ACERC
Abstracts - 1990 |
ACERC
Abstracts - 1990 |
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Thrust Area 1: Fuel Structure and Reaction Mechanisms |
Meuzelaar, H.L.C., Editor
Plenum Publishing Corporation, 1990 (In press). Funded by ACERC (National Science
Foundation and Associates and Affiliates).
The Second Hidden Peak Symposium on Computer-Enhanced Analytical Spectroscopy, held in June, 1988, at the Snowbird Resort (Salt Lake City, Utah), centered around twelve keynote lectures delivered by some of the foremost experts and pioneers in this rapidly expanding field. The primary objective of this volume is to present a representative cross-section of current activities in the field while balancing out the lighter coverage of some topics and areas in Volume I.
An exciting new topic, remote IR sensing, is covered in Chapters 4 and 5. Deconvolution and signal-processing methods have now been extended to UV/VIS (Chapter 1) and GC/MS (Chapter 3) applications. Furthermore, the development and testing of novel factor analysis techniques in the areas of UV/VIS and IR spectroscopy are discussed in Chapters 2 and 12, respectively. Fundamental aspects of library search techniques are presented in Chapters 7 (MS) and 9 (NMR). Chapters 6, 10, and 11 cover selected uses of expert systems in IR, NMR, and MS, respectively. Finally, an integrated expert system approach to the interpretation of GC/IR/MS data is outlined in Chapter 8.
In an attempt to facilitate access to the various topics for the newcomer to the field, the twelve chapters have been organized into two main parts: Unsupervised Methods: Spectral Enhancement, Deconvolution, and Data Reduction, and Supervised Methods: Expert Systems, Modeling, and Quantitation.
All in all, the second volume is intended to constitute a logical complement to Volume I. Consequently, for a more comprehensive update of developments in the field over the past five years or so, the reader is encouraged to consult both Volume I and Volume II.
Simmleit, N.; Yun, Y.; Meuzelaar,
H.L.C. and Schulten, H.R.
Advances in Coal Spectroscopy, Meuzelaar, H.L.C., Editor, Plenum Publishing
Corp., New York, 1990 (In press). Funded by ACERC (National Science Foundation
and Associates and Affiliates).
Analytical pyrolysis techniques are widely used for the thermochemical analysis of coals and coal-derived products. During heating, complex mixtures of chemical substances are released from coal by distillation, desorption and thermal degradation processes. The amount and chemical nature of the volatilized coal products are dependent mainly on the composition and structure of the coal and on heating conditions. Therefore, the results of chemical analyses of the volatilized coal products should provide information on the original structure of coal. For detailed on-line analysis of volatilized coal products usually chromatographic and/or spectroscopic methods have been used. For positive identification of compounds gas chromatography/mass spectrometry (GC/MS) is a common approach, e.g. in direct combination with pyrolysis techniques. However, due to the relatively long analysis times, in particular for high molecular weight products, GC/MS is not suited for a universal on-line monitoring of evolving coal products during heating. For rapid fingerprinting of volatilized coal products on a molecular basis direct MS analysis is often the preferred method. Small amounts of coal or coal-derived products are heated in front of the ionization region under high vacuum conditions. Depending on the type of mass spectrometer used and the experimental conditions, on-line monitoring of evolving coal products is possible for a wide range of heating rate. Heating rates as low as 10-2 C/s may be used in the combined thermogravimetry (TG)/MS whereas heating rates in the 104 - 106 C/s range can be obtained by CO2 laser heating.
Meuzelaar, H.L.C., Editor
Computer-Enhanced
Analytical Spectroscopy, Volume II, Plenum Publishing Corporation, 1990
(In press). Funded by ACERC (National Science Foundation and Associates and
Affiliates).
Coals may be regarded as highly complex, fossilized assemblages of more or less strongly decomposed plant matter, microorganisms and humic substances in addition to a range of possible mineral constituents. Specific coal seams may represent peat-forming palaeoenvironments as diverse as river delta swamps, salt water marshes or rain forest bogs, thus explaining the intrinsic heterogeneity of coal at the macroscopic as well as microscopic levels. Macroscopically, coal heterogeneity is often readily visible in the form of discrete bands representing successions of different depositional environments or, perhaps, catastrophic events such as floods and forest fires. At the microscopic level most coals display an even broader scale of diversity and heterogeneity in the form of microscopically distinct coal components generally referred to as "macerals."
Orendt, A.M.; Solum, M.S.;
Sethi, N.K.; Pugmire, R.J. and Grant, D.M.
Advances in Coal Spectroscopy, Meuzelaar, H.L.C., Editor, Plenum Publishing
Corp., New York, 1990 (In press). Funded by ACERC and US Department of Energy.
Techniques in C-13 nuclear magnetic resonance spectroscopy applied in the study of coal and coal chars are discussed along with details of the analysis of the spectral results. The results are compared for various methods of analysis: cross polarization with magic angle spinning (CP/MAS), dipolar dephasing (DD), MAS with block decays (BD), and chemical shielding anisotropy (CSA) measurements. Results of the CP/MAS and DD experiments on the Argonne premium coals as well as other coals and coal chars are reported in terms of twelve structural parameters, including aromaticity. Methods used to determine average cluster size and molecular weight are discussed. Models of coal structure and devolatilization processes are presented along with an analysis of the information obtained from the C-13 NMR experiments.
Fletcher, T.H.; Kerstein,
A.R.; Pugmire, R.J. and Grant, D.M.
Energy & Fuels, 4 (54), 1990. Funded by Pittsburgh Energy Technology
Center, US Department of Energy, National Science Foundation and ACERC.
The chemical percolation devolatilization (CPD) model previously developed to describe the devolatilization behavior of rapidly heated coal was based on the chemical structure of the parent coal. Percolation lattice statistics are employed to describe generation of finite tar clusters as labile bonds are cleaved in the infinite coal lattice. The model is used here to describe effects of heating rate and temperature on tar and gas release from coal. Coefficients for the net rate of competition between char formation and side-chain formation are generated from heated screen data performed at five different heating rates. The model also compares well with heated screen data obtained at 1000 K/s and different hold times at the final temperature as well as with data from entrained-flow reactors obtained at higher heating rates (104 K/s) where particle temperatures have been measured. Results indicate that the CPD model predictions yield good agreement with published data for a wide range of coals and particle heating rates.
Dunkel, R.; Mayne, C.L.;
Curtis, J.; Pugmire, R.J. and Grant, D.M.
Journal of Magnetic Resonance, 90, 290-302, 1990. Funded by ACERC and
US Department of Energy.
The extraction of carbon-carbon bond information from two-dimensional INADEQUATE spectra is both time consuming and complex due to the low sensitivity of the method, the incomplete suppression of single-quantum signals, and the large size of the data sets. A computerized analysis technique is introduced which detects bonds through a nonlinear regression analysis of carefully chosen subsets of the spectral data. A quantitative one-dimensional carbon spectrum is used to establish initial values for the regression and to determine the data subsets to be used. Using statistical analysis techniques, bonds are detected with reliability and sensitivity comparable to those of careful manual interpretation.
Pugmire, R.J.; Solum, M.S.;
Grant, D.M.; Critchfield, S. and Fletcher, T.H.
Fuel, 1990 (In press). Funded by ACERC.
Solid-state C-13 and H-1 nuclear magnetic resonance (NMR) spectroscopy techniques are used to investigate the relationship between chemical structures of coal and the char particles and condensed tar vapors produced from coals of various ranks at rapid heating conditions. The C-13 NMR analysis of the coal chars indicate that significant amounts of aliphatic material is released from the coal during devolatilization with little initial change to the aromatic cluster size or number of cross links per cluster. The evolution of the char structure following tar release is a function of the time/temperature history of the char. The structures of the primary tars are compared to the parent coal and the gas phase evolution of the tar structure is followed with time.
Crelling, J.C.; Pugmire,
R.J.; Meuzelaar, H.L.C.; McClennen, W.H.; Huai, H. and Karas, J.
Energy & Fuels, 1990 (In press). Funded by ACERC and US Department of
Energy.
Although the maceral resinite occurs in most U.S. coals, it is particularly abundant in the coal seams of the Wasatch Plateau coalfield in 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. Details of the chemical structure of the micropetrographically defined maceral resinite have generally been lacking because it is noncrystalline and is only partially soluble in organic solvents. In contrast with the abundance of spectroscopic and chromatographic data available on some of the better known fossil resin types, e.g., Baltic amber, Utah coal resins appear to have generated relatively little interest among coal scientists. The overall objective of the present study was to examine the structure of Utah Wasatch Plateau coal resinite macerals that have been separated from the coal matrix, purified, and most important, carefully characterized by fluorescence spectral analysis. The samples were then analyzed by means of CP/MAS C NMR and by Curie-point pyrolysis in direct combination with mass spectrometry (Py-MS) or via preseparation by gas chromatography (Py-GC/MS).
Yun, Y.; Meuzelaar, H.L.C.;
Simmleit, N. and Schulten, H.R.
Energy & Fuels, 1990 (In press). Funded by ACERC.
Three different vacuum pyrolysis mass spectrometry techniques, viz. Pyrolysis-Field Ionization Mass Spectrometry, Thermogravimetry/Low Voltage Electron Ionization Mass Spectrometry and Curie-point Pyrolysis-Low Voltage Electron Ionization Mass Spectrometry were used to analyze samples of Pittsburgh #8 coal obtained from the Argonne National Laboratory Premium Coal Sample Program. The primary objective was to assess the effects of differences in experimental techniques and conditions, e.g., with regard to heating rates, pyrolysis methods and soft ionization procedures (FI vs. Low Voltage EI) on the mass spectral patterns. A second objective was to further characterize and study the pyrolysis behavior of Pittsburgh #8 coal. The results indicate that the distribution and the type of the primary pyrolysis products are largely independent of marked differences in heating rate (10-2 K/s - 104 K/s range) and sample size (2.5 x 10-5g - 5.0 x 10-2g range) as well as overall vacuum pyrolysis MS configurations and conditions used. All three vacuum pyrolysis MS techniques produce remarkably similar mass spectral patterns when analyzing Pittsburgh #8 coal. The results show that Pittsburgh #8 coal contains a significant amount of low temperature (<380ºC) evolving "bitumen" consisting primarily of alkyl-substituted aromatic components. The bitumen evolution step is followed by a partially overlapping "bulk pyrolysis" step characterized by the evolution of abundant hydroxy- and dihydroxy substituted aromatic compounds, thought to be primarily derived from vitrinitic components. During the bitumen evolution step the average MW of the compounds increases with temperature while maintaining a relatively narrow distribution. By contrast, during the bulk pyrolysis step, the average MW tends to decrease while exhibiting a much broader distribution.
Chakravarty, T.; Khan, M.R.
and Meuzelaar, H.L.C.
Industrial and Engineering Research, 29 (11), 2173-2180, 1990. Funded
by Consortium for Fossil Fuel Liquifaction Science.
Low-voltage electron ionization mass spectrometry (LV-EIMS) was performed on 25 fossil fuel samples (21 coals, 2 oil shades, 1 tar sand, and 1 coal resin concentrate) and their respective pyrolysis liquids prepared at Morgantown Energy Technology Center (METC) by means of a fixed-bed reactor. By using principal component analysis, the tar evaporation spectra and the solid fuel pyrolysis spectra were classified in terms of the underlying structural variables. In both data sets, all 4 non-coal samples, as well as 2 less typical coal samples, were found to be outliers. After removing the 6 outliers, canonical correlation analysis was performed on the remaining subsets of 19 coal samples in order to bring out the compositional similarities and differences between the fossil fuel samples and their pyrolysis liquids. By determining the common sources of variance between the two data sets by means of canonical correlation analyses, it was demonstrated that the canonical variate model enabled prediction of the mass spectrum of a given coal tar sample from the measured pyrolysis mass spectrum of the corresponding coal sample. Agreement with the experimental results was reasonably good.
Taghizadeh, K.; Hardy, R.H.,
Davis, B.H. and Meuzelaar, H.L.C.
Fuel Processing Technology, 1990 (In press). Funded by Consortium for
Fossil Fuel Liquifaction Science, Commonwealth of Kentucky, Kentucky Energy
Cabinet and US Department of Energy.
Low voltage - Electron Ionization (LV-EI) and Field ionization (FI) mass spectra of coal-derived liquids (CDLs) obtained from the Wilsonville Coal liquefaction pilot plant before and after hydrotreatment were compared. LV-EIMS (12 eV) analysis of Wilsonville CDL'S before and after hydrotreatment produces very similar spectral patterns as obtained by FIMS. This is especially true for the more highly aromatic hydrotreater feed samples since the hydroaromatic compounds that dominate the hydrotreater product sampler 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 is severely under-represented in the LV-EIMS patterns, due to lower inlet temperatures and to mass discrimination effects in quadrupole MS systems. 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.
Juvancz, Z.; Payne, K.M.;
Markides, K.E. and Lee, M.L.
Analytical Chemistry, 62, 1990. Funded by Brigham Young University.
An on-line two-dimensional supercritical fluid chromatographic system (SFC/SFC) was constructed by utilizing a rotary valve interface to provide independent flow control of the two dimensions. A cold trap was employed to refocus solutes from single or multiple fractional cuts, after being transferred to the second dimension. Improved performance, including time savings, was achieved with a packed capillary to open tubular column arrangement and two independently controlled pumps, compared to earlier reported single-pump open tubular column SFC/SFC and packed capillary column SFC/SFC systems. The packed capillary in the first dimension provided a rapid chemical class separation, while the open tubular column in the second dimension provided high resolution of closely related isomers.
Rasband, P.B. and Hecker,
W.C.
Catalysis Today, 8, 99-111, 1990. Funded by Brigham Young University.
Several 2% Rh/silica catalysts containing from 0 to 6% Nb205 were prepared by consecutive impregnations with aqueous solutions of niobium oxalate and rhodium trichloride. These catalysts were studied using Fourier Transform Infrared Spectroscopy (FTIR) to determine Rh oxidation state and dispersion. The addition of Nb205 to Rh/SiO2 resulted in a decrease in Rh(0) for relatively low niobia loadings (0 to 3% Nb2O5) and an increase in Rh(1) for higher niobia loadings (3 to 6% Nb205). These two effects combined to give a minimum Rh dispersion for a catalyst containing approximately 3% Nb2O5. For the reduction of NO by CO the niobia addition decreased the observed rate (per gram catalyst) but had little effect on activation energy or concentration dependencies. A combination of the observed rate and Rh dispersion data suggests that specific rate varies inversely with Rh dispersion for these catalysts and conditions.
Wells, W.F. and Smoot, L.D.
Fuel, 1990 (In press). Funded by Pittsburgh Energy Technology Center.
Causal relationships were determined for the chemical and physical properties and reaction characteristics of three coals and two types of chars derived from these coals. The reactivities of the virgin coals and extract chars correlated well with the fuel rank. The higher proximate volatiles contents in these prepared fuels resulted in reactivities higher than those measured for the low volatile pyrolysis chars. The reactivities of the pyrolysis chars were strongly correlated with fuel properties, whose relative order of importance was: catalytic elements > porosity > hydrogen types > cluster size.
Facelli, J.C.; Grant, D.M.;
Bouman, T.D. and Hansen, A.E.
Journal of Computational Chemistry, 11 (32), 1990. Funded by National
Institutes of Health, US Department of Energy, National Science Foundation and
the Carlsberg Foundation.
The individual gauge for localized orbitals (IGLO) and localized orbital/local origin (LORG) methods for the calculation of chemical shieldings are compared from their theoretical and computational viewpoints. A detailed analysis of the fluorine substituent effect in a series of fluoromethanes is given in terms of the IGLO and LORG bond contributions. The performance of both methods is discussed for molecular systems of fairly different sizes.
Alderman, D.W.; Sherwood,
M.H. and Grant, D.M.
Journal of Magnetic Resonance, 86, 60-69, 1990. Funded by US Department
of Energy.
Chemical-shift tensors can be determined from a single crystal placed in six or more orientations in a magnetic field. The sensitivity of this determination as a function of the selected crystal orientations is considered with a statistical figure of merit. A variety of configurations are examined, and it is found that the set of six orientations based on the vertices of an icosahedron optimizes the figure of merit and results in the most sensitive determination of the tensor. The relationship of these optimal orientations to those used previously in two-dimensional chemical-shift tensor correlation spectroscopy is discussed. It is shown that the high symmetry of the icosahedron simplifies the design on which the construction of a new sample orienting mechanism may be based.
Gan, Z.H. and Grant, D.M.
Chemical Physics Letters, 168 (3,4), 1990. Funded by a National Institute
of Health research grant from the Institution of General Medical Science.
In the magic angle spinning NMR experiment, a rotational resonance phenomenon occurs whenever a spin-lock rf field is either equal to or twice the sample spinning speed. The resonance occurs in the rotating frame where the spin-lock field assumes the role of the "Zeeman" interaction and the chemical shift modulated by the sample rotation is the "radio frequency" irradiation. The importance of good rf field homogeneity to the experiment is shown.
Sethi, N.K.; Alderman, D.W.
and Grant, D.M.
Molecular Physics, 71 (2), 217-238, 1990. Funded by US Department of
Energy.
A new method is described for calculating NMR spectra of powdered solids spinning at any speed and at any angle relative to the magnetic field. The algorithm provides the intensities and shapes of the center band and all sidebands through a computation involving the solution of homogeneous linear equations. The method is also applicable to cases where two or more inter-actions simultaneously affect the spectral response. A simple extension of the algorithm treats cases where an analytical expression for the resonance frequency is not available. The method is demonstrated with simulations and experimental examples of anisotropic chemical-shift spectra obtained by spinning samples at various low speeds and angles. The technique is also applied to a spin-1/2 nucleus with both an anisotropic chemical shift and a dipolar coupling either to a heteronuclear spin-1/2 nucleus or to a spin-1 nucleus experiencing a strong quadrupole interaction.
Gan, Z.H. and Grant, D.M.
Journal of Magnetic Resonance, 1990 (In press). Funded by National Institute
of Health.
A sample-spinning solid-state NMR study of a spin-1/2 nucleus coupled to a quadrupolar nucleus is presented. Using a simple approach, the quadrupolar effect is expanded in terms of irreducible spherical tensor components up to / = 4. Information on the electric field gradient tensor orientation, dipolar coupling, and chemical-shielding tensor for the C-13/N-14 system can be obtained experimentally from the magic-angle and the off-magic-angle sample-spinning spectra. Satisfactory results are obtained by comparing the simulations with the experimental spectra of tetramethylpyrazine, dimethyglyoxime, and triethylenediamine.
Sherwood, M.H.; Facelli,
J.C.; Alderman, D.W. and Grant, D.M.
Am. Chem. Soc., 1990 (In press). Funded by US Department of Energy.
Carbon-13 chemical shift tensors have been determined in single crystal nephthalene. The high field component of every tensor is oriented perpendicular to the molecular plane, as in other aromatic compounds. The bridgehead carbon tensor is nearly axially symmetric, with its low field component approximately perpendicular to the central bridging bond, in agreement with theoretical predictions. Protonated carbon tensors in naphalene are more asymmetric, with their low-field components directed approximately along the C-H bonds. The Pople model of chemical shielding with MNDO wave functions reproduces the experimental in-plane shielding components. These calculations show that the in-plane components of the carbon shift tensors are governed by the bond orders of the adjacent bonds, and shift tensors thus provide valuable information relating to aromaticity. The measured tensors deviate significantly from the symmetry of an isolated naphthalene molecule because of the lower symmetry of the molecular site in the crystal.
Carlson, R.E.; Critchfield,
S.; Vorkink, W.P.; Dong, J.-Z.; Pugmire, R.J.; Bartle, K.D. and Lee, M.L.
Fuel, 1990 (In Press). Funded by US Department of Energy, Gas Research
Institute and ACERC.
A selective, low temperature depolymerization procedure has been applied to four Argonne coals of different rank to produce products that are representative of the original coal macromolecular structure, and that are amenable to chromatographic analysis. The products of this depolymerization procedure retained most of the original aromatic and functional group structures of the original coals. A comparison of liquid C-13 NMR spectra of the products and solid-state C-13 NMR spectra of the original coals showed only minor changes in the aromaticities of two of the coals, and some loss of the carbonyl carbons in all of the coals.
Tetrahydrofuran pre-extracts of the four coals and their depolymerized products were separated into chemical classes by adsorption chromatography. Two of these fractions, which contained aliphatic hydrocarbons and polycyclic aromatic hydrocarbons were analyzed using gas chromatography/mass spectrometry. Structural identifications were based on a combination of chromatographic retention and mass spectral fragmentation data. For the lower rank coals, the compositions of the pre-extracts were quite different from the corresponding depolymerized products, and they contained an abundance of molecular biological markers. The compositions of the pre-extracts became more similar to the depolymerized products as rank increased.
Smith, K.L. and Smoot, L.D.
Prog. Energy Combust. Science, 16, 1-53, 1990. Funded by ACERC.
This review summarizes the selection and characterization of a set of coals commonly used in research programs in the United States. These coals have been selected from available U.S. coal databases. Organizations that provide coal samples and/or coal characterization data include the following: (1) Pennsylvania State University, which has characterized many of the Nation's coal resources, as documented in 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. The selection of eleven coals from these national banks provides a standard suite of coals for the Advanced Combustion Engineering Research Center of Brigham Young University and the University of Utah. These standard coals were selected according to the following criteria: (1) representative of a variety of characteristics, ranks and properties, (2) available analyses of chemical and physical properties with wide property variations among coal types and ranks, (3) availability from major producing seams, (4) future production expected, (5) wide geographical distribution within the U.S., (6) used in previous combustion research work, (7) common to existing prominent coal banks, and (8) availability of small, controlled samples. Information about the general aspects of coal characterization is summarized. Experimental data on the physical and chemical properties of these coals are documented, and the selected coals are related to the coal data banks. Major combustion research studies where these coals have been or are being used are referenced. General use of these well-characterized coals will help coordinate and integrate a national research effort in coal combustion and conversion.
Chang, H.-C.K.; Skelton,
R.J. Jr.; Markides, K.E. and Lee, M.L.
Polycyclic Aromatic Compounds, 1:251-264, 1990. Funded by Gas Research
Institute and ACERC.
Detailed identification of sulfur-containing polycyclic aromatic compounds (S-PAC) was accomplished for solvent extracts of five different coals. The S-PAC were isolated by ligand-exchange chromatography. Due to the great complexities of these samples, capillary gas chromatography (GC) was employed for their analysis. An element selective radio frequency plasma detector was used to provide sulfur selective detections. Gas chromatography-mass spectrometry was used to identify individual compounds in isolated sulfur fractions. Condensed thiophenic compounds were found to be the major constituents in all five S-PAC fractions. Diaryl sulfides were also detected in the high volatile bituminous Illinois #6 coal. The prevalence of various S-PAC in different coal extracts was observed as a function of their rank.
Fletcher, T.H.; Kerstein,
A.R.; Pugmire, R.J.; Solum, M.S. and Grant, D.M.
Polycyclic Aromatic Compounds, 1:251-264, 1990. Funded by Gas Research
Institute and ACERC.
The chemical percolation devolatilization (CPD) model describes the devolatilization behavior of rapidly heated coal based on the chemical structure of the parent coal. Percolation lattice statistics are employed to describe the generation of tar precursors of finite size based on the number of cleaved labile bonds in the infinite coal lattice. The chemical percolation devolatilization model described here includes treatment of vapor-liquid equilibrium and a cross-linking mechanism. The cross-linking mechanism permits reattachment of metaplast to the infinite char matrix. A generalized vapor pressure correlation for high molecular weight hydrocarbons, such as coal tar, is proposed based on data from coal liquids. Coal-independent kinetic parameters are employed. Coal-dependent chemical structure coefficients for the CPD model are taken directly from C-13 NMR measurements, with the exception of one empirical parameter representing the population of char bridges in the parent coal. This is in contrast to the previous and common practice of adjusting input coefficients to precisely match measured tar and total volatiles yields. The CPD model successfully predicts the effects of pressure on tar and total volatiles yields observed in heated grid experiments for both bituminous coal and for lignite. Predicted tar molecular weights are consistent with size-exclusion chromatography (SEC) data and field ionization mass spectrometry (FIMS) data. Predictions of average molecular weights of aromatic clusters as a function of coal type agree with corresponding data from NMR analyses of parent coals. The direct use of chemical structure data as a function of coal type helps justify the model on a mechanistic rather than an empirical basis.
Lo, R.; Pugmire, R.J.; Fletcher,
T.H. and Meuzelaar, H.L.C.
Preprints for Papers Presented at the 200th ACS National Meeting, 35
(3), 697-704, Washington, D.C., 1990. Funded by ACERC and Consortium for Fossil
Fuel Liquifaction Science.
Curie-point desorption in combination with Gas Chromatography/Mass Spectrometry (GC/MS) and, alternatively, with direct Low Voltage Mass Spectrometry (LV-MS) was used to investigate the chemical composition and structure of condensed tar vapors produced during rapid devolatilization (heating rate ~10,000 K/sec) of carefully sized coal particles representing the Beulah Zap, Big Blue, Illinois #6, Pittsburgh #8, and Pocahontas #3 seams, respectively, using the laminar flow reactor described by Fletcher et al at two gas temperatures (1050 K and 1250).
Tar samples were collected by means of a special probe at different points downstream of and corresponding to residence times between 70 and 250 ms. GC/MS analyses of the corresponding tars indicate that the degree of aromaticity increased rapidly as a function of residence time at the 1250 K gas temperature condition. Moreover, at 1250 K devolatilization is complete within 70 ms and beginning secondary gas phase reactions of tar vapors (viz. marked increases in PNAH content and corresponding decreases in phenolic components) are observed within less than 100 ms. However, at 1050 K the coal devolatilization process appears to be barely complete after 250 ms and little or no evidence of secondary gas phase reactions is found.
Maswadeh, W.; Arnold, N.S.
and Meuzelaar, H.L.C.
Proc. of the 38th ASMS Conference on Mass Spectrometry and Allied Topics,
Tucson, AZ, 599-600, 1990. (Also presented at Pyrolysis 90, Amsterdam,
The Netherlands, 1990; ACS Joint 45th Northwest/Rocky Mountain Regional Meeting,
Salt Lake City, UT, 1990; ACS Division of Fuel Chemistry and Preprints for
Papers Presented at the 200th ACS National Meeting, 35 (3), 755-762, Washington,
D.C., 1990). Funded by ACERC.
A laser pyrolysis transfer line gas chromatography/mass spectrometry (laser Py-TLGC/MS) system based on the combination of an electronically pulsed CW C02 laser with an electrodynamic balance (EDB), a heated capillary ("transfer line") GC column and an ion trap mass spectrometer (ITMS) was constructed.
The main purpose of the system is to study the devolatilization behavior of single, levitated coal particles at very high heating rates, e.g., 105 - 106 K/sec, while comparing the composition of the devolatilization products to those observed at much lower heating rates, e.g., 10-2 - 10-2 K/sec.
McClennen, W.H.; Arnold,
N.S.; Sheya, S.A.N.; Lighty, J.S. and Meuzelaar, H.L.C.
Preprints for Papers Presented at the 200th ACS National Meeting, 35
(3), 713-720, Washington, D.C., 1990. Funded by ACERC.
An on-line gas and vapor analysis method has been developed to monitor combustion products by short column ("transfer line") Gas Chromatography/Mass Spectrometry. An automated vapor-sampling inlet with only inert materials (quartz and fused silica) in the sample path is utilized to introduce flue gases into a 1 m long "transfer line" capillary GC column for rapid, repetitive chromatographic separation of products. The column effluent is introduced directly into the source of an ion trap type mass spectrometer. Combustion products from a gas fired rotary kiln were monitored by this method using a standard Ion Trap Detector (ITD). Detection limits of 20 to 50 ppb were obtained for various substituted benzenes. Monitoring of polycyclic aromatic hydrocarbons (PAHs) from the thermal desorption of contaminated soils in a fixed bed reactor utilized a modified Ion Trap Mass Spectrometer (ITMS). Varying isothermal column temperature allowed analysis of PAHs from naphthalene through 6 ring PAHs. The ITMS system provides higher sensitivity (~4 ppb for benzene) in addition to tandem MS and chemical ionization capabilities for unambiguous identification of combustion products incompletely resolved by the transfer line GC approach.
Holbrook, K.M.; Buchanan,
R.M. and Meuzelaar, H.L.C.
Proc. of the 38th ASME Conference on Mass Spectrometry and Allied Topics,
900-901, Tucson, AZ, 1990. Funded by ACERC and Hewlett Packard Corp.
Combined TG/IR and, to some extent, TG/MS techniques are finding increased application for structure/reactivity studies as well as for characterization and quality control of synthetic polymers, fossil fuels and natural products. Unfortunately, the high cost of most integrated TG/MS and TG/IR (let alone TG/MS) systems has kept these techniques well out of reach for most analytical laboratories.
Urban, D.T.; Arnold, N.S.
and Meuzelaar, H.L.C.
Proc. of the 38th ASMS Conference on Mass Spectrometry and Allied Topics,
615-616, Tucson, AZ, 1990. Funded by ACERC and Hewlett Packard Corp.
In many potentially dangerous situations of environmental contamination from volatile organic compounds, rapid on-site analysis is essential to the protection of human life. Mobile GC/MS laboratories have been developed for this purpose, yet in many situations terrain limitations or decontamination worries make a vehicle-based system undesirable. To circumvent this vehicular limitation and provide in-situ analysis, a man-portable transfer line GC/MS system is being developed.
Huai, H.; Lo, R.; Yun, Y.
and Meuzelaar, H.L.C.
ACS Division of Chemistry, 35 (3), Washington, D.C., 1990. (Also Proc.
of the 38th ASMS Conference on Mass Spectrometry and Allied Topics, Tucson,
AZ, 601-602, 1990). Funded by Consortium for Fossil Fuel Liquefaction Science.
Eight U.S. coals of different rank and/or composition, obtained through the Argonne National Laboratory Premium Coal Sample Program, were analyzed by means of several different pyrolysis-MS (Py-MS) techniques, namely: direct Curie-Point Py-MS, Curie-point Py-GC/MS (including GC/EIMS, GC/CIMS and "short column" GC/CIMS), and vacuum thermogravimetry/MS (TG/MS). The data obtained were compared to Pyrolysis-Field Ionization MS (Py-FIMS) data.
The results show a very good agreement between all techniques used in spite of the marked differences in pyrolysis techniques (Curie-point, furnace, direct probe), "soft" ionization methods (low voltage EI, CI FI) and mass spectrometer types (quadrupole, ion trap, magnetic sector) used. As might be expected, the most pronounced variations between techniques appear to be due to mass dependent differences in ion transmissivity and detector response, with the type of soft ionization method taking second place and the type of pyrolysis technique showing least effect on the results. Whereas Py-FIMS provides the most complete and detailed overview of the coal pyrolysis tars, Cuire-point Py-MS and TG/MS methods provide more reliable information on relatively light gaseous products, and Curie-point Py-GC/MS shows the detail composition of the 2/3 of the total pyrolysis tars.
McDonald, K.M.; Hyde, W.D.
and Hecker, W.C.
Western States Section/The Combustion Institute, San Diego, CA, 1990.
Funded by ACERC.
An accurate char oxidation submodel is an essential element of a realistic model of coal combustion. To aid in the development and validation of such a submodel, which will be used in comprehensive combustion codes being developed at ACERC, oxidation rates and rate parameters were measured for chars prepared from ACERC coals. In this study, chars derived from Beulah-Zap (lignite A) and Dietz (sub-bituminous B) coals were prepared in three different reactor systems: (1) a flat-flame methane burner, (2) an inert-atmosphere drop tube reactor, and (3) a muffle furnace. Low temperature oxidation rates and kinetic parameters were determined using isothermal thermogravimetric analysis (TGA) at temperatures between 550 and 950 K.
Reactivities at different oxidation burnout levels (10%-75%) were compared on both an initial mass and an available mass basis. The initial mass basis provided no clear distinction from which behavioral differences in the different burnout levels could be deduced. Basing rates on the available mass, however, elucidated the fact that in the intrinsic regime, rates are nearly identical for the different burnout levels. The available mass basis also made clear the fact that the lower burnout levels are more highly influenced by diffusion effects. This was manifest by a decrease in the slope of the Arrhenius plot beginning at a temperature of about 750 K for the char at 10% burnout compared to a temperature of nearly 900 K for the char at 75% burnout.
In comparing the chars produced in the three different reactors, reactivities in the reaction control regime showed that, for both coals, the drop tube char was more reactive than either the flat flame or muffle furnace char. Further tests indicated that the drop tube chars had a hydrogen to carbon ratio that was 2.5 to 5 times greater than the char from either of the other reactors and the percent conversion for devolatilization was significantly less. The activation energy for all three Beulah-Zap chars and for the Dietz muffle furnace and flat flame chars was found to be 28.10.6 kcal/mol. Data from the Dietz drop tube char is as yet insufficient to yield an accurate activation energy value.
A comparison of the reactivities for the flat flame burner chars of the lignite and the sub-bituminous showed that the lignite chars were more reactive by a factor of two. This was consistent over all burnout levels. Further work with the Dietz flat flame char showed an apparent reaction order of 0.66. This is in excellent agreement with data found in the literature.
Orendt, A.M.; Solum, M.S.;
Sethi, N.K.; Hughes, C.D.; Pugmire, R.J. and Grant, D.M.
Magnetic Resonance of Solid Carbonaceous Fuels, ACS Symposium Series,
Botto, R.E. and Sanada, Y., Editors, 1990 (In press). Funded by ACERC and US
Department of Energy.
The methods available in nuclear magnetic resonance to obtain the principal values of the shielding tensor are discussed. Applications to coal and to compounds that model structures that might be important in coal are presented. The composition of aromatic carbons in coal as determined by chemical shielding powder patterns is compared to results obtained by cross polarization with magic angle spinning (CP/MAS) and dipolar dephasing (DD).
Yun, Y.; Meuzelaar, H.L.C.;
Simmleit, N. and Schulten, H.R.
Recent Advances in Coal Science: A Symposium in Remembrance of Peter H. Given,
Schobert, H.; Bartle, K. and Lynch, L., Editors, ACS Symposium Series,
American Chemical Society, Washington, D.C., 1990 (In press). Funded by ACERC.
Seven Argonne Premium coal samples ranging from lignite to low volatile bituminous in rank were analyzed by Pyrolysis-Field Ionization Mass Spectrometry (Py-FIMS) in order to determine the existence and structural nature of a thermally extractable "mobile phase." In addition, Curie-point Pyrolysis-Low Voltage Mass Spectrometry (Py-LVMS) was employed to demonstrate the importance of mild oxidation on the thermally extractable mobile phase components. Py-FIMS results clearly reveal the existence of a thermally extractable, bitumen-like fraction which is chemically distinct from the remaining coal components.
Py-FIMS results clearly reveal the existence of a thermally extractable, bitumen-like fraction that is chemically distinct from the remaining coal components. In lignite, several biomarker compounds were noticeable in the mobile phase components while bituminous coals contain various alkylsubstituted aromatic compounds in the mobile phase. Blind Canyon coal, which contains 11% resinite, exhibits mobile phase components believed to originate from terpenoid aromatization. Curie-point Py-LVMS results illustrate the importance of the oxidation status of coal for studying the mobile phase since mild air oxidation severely changes the structural characteristics of the thermally extractable mobile phase.
Page, S.H.; Goates, S.R.
and Lee, M.L.
Twelfth International Symposium on Capillary Chromatography, Kobe, Japan,
1990. Funded by Gas Research Institute.
The phase behaviors of binary compositions of carbon dioxide with organic modifiers (acetonitrile, methanol and propylene carbonate) were studied using laser light scattering in the near critical region (0-20 mol%, 80-400 atm, and 60-120ºC). In order to maintain supercritical fluid conditions, the pressure, temperature, and mole percent must be properly adjusted for each composition. The three regions of two-phase phenomena are described.
Fletcher, T.H.; Solum, M.S.;
Grant, D.M.; Critchfield, S. and Pugmire, R.J.
Twenty-third Symposium (International) on Combustion, The Combustion
Institute, France, 1990 (In press). Funded by US Department of Energy and
ACERC.
Solid-state C-13 and H-1 nuclear magnetic resonance (NMR) spectroscopy techniques are used to investigate the chemical structure of char particles and condensed tar vapors produced as pyrolysis products from an Illinois #6 coal at rapid heating conditions (~104 K/s) at two gas conditions (maximum gas temperatures of 1250 K and 1050 K). The temperature history of particles in the flow reactor is determined using a unique infrared sizing-pyrometry system. The C-13 NMR analyses of the coal chars indicate that significant amounts of aliphatic material are released from the coal during devolatilization, with little change to the aromatic cluster size or number of attachments per cluster. At long residence times, and at higher temperatures, small increases in the cluster size in the char are observed. The H-1 NMR analyses indicate that thermal decomposition of tar vapor occurs at the 1250 K gas condition, as evidenced by increases in the aromaticity and decreases in the peripheral aliphatic groups, such as methyl groups and aliphatic bridge material.
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