Time-resolved in situ X-ray diffraction studies of a lithium nickel oxide catalyst during the oxidative coupling of methane
- Royal Institution of Great Britian, London (United Kingdom)
A lithium nickel oxide catalyst of composition Li[sup +][sub x]Ni[sup 2+][sub 1-2x]Ni[sup 3+][sub x]O, x = 0.45, active in the oxidative coupling of methane, has been studied in the presence and absence of added gaseous oxygen at 700[degrees]C using simultaneous in situ X-ray powder diffraction with gas chromatography. In the presence of gaseous oxygen the bulk structure remains essentially unchanged for more than 5 h, and during this time the catalyst is selective for C[sub 2] production; following this there is rapid reduction of the catalyst through NiO to Ni metal, with corresponding evolution of CO[sub 2] and finally CO as the dominant gaseous products. By contrast, in the absence of gaseous oxygen the bulk structure immediately starts to decompose, yielding successively a total of four rock salt-type lithium nickel oxide phases. In this case the initial selectivity for C[sub 2] production is 100% and declines as the solid phases during the experiments with variations in the rate of production of gaseous products, giving important insights into the behavior of this material as a catalyst. A reaction scheme is proposed based on the catalytic and structural results. Additional studies of the structure of Li[sup +][sub 0.45]Ni[sup 2+][sub 0.10]Ni[sup 3+][sub 0.45]O as a function of temperature in air using Rietveld structure refinements have been carried out to augment the in situ studies, showing that the ordered lithium nickel oxide structure is essentially invariant up to 700[degrees]C in air. 28 refs., 7 figs., 3 tabs.
- OSTI ID:
- 5147461
- Journal Information:
- Chemistry of Materials; (United States), Vol. 4:5; ISSN 0897-4756
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
10 SYNTHETIC FUELS
LITHIUM OXIDES
STRUCTURAL CHEMICAL ANALYSIS
METHANE
OXIDATION
NICKEL OXIDES
CATALYSTS
CATALYTIC EFFECTS
HETEROGENEOUS CATALYSIS
STOICHIOMETRY
TIME RESOLUTION
ALKALI METAL COMPOUNDS
ALKANES
CATALYSIS
CHALCOGENIDES
CHEMICAL REACTIONS
HYDROCARBONS
LITHIUM COMPOUNDS
NICKEL COMPOUNDS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
RESOLUTION
TIMING PROPERTIES
TRANSITION ELEMENT COMPOUNDS
400201* - Chemical & Physicochemical Properties
100200 - Synthetic Fuels- Production- (1990-)