Catalytic and electrocatalytic oxidation of methane in a stabilized zirconia cell

Thesis/Dissertation · Thu Jan 01 04:00:00 EST 1987

OSTI ID:6630431

Seimanides, S G

The oxidation of methane on porous polycrystalline silver and palladium supported on yttria-stabilized zirconia was studied at atmospheric total pressure in a continuous stirred tank reactor (C.S.T.R.) at temperatures between 450 and 600 C. The technique of solid electrolyte potentiometry (SEP) was used to measure in situ the thermodynamic activity of oxygen adsorbed on the catalyst surface. The reaction kinetics of both the Ag-catalyzed and the Pd-catalyzed reaction are consistent with an Eley-Rideal model according to which adsorbed atomic oxygen reacts with gaseous methane. The potentiometric measurements suggest that only one oxygen atom is involved in the rate limiting step in both cases. Kinetic models that satisfy both kinetic and SEP results are discussed. The oxidation of methane was also studied on Ag-Li/MgO and Au-Li/MgO catalysts supported on yttria-stabilized zirconia between 650 and 800 C. It was found that the intrinsic activity and selectivity of these metal-metal oxide catalysts can be significantly altered by using an electrochemical oxygen pump. Under open circuit conditions the catalyst electrodes exposed to CH/sub 4/-O/sub 2/ mixtures act as normal catalysts for methane oxidation to CO/sub 2/, C/sub 2/H/sub 6/, C/sub 2/H/sub 4/ and CO. When external voltages are applied to the cell and O/sup 2 -/ is pumped to the catalyst the rates of product formation generally increase. The opposite effect is observed upon inversion of the voltage polarity. A possible mechanisms is discussed. Overpotential and exchange-current density measurements were taken in order to gain a better understanding of reactions taking place at the electrode-electrolyte interface during the oxidation of methane.

• Research Organization: Tufts Univ., Medford, MA (USA)
• OSTI ID: 6630431
• Country of Publication: United States
• Language: English

Related Subjects

090110* -- Hydrocarbon Fuels-- Properties-- (1979-1989)
10 SYNTHETIC FUELS
ALKALI METALS
ALKALINE EARTH METAL COMPOUNDS
ALKANES
CATALYSIS
CATALYSTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTIONS
ELECTROCATALYSTS
ELEMENTS
HYDROCARBONS
LITHIUM
MAGNESIUM COMPOUNDS
MAGNESIUM OXIDES
METALS
METHANE
ORGANIC COMPOUNDS
OXIDATION
OXIDES
OXYGEN COMPOUNDS
PALLADIUM
PLATINUM METALS
SILVER
TEMPERATURE EFFECTS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
YTTRIUM COMPOUNDS
YTTRIUM OXIDES
ZIRCONIUM COMPOUNDS
ZIRCONIUM OXIDES