Structural effects in Fischer-Tropsch synthesis over bimetallic supported catalysts
The effect of copper on the activity/selectivity of Ru/SiO/sub 2/ catalysts in CO hydrogenation has been investigated in terms of geometric and/or electronic effects. Two series of catalysts were prepared: the aqueous impregnation method resulted in the Ru dispersion of 4.6%, while non-aqueous method gave Tu dispersion of 31%. The catalysts were characterized using x-ray line broadening, hydrogen chemisorption, temperature-programmed desorption, and transmission electron microscopy techniques. For low-dispersion Ru-Cu/SiO/sub 2/ catalysts, the effect of Cu has been observed to be primarily geometric through the blockage of the active Ru surface sites. The changes observed can be explained in terms of reduction in the Ru surface area as measured by hydrogen chemisorption, as well as several other observations: (1) the methanation turnover numbers and the activation energy of methanation over Ru remain constant, (2) the hydrocarbon product distribution is unaffected by the presence of Cu, nd (3) the CO bonding to Ru surface is unaffected by the presence of Cu. For high-dispersion R-Cu/SiO/sub 2/ catalysts, the changes observed are interpreted in terms of interactions between Ru and Cu of an electronic nature. This is based on the following observations: (1) the methanation turnover numbers and the activation energy of methanation over Ru, both change in the presence of Cu, (2) the product distribution, namely the higher hydrocarbons, is influenced by the presence of Cu, and (3) the CO bonding undergoes a change due to Cu as shown by the temperature-programmed desorption study. Furthermore, these studies also shed some light on the intermediates involved in the Fischer-Tropsch reactions.
- Research Organization:
- Georgia Inst. of Tech., Atlanta (USA)
- OSTI ID:
- 5519622
- Country of Publication:
- United States
- Language:
- English
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010404* -- Coal
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ACTIVATION ENERGY
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CATALYSIS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL COMPOSITION
CHEMICAL PREPARATION
CHEMICAL REACTIONS
COPPER
ELEMENTS
ENERGY
FISCHER-TROPSCH SYNTHESIS
HYDROCARBONS
METALS
METHANATION
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PLATINUM METALS
REACTION INTERMEDIATES
RUTHENIUM
SURFACE AREA
SURFACE PROPERTIES
SYNTHESIS
TRANSITION ELEMENTS