Steam gasification of carbon solids catalyzed by a nickel-potassium mixed oxide: Kinetic and surface characterization studies
The kinetic study on graphite gasification shows the nickel-potassium mixture has distinct catalytic properties for this reaction, when compared with potassium-alone and nickel-alone catalysts. The mixture is active at relatively low temperatures (800 K) compared with the potassium-alone catalyst, and does not deactivate with time, contrary to the case of nickel alone. The morphology study was based on controlled atmosphere electron microscopy results. The mobile mixture spreads over the edge planes of graphite, and favors the steam attack by edge recession in the (1120) crystallographic direction. The surface-chemistry study, based on X-ray photoelectron spectroscopy, shows the nickel-potassium interaction stabilizes NiO and KOH on the graphite surface. The formation of a nickel-potassium mixed oxide is responsible for the distinct properties of this catalyst. This species is either directly involved in the gasification process, or becomes a support for an active nickel metal species, increasing its mobility and preventing its deactivation. The performance of the nickel-potassium catalysts in the steam gasification of coal-chars was investigated. The mixture is a better catalyst for steam gasification of low ash chars, than both nickel-alone and potassium-alone catalyst. If the ash content is high ({approx}50 wt.% of nonvolatile components in the char), however, the interaction of both nickel and potassium with the minerals present decreases substantially its activity toward steam gasification. A temperature programmed desorption and X-ray photoelectron spectroscopy study on the adsorption of O{sub 2}, H{sub 2}O, CO and CO{sub 2} on clean graphite is also presented. It is proposed that all four gases from the same type of oxygen containing surface species, after chemisorption.
- Research Organization:
- California Univ., Berkeley, CA (USA)
- OSTI ID:
- 5004553
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
010404* -- Coal
Lignite
& Peat-- Gasification
ALKALI METAL COMPOUNDS
ALKALI METALS
BINARY MIXTURES
CARBON
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON MONOXIDE
CARBON OXIDES
CARBONACEOUS MATERIALS
CATALYTIC EFFECTS
CHALCOGENIDES
CHARS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHEMISORPTION
COAL
COAL GASIFICATION
CONTROL
DEACTIVATION
DESORPTION
DISPERSIONS
ELECTRON MICROSCOPY
ELECTRON SPECTROSCOPY
ELEMENTAL MINERALS
ELEMENTS
ENERGY SOURCES
FOSSIL FUELS
FUELS
GASIFICATION
GRAPHITE
HIGH TEMPERATURE
HYDROGEN COMPOUNDS
HYDROXIDES
KINETICS
MATERIALS
METALS
MICROSCOPY
MINERALS
MIXTURES
MORPHOLOGY
NICKEL
NICKEL COMPOUNDS
NICKEL OXIDES
NONMETALS
OXIDES
OXYGEN
OXYGEN COMPOUNDS
PHOTOELECTRON SPECTROSCOPY
POTASSIUM
POTASSIUM COMPOUNDS
POTASSIUM HYDROXIDES
PYROLYSIS PRODUCTS
REACTION KINETICS
SEPARATION PROCESSES
SORPTION
SPECTROSCOPY
STEAM
SURFACE PROPERTIES
TEMPERATURE CONTROL
TEMPERATURE EFFECTS
THERMOCHEMICAL PROCESSES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
VERY HIGH TEMPERATURE
WATER
X-RAY SPECTROSCOPY