Kinetic models for uncatalyzed and potassium-catalyzed gasification of char by carbon dioxide
A differential packed-bed reactor has been employed to study the gasification of uncatalyzed and 7.5 wt% K/sub 2/CO/sub 3/-catalyzed Saran char in carbon dioxide/carbon monoxide mixtures at a total pressure near 1 atm (101.3 kPa). The gasification temperature was varied between 1131 and 1229 K for the uncatalyzed case, and between 922 and 1046 K for the catalyzed case. Gasification rate data were tested with a model which involves two-site adsorption and subsequent dissociation of CO/sub 2/ on the char surface. The results indicate that this model adequately explains both the uncatalyzed and catalyzed gasification data. However, higher concentrations of carbon-oxygen complex, (C(O)), exist on the surface during catalyzed gasification. The increase in (C(O)) weakens carbon-carbon bonds and thus lowers the activation energy for desorption of the C(O) complex. Adsorption of CO and CO/sub 2/ on both catalyzed and uncatalyzed chars was also followed with a volumetric adsorption apparatus at pressures between 1 and 100 kPa and temperatures from 273 to 725 K. The catalyzed char adsorbed an order of magnitude more CO/sub 2/ at 559 K than the uncatalyzed char. Subsequent dissociation of CO/sub 2/ on the carbon surface does not appear to be catalyzed by potassium. Thus, the catalysts' role is to augment the efficiency and/or number of sites for CO/sub 2/ adsorption, thereby creating more oxygen on the surface. The higher rate during catalyzed gasification can be attributed to a combination of increased (C(O)) and a smaller activation energy for desorption of C(O).
- Research Organization:
- Purdue Univ., Lafayette, IN (USA)
- OSTI ID:
- 7180919
- Country of Publication:
- United States
- Language:
- English
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CARBON OXIDES
CATALYSIS
CATALYTIC EFFECTS
CHALCOGENIDES
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