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Chemisorption and catalytic reactivity of cobalt and sulfur monolayers on ordered molybdenum surfaces [electronic resource].

Published
Washington, D.C. : United States. Dept. of Energy, 1992.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy.
Physical Description
Pages: (162 pages) : digital, PDF file
Additional Creators
Lawrence Berkeley National Laboratory, United States. Department of Energy, and United States. Department of Energy. Office of Scientific and Technical Information
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Summary
Complex Co/Mo sulfide catalysts are modelled by the chemisorption of layers on Mo single crystal surfaces. Growth and structure of overlayers on flat, stepped and kinked surfaces were investigated. Growth of Co overlayers on clean and S covered Mo surfaces was studied using AES and CO chemisorption; results reveal that Co grows as a flat monolayer on clean Mo surfaces. Co multilayers then form 3-D islands. When Co is deposited on S covered surfaces, the S overlayer migrates to the top; this topmost overlayer reduces CO adsorption capacity. While growth mode of Co overlayers are similar on flat and stepped surfaces, the number and type of ordered Co and S structures on flat and stepped surfaces are different. In the case of Co, an ordered (3 × 1) structure is formed on Mo(910) and (28,4,1) surfaces; this structure does not develop on clean (100) surface. Only one of two possible (3 × 1) Co domains are formed on Mo(910) and Mo(28,4,1) surfaces. These domains have one side of (3 × 1) unit cell parallel to the step edges, suggesting that Co adsorbs at the step edges. The (3 × 1) structure does not form on Mo(911) surface, indicating that step orientation can restrict formation of ordered overlayers. For chemisorbed S, only a subset of ordered overlayers on flat (100) surface nucleate on (910) and (911) and (28,4,1) surfaces. Ordered S overlayers also form domains that maximize the number of sulfur-step atom bonds. The adsorption and ordering of S overlayers on stepped and kinked Mo surfaces lead to doubling of step height and terrace width. Thiophene hydrodesulfurization (HDS) reactions were performed over Mo crystal surfaces modified by chemisorption of S, Co, C, and S + Co. The stepped and kinked Mo surfaces have reactivities greater than low Miller index (100) surface. Chemisorption of adsorbates decreased the thiophene HDS reactivity. Deposition of Co on Mo single crystal surfaces did not lead to increased HDS activity.
Report Numbers
E 1.99:lbl-32444
lbl-32444
Subject(s)
Other Subject(s)
Note
Published through SciTech Connect.
03/01/1992.
"lbl-32444"
"DE92041175"
Knight, C.C.
Funding Information
AC03-76SF00098
View MARC record | catkey: 14397197