The concept of reactive surface area applied to uncatalyzed and catalyzed carbon (char) gasification in carbon dioxide and oxygen
The virtues of, and/or problems with, utilizing the concepts of total and active surface area to explain the reactivity profiles were evaluated and discussed. An alternative approach, involving the concept of reactive surface area (RSA), was introduced and results based on the direct measurement of RSA were presented. Here, reactive surface area is defined as the concentration of carbon atoms on which the carbon-oxygen C(O) surface intermediate forms and subsequently decomposes to give gaseous products. The transient kinetics (TK) approach gave a direct measurement of RSA for chars gasified in CO{sub 2} and O{sub 2}. A temperature-programmed desorption technique was also used to determine the amount of reactive surface intermediate formed on these chars during gasification. A comparison of turnover frequencies for different chars gasified in 1 atm CO{sub 2} suggested that char gasification mat be a structure sensitive reaction. The concept of RSA was also used to achieve a better quantitative understanding of catalyzed char reactivity variations with conversion in CO{sub 2}. For a calcium-exchanged lignite char gasified in 1 atm CO{sub 2}, a poor correlation was found between RSA and reactivity, suggesting that in addition to the direct decomposition of the reactive C(O) intermediate, other processes, e.g., oxygen spillover, contributed to the transient evolution of CO. An extensive study of Saran char loaded with calcium, potassium or nickel by impregnation to incipient wetness (IW) or ion exchange (IE) was undertaken. An excellent correlation was found between reactivity and RSA variations with conversion for both IW and IE K-catalyzed chars, suggesting that TK indeed titrates the reactive K-O-C complexes formed during gasification in CO{sub 2}.
- Research Organization:
- Pennsylvania State Univ., University Park, PA (United States)
- OSTI ID:
- 6097382
- Country of Publication:
- United States
- Language:
- English
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010404* -- Coal
Lignite
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ACTIVATION ENERGY
ALKALI METALS
ALKALINE EARTH METALS
BROWN COAL
CALCIUM
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON MONOXIDE
CARBON OXIDES
CARBONACEOUS MATERIALS
CATALYSIS
CATALYTIC EFFECTS
CHALCOGENIDES
CHARS
CHEMICAL PREPARATION
CHEMICAL REACTION KINETICS
COAL
COAL GASIFICATION
COMPARATIVE EVALUATIONS
CONTROL
DESORPTION
ELEMENTS
ENERGY
ENERGY SOURCES
EVALUATION
FOSSIL FUELS
FUELS
GASIFICATION
IMPREGNATION
ION EXCHANGE
KINETICS
LIGNITE
MATERIALS
METALS
NICKEL
NONMETALS
OXIDES
OXYGEN
OXYGEN COMPOUNDS
POTASSIUM
PYROLYSIS PRODUCTS
REACTION INTERMEDIATES
REACTION KINETICS
SURFACE AREA
SURFACE PROPERTIES
SYNTHESIS
TEMPERATURE CONTROL
THERMOCHEMICAL PROCESSES
TRANSITION ELEMENTS