Thermochemical processing of biomass produces a solid product containing char (mostly carbon) and ash. This char can be combusted for heat and power, gasified, activated for adsorption applications, or applied to soils as a soil amendment and carbon sequestration agent. The most advantageous use of a given char depends on its physical and chemical characteristics, although the relationship of char properties to these applications is not well understood. Chars from fast pyrolysis and gasification of switchgrass and corn stover were characterized by proximate analysis, CHNS elemental analysis, Brunauer-Emmet-Teller (BET) surface area, particle density, higher heating value (HHV), scanning electron microscopy, X-ray fluorescence ash content analysis, Fourier transform infrared spectroscopy using a photo-acoustic detector (FTIR-PAS), and quantitative 13C nuclear magnetic resonance spectroscopy (NMR) using direct polarization and magic angle spinning. Chars from the same feedstocks produced under slow pyrolysis conditions, and a commercial hardwood charcoal, were also characterized. Switchgrass and corn stover chars were found to have high ash content (32–55 wt %), much of which was silica. BET surface areas were low (7–50 m2/g) and HHVs ranged from 13 to 21 kJ/kg. The aromaticities from NMR, ranging between 81 and 94%, appeared to increase with reaction time. A pronounced decrease in aromatic CH functionality between slow pyrolysis and gasification chars was observed in NMR and FTIR-PAS spectra. NMR estimates of fused aromatic ring cluster size showed fast and slow pyrolysis chars to be similar (∼7–8 rings per cluster), while higher-temperature gasification char was much more condensed (∼17 rings per cluster). © 2009 American Institute of Chemical Engineers Environ Prog, 2009

Characterization of biochar from fast pyrolysis and gasification systems

Sulfur-doped porous carbons: Synthesis and applications

Geochemical evolution of organic-rich shales with increasing maturity: A STXM and TEM study of the Posidonia Shale (Lower Toarcian, northern Germany)

Formation of nanoporous pyrobitumen residues during maturation of the Barnett Shale (Fort Worth Basin)

Molecular modeling is applied to a representative array of kerogens for the purpose of obtaining quantitative predictions of thermodynamic properties from quantum mechanics and volumetric properties from molecular dynamics. The kerogen model units (175–260 carbon atoms) have been built in the MedeA environment from the sole consideration of the elemental analysis and functional group analysis documented in the work of Exxon and IFP-EN scientists [Kelemen, S. R., et al., Energy Fuels, 2007, 21 (3), pp 1548–1561]. The density results are in good agreement with the well-documented trends of kerogen density with thermal maturity and organic type. The heat capacity in the ideal gas state is predicted to increase as a function of temperature, as obtained from quantum mechanics at the semiempirical level (MOPAC-PM7). This result is in quantitative agreement with experimental heat capacity data on type I kerogen and on coal. This behavior appears clearly as a nonclassical feature, because of the quantization of e...

Molecular Modeling of the Volumetric and Thermodynamic Properties of Kerogen: Influence of Organic Type and Maturity

A combination of solid-state 13C NMR, X-ray photoelectron spectroscopy (XPS) and sulfur X-ray absorption near edge structure (S-XANES) techniques are used to characterize organic oxygen, nitrogen, and sulfur species and carbon chemical/structural features in kerogens. The kerogens studied represent a wide range of organic matter types and maturities. A van Krevelen plot based on elemental H/C data and XPS derived O/C data shows the well established pattern for type I, type II, and type III kerogens. The anticipated relationship between the Rock−Eval hydrogen index and H/C is independent of organic matter type. Carbon structural and lattice parameters are derived from solid-state 13C NMR analysis. As expected, the amount of aromatic carbon, measured by both 13C NMR and XPS, increases with decreasing H/C. The correlation between aromatic carbon and Rock−Eval Tmax, an indicator of maturity, is linear for types II and IIIC kerogens, but each organic matter type follows a different relationship. The average al...

F. Behar

Papers

Direct characterization of kerogen by x-ray and solid-state **13c nuclear magnetic resonance methods