A TPD and XPS investigation of palladium on modified alumina supports used for the catalytic decomposition of methanol

Journal Article · Fri Mar 01 04:00:00 EST 1991 · Journal of Catalysis; (USA)

DOI:https://doi.org/10.1016/0021-9517(91)90077-H· OSTI ID:5581166

Wickha, D T; Logsdon, B W; Cowley, S W ^[1]; Butler, C D ^[2]

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1. Colorado School of Mines, Golden (USA)
2. Rocky Mountain Labs., Golden, (USA)

A series of modified palladium catalysts on alumina supports previously have been prepared and evaluated for selectivity, activity, and thermal stability in decomposing methanol into CO and H{sub 2}. In this investigation the modified palladium catalysts are characterized by X ray photoelectron spectroscopy (XPS) and CO and NH{sub 3} temperature-programmed desorption (TPD). Average particle sizes of the palladium crystallites were also determined using chemisorption techniques. The XPS results indicate that the lithium-modified catalyst, which deactivated substantially during methanol decomposition testing, exhibited a significant build-up of carbon on the catalyst under identical conditions. The CO TPD results show that the lithium-, sodium-, and barium-modified catalysts, which deactivate during methanol decomposition testing, produce a much greater amount of CO{sub 2} relative to the amount of CO desorbed than do the potassium-, rubidium-, cesium-, and lanthanum-modified and the unmodified catalysts, which do not deactivate considerably under identical conditions. Ammonia TPD and chemisorption results indicate that no correlation exists between support acidity or particle size and the degree of CO dissociation. Finally, a correlation between the charge density of the modifier and the degree of CO disproportionation is presented which fits for all cases except one. This appears to support an electrostatic model for the promotion of CO bond cleavage by the alkali modifier.

• OSTI ID: 5581166
• Journal Information: Journal of Catalysis; (USA), Journal Name: Journal of Catalysis; (USA) Vol. 128:1; ISSN 0021-9517; ISSN JCTLA
• Country of Publication: United States
• Language: English

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ALKALI METALS
ALKALINE EARTH METALS
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
AMMONIA
AUTOMOTIVE FUELS
BARIUM
CARBON
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CHEMICAL BONDS
CHEMICAL REACTIONS
CHEMISORPTION
CONTROL
DEACTIVATION
DECOMPOSITION
DEPOSITION
DESORPTION
DISSOCIATION
EFFICIENCY
ELECTRON SPECTROSCOPY
ELEMENTS
ENERGY EFFICIENCY
FUELS
HYDRIDES
HYDROGEN
HYDROGEN COMPOUNDS
HYDROXY COMPOUNDS
LANTHANUM
LITHIUM
METALS
METHANOL
NITROGEN COMPOUNDS
NITROGEN HYDRIDES
NONMETALS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PALLADIUM
PARTICLE SIZE
PHOTOELECTRON SPECTROSCOPY
PLATINUM METALS
POTASSIUM
PROMOTERS
RARE EARTHS
RUBIDIUM
SEPARATION PROCESSES
SIZE
SODIUM
SORPTION
SPECTROSCOPY
STABILITY
SYNTHESIS
TEMPERATURE CONTROL
TRANSITION ELEMENTS
X-RAY SPECTROSCOPY