二苯并噻吩加氢脱硫过程在镍钼硫催化剂表面的吸附

Adsorption of dibenzothiophene hydrodesulfurization process over NiMoS Catalyst

二苯并噻吩(DBT)作为石油中最难脱除的含硫组分之一,对其加氢脱硫(HDS)过程的研究有着十分重要的意义.针对二苯并噻吩在加氢脱硫过程中各含硫物质在镍钼硫(NiMoS)催化剂表面吸附情况,采用量子化学中密度泛函理论方法,计算了二苯并噻吩(DBT)、四氢二苯并噻吩(4H—DBT)、六氢二苯并噻吩(6H—DBT)和十二氢二苯并噻吩(HY—DBT)等四种含硫物质于NiMoS催化剂表面上吸附能.主要研究垂直吸附和平行吸附两种吸附方式,研究结果表明,各含硫化合物在NiMoS催化剂表面上的吸附过程都是放热过程.当DBT、4H—DBT、6H—DBT和HY—DBT四种硫化物垂直吸附于催化剂表面,此时形成稳定构象,且各体系吸附能逐渐增大;而当各硫化物平行吸附时,各体系吸附能呈减小的趋势.其中DBT在催化剂表面吸附时,垂直吸附形式和平面吸附形式可能同时存在,而4H—DBT、6H—DBT和HY—DBT三种含硫物质则更易以垂直吸附形式吸附于催化剂表面.同时DBT、4H—DBT、6H—DBT和HY—DBT在NiMoS催化剂上吸附能较硫化钼(MoS2)催化剂更低.

Dibenzothiophene （DBT）is a difficult removal sulfur compound in the petroleum, whose hydrodesulfurization （HDS） process studies have great significance. The surface adsorption of DBT and its hydrogenation sulfur compounds were studied on NiMoS catalyst surface during hydrodesulfurization （HDS） process. The surface adsorbed energies of Dibenzothiophene （DBT）, tetrahydrodibenzothiophene （4H- DBT）, hexahydro-dibenzothiophene （6H-DBT）, and completely hydrogenated dibenzothiophene （HY-DBT） were computed based on density functional theory in quantum chemistry. Two different adsorbed configurations as perpendicular and flat adsorptions, were studied. The results show that it is an exothermic process for the adsorption process of DBT and its hydrogenation sulfur compounds on NiMoS catalyst surface. The stable configurations are obtained when DBT, 4H--DBT, 6H-DBT and HY-DBT are perpendicular absorbted on the surface of catalyst, at same time their adsorption energies are grown up by increasing of the hydrgen atoms; the opposite results are got when they are flat absorbted on the surface of catalyst. And then there are both perpendicular and flat adsorptions for DBT on the surface of NiMoS catalyst, but the others sulfur compounds such as 4H-DBT, 6H-DBT and HY-DBT are easier perpendicular adsorbed on NiMoS catalyst surface. Meanwhile the adsorption energies on the surface of NiMoS catalyst are lower than the the surface of MoS2 catalyst.