Temperature-programmed desorption studies of coal char gasification
In recent years, it has become increasingly clear that the understanding of char gasification kinetics requires more detailed information about the nature of the surface intermediates (carbon-oxygen complexes) formed during reaction. The first step in char (carbon) gasification is the dissociative chemisorption of reactant gas molecules (O/sub 2/, CO/sub 2/, H/sub 2/O) on the active sites of carbon, located at the edges of, and imperfections within, the turbostratic carbon crystallites. A distribution of activities is known to exist among these carbon active sites; some sites are more active than others. The sites which are important for predicting gasification rates are thought to be the ones that have intermediate activity, i.e., the ones that are sufficiently active to chemisorb dissociatively the reactant gas, but not to the extent that a stable C-O complex is formed. Temperature-programmed desorption (TPD), an experimental technique widely used in the field of heterogeneous catalysis and recently applied in coal char gasification studies, may be used to discern the nature of this distribution. TPD spectra provide useful information not only on the extent but also on the energetics of desorption of C-O complexes from the char surface. In order to gain new insights into char gasification kinetics, it should prove beneficial to analyze TPD spectra, both qualitatively and quantitatively, with respect to factors which are known to significantly influence rates of gasification, e.g., nature of reactant gas, level of conversion (or extent of reaction), and the presence of inorganic impurities. The main objective of this study is to characterize the energetic heterogeneity of surfaces of coal chars, and carbons in general, and to relate it to their observed catalyzed and uncatalyzed gasification behavior in O/sub 2/ and CO/sub 2/.
- Research Organization:
- Pennsylvania State Univ., University Park (USA)
- OSTI ID:
- 5955997
- Report Number(s):
- CONF-8904169-
- Journal Information:
- Prepr. Pap., Am. Chem. Soc., Div. Fuel Chem.; (United States), Journal Name: Prepr. Pap., Am. Chem. Soc., Div. Fuel Chem.; (United States) Vol. 34:1; ISSN ACFPA
- Country of Publication:
- United States
- Language:
- English
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ACTIVATION ENERGY
ALKALINE EARTH METALS
ATMOSPHERIC PRESSURE
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BLACK COAL
BROWN COAL
CALCIUM
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON OXIDES
CARBONACEOUS MATERIALS
CATALYSIS
CHALCOGENIDES
CHARS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISORPTION
COAL
COAL GASIFICATION
COMPLEXES
CONTROL
DECOMPOSITION
DEMINERALIZATION
DESORPTION
ELEMENTS
ENERGY
ENERGY SOURCES
FLUIDS
FOSSIL FUELS
FUELS
GASES
GASIFICATION
ION EXCHANGE
KINETICS
LIGNITE
MASS SPECTRA
MASS SPECTROSCOPY
MATERIALS
METALS
NONMETALS
OXIDES
OXYGEN
OXYGEN COMPLEXES
OXYGEN COMPOUNDS
PYROLYSIS
PYROLYSIS PRODUCTS
REACTION KINETICS
SEPARATION PROCESSES
SORPTION
SPECTRA
SPECTROSCOPY
SURFACE PROPERTIES
TEMPERATURE CONTROL
THERMOCHEMICAL PROCESSES
VAPORS
WATER VAPOR