THEORETICAL CALCULATION OF THE INTERACTIONS OF SULFUR COMPOUNDS WITH NANOSTRUCTURED MOLYBDENUM CARBIDE AND NITRIDE

摘要

Potential energy calculation was used to estimate the interaction of sulfur compounds with carbides and nitrides. This paper describes an investigation of the adsorptive interactions between different fuel sulfur compounds such as thiophene and tetrahydrothiophene, and Mo carbide and nitride surfaces under different assumptions. The interaction energy was approximated using potential energy theory. Results from this investigation showed that tetrahydrothiophene has higher interaction energy with the Mo carbide and nitride surfaces as compared to the organosulfur compounds. Experimentally, x-ray diffraction indicated that the bulk structures were not affected by sulfur adsorption; the affects of sulfur were restricted to the surface. In addition, experiments of adsorption isotherms showed that tetrahydrothiophene had a higher affinity than the other organosulfur compounds for the M02C and Mo_2N surfaces by having a faster and better selective adsorption on the material surfaces. This could be due to different adsorption mechanisms as through sulfur element versus n-complexation bonding of the ring which is expected for the other organosulfur compounds. As carbides and nitrides do not have very high surface area, and since the interaction is restricted on the surface, depositing these active materials on a highly porous media substrate will give us a better performance. These and other results provide important insights regarding the nature of interactions between sulfur and carbides or nitrides, which in turn helps design a good sorbent for sulfur removal application.