AVS 47th International Symposium
    Surface Science Tuesday Sessions
       Session SS1-TuA

Paper SS1-TuA5
Chemistry of Thiophene, H@sub 2@S, and SO@sub 2@ on Carbide-Modified Mo(110) and Mo@sub 2@C Powders

Tuesday, October 3, 2000, 3:20 pm, Room 208

Session: Mechanisms and Control of Surface Reactions
Presenter: J. Dvorak, Brookhaven National Laboratory
Authors: J. Dvorak, Brookhaven National Laboratory
T. Jirsak, Brookhaven National Laboratory
J.C. Hanson, Brookhaven National Laboratory
J.A. Rodriguez, Brookhaven National Laboratory
Correspondent: Click to Email
The most widely used catalysts in hydrodesulfurization (HDS) reactions consist of a mixture of cobalt and molybdenum sulfide on an alumina support. More stringent environmental legislations stress the need to develop a new generation of HDS catalysts that lead to the ultimate goal of clean burning fuels. Recently, it has been shown that molybdenum-carbide catalysts have the potential to replace sulfided Mo catalysts in industrial HDS reactors. We have investigated the chemistry of a series of S-containing molecules on carbide-modified Mo(110) [i.e. MoC@sub x@] and Mo@sub 2@C powders using synchrotron-based photoemission, x-ray absorption near-edge spectroscopy and time-resolved x-ray diffraction. Thiophene adsorbs molecularly on MoC@sub x@ at 100 K. By 200 K, upon desorption of the thiophene multilayer, chemisorbed thiophene and its decomposition products (S and C@sub x@H@sub y@ fragments) coexist on the MoC@sub x@ surface. At 250 K, no C-S bonds are left. H@sub 2@S and SO@sub 2@ are also very reactive on MoC@sub x@, with the cleavage of H-S and S-O bonds taking place at temperatures well below 300 K. For these systems, the chemistry observed on carbide-modified Mo(110) is quite similar to that seen on Mo@sub 2@C powders.