Nishioka, M
1988-1986
Identification and Comparison of Low-Molecular-Weight Neutral Constituents in Two Different Coal Extracts
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.
Preferred Annellated Structures of Polycyclic Aromatic Compounds in Coal-Derived Materials
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.
Structural Characteristics of Polycyclic Aromatic Hydrocarbon Isomers in Coal Tars and Combustion Products
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.
Sulphur Heterocycles in Coal-Derived Products: Reduction Between Structure and Abundance
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.
Nishioka, M
1988-1986
Identification and Comparison of Low-Molecular-Weight Neutral Constituents in Two Different Coal Extracts
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.
Preferred Annellated Structures of Polycyclic Aromatic Compounds in Coal-Derived Materials
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.
Structural Characteristics of Polycyclic Aromatic Hydrocarbon Isomers in Coal Tars and Combustion Products
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.
Sulphur Heterocycles in Coal-Derived Products: Reduction Between Structure and Abundance
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.