Surface Science Studies of Catalyzed Methanol Synthesis on Model Copper and Cu-Zn-O Surfaces [Thesis]

Thesis/Dissertation · Sat Jun 01 00:00:00 EDT 1991

OSTI ID:5478711

Fu, Sabrina Su-Bin ^[1]

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1. Univ. of California, Berkeley, CA (United States). Dept. of Chemistry; Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)

Cu-Zn-O surfaces that are catalysts for methanol synthesis from CO, CO₂, and H₂ are modeled using zinc oxide overlayers on copper single crystals. These studies were performed in ultra-high vacuum (UHV) utilizing Temperature Programmed Desorption, Auger Electron Spectroscopy, and Low Energy Electron Diffraction techniques. The chemisorption of O₂, CO, CO₂, and D₂ were compared on a stepped Cu(311), and a flat Cu(110). At low pressures (~10^-6 Torr), Cu(311) was found to be much more reactive than Cu(110) for the dissociative adsorption of CO₂ and D₂, and the formation of CO₂ from surface oxygen and CO. Since these reactions are important in methanol synthesis, these results suggest that methanol synthesis over copper may be a structure sensitive reaction. The interaction of copper, zinc, and oxygen were examined by the deposition of submonolayers to multilayers of zinc and oxygen in UHV on Cu(110). Carbon monoxide adsorbs well on copper at 150 K and low pressures (<10^-6 Torr), but only poorly on the oxides of copper and zinc. Carbon dioxide adsorbs on ZnO at 150 K and low pressures (<10^-6 Torr), but not on copper or oxidized copper. We used a combination of CO and CO₂ adsorption to follow the initial growth of two-dimensional ZnO_x islands and the effects of heat and oxygen treatments on these islands. Heating above 300 K leads irreversibly to three-dimensional island formation. In addition, the behavior of ZnO_x overlayers on Cu(311) and a high defect concentration Cu(111) were compared to ZnO_x overlayers on Cu(110). The interaction of methanol with these model Cu-Zn-O surfaces was also studied. Oxygen was adsorbed onto the exposed copper part of the surface to form ZnO_x/y ML O/Cu(110) surfaces. The roles of ZnO_x islands and chemisorbed oxygen on copper were investigated by monitoring methanol decomposition, into surface formate and methoxy species, on these ZnO_x/y ML O/Cu(110) surfaces. The role of chemisorbed oxygen on Cu(110) in the ZnO_x/y ML O/Cu(110) system is to keep the zinc oxidized and to increase the amount of formate formed on the ZnO_x component of the surface. The presence of ZnO_x increases the surface formate to methoxy ratio from that of O/Cu(110).

• Research Organization: Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES)
• DOE Contract Number: AC03-76SF00098
• OSTI ID: 5478711
• Report Number(s): LBL--30795; ON: DE91016425
• Country of Publication: United States
• Language: English

Related Subjects

10 SYNTHETIC FUELS
100200 -- Synthetic Fuels-- Production-- (1990-)
36 MATERIALS SCIENCE
360102 -- Metals &amp; Alloys-- Structure &amp; Phase Studies
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical &amp; Physicochemical Properties
ALCOHOLS
AUGER ELECTRON SPECTROSCOPY
CATALYTIC EFFECTS
CHALCOGENIDES
CHEMICAL REACTIONS
CHEMISORPTION
COHERENT SCATTERING
COPPER
COPPER COMPOUNDS
COPPER OXIDES
DIFFRACTION
ELECTRON DIFFRACTION
ELECTRON SPECTROSCOPY
ELEMENTS
HYDROXY COMPOUNDS
METALS
METHANOL
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
SCATTERING
SEPARATION PROCESSES
SORPTION
SPECTROSCOPY
SYNTHESIS
TRANSITION ELEMENT COMPOUNDS
TRANSITION ELEMENTS
ZINC COMPOUNDS
ZINC OXIDES