Greegor, RB
1989
Investigation of the Molecular Structure of Organic Sulfur in Coal by XAFS Spectroscopy
Huffman, G.P.; Huggins, F.E.; Mitra, S.; Shah, N.; Pugmire, R.J.; Davis, B.H.; Lytle, F.W. and Greegor, R.B.
Energy & Fuels, 3, 200, 1989. Funded by US Department of Energy.
X-ray absorption fine structure (XAFS) spectroscopy has been used to investigate the molecular structure of organic sulfur in a suite of maceral separates and in several biodesulfurized and extracted coal specimens. For most samples, the X-ray absorption near-edge structure (XANES) exhibits sharp peaks just above the absorption edge that are characteristic of s Æ p transitions of compounds containing an aromatically bound sulfur atom and a broad, structured maximum at somewhat higher energies. The latter maximum is believed to arise from resonant backscattering of photoelectrons by carbon atoms 3.5-4.1 Å from the sulfur atom and possibly from s Æ p transitions of sulfur bonded to oxygen. The radial structure functions derived by Fourier analysis of the EXAFS exhibit peaks at distances that are compatible with the first three neighbor shells surrounding an aromatically bound sulfur atom.
1988-1986
EXAFS Investigation of Organic Sulfur in Coal
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.
Investigation of the Atomic and Physical Structure of Organic and Inorganic Sulfur in Coal
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.
Greegor, RB
1989
Investigation of the Molecular Structure of Organic Sulfur in Coal by XAFS Spectroscopy
Huffman, G.P.; Huggins, F.E.; Mitra, S.; Shah, N.; Pugmire, R.J.; Davis, B.H.; Lytle, F.W. and Greegor, R.B.
Energy & Fuels, 3, 200, 1989. Funded by US Department of Energy.
X-ray absorption fine structure (XAFS) spectroscopy has been used to investigate the molecular structure of organic sulfur in a suite of maceral separates and in several biodesulfurized and extracted coal specimens. For most samples, the X-ray absorption near-edge structure (XANES) exhibits sharp peaks just above the absorption edge that are characteristic of s Æ p transitions of compounds containing an aromatically bound sulfur atom and a broad, structured maximum at somewhat higher energies. The latter maximum is believed to arise from resonant backscattering of photoelectrons by carbon atoms 3.5-4.1 Å from the sulfur atom and possibly from s Æ p transitions of sulfur bonded to oxygen. The radial structure functions derived by Fourier analysis of the EXAFS exhibit peaks at distances that are compatible with the first three neighbor shells surrounding an aromatically bound sulfur atom.
1988-1986
EXAFS Investigation of Organic Sulfur in Coal
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.
Investigation of the Atomic and Physical Structure of Organic and Inorganic Sulfur in Coal
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.