Processing and Utilization of High Sulfur Coals II, 3-12, 1987. 10 pgs.
Funded by US Department of Energy.
A complete description of the microstructure and molecular state of sulfur in coal can be achieved by combining several experimental techniques. For quantitative analysis of pyrite and its transformation products resulting from oxidative or reductive processes, Fe Mossbauer spectroscopy appears to be the best technique available. Computer-controlled scanning electron microscopy (CCSEM) provides an excellent method of measuring the particle size distributions of pyrite and its transformation products, information that is critical in physical and biological cleaning processes. Finally, it is shown that X-ray absorption fine structure spectroscopy, usually referred to as EXAFS spectroscopy, is capable of determining the atomic structure of organic or other forms of sulfur in coal and coal derivatives. EXAFS data will be presented on organic sulfur in standard compounds, maceral separates, and microbially desulfurized coal.
Taghizadeh, K.; Davis, B.H.;
Windig, W. and Meuzelaar, H.L.C.
Fossil Fuel Analysis by Mass Spectrometry, 1988, T.A. Milne, (ed.), in
press. Funded by Commonwealth of Kentucky, Kentucky Energy Cabinet, US Department
of Energy and Consortium For Fossil Fuel Liquefaction Science.
Compositional changes of Coal-Derived Liquids (CDL's) during hydrotreatment on fixed bed catalysts can be investigated by Low Voltage (12 eV) MS in combination with multivariate analysis without chromatographic preseparation. Low voltage (12 eV) MS data were obtained and compared under two inlet conditions; MS inlet (1) at ambient temperatures and (2) preheated to about 200ºC. The major trend found in both data sets by Factor analysis was the hydrotreatment effect, namely hydroaromatic (hydrotreater product) vs. aromatic (hydrotreater feed) compounds. A second "time + temperature" trend which reflected the aging of the catalyst as well as the temperature of the hydrotreater reactor was only obtained under ambient inlet temperature conditions. Numerically extracted spectra along the second trend show that more low molecular weight components were found early in the process and also at lower temperatures, whereas more of the higher molecular weight components, primarily alkyl substituted polynuclear aromatics, were obtained later in the process at higher temperatures of the hydrotreater.
A supercritical fluid chromatographic system was constructed to provide separations and fraction collection on a semipreparative scale. Columns packed with silica materials of intermediate particle sizes (30-70 mm) were used to allow dynamic pressure programming with minimum pressure drop of the CO2 mobile phase along the length of the column. A variety of complex coal- and petroleum-derived polycyclic aromatic compound mixtures were fractionated according to the number of aromatic rings using columns packed with an NH2- modified stationary phase bonded on silica particles. The CO2 mobile phase was programmed with an alternating series of linear pressure ramps and isobaric intervals to effect even peak spacing and near base line resolution of compounds of differing ring number in a coal tar. A solvent refined coal heavy distillate and a crude oil were similarly fractionated. Effluents were monitored with an ultraviolet spectrophotometer at 254 nm and a flame ionization detector while fractions were collected in pressurized vessels for subsequent analysis by capillary gas chromatography. Sample capacities of up to 20 mg were possible with this system.
Nishioka, M.; Chang, H.-C.
K. and Lee, M.L.
Environ. Sci. Technol. 20, 1023-1027, 1986. 4 pgs. Funded by US Department
of Energy.
Coal-derived products and thermally cracked petroleum oils are highly aromatic in nature and contain polycyclic aromatic hydrocarbons (PAH) as major components. Although average descriptive parameters are usually obtained for such materials (i.e., distillation curve, molecular weight range, aromaticity, etc.), it is oftentimes very important to obtain detailed compositional and structural information.
Isomeric polycyclic aromatic hydrocarbons (PAH) with two to six rings in coal-derived products and in a carbon black were separated, identified, and quantified by using capillary column gas chromatography and gas chromatography-mass spectrometry. A newly synthesized smectic liquid-crystalline polysiloxane and a conventional polymethylsiloxane were utilized as stationary phases. Many previously difficult-to-separate isomeric PAH (i.e., methylphenanthrenes/methylanthracenes, triphenylene/chrysene, methylchrysenes, benzofluoranthenes, and pentaphene/benzo [b] chrysene) were identified. The relative abundances of the PAH in these samples were compared and correlated to the reaction conditions during their production. The relationship between abundance and structure for the identified PAH was also discussed.
Nishioka, M.; Lee, M.L.
and Castle, R.N.
Fuel, 65, 390-97, 1986. 7 pgs. Funded by US Department of Energy.
Sulphur is present in various forms in all crude fossil fuels. The organic sulphur compounds found in these materials have been categorized according to functionality; thio (-SH) disulphide (-S-S-) sulphide (-S-), and thiophene. The thiophenes are the major organosulphur compounds in shale oils, coal-derived liquids and heavy petroleum distillates. In thermally cracked oils and coal liquids, multi-ring polycyclic aromatic sulphur heterocycles (PASH) are especially abundant.
The sulphur content in coal and crude oil varies in the range 0.2-12-wt %. Sulphur-containing gases produced at fossil fuel combustion facilities are major contributors to air pollution. The detailed identification of heteroatom-containing polycyclic aromatic compounds, such as the PASH, in coal-derived products could provide important information relevant to coal structure.
Sulphur heterocyles in a coal tar and in a coal liquid vacuum residue were isolated by ligand exchange chromatography using PdCl2 on silica gel. Subsequent fractions were analyzed by capillary column gas chromatography and gas chromatography-mass spectrometry. Two new selective stationary phases (a smectic liquid-crystalline polysiloxane and a biphenyl polysiloxane), as well as a methylpolysiloxane, were used to resolve the numerous isomers. All major sulphur heterocyles with 3 - 6 rings were identified by comparison of retention times of mixture components with those of standard reference compounds. The structures and relative abundances of the major sulphur heterocyles were analogous to those of the major polycyclic aromatic hydrocarbons in the same or similar samples.
Germane, G.J.
SAE Fuels and Lubricants Transactions, 1, 876-878, 1986. 2 pgs. Funded
by Angus Chemical Company.
Automobile racing engine performance has historically progressed with and aided the development of automotive technology. Racing engine performance has been improved in various applications with specialized liquid fuels, such as nitroparaffins, alcohol (methanol) and certain hydrocarbons used in racing gasolines.
This paper presents physical and thermodynamic properties of commonly used racing fuels and selected additives, including nitrous oxide and hydrazine. Improving the antiknock properties of gasoline for racing purposes is also discussed. Engine operating characteristics and power output for each fuel are discussed in terms of appropriate fuel properties and engine parameters such as air/fuel ratio and compression ratio. Combustion of various fuels is discussed along with the effect of dissociation and heat loss of performance. Some experimental performance data are presented, and theoretical and practical considerations that affect fuel utilization are also discussed.
Jackson, W.P.; Markides,
K.E. and Lee, M.L.
J. High Resoln. Chromatogr./Chromatogr. Commun. 9, 213-217, 1986. 5 pgs.
Funded by Dow Chemical Company and Gas Research Institute.
One class of compounds which is particularly well-suited for analysis by capillary supercritical fluid chromatography (SFC) is the large, non-volatile polycyclic aromatic hydrocarbons (PAH). These aromatic compounds typically occur in very complex samples, particularly those samples derived from coal.
As is the case with any form of chromatography, sample introduction and detection must be optimized in capillary SFC to prevent a loss of resolution due to extra-column effects. Several modes of sample introduction into the SFC system have been reported. The most widely used and apparently most successful method appears to be valved, sample-loop liquid injection as is used in HPLC.
In this study, a sample introduction system for capillary supercritical fluid chromatography, which allows the dissolution of the sample in the supercritical mobile phase before being introduced into the column, was constructed and evaluated. Supercritical n-pentane was shown to solvate high-molecular-weight polycyclic aromatic compounds that could not be solvated using cyclic aromatic compounds that could not be solvated using typical liquid solvents. In addition, split injection of a supercritical fluid solution was bound to be more reproducible than split injections of a liquid solution. The potential of such an injection system was demonstrated, although further developments are needed in order to make the technique of practical utility.
Windig, W.; Chakravarty,
T.; Richards, J.M. and Meuzelaar, H.L.C.
Analytical Chemical Acta, 9, 205-2l8, 1986. 13 pgs. Funded by Army Research
Office and Hercules.
Multivariate analysis of time-resolved pyrolysis/mass spectrometric data is described. The approach is based on the variance diagram (VARDIA), a recently developed technique that quantifies the clustering of variables in two-dimensional factor analysis (sub)spaces in a rotational scanning procedure. A maximum in the VARDIA plot indicates a correlated behavior of the mass variables, indicating a common origin. This common origin is generally caused by a change in the concentration of a chemical component. With this information the "factor spectrum" and the scores of the component can be retrieved. For time-resolved serial data, consideration of the clustering behavior of the variables as a function of time is more appropriate than a rotational scanning procedure. Adaptation of the VARDIA for serial data, such as time-resolved data, is described. This approach has the advantage that all the factors can be used. It will be shown that the resolution of the obtained curve can be higher than the total ion current curve as a function of time. Examples will be given for time-resolved data of coal, rubber and wood samples.
West, W.R. and Lee, M.L.
Journal of High Resolution Chromatography and Chromatography Communications,
9, 161-167, 1986. 7 pgs. Funded by Coordinating Research Council.
A thermionic detector was evaluated for capillary supercritical fluid chromatography of polar nitro-containing polycyclic aromatic compounds (nitro-PAC). Three modes of detector operation were studied. The best performance was obtained using a nitro-selective mode of detection. Although linearity was confined to a narrow range for a given source current, the sensitivity was excellent; 20 pg injected for p-nitrophenol gave a signal-to-noise ratio of 3. Conventional thermionic detection also produced good sensitivity; however, serious baseline drift was observed at high operating temperatures using density programming. A third mode, flame thermionic detection, was not acceptable because of low sensitivity. A number of nitro-PAC were successfully chromatographed using density programming at 101ºC. Hydropxynitropyrenes, nitropyrene quinones, and 9-hydroxy-2-nitrofluorene, which could not be eluted in capillary gas chromatography, were successfully chromatographed here. Retention of these compounds increased sequentially on 50% n-octyl-, 5% phenyl-, and 25% biphenyl polysilozane stationary phases, respectively. Stationary phase interactions appeared to be more a function of the polar functional groups on the aromatic rings than of the hydrocarbon character of the compounds. Solute solubility in the mobile phase and volatility were additional factors contributing to the elution of these molecules. Finally, these results were used to identify a number of nitro-PAC in a polar subfraction of a diesel particulate extract.
Sethi, N.K.; Grant, D.M.
and Pugmire, R.J.
Journal of Magnetic Resonance, 71, 476-479, 1987. 4 pgs. Funded by US
Department of Energy.
Spinning the sample at angles other than the magic angle is shown to have interesting applications for obtaining chemical shielding anisotropies for systems where severe overlapping makes the analysis of static powder pattern either cumbersome or impossible. Results for 1,3,5-trimethoxybenzene and p-dimethoxybenzene are in excellent agreement with those obtained via single-crystal studies.
Wells, W.F. and Smoot, L.D.
Combustion and Flame, 68, 81-83, 1987. 3 pgs. Funded by the Pittsburgh
Energy Technology Center.
Studies of the reactivity of coal chars are limited in both scope and number, particularly for process chars from US coals at high temperatures. Pioneering work in coal char combustion was conducted by Field (1). He studied the effects on particle size on reactivity for a laboratory char prepared from a British coal. Smith (2) reviewed the extensive work performed by himself and coworkers. They have investigated the effects of size variation on reactivity for a wide variety of Australian coals. The work on US chars is more limited. Among those that have been reported is the study of Goetz et al. (3) for chars derived from Illinois bituminous, Wyoming subbituminous, and Texas lignite coals. The particle size distribution for these chars was very wide (-200 +400 mesh). Chen et al. (4) studied the ignition temperature for several process coal chars which were derived from US coals, one of which was also examined by this study (FMS COED), but they did not conduct high temperature reactivity measurements. Gomez and Vastola (5) studied char from a Wyoming subbituminous coal with particle sizes from 850 to 1000 mm. Due to the large particle size the reaction mechanism could be different than that for much smaller particles (6). Young et al. (7) have presented preliminary data for a North Dakota lignite char, but have not presented any data concerning effect of particle size on reactivity. This brief communication presents new results on the dependence of char reactivity at high temperature on particle diameter for five process chars and interprets these data and companion results of a previous study (8) as they relate to reaction zone.
Crelling, J.C.; Pugmire,
R.J.; Meuzelaar, H.L.C.; McClennen, W.H. and Karas, J.
Submitted to Coal Geology, 1987. Funded by ACERC (National Science Foundation
and Associates and Affiliates).
Although the maceral resinite occurs in most US coals, it is particularly abundant in the coal seams of central Utah. The high resinite content of the coals of central Utah has long been known and commercially exploited but little work has been reported on the elucidation of the chemical composition of this material. Indeed, there is little such information on the resinite of any coal. The resinite occurrences have been described by Spieker and Baker, Tomlinson, Theissen and Sprunk, and Buranek and Crawford. An unusual feature of the coal seams in Utah is that most of the resinite occurs in a secondary manner as cleat, fissure, or other void fillings. Similar occurrences have been reported in British coals by Jones and Murchison and Murchison and Jones. They concluded that the metamorphic effects of coalification in the bituminous rank range caused the resinite to be gently mobilized without the more severe manifestations of metamorphism such as vesiculation or increased refectance. Teichmuller, observed that secondary resinite (exudatinite) seemed to be exuded from other coal macerals during coalification in the lower bituminous range.
Entrained gasification tests with a Utah high-volatile bituminous coal were performed at atmospheric pressure to assess the influence of particle size, coal feed rate, steam-coal ratio and oxygen-coal ratio. Independent argon-carbon balanced and ash balance methods were used to evaluate carbon conversion, with good agreement observed between the methods. A higher O2-coal ratio for finer particles increased the carbon conversion. Carbon conversion and hydrogen formation showed little dependence on the amount of steam injected in the secondary stream, indicating minimal steam-coal reaction. When the coal feed rate was varied from 23 to 27 kgh-1, a small increase in carbon conversion was observed with no significant change in the gas composition.
Solum, M.S. and Pugmire,
R.J.
Energy & Fuels, 448, 1987. 1 pg. Funded by ACERC (National Science Foundation
and Associates and Affiliates).
Axelson has written a valuable book for those interested in the field of NMR spectroscopy of fossil fuels and polymers. This book is best suited for those who have had some experience with solid-state NMR but not perhaps with application to fossil fuels. The Introduction and Appendix A give a brief description of some of the more common fossil fuel terminology and standard analysis techniques, which was quite helpful. In Chapter 1 a very brief description of line broadening mechanisms in solids is given and cross-polarization and magic angle spinning are introduced. The different carbon and proton relaxation parameters and the pulse sequenced used to measure them are discussed in Chapter 2. This chapter is excellent as a quick reference for help in setting up these experiments. Examples of relaxation times of model organic compounds, polymers, and fossil fuels are given, and their relationship to quantitative analysis of fossil fuels is discussed in Chapter 3. Chapter 4 deals with the removal of instrumental artifacts from the NMR spectrum including spinning sideband suppression methods. Also discussed in this chapter are the causes of many instrumental problems. This chapter is recommended to those who are not experienced in solid-state NMR but are initiating these types of experiments. Line-broadening mechanisms in solid-state NMR arising from both natural and instrumental factors are discussed in Chapter 5. Chapter 6, dealing with resolution enhancement, contains a good section on the dipolar-dephasing experiment and the structural parameters that may be obtained from this experiment. Some less common and more selectively useful NMR pulse sequences are also treated. Chapter 7 provides the fa value for a variety of fossil fuels.
While the treatment of many topics in this book is at an overview level, there is a large selection of references at the end of each chapter where a more in-depth discussion of the topics may be found. This book is recommended as a reference for those interested in solid-state NMR in general and, in particular, in application to coals. The book provides an excellent overview of the work published prior to the appearance of this treatise. For the beginner, the fundamentals of solid NMR techniques are not well developed and one should consult other works in order to obtain the necessary basic foundation. In the main, Axelson has provided a very useful reference for those who work in the fossil energy field.
Windig, W.; McClennen, W.H.
and Meuzelaar, H.L.C.
Chemometrics and Intelligent Laboratory Systems, 1, 151-165, 1987. 14
pgs. Funded by US Air Force, Army Research Office and BF Goodrich.
Factor analysis of the "correlation around the origin" matrix as applied to (pyrolysis-) mass spectrometry data is described. This approach makes it possible to calculate the spectra of pure components from a data set of mixtures in which these pure components are not present. Further, the fractional concentrations of the components in the mixtures can be calculated. Examples are given of results obtained on data sets consisting of (pyrolysis) mass spectra from biopolymers, jet fuels and technical polymers.
Meuzelaar, H.L.C.; Hoesterey,
B.L.; Windig, W. and Hill, G.R.
Fuel Processing Technology, l5, 59-70, 1987. 11 pgs. Funded by Electric
Power Research Institute and US Department of Energy.
Report on the use of Curie-point pyrolysis MS as a microscale modeling technique for the conversion of four Western US coals into pyrolytic tars and for the production of SO2 during the combustion of l6 Gulf Province lignites.
Windig, W.; Jakab, E.; Richards,
J.M. and Meuzelaar, H.L.C.
Anal. Chem. 59, 317-323, 1987. 6 pgs. Funded by The Center for Micro
Analysis.
A self-modeling technique for curve resolution of overlapping processes is presented. This method uses factor analysis combined with the variance diagram technique to resolve the total ion current (TIC) curves from time-resolved pyrolysis mass spectrometry data into chemical component curves and their spectra. Examples are presented of time-resolved pyrolysis mass spectrometry data from a biopolymer mixture (deoxyribonucleic acid, bovine serum albumin, and glycogen), Douglas fir wood, and a rubber copolymer. The analysis of each of these samples resulted in the resolution of the TIC's into chemical component curves. The spectra corresponding to the chemical components were clearly similar to reference spectra.
Metcalf, G.S.; Windig, W.;
Gill, G.R. and Meuzelaar, H.L.C.
International Journal of Coal Geology, 7, 245-268, 1987. 23 pgs. Funded
by US Department of Energy, Phillips Petroleum, and State of Utah.
Sixteen Texas (Gulf Province) lignite samples and six Montana and Wyoming (Northern Plains province) lignite samples were obtained from the Penn state coal sample collection and analyzed in triplicate by pyrolysis mass spectrometrey (Py-MS) using Curie-point pyrolysis (equilibrium temp. 610ºC) in combination with low voltage (12 eV) electron ionization. The spectra obtained were evaluated by means of factor analysis, followed by discriminant analysis using only factors with eigenvalue >= 1 and regarding each set of triplicate spectra as a separate category. The discriminant analysis results showed a definite separation between lignites from the two provinces as well as some clustering of samples from the same seam field or region. Six additional lignite samples obtained from an independent source and representing other regions of the Gulf province were found to cluster with the Texas lignite samples when treated as "unknowns" in the discriminant analysis procedure.
Chemical interpretation of the spectral differences underlying the clustering behavior of the lignite samples in the discriminant analysis procedure was attempted using a newly developed, unsupervised numerical extraction method for chemical components in complex spectra. This procedure the Variance Diagram (VARDIA) technique revealed the presence of six major chemical component axes. Examination of the spectral patterns corresponding to these component axes showed a softwood lignin-like component (high in Northern Plains lignites) and an aliphatic (algal?) hydrocarbon component (high in Gulf lignites) to be primarily responsible for the differences between the two provinces. In addition, two biomarker patterns, namely a terpenoid resin-like component and an unknown component, were shown to be highly characteristic for the Northern Plains and Gulf Province lignites respectively. Two other component axes were found to consist largely of sulfur-containing ion series, one of which appeared to represent an obvious marine influence on the South Texas region of the Gulf province.
Furthermore, a set of seventeen conventional coal parameters, including petrographic, ultimate and proximate analysis data as well as sulfur content, calorific value and vitrinite reflectance, obtained from the Penn State coal data bank on all twenty-two lignite samples, was also submitted to factor analysis. Comparison of the scores of the first two factors from this set with the scores of the first two discriminant functions of the Py-MS data set revealed an overall similarity in clustering behavior of the lignite samples from the two provinces. Subsequently, canonical variate analysis was used to rotate both the conventional and Py-MS data sets to a common set of vectors describing and correlating ("overlapping") portions of both data sets. Examination of the first two pairs of canonical variate functions revealed strong correlations between the conventional data and the Py-MS data, e.g., with regard to aliphatic vs. aromatic or hydrocarbon tendencies, as well as sulfur containing moieties. This enabled a final, tentative synthesis of all the lignite data into several highly simplified schemes relating compositional aspects to depositional environments.
Jakab, E.; Windig, W. and
Meuzelaar, H.L.C.
Energy and Fuels, 1, 161-167, 1987. 6 pgs. Funded by US Department of
Energy and Utah Power and Light.
Time-resolved Curie-point pyrolysis mass spectrometry (Py-MS) is demonstrated to be a promising new method for studying thermal decomposition reactions in coal. The effect of low temperature oxidation ("weathering") on the structural characteristics of a high volatile bituminous Hiawatha coal was investigated. Microgram amounts of coal were heated to 610ºC at a rate of 10²K/s. As many as 40 low voltage mass spectra were obtained within 8 s and subsequently evaluated by means of factor analysis. The results were compared with those of conventional time-integrated Curie-point Py-MS as well as combined thermogravimetry/mass spectrometry.
It was found that the decomposition of Hiawatha coal takes place in several stages while heating the samples up to 610ºC. The evaporation of "trapped" compounds and the decomposition of labile functional groups around 300ºC represent the first steps followed by the rapid decomposition of the char residue.
The weathered coal sample has undergone substantial changes as reflected by the pyrolysis results. The amount of "trapped" volatile components (primarily alkylnaphthalenes) is markedly decreased in the weathered coal accompanied by a decrease in the abundance of hydroxyaromatic compound series (primarily alkylphenols). Furthermore, the yield of short chain aliphatic carboxylic and carbonylic moieties is strongly increased.
Soderquist, A.; Burton,
D.J.; Pugmire, R.J.; Beeler, A.J.; Grant, D.M.; Durand, B. and Huk, A.Y.
Energy and Fuels, 1, (1), 50-55, 1987. 6 pgs. Funded by US Department
of Energy and Standard Oil Co.
We report the structural variations of a number of coals and coal macerals. Through the time constants associated with dipolar-dephasing techniques, CP/MAS spectral data reveal the presence of segmental motion in certain low-rank coal samples. The motion detailed is in the aliphatic region and is thought to be due to CH2 groups associated with hydroaromatic and/or polymethylene structural units.
Jiang, Y.J.; Pugmire, R.J.
and Grant, D.M.
Journal of Magnetic Resonance, 71, 485-494, 1987. 10 pgs. Funded by Standard
Oil, US Department of Energy, Office of Energy Research and Basic Energy Sciences.
A simple double-tuned C-13/H-1 probe for high-field CP/MAS NMR is described. The tuning and matching can be adjusted separately in each channel and made exactly equal to 50 W. Isolation between H-1 and C-13 channels exceeds 40 dB. The sensitivity (S/N) of the observation channel (C-13) for methyl carbons is close to 47 in a CP/MAS experiment of 10 scans on 70 mg of a sample of hexamethylbenzene for the rotor sample volume of 140 ml. The probe delivers a 2.4 ms 90º proton pulse with only 90 W at 200 NHz and 250 W at 50.3 MHz. Examples are presented of limewidth reduction with higher decoupling power. The effects of anisotropy in the bulk magnetic susceptibility are also discussed.
Jiang, Y.J.; Woolfenden,
W.R.; Alderman, D.W.; Mayne, C.L.; Pugmire, R.J. and Grant, D.M.
Rev. SCI Instrum, 58, (5), 755-758, 1987. 4 pgs. Funded by US Department
of Energy and Office of Basic Energy Sciences.
A newly designed stator assembly for cylindrical spinners used in magic-angle spinning nuclear-magnetic resonance experiments is described. Separate driving and bearing gas chambers allow variable and stable spinning speeds, and this design permits easy starting and stopping of the rotor. Isolation of the chambers is achieved with the application of pressure screws rather than O-rings or glue lines to avoid leakage at high gas pressures. The overall dimensions are optimal to facilitate easy assembly. Some significant modifications have been made to an earlier spinner design. These improvements give better efficiency and concentricity of the spinner. Applications are illustrated with carbon-13 cross polarization/magic angle spinning (CP/MAS) spectra carried out at different rotor spinning rates.
Pugmire, R.J.; Smith, J.C.;
Grant, D.M.; Stanovnik, B.; Tisler, M. and Vercek, B.
J. Heterocyclic Chem, 24, 805-809, 1987. 5 pgs. Funded by Institute of
General Medical Sciences of the National Institutes of Health and by the Council
of Yugoslav Academies, the Slovene Academy of Science and Arts, and the US National
Academy of Sciences.
Carbon-13 nuclear magnetic resonance data have been acquired on 22 azoloazines. Chemical shifts have been correlated by a step-wise linear multiple regression with nitrogen substituents in both the 5- and 6- membered rings using pyrrolo [1,2-a] pyridine as the reference for chemical shift correlation. The data demonstrate that a highly correlated set of chemical shift parameters exist. Nitrogen substitution in the five-membered ring produces larger cross-ring effects than is observed in the five-membered ring when substitution occurs in the six-membered ring. Within the six-membered ring a constant para-substituent parameter is noted. The meta- and para- parameters are more complex and fall into two groups for each parameter. Within the five-membered ring, a highly regular chemical shift pattern is observed which reflects an attenuated perturbation from nitrogen substitution in the six-membered ring.
Smith, P.J. and Fletcher,
T.H.
Accepted for publication in Combustion Science and Technology, 1988.
24 pgs. Not externally funded.
Research efforts with comprehensive computer models that have tried to predict the performance of coal combustors have either neglected the effect of the turbulence on the mean chemical properties or have used one of two approximate methods. This paper focuses on the impact of the turbulence on the chemical reactions of the volatile products of coal combustion processes. It is shown that by ignoring the effect of the turbulence on mean combustion properties significant differences occur as compared to experimental data and predicted by both of the more rigorous models. The first method, the volatile reactances model, is an extension of an approach for premixed gaseous combustion presented by Magnussen and Hjertager. The second method, the statistical, coal-gas mixture fraction model, is an extension of gaseous diffusion flame approaches. These two methods are examined, analyzed and evaluated by comparing predictions from each method with experimental data from three laboratory furnaces. It is shown that while the first method takes only half as much computational time, the second method is required if species and temperatures in zones containing other than mixtures of pure fuel, pure oxidant and pure stoichiometric product are needed. The distribution of eddy mixtures as formulated in the second method is shown to be more consistent with existing limited experimental data.
Young, B.C.; McCollor, D.P.;
Weber, B.J. and Jones, M.L.
Fuel, 67, 1988, 5 pgs. Funded by US Department of Energy and Pittsburgh
Energy Technology Center.
A novel laminar-flow flameless reactor has been designed and constructed for investigating the combustion behavior of individual coal particles, incorporating a three-color optical pyrometer for measuring single-particle temperatures. Results for the combustion of Beulah (North Dakota) lignite char at sizes below 200 mm and at gas temperatures between 760K and 1270K are presented. It was found that the particle temperature in all cases studied exceeded the local gas temperature by several hundred degrees. The burning rates were controlled by the mass diffusion of oxygen, and the mean particle temperature was linearly dependent on oxygen mole fraction in the gas phase over the range 0.05 to 0.16. The particle temperature also showed an inverse relationship with particle size.
Richards, J.M.; McClennen,
W.H.; Bunger, J.A. and Meuzelaar, H.L.C.
Finnigan Application Note, (214), 1988. Funded by Finnigan MAT.
The results in this report show the capabilities of a short column equipped with a flash pyrolysis/evaporation inlet and interfaced directly to an ITD. The system has proven to be capable of rapid analysis of complex natural and synthetic materials, with relatively little loss in resolution relative to longer columns.
Hoesterey, B.L.; Meuzelaar,
H.L.C. and Pugmire, R.J.
Submitted to Anal. Chem., 1988. 28 pgs. Funded by ACERC (National Science
Foundation and Associates and Affiliates).
Twelve physico-chemical and thermodynamic properties including molecular weight, boiling point, flash point, density, refractive index, volumetric, gravimetric, and molar heats of combustion, atomic H/C, carbon number, hydrogen number and the fuel-related threshold sooting index for 47 C5 to C10 hydrocarbons were subjected to factor analysis. Two factors with eigenvalues greater than 1.0 were found, accounting for 95% of the variance. The major groups of variables were interpreted as arising from either molecular size (boiling point, flash point, molar heat of combustion, molecular weight and carbon number) or degree of unsaturation (density, refractive index, volumetric heat of combustion, threshold sooting index, H/C and gravimetric heat of combustion). When three factors from the physicochemical and thermodynamic properties factor space were used for canonical correlation analysis with the Wiener topological index, molecular size related papers were found to correlate with it. Canonical correlation analysis of the properties factor space with mass spectrometry/Kavats retention index data showed that characteristic mass spectral variables correlated closely with the degree of unsaturation by differentiating aliphatic from aromatic compounds. The Kovats retention index variable, not unexpectedly, modeled molecular size related parameters such as carbon number.
Jakab, E.; Hoesterey, B.L.;
Windig, W.; Gill, G.R. and Meuzelaar, H.L.C.
Fuel, 67, (1), 73-79, 1988. 6 pgs. Funded by US Department of Energy
and Utah Power and Light.
Two high volatile bituminous coals (Upper Freeport and Hiawatha seams), a subbituminous coal (Adaville seam) were used to investigate the effect of low temperature air oxidation ("weathering") on the yield and composition of vacuum pyrolysis products. Fresh coal samples were exposed to air at 80º and 100ºC for up to 10 days under controlled laboratory conditions. Curie-point pyrolysis mass spectrometry combined with computerized data analysis was applied to study the weathering induced changes in a series of samples weathered for various lengths of time. It was found that the abundance of small oxygen-containing molecules such as carbon monoxide, carbon dioxide and aliphatic carboxylic acids increased in the pyrolysate of all samples, whereas phenols and dihydroxybenzenes showed decreased yields, especially in the two lowest rank coals. Besides phenols, alkylnaphthalenes and alkyltetralins showed decreased abundances in the pyrolysis mass spectra of the two high volatile bituminous coals. An attempt is made to explain the difference in pyrolysis patterns observed before and after weathering experiments in terms of underlying structural changes.
Fields, S.M.; Markides,
K.E. and Lee, M.L.
Analytical Chemistry, 60, 802-806, 1988. 5 pgs. Funded by Dow Chemical
Company and Gas Research Institute.
A major emphasis on current research in capillary supercritical fluid chromatography (SFC) is concerned with the use of mixed mobile phases to expand the analytical capabilities of SFC to more polar and higher molecular weight solutes than possible with single fluid mobile phases such as CO2. The mixed mobile phases that have been studied are primarily polar organic liquids in CO2. Low percentages (less than 1 mol %) of modifiers do not appear to cause any significant change in solute retention. Higher percentages (up to 20 mol %) have been shown to produce significant retention charges.
Since mobile phase flow rates and solute quantities are low in capillary SFC, it is desirable to analyze the entire effluent. However, the high percentages of organic modifiers anticipated in mixed mobile phase studies preclude the use of a flame ionization detector due to high background levels and to baseline changes during pressure or density programming. Ultraviolet-adsorption provides a simple and inexpensive detection system for use with mixed mobile phases.
Capillary SFC analysis creates stringent demands on allowable UV-absorption cell volumes, so an optical cell was developed based on fused silica capillary tubing available for gas chromatography. Highly compressible mobile phases such as CO2 create a problem in capillary UV-absorption detection that is not present for high critical temperature, low compressibility mobile phases such as n-pentane. The compressibility of CO2 produces significant density changes in the cell during pressure or density programming which leads to refractive index changes and significant base-line drift.
These effects were reduced to acceptable levels by cooling a newly designed and constructed detector cell. The system is sensitive and useful in studies of mixed mobil phases in capillary SFC. An 8.9 mol % mixture of 2-propanol or nitromethane in CO2 produced significant decreases in retention of polar and nonpolar polycyclic aromatic compounds. The 2-propanol/CO2 mobile phase effects the elution of ovalene at moderate temperature and pressure.
Chang, H.-C.K.; Nishioka,
M.; Bartle, K.D.; Wise, S.A.; Bayona, J.M.; Markides, K.E. and Lee, M.L.
Fuel, 67, 45-48, 1988. 4 pgs. Funded by Gas Research Institute.
Determination of the chemical structural features of coals is a continuing major goal of fuel science because of the vital energy source represented by this material. Coals are now perceived to be cross-linked macromolecular networks in which are trapped lower molecular weight materials either in sites readily accessible to solvent or in 'cages' analogous to clathrates. How representative this extractable material is of the multipolymeric macromolecular structure in which it is embedded in clearly open to question. However, the generally lower molecular weights of components in solvent extracts lead to much greater ease of analysis, and such extracts may provide insights into metamorphic changes undergone by the macromolecular structure during coal formation.
A two-step pyridine and then tetrahydrofuran solvent extraction procedure at room temperature under nitrogen gas flow was used to extract two different US coals, PSOC-592 (Illinois No. 5) and PSOC-521 (Rock Springs No. 7, Wyoming). Aliphatic and aromatic hydrocarbons were separated using neutral alumina column chromatography. The aromatics were then fractionated according to the number of aromatic carbons by high performance liquid chromatography. These neutral compounds were identified by gas chromatography (g.c.) and gas chromatography/mass spectrometry. n-Alkanes (C17-C31), pristane, phythane, hopanes (17aH, 21bH), and moretanes (17bH, 21aH) were found in aliphatic fractions of both coal extracts. Low-molecular-weight (2-4 rings) polycyclic aromatic hydrocarbons (PAH) were the major compounds in the aromatic fraction of the PSOC-592 coal extract. However, pentacyclic triterpenoid-like hydroaromatic hydrocarbons were the major components in the extract of the PSOC-521 coal. A number of new compounds were identified for the first time.
Huang, E.C.; Jackson, B.J.;
Markides, K.E. and Lee, M.L.
Chromatographia, 25, 51-54, 1988. 4 pgs. Funded by US Department of Energy
and Gas Research Institute.
It is estimated that the majority of analyses by supercritical fluid chromatography (SFC) involves the use of the flame ionization detector (FID) or the UV-absorbance detector. Unfortunately, each of these detectors can only be used when the SFC mobile phase and the sample being chromatographed fill certain requirements; the FID is limited to the use of only a few supercritical mobile phases, and the UV-absorbance detector can be used only when the sample molecules contain chromophores. The demand for a universal detector for SFC has intensified as the range of applicability of the technique has expanded. Coupled chromatography/mass spectrometry systems are among the most powerful analytical instruments available today for the analysis of organic mixtures. The successful marriage of gas chromatography/mass spectrometry (GC/MS) and the considerable progress in coupling liquid chromatography with the mass spectrometer (LC/MS) have naturally led to studies of SFC/MS.
The coupling of a capillary supercritical fluid chromatograph with a high resolution double focusing mass spectrometer has been accomplished without any modifications to the pumping or ion source systems. The interface utilizes a direct insertion probe (DIP), which was originally designed for the direct analysis of solid samples, together with a frit restrictor as a decompression device. The DIP is placed opposite to the SFC restrictor, and it provides sufficient heat to prevent cluster formation and cooling resulting from the expansion of the supercritical fluid into the vacuum environment. Excellent mass spectra of standard polycyclic aromatic hydrocarbons under chemical-ionization (CI) conditions using methane as the reagent gas, and under charge-exchange (CE) conditions using CO2 as the charge exchange medium were obtained.
Brewster, B.S.; Baxter,
L.L. and Smoot, L.D.
Energy & Fuels, 2, (4), 362-370, 1988. 9 pgs. Funded by Morgantown Energy
Technology Center through subcontract from Advanced Fuel Research Co.
Comprehensive combustion codes typically use simple empirical models to predict weight loss associated with coal devolatilization. Individual evolved species are not taken into account nor are the individual products of heterogeneous char reaction. The effects of all particle reactions are lumped into a single overall rate of weight loss, and coal off gas composition and heating value are assumed constant. More detailed devolatilization models that consider the evolution of individual species and predict both rate and composition of the volatiles are now available. These models use general kinetic parameters for each coal constituent that are nearly independent of rank. Such models provide a basis for predicting composition and heating value of the volatiles as a function of burnout and reactor conditions for a wide range of coals. This paper presents a generalized theory based on the existing coal gas mixture fraction model, which allows the variation of off gas composition and heating value to be taken into account in comprehensive code predictions. Results are presented for a swirling combustion case. Results illustrating code sensitivity to several thermal parameters affecting devolatilization and to turbulent fluctuations are also presented. This publication also relates directly to Thrust Area 4.
Sethi, N.K.; Pugmire, R.J.;
Facelli, J.C. and Grant, D.M.
Analytical Chemistry, 60, 1574-1606, 1988. 32 pgs. Funded by ACERC (National
Science Foundation and Associates and Affiliates).
C-13 NMR shielding tensors have been determined for two anthracite coals and a fusinite maceral using powder pattern line-shapes that have been analyzed as a superposition of three different bands due to benzene-like, condensed (bridgehead and inner) and substituted carbons. Theoretical calculations on circumcoronene (I) as a model compound support the interpretations of the experimental data. Determination of the ratio of non-protonated to protonated aromatic carbons obtained on the anthracites by the spectroscopic analysis is in excellent agreement with the elemental analysis and previous studies by dipolar dephasing NMR techniques. The method therefore constitutes a valuable way to analyze the structure of high rank coals and should be useful in char characterization. The mole fraction of condensed carbons obtained by this technique is used to estimate the average cluster size in these polycondensed aromatic hydrocarbon materials.
Taghizadeh, K.; Hardy, R.H.;
Davis, B.H. and Meuzelaar, H.L.C.
Submitted to Analytical Chemistry, 1988. Funded by Commonwealth of Kentucky,
Kentucky Energy Cabinet, and US Department of Energy.
Low voltage (LV) and field ionization (FI) mass spectral of coal-derived liquids (CDL) before and after hydrotreatment from the Wilsonville Coal liquefaction pilot plant were compared. LV-MS (12eV) analysis of Wilsonville CDL'S before and after hydrotreatment produces very similar spectral patterns as obtained by FI-MS. This is especially true for the more highly aromatic hydrotreater feed samples since hydroaromatic compounds tend to fragment more under LV-MS conditions. Canonical variate analysis confirms that the mass spectral patterns produced by both techniques are highly correlated with the exception of the higher mass range (above m/z 300) that appears to be underrepresented in the LV-MS patterns, primarily as a result of lower inlet temperatures. Furthermore, in spite of the highly complex nature of the original spectral profiles, use of multivariate statistical analysis techniques, such as factor analysis and canonical correlation analysis, enables "numerical extraction" of simplified spectral patterns which can be tentatively interpreted in terms of chemical components or compound series.
Orendt, A.M.; Facelli, J.C.;
Beeler, A.J.; Reuter, K.; Horton, W.J.; Cutts, P.; Grant, D.M. and Michl, J.
American Chemical Society, 110, 3386, 1988. Funded by US Department of
Energy.
The principal values of the C-13 NMR shielding tensor were measured at cryogenic temperatures for a series of olefinic carbons, including methyl-substituted ethylenes, 1-methyl- and 1,2-dimethylcycloalkenes, methylenecycloalkanes, and bicyclo (n,m.0) alkenes. Information on the orientation of the principal axes was obtained from ab initio calculations of the chemical shielding tensor using the IGLO (individual gauge for localized orbitals) method. The results for several compounds with unusual principal values of the shielding tensor were analyzed in terms of the bond contributions in the principal axis system.
Carter, C.M.; Facelli, J.C.;
Alderman, D.W.; Grant, D.M.; Dalley, N.K. and Wilson, B.E.
J. Chem. Soc. Faraday Trans. 1, 1988. Funded by US Department of Energy.
Using a two-dimensional NMR orientation correlation technique carbon-13 chemical-shift tensors have been measured in single crystals of 1.4-dimethoxybenzene. 1,3,5-trimethoxybenzene and 1,2,3-trimethosybenzene. The two-dimensional technique greatly extends the single-crystal method to materials with a much larger number of different carbon-13 resonance lines. The manner of dealing with chemically identical, but magnetically non-equivalent carbons in the unit cell is discussed. The X-ray structure of 1, 2, 3-trimethoxybenzene is reported for the first time, and a redetermination of the X-ray structure for 1.4-dimethoxybenzene is given. The principal values of all carbon-13 chemical-shift tensors in the three molecules and the orientation of their principal axes have been obtained. Using multiple regressional analysis the principal values of the tensors have been discussed in terms of additive substituent effects. AB initio calculations of the shielding tensors in anisole (methoxybenzene) and benzene were used to calculate substituent effects that agree closely with the parameters obtained from the regressional analysis.
Newmark, R.D.; Alderman,
D.W. and Grant, D.M.
Submitted to Phys. Rev., 1988. Funded by US Department of Energy.
The double resonance interferometry experiment of Stoll, Vega and Vaughan is examined with numerical simulations employing the complete Redfield matrix. It is shown that their observed doublet asymmetry is a consequence of random field relaxation mechanisms. The relaxation pathways in the system are examined in detail to explain the coherence transfer that takes place during the SVV experiment. The simulations must include relaxation during the selective carbon-13 pulses in order to agree with the experimental results thereby indicating the need for care in using impulse approximations for selective pulses in some double resonance experiments.
Gan, Z.H.; Facelli, J.C.
and Grant, D.M.
Submitted to J. Chem. Phys., 1988. Funded by US Department of Energy.
The C-13 dipolar powder spectra of C-13H3P-31O(OH)2 at room temperature and C-13H3F-19 at low temperature (T=25K) are reported. An intense peak is observed in the center of the Pake doublet. This phenomenon is explained by the transverse cross relaxation mechanism between the C-13 and either the P-31 or F-19 nuclei. The chemical shielding tensors and dipolar coupling constants of these two molecules are obtained by fitting the experimental spectra.
Heeschen, W.A.; Alderman,
D.W. and Grant, D.M.
Submitted to J. Phys. Chem, 1988. Funded by US Department of Energy.
A time-domain fitting routine is described and applied to the analysis of a H-1-NMR spectrum of a solute in a liquid-crystalline solvent. Principles of the time-domain fitting technique are described in terms of data selection, baseline compensation and computational advantage over other fitting methods. Also, the use of fitting coefficients based on structural variation is described and found to provide rapid, reliable spectrum fits with physically reasonable structures. Solute ordering information is determined through interpretation of high-resolution spectra using director reorientation by the variable-angle sample spinning technique to provide a starting point for the fitting. Spectra from norbornadiene dissolved in the liquid crystal p-pentylphenyl 2-chloro-4-(p-pentylbenzoyloxy) benzoate are used to demonstrate the method. The resultant fit of the norbornadiene structure is compared to results obtained previously by other workers.
Solum, M.S.; Facelli, J.C.;
Gan, Z.H. and Grant, D.M.
Submitted to Molecular Physics, 1988. Funded by US Department of Energy.
The C-13 low temperature (25K) dipolar spectrum of C-13H3N-14O2 is reported. The spectrum was fit and the principal values of the C-13 shielding tensor are given. The C-13 shielding tensor principal values are similar to those found in other C-13H3 groups. Also, the N-14 quadrupolar parameters and the direct dipolar couplings were obtained from the fit. Because of librational motions an effective trace term in the dipolar interaction has to be included in the fit.
Curtis, J. and Grant, D.M.
Submitted to J. Am. Chem. Soc., 1988. Funded by US Department of Energy.
Distortions in six-membered aliphatic ring systems were examined using deuterium chemical shifts and multiple linear regression analysis. A new set of regression parameters has been developed which successfully interprets not only spectra for those methylcyclohexanes with normal chair conformations, but also spectra for cis- and trans-decalin and for three highly distorted trimethylcyclohexanes with skw boat type distortions to their equilibrium conformations. The origin of deformations in the cyclohexane ring and the effect of distortions on ring hydrogen/deuterium chemical shifts are discussed in terms of gauche interactions between vicinal C-C and C-D bonds. The fits for 115 deuterium shifts in these cyclic alkanes exhibited a multiple R-=0.9816 and s=0.0623 ppm for an overall shift range of about 1.5 PPM As the 14 structural parameters obtained in this study are very sensitive to distortions and conformational features, the results indicate that 2H NMR methods should be very powerful in those cyclic paraffins in which highly second-order banding is observed in the corresponding proton NMR spectrum.
Chakravarty, T.; Meuzelaar,
H.L.C.; Windig, W. and Hill, G.R.
Energy & Fuel, 2, 400-405, 1988. 5 pgs. Funded by ACERC (National Science
Foundation and Associates and Affiliates).
Most coal devolatilization studies so far have focused on the determination of reaction rates for reactions occurring under widely different conditions encountered in liquefaction, gasification, coking or combustion processes. Published rates on more or less comparable coals may differ by several orders of magnitude, especially when obtained at high temperatures (>1000 K) and/or high heating rates (10²-105 K/s).
At the present state-of-the-art in coal devolatilization research, more emphasis should perhaps be placed on elucidating the mechanisms of the chemical reactions underlying the observed phenomena. When studying thermal conversion reactions in coal it seems correct to concentrate first on the so-called "primary" reactions before attempting to elucidate the many possible secondary reaction pathways. This is especially true since most secondary reaction pathways are strongly influenced by reactor design and experimental conditions.
The devolatilization behavior of coal will be determined primarily by the chemical composition of coal and secondly by the experimental conditions. Under properly designed vacuum micropyrolysis experiments working with sufficiently small particles (<50 mm diameter), it is possible to avoid mass and heat transport limitations and minimize the secondary reactions. Using unoxidized or well preserved coal samples, the chemical composition can be well defined and possibly characterized by major factors such as rank and depositional environment. Recent advances in pyrolysis mass spectrometry (Py-MS), viz, time-resolved Py-MS (TR Py-MS), along with multivariate analysis techniques enable extraction of underlying chemical components from a single experiment, thus reducing the uncertainty due to varying reactions conditions in different experiments. This paper demonstrates the feasibility of obtaining valuable mechanistic and kinetic data using microgram amounts of carefully selected coal samples under properly designed reaction conditions using TR Py-MS techniques in combination with advanced multivariate data analysis methods.
McDonald, J.B.; Richards,
D.O.; Smith, P.J. and Sowa, W.A.
Annual Meeting of the American Statistical Assoc., 1986. 18 pgs. Not
externally funded.
Coal particle size distributions for a Utah bituminous coal and a Wyoming subbituminous coal were modeled using four different probability density functions (GB1, GB2, lognormal, and lognormal by method of moments) and two engineering approximations. The pdf models of the particle size distributions were discretized and compared to the engineering approximations by simulating a coal combustion case and a coal gasification case using the comprehensive combustion model, PCGC-2. The gasification case used the Utah coal and the combustion case used the Wyoming coal. Significant differences were noticed between predictions using engineering approximations of the particle size distribution and predictions using discretized pdf approximations of the particle size distribution. The different methods of describing the particle size distribution affected most notably the simulators prediction of NOx.
Hill, G.R. and Meuzelaar,
H.L.C.
Proc. New Fuels Forms Workshop, 1986. Funded by US Department of Energy,
Electric Power Research Institute, Utah Power and Light, and State of Utah.
Although liquefaction yields in the 80-100% range have been regularly reported, it is becoming increasingly clear than an economically viable approach to the production of liquid fuels from coals should seek to optimize rather than maximize liquid yields. These considerations have prompted us to pursue new, "differential" liquefaction avenues characterized by disproportionation of the feedstock coal into two or more valuable end products.
Sethi, N.K.; Pugmire, R.J.
and Grant, D.M.
1987 International Conference of Coal Science, 1987, 41-44, Science,
Holland, 1987. 4 pgs. Funded by US Department of Energy, Basic Energy Sciences,
and ACERC (National Science Foundation and Associates and Affiliates).
Carbon-13 NMR spectroscopy has become an important tool in the structural determination of coal. The major techniques used are cross polarization magic angle spinning (CP/MAS) and dipolar dephasing (DD/MAS) experiments. The CP/MAS technique has been extensively used on both whole coals and macerals by this laboratory as a direct method for determining the fraction of aromatic carbons, fa, in these samples. The dipolar dephasing experiment (DD/MAS) provides additional definition of the structure of coal by using the C-13-H-1 dipolar coupling to separate the carbons into sub-classes, i.e., those that are strongly coupled to protons from those that are weakly coupled in both the aromatic and aliphatic regions of the spectrum. The application of the technique to coals has been thoroughly described.
MAS experiments produce narrow lines in solids but, in doing so, valuable chemical shift anisotropy (CSA) information is lost as the chemical shift tensors are averaged to their isotropic values. CSA is a second rank tensor and is characterized by three unique resonance frequencies s11, s22 and s33 called the principal values of the tensor elements . Knowledge of all three frequencies in addition to the isotropic value (average of tensor elements) in a source of information which is indispensable for molecular characterization and independent peak assignments. Measurement of the tensor elements is carried out by recording the C-13 NMR spectrum of a finely powdered sample to obtain the solid state line shape which can then be analyzed to determine tensor elements of chemically and structurally different types of carbons. Other noteworthy techniques for extracting such data are analysis of spinning sidebands from slow magic angle spinning experiments and non-magic angle sample spinning referred to in this paper as variable angle sample spinning (VASS). In the present study, we have analyzed both static and variable angle sample spinning line shapes to obtain the CSA tensor values and population factors for the aromatic carbons of coals.
Yun, Y.; Hoesterey, B.L.;
Meuzelaar, H.L.C. and Hill, G.R.
ACS Preprints, 32, 4, 1987, New Orleans. Funded by US Department of Energy.
In order to develop a reliable, simple procedure for determining the oxidation status ("weathering index") of a coal sample, several candidate methods were tested with all eight coals from the Argonne Premium Coal Sample Program after air oxidation under relatively mild, controlled environmental conditions. Twenty-five gram aliquots of all eight PCSP coals were exposed to a 10-ml/min dry airflow at 100ºC in all-glass reactors for eight days. Weight changes and O2, CO2, and H2O exchange rates were recorded. Among the various characterization methods tested were FSI, slurry pH, Zeta potential and thermogravimetry. Pyrolysis mass spectrometry and Fourier transform IR spectroscopy were used to monitor structural changes. Results obtained to data show that FSI is a good indicator of oxidation state for low-to-medium caking coals of bituminous rank whereas slurry pH appeared to be less useful for most coals. Although Zeta potential and thermogravimetry tests are still underway, it is becoming quite clear that a reliable, generally useful "weathering index" may have to be based on a fairly comprehensive battery of tests rather than on a single technique.
Yun, Y.; Jakab, E.; McClennen,
W.H.; Hill, G.R. and Meuzelaar, H.L.C.
ACS Preprints, 32, (1), 1987, Denver, CO. Funded by US Department of
Energy.
Low temperature (<100ºC) coal oxidation processes are known to have a pronounced effect on important coal properties such as coking and caking behavior, heat of combustion, floatability, slurry pH, tar yield and extractability. However, the mechanisms and kinetics of the chemical reactions underlying such weathering processes in coal are far from well understood. In this article new Py-MS data on low temperature oxidation effects in several US coals of different rank and origin will be discussed with special emphasis on the role of different coal macerals.
Taghizadeh, K.; Davis, B.H.
and Meuzelaar, H.L.C.
ACS Preprint, 32, 4, 1987, New Orleans. Funded by Commonwealth of Kentucky,
Kentucky, Energy Cabinet, US Department of Energy and Consortium For Fossil
Fuel Liquefaction Science.
Due to the high complexity of coal-derived liquids no single analytical method provides adequate compositional information. In this study, low voltage MS data on Wilsonville coal liquid samples from a single 67-day run in the ITSL mode using Illinois #6 coal were combined with available H and C-13 NMR data, as well as conventional characterization data, by means of computerized multivariate analysis techniques, viz. canonical correlation analysis. The low voltage MS data revealed a high degree of correlation with the NMR data as well as the conventional data. As expected, the hydrotreatment step is characterized by an increase in the relative abundance of hydroaromatic compounds accompanied by a decreased abundance of condensed aromatic hydrocarbons, as well as a strong reduction in heteroatomic compounds. Moreover, the combined effect of catalyst aging and reactor temperature is a decrease in the relative abundance of lower molecular weight-compounds and more reactive chemical structures (e.g., alkyltetralins). Furthermore, during the later stages of the run nitrogen- and sulfur-containing moieties appear to be less efficiently removed in the hydrotreatment step.
Meuzelaar, H.L.C.; Roberts,
K.A. and Yun, Y.
Western States Combustion Institute Proceedings, 1987. Funded by ACERC
(National Science Foundation and Associates and Affiliates).
Among modern spectroscopic techniques applied to the study of coal devolatilization processes Fourier transform infrared spectroscopy (FTIR) has established a prominent position whereas comparatively little use has been made of mass spectrometry (MS), in spite of its widely recognized speed, sensitivity and high information yields.
Lee, M.L.; Bartholomew,
C.H. and Hecker, W.C.
ERC Symposium, Annual ASEE Meeting, 1987, Reno, Nevada. Funded by ACERC
(National Science Foundation and Associates and Affiliates).
The main goal of the Advanced Combustion Engineering Research Center is the development and implementation of advanced combustion models. The Center research is organized around six major thrust areas focused on the clean and efficient use of low-grade fuels such as coal. These thrust areas will provide data on kinetics, fuel properties, and process-performance design characteristics that will be integrated into a comprehensive computer model used in the design and optimization of advanced combustion systems. This paper deals with the work in the fuel characterization and reaction mechanisms thrust area.
The research project in the fuel characteristics and reaction mechanisms thrust area are focused on relating the kinetic rates and mechanisms of rapid coal devolatilization and char reactivity with the physical and chemical structure of coal and pyrolysis tars and chars. This paper summarizes the results from four integrated research programs in this thrust area.
Supercritical solvent extraction is employed to determine the amount and nature of hydrocarbons that are physically absorbed or only weakly bound within the coal structure and are expected to be liberated early in the devolatilization process. Both paraffin (n-alkanes, isoprenoids, and pentacyclic triterpanes) and polycyclic aromatic (two to five fused aromatic rings) hydrocarbons have been identified. Pyrolysis mass spectroscopy provides both rate data and pyrolysis tar data on coals during slow devolatilization. The physical properties (surface area and pore size distribution) of the parent coals and pyrolysis chars are studied in order to relate these properties to coal and char reaction rates. Advanced solid-state NMR techniques are used to obtain the carbon skeletal structure of the parent coals and pyrolysis chars. High field, high-resolution NMR spectroscopy experiments provide data on the structural features of the pyrolysis tars.
The experiments in this thrust area are carried out on a common set of standard coals. The devolatilization studies to be initially carried out in collaboration with other laboratories will be summarized. A description will be provided for the analysis and integration of the various experimental data. These data are used in the development of coal devolatilization and char reaction sub-models in comprehensive combustion models. The means for integrating the chemical data into the combustion code will be described.
Solum, M.S.; Pugmire, R.J.
and Grant, D.M.
ACS division of Fuels, Preprint, 32, (4), 273-279, 1987. 8 pgs. Funded
by ACERC (National Science Foundation and Associates and Affiliates).
Solid state C-13 cross polarization (CP) magic angle spinning (MAS) NMR experiments have become very useful for the study of the structure of coal and other fossil fuels (1, 2). Solid-state NMR techniques have the advantage over liquid NMR methods because the whole solid coal can be analyzed in a nondestructive manner and no assumption need be made that the soluble portion represents the whole organic portion of the coal. From CP/MAS experiments twelve NMR structural parameters may be determined including the aromaticity, fa, that give information on the carbon skeletal backbone. The variation of the NMR structural parameters for coals of different rank from lignite to anthracite has been demonstrated (3). The coals in the Premium Coal Sample Bank (PCSB) have been included in the set of coals studied at the Advanced Combustion Engineering Research Center. The NMR data obtained on these coals will be used to provide chemical structural parameters for refinement of the devolatilization sub-model of the PCGC-2 combustion model.
This paper reports the twelve structural parameters for two of the PCSB coals, Pittsburgh #8 (HVB) and Blind Canyon (HVB). These data were derived from integrated intensities in a normal CP/MAS experiment along with a complete set of dipolar dephasing experiments. In addition, the proton spin lattice relaxation times for these coals have been determined. From relaxation experiments on the Pittsburgh #8 coal there is some evidence of heterogeneity between different sample vials of the same standard coal.
Sethi, N.K.; Pugmire, R.J.
and Grant, D.M.
ACS Div. of Chemistry, Preprints, 32, (4), 155-167, 1987. 13 pgs. Funded
by Office of Basic Energy Science and US Department of Energy.
Carbon-13 NMR spectroscopy has been widely accepted as a major analytical technique for studying fossil fuels. Axelson and Davidson have reviewed the various solid state NMR spectroscopic techniques for coal studies. Cross polarization/magic angle spinning (CP/MAS) provides information on aromaticity while the dipolar dephasing technique (DD/MAS) provides additional definition of the structure of coal by using the C-13/H-1 dipolar coupling to separate the carbons into subclasses; i.e., those that are strongly coupled to protons from those that are weakly coupled in both the aliphatic and aromatic regions of the spectrum. The combination of these two experimental procedures permits one to derive a carbon skeletal structure of coal samples.
MAS experiments produce narrow lines in solids but valuable structural information is lost; i.e., the chemical shift anisotropy (CSA) which is a manifestation of the three-dimensional shielding of the nucleus by the surrounding electrons. The CSA is a second-rank tensor having three principal elements s11, s22, and s33 characterized by unique resonance frequencies. These three tensor components taken together with the isotropic shielding value (the MAS value which is the average of the three tensor components) provide valuable data regarding the local electric environment. The tensor can be obtained from the C-13 NMR spectrum of a finely powdered sample and the tensor elements are extracted by analysis of the line shape. This technique provides not only tensor components but population values as well. However, the spectral analysis is complicated if more than one tensor is present and unique results are not always achievable. Evenso, Pines, et al. used the technique to analyze the static spectra of several coals. These workers succeeded in differentiating the contributions from aromatic and condensed aromatic carbons. Furthermore, they pointed out that there is little difference in the isotropic chemical shifts between these types of carbons and these shift differences cannot be resolved in a CP/MAS experiment. The DD/MAS experiment has been shown to differentiate between benzene-like (i.e., C-H) and non-protonated aromatic carbons (substituted plus inner, or bridgehead) but the resolution of substituted and inner carbons is not readily attainable with standard MAS experiments. The shielding anisotropies of the three general types of aromatic carbons are quite different and, in principal, should be resolvable in the "non-spinning" experiment.
Only for isolated carbons, or for simple compounds where breakpoints in the powder pattern are discernible, is it possible to obtain unique fits of the line shape. Tensor information can be extracted by other techniques such as analysis of the spinning side bands from slow spinning MAS experiments and variable angle sample spinning (VASS). In this study we have used the static and VASS methods to study pertinent model compounds and have used these data as a guide to analyze line shapes and extract CSA tensor values and population factors in coals. The experimental techniques are applicable to chars as well as coals. The data permit us to estimate the size of the polycondensed aromatic structure that is the main structural component in chars. The aromatic structure of coal chars should provide valuable information regarding their reactivity.
Meuzelaar, H.L.C. and Isenhour,
T.L.
Proc. Snowbird Conference, 1987. Funded by Army Research Office.
This book provides a relatively broad overview of recent advances in computerized optimization, data exploration and spectral interpretation methods in mass spectrometry (MS), infrared spectroscopy (NMR) and nuclear magnetic resonance spectroscopy (NMR).
Hoesterey, B.L.; Windig,
W.; Meuzelaar, H.L.C.; Eyring, E.M.; Grant, D.M. and Pugmire, R.J.
Processing of Pyrolysis Oils, 1988, E.J., Soltes (ed.) ACS Symp. Series,
in press. Funded by Consortium for Fossil Fuel Liquefaction Science and US Department
of Energy.
The hydrocarbon ("oil") fraction of a coal pyrolysis tar prepared by open-column liquid chromatography (LC) was separated into l6 subfractions by a second LC procedure. Low voltage mass spectrometry (MS), infrared spectroscopy (1R), and proton (PMR) as well as carbon-13 nuclear magnetic resonance spectrometry (CMR) were performed on the first 13 subfractions. Computerized multivariate analysis procedures such as factor analysis followed by canonical correlation techniques were used to extract the overlapping information from the analytical data. Subsequent evaluation of the integrated analytical data revealed chemical information that could not have been obtained readily from the individual spectroscopic techniques. The approach described is generally applicable to multisource analytical data on pyrolysis oils and other complex mixtures.
Yun, Y. and Meuzelaar, H.L.C.
ACS Preprint, 1988, Los Angeles. Funded by ACERC (National Science Foundation
and Associates and Affiliates).
The most serious limitations of many coal gasification and liquefaction models are due to the lack of char and total volatiles yield data, of accurate kinetic parameters, and of reliable data on the composition of the total volatiles in the initial devolatilization step. Consequently, a vacuum thermogravimetry/mass spectrometry (TG/MS) system of a Mettler TA1 Thermoanalyzer and a Finnigan MAT 32000 quadrupole mass filter was built to obtain accurate quantitative and qualitative data on coal devolatilization processes at heating rates in the 10-2-10-1 K/s range. Hundreds of mass spectra can be obtained during a single TG run, thereby providing detailed information about the concentration of various devolatilization products as a function of temperature while continuously recording the sample weight loss. Moreover, factor-analysis-based methods enable deconvolution of overlapping trends and numerical extraction of chemical component spectra. TG/MS results on four Argonne PSCP coals are discussed.
Chakravarty, T.; Meuzelaar,
H.L.C.; Jones, P.R. and Khan, M.R.
ACS Preprints, 33, (2), 235-241, 1988. Toronto, CA. Funded by ACERC (National
Science Foundation and Associates and Affiliates).
Numerical comparison of compositional data on coals and their corresponding pyrolysis tars enables the construction of empirical mathematical models to predict liquid yield and composition from spectroscopic data of the parent coal. This approach was successful when using spectroscopic methods combined with vacuum micropyrolysis techniques, viz. Curie-point pyrolysis mass spectrometry. Nineteen US coals and the corresponding pyrolysis liquids prepared by the SHRODR method were analyzed by means of Curie-point pyrolysis low voltage MS. The pyrolysis mass spectra of the coals were composed of mainly primary pyrolysis products typical of vacuum micropyrolysis and were substantially different from the low voltage mass spectra of the corresponding SHRODR tars produced under batch autoclave conditions which promote the formation of secondary pyrolysis products. Nevertheless, it proved feasible to model and predict SHRODR tar spectra from the vacuum micropyrolysis spectra of the coals with a high degree of precision by means of factor analysis-based canonical correlation methods.
Yeh, G.C.; Ward, B.; Quigley,
D.R.; Crawford, D.L. and Meuzelaar, H.L.C.
ACS Preprints, 1988, Los Angeles, CA, in press. Funded by US Department
of Energy.
Curie-point pyrolysis mass spectra of twelve low-rank US coals with various degrees of natural weathering were correlated with the results of biosolubility screening tests involving six selected microorganisms as well as with a specially designed alkaline solubility test. The main objectives of this study were to determine which mass spectral characteristics, if any correlated with the degree of biosolubilization trends, a main trend which correlates positively with the presence of severely oxidized aromatic moities in the coal and apparently enables biosolubilization by all six microorganisms, and a second trend which correlates with relatively high concentrations of acid components and enables biosolubilization by only two or three of the organisms. The chemical and biological significance of these trends is not yet completely understood. Finally, in agreement with previous reports a strong positive correlation was observed between biosolubility and alkaline solubility.
Bartholomew, C.H.; White,
W.E.; Thornock, D.; Wells, W.F.; Hecker, W.C.; Smoot, L.D.; Smith, D.M. and
Williams, F.L.
Preprint ACS Fuels Chem. Divl., 1988, Los Angeles. 9 pgs. Funded by ACERC
(National Science Foundation and Associates and Affiliates).
Surface areas, pore volumes, pore size distributions, and solid densities were measured for three ANL coals (Pittsburgh No. 8, Wyodak, and Beulah Zap Lignite), two PETC coals (Lower Wilcox, and Dietz) and a Utah Scofield coal and for chars derived from these coals. Surface areas were measured using nitrogen and carbon dioxide adsorptions; pore volumes were determined using nitrogen adsorption, mercury porosimetry, and NMR spin-lattice relaxation measurements of samples saturated with water. Solid densities were obtained using helium displacement. The results indicated that chars have larger surface areas and pores relative to coals; large fractions of the internal surfaces of coals are not penetrated by nitrogen molecules but are penetrated by carbon dioxide suggesting that the pores are mostly smaller than 1 NM
Grant, D.M.; Pugmire, R.J.;
Fletcher, T.H. and Kerstein, A.R.
ACS Div. of Fuel Chemistry, 33, (2), 322-332, 1988. 10 pgs. Funded by
ACERC (National Science Foundation and Associates and Affiliates).
We have developed a model for coal devolatilization that incorporates the diversity of coal structure in such a way that the analytical data obtained from solid state NMR provides the initial input data. Using experimentally determined kinetic rate parameters, it is possible to fit the gas, tar and char production of a lignite and high volatile bituminous coal. We have employed percolation theory to provide analytical expressions for the lattice statistics required in devolatilization modeling. The percolation theory allows one to avoid the more time-consuming Monte Carlo technique with no loss of generality or important statistical features. Percolation theory analytically describes the size distribution of finite clusters of sites joined by intact bridges but isolated from all remaining sites by broken bridges. The theory specifies a critical bridge population, depending only on the site coordination number, above which infinite arrays will coexist with clusters of finite size. It is a simple matter to adapt the structural features of percolation theory to both the tar and gas obtained in coal pyrolysis. The infinite arrays of percolation theory are interpreted as the macroscopic lattice of unreacted coal and/or char while the relatively small tar molecules may be identified with the fine clusters of percolation theory. The details of the model will be discussed together with the results obtained in modeling devolatilization behavior of coals of various ranks.
Huffman, G.P.; Huggins,
F.E.; Shah, N.; Bhattacharyya, D.; Pugmire, R.J.; Davis, B.H.; Lytle, F.W. and
Greegor, R.B.
ACS Div. of Fuel Chemistry, 33, (1), 200-208, 1988. 9 pgs. Funded by
US Department of Energy.
EXAFS spectroscopy is shown to be a very promising technique for investigating the molecular structure of organically bound sulfur in coal and coal derivatives. The current paper presents sulfur K-shell EXAFS results for a number of a maceral separates prepared by density gradient centrifugation and for several biodesulfurized coals. Both the near-edge structure and the radial structure functions exhibit some similarities to dibenzothiophene. However, a broad peak occurs in the XANES region of the coal spectra that is not observed for the molecular structures usually ascribed to organic sulfur in coal. This is believed to arise from resonant photoelectron scattering from second and third nearest neighbor carbon shells and from sulfur bonded to oxygen.
Pugmire, R.J.; Sethi, N.K.;
Solum, M.S.; Facelli, J.C. and Grant, D.M.
Proc. Carbon Conference, 1988. 3 pgs. Funded by US Department of Energy
and Basic Energy Sciences.
Magic angle spinning experiments produce narrow lines in solids but valuable chemical shift anisotropy (CSA) information is lost as the chemical shift tensors are averaged to their isotropic values. CSA is a second rank tensor and is characterized by three unique resonance frequencies s11, s22 and s33 called the principal values of the tensor elements [1]. Knowledge of all three frequencies with the isotropic value is a source of information that is indispensable for molecular characterization. Measurement of the tensor elements is carried out by recording the C-13 NMR spectrum of a finely powdered sample to obtain the solid-state line shape which can then be analyzed to determine tensor elements of chemically and structurally different types of carbons. We have analyzed both static and variable angle sample spinning line shapes [2, 3] to obtain the CSA tensor values and population factors for the aromatic carbons of coals, macerals and carbonaceous materials from which aromatic cluster size is estimated.
Smith, L. and Smoot, L.D.
ACERC Report, 1987. Funded by ACERC (National Science Foundation and
Associates and Affiliates).
This report, Selection and Characteristics of Standard ACERC Coals, summarizes the selection and characterization of a standard set of eleven coals to be used in research programs of the Advanced Combustion Engineering Research Center (ACERC). The report also documents the experimental data on the physical and chemical properties of these coals, relates these coals to other coal data banks, identifies major studies where these coals have been or are being used and documents selected references where the coals have been tested in combustion systems. Also included in the report is information about the general aspects of coal characterization. The standard coals were selected according to the following set of criteria: (1) available chemical and physical properties with wide property variations among coal types and ranks, (2) obtained from major producing seams, (3) future production expected, (4) wide geographical distribution within the US, and (5) used in previous work. The suite of eleven ACERC coals was selected because of their general availability and past record of use both nationally and in labs related to ACERC. National centers that provide coal samples and/or coal characterization data include the following: (1) Pennsylvania State University's program aimed at characterizing the Nation's coal resources, including the Penn State Coal Sample Bank and the Penn State Coal Data Base operated by the Energy and Fuels Research Center, (2) the coal sample suite used in the Direct Utilization-Advanced Research and Technology Development program managed by the Pittsburgh Energy Technology Center, and (3) Argonne National Laboratory's Premium Coal Sample Program. These sources were a key element in the selection of coals for ACERC study. The selection of the eleven Standard ACERC Coals relied mostly on standard coals that were already specified and in use by these major coal banks nation-wide. Thus, a source of pristine coal samples is available for most of the Standard ACERC Coals. This suite of well-selected coals will help coordinate the large experimental research effort of ACERC. This report provides a foundation of information on the properties and characteristics of ACERC coals and will facilitate their use in the Center. The report has been published in expandable form so that the information can be updated periodically as needed.
Merrill, R.; Bartholomew,
C.H. and Hecker, W.C.
ACERC Report, 1987. Funded by ACERC (National Science Foundation and
Associates and Affiliates).
During summer 1987 a facility for preparation of coal chars was designed and constructed in a cooperative effort of the catalysis and combustion laboratories. The system devolatilizes coal particles fed up through a flat-flame burner after which they are collected on a water-cooled, gas-quenched probe. The system has been successfully tested in the preparation of a char from a Texas lignite coal. The system is capable of producing about 5-10 g/hr of high-temperature char.
Nishioka, M. and Lee, M.L.
ACS Symp. Ser., 14, 235-253, 1988. 19 pgs. Funded by US Department of
Energy.
Coal-derived material such as coal liquids and coal tars are highly aromatic, and these materials contain polycyclic aromatic compounds (PACs) as major components. Although average descriptive parameters such as molecular weight range, aromaticity, and abundances of functional groups are usually obtained to characterize such materials, detailed chemical analysis is also important for properly assessing health risks due to exposure to such materials and for understanding fundamental chemical reactions involved in upgrading technologies such as coal gasification and liquefaction. In addition, detailed identification of constituents in coal-derived products could provide important information relevant to coal structure.
The structures and relative abundances of polycyclic aromatic compounds (both hydrocarbons and heterocycles) in a solvent-refined coal liquid and in a coal tar were compiled and compared. These structures and relative abundances were determined by detailed analyses performed in our laboratory during the past 7 years. The purpose of this comparison was to determine (1) if preferred aromatic structural features exist in the complex mixture of compounds present in a single coal-derived material and (2) to what extent these preferred structures are evident in different coal-derived materials produced from different feedstocks and under different conditions. Although different feedstocks and process conditions were associated with each of the two coal-derived products studied, remarkably similar structural trends could be seen. If one disregards the structures of the compounds produced by mild autocatalytic hydrogenation in the solvent-refined coal-liquefaction process, the structures of the remaining polycyclic aromatic compounds in both samples are similar. These results suggest that the major compounds identified are either representative of similar aromatic moieties in the original coal feedstock or are a result of processing conditions involving complex reactions that lead to similar stable final products. Because many similar aromatic moieties are found in coal in comparison with coal-derived materials many of the same complex reactions may occur during diagenesis. Such reactions may include cyclo-coupling dehydrogenation.
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