Electronic Factors in Thiophene Adsorption and Hydrodesulfurization on MoS2 Surfaces

摘要

Hydrodesulfurization, the removal of sulfur in the form of H2S from petroleum compounds, is a crucial step in industrial refinement processes. In spite of numerous recent experimental and theoretical studies, many aspects of the complex HDS system remain obscure. We will focus on the MoS2/thiophene system in this work. MoS2 based systems are among the most frequently used and studied catalysts. The microscopic nature of the active surface is not well defined, although several points can be made. Crystallites of the material are bound to an Al2O3 support, which is generally considered to be inert. MoS2 is a layer compound; the crystals cleave readily between the S-Mo-S sandwiches to expose all-sulfur faces. However, this surface, the basal plane, is believed to be inactive in HDS. The catalytic surface contains exposed Mo atoms. A good candidate is the edge plane perpendicular to the sulfur layers. Corner sites along the edge and defect sites arising from missing surface sulfur atoms, in particular, have been implicated as the active sites. These Mo atoms are coordinatively unsaturated, thus it is not unreasonable that adsorption may occur here.