Effect of additives on the reactivity of palladium surfaces for the chemisorption and hydrogenation of carbon monoxide: A surface science and catalytic study

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

OSTI ID:5701216

Rucker, T G

The effect of Na, K, Si, P, S, and Cl on the bonding of Co and hydrogen and on the cyclotrimerization of acetylene on the (111), (100) and (110) faces of Pd has been investigated in addition to the role of TiO{sub 2} and SiO{sub 2} overlayers deposited on Pd foils in the CO hydrogenation reaction. The surface characterization and catalytic reactions were performed in a combined ultra-high vacuum/high pressure chamber equipped with the standard surface analytical techniques. Pd, only in the presence of oxide overlayers, are methane or methanol formed from CO and H{sub 2}. The maximum rate of methane formation is attained on Pd foil where 30% of the surface is covered with titania. Methanol formation can be achieved only if the TiO{sub x}/Pd surface is pretreated in 50 psi of oxygen at 550 C prior to the reaction. Temperature Programmed Desorption and X-ray Photoelectron Spectroscopy results and kinetic studies suggest that methane forms on a stable mixed TiO{sub x}/Pd catalytic sites whereas methanol, which is produced only during the first few minutes of the reaction, forms on an unstable heavily oxidized TiO{sub x}/Pd surface. The structural interaction induced by the additives are evidenced by surface reconstruction, changes in Pd ensemble size, site blocking and changes in the CO bonding configuration on palladium. In general, the electron donating additives increase the desorption temperature of CO and increase the rate of acetylene cyclotrimerization and the electron withdrawing additives decrease the desorption temperature of CO and decrease the rate of benzene formation from acetylene.

• Research Organization: California Univ., Berkeley, CA (USA)
• OSTI ID: 5701216
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
010408* -- Coal
Lignite
& Peat-- C1 Processes-- (1987-)
ACETYLENE
ALCOHOLS
ALKALI METALS
ALKANES
ALKYNES
AROMATICS
BENZENE
CARBON COMPOUNDS
CARBON MONOXIDE
CARBON OXIDES
CATALYSIS
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL BONDS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
CHLORINE
CONTROL
DEPOSITS
DESORPTION
ELECTRON SPECTROSCOPY
ELEMENTS
FISCHER-TROPSCH SYNTHESIS
HALOGENS
HYDROCARBONS
HYDROGENATION
HYDROXY COMPOUNDS
KINETICS
METALS
METHANATION
METHANE
METHANOL
NONMETALS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
PALLADIUM
PHOSPHORUS
PHOTOELECTRON SPECTROSCOPY
PLATINUM METALS
POTASSIUM
REACTION KINETICS
SEMIMETALS
SILICON
SILICON COMPOUNDS
SILICON OXIDES
SODIUM
SPECTROSCOPY
SULFUR
SURFACE PROPERTIES
SYNTHESIS
TEMPERATURE CONTROL
TITANIUM COMPOUNDS
TITANIUM OXIDES
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
X-RAY SPECTROSCOPY