Effects of metal-support and metal-promoter interactions on rhodium catalysts for carbon monoxide hydrogenation

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1986

OSTI ID:5457699

Underwood, R P

An investigation was conducted to establish the effects of support composition and promoter content on the hydrogenation of CO over rhodium. Comparisons of Rh supported on SiO/sub 2/, La/sub 2/O/sub 3/, Nd/sub 2/O/sub 3/, and Sm/sub 2/O/sub 3/ demonstrated that rare earth oxide supports provide high selectivities for methanol and ethanol synthesis, whereas silica provides a high selectivity to methane. Detailed studies of Rh/SiO/sub 2/ and Rh/La/sub 2/O/sub 3/ indicate that there is a metal-support interaction between Rh and La/sub 2/O/sub 3/. The metal-support interaction is a result of a modification of the catalytic and chemisorptive properties of the surface of the Rh crystallites by the deposition of LaO/sub x/ moieties derived from the support. The effect of Rh particle size was studied by investigating Rh/SiO/sub 2/ and Rh/La/sub 2/O/sub 3/ catalysts varying in Rh loading. The intrinsic effects of Rh particle size on the activity and selectivity were determined from the results for Rh/SiO/sub 2/. The catalytic and chemisorptive properties of a particular Rh/La/sub 2/O/sub 3/ catalyst are determined by a combination of the intrinsic effect of Rh particle size and the extent of coverage of the Rh crystallites by LaO/sub x/ moieties. In order to investigate in more detail the specific effects of LaO/sub x/ decoration in the absence of changes in Rh particle size, Rh/SiO/sub 2/ was promoted with varying quantities of La. La promotion results in increases in the turnover frequencies for the formation of all products and an increase in the selectivity for oxygenates. Activity and selectivity are also found to be strong functions of La content. Chemisorbed CO is believed to occur near the periphery of LaO/sub x/ patches, where lanthanum cations interact directly with the oxygen end of the CO molecule. The effect of the CO-La cation interaction is to weaken the C-O bond, thereby making it more susceptible to cleavage and/or hydrogenation.

• Research Organization: California Univ., Berkeley (USA)
• OSTI ID: 5457699
• Country of Publication: United States
• Language: English

Related Subjects

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10 SYNTHETIC FUELS
ALCOHOLS
ALKANES
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CATALYSIS
CATALYST SUPPORTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTIONS
ELEMENTS
ETHANOL
HYDROCARBONS
HYDROGENATION
HYDROXY COMPOUNDS
LANTHANUM COMPOUNDS
LANTHANUM OXIDES
METALS
METHANATION
METHANE
METHANOL
MINERALS
NEODYMIUM COMPOUNDS
NEODYMIUM OXIDES
ORGANIC COMPOUNDS
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
PLATINUM METALS
RARE EARTH COMPOUNDS
RHODIUM
SAMARIUM COMPOUNDS
SAMARIUM OXIDES
SILICA
SILICON COMPOUNDS
SILICON OXIDES
SYNTHESIS
TRANSITION ELEMENTS