A radiotracer ( 14C) and catalytic study of thiophene hydrodesulfurization on the clean and carbided Mo(100) single-crystal surface

Abstract

The role of adsorbed carbon overlayers and possible product poisoning (H 2S and cis-2-butene) in the thiophene hydrodesulfurization (HDS) reaction over Mo(100) single-crystal surfaces was investigated. Using the β − emitting 14C isotope, it was shown that adsorbed carbon remains on the Mo(100) surface after many thiophene turnovers (TN ≈ 10 3). HDS activities measured for carbided surfaces were found to be identical to that of initially clean Mo(100) single crystals, suggesting that the active catalyst surface is carbon covered. Deactivation of the single-crystal catalysts was caused by adsorption of H 2S onto the active HDS sites. Removal of the H 2S by evacuation of the reaction mixture readily regenerated the catalyst's activity toward a fresh mixture of thiophene and hydrogen. The product cis-2-butene had no effect on the activity of the catalysts.