| Deep desulfurization of middle distillate involves the removal of residual sulfur compounds such as alkyl substituted benzothiophenes, dibenzothiophenes. There is a renewed interest in study of hydrodesulphurization of these refractory sulfur compounds due to the requirement to use new feed stocks and the application of more severe environmental legislations. Therefore there is a need to study HDS of these refractory compounds to achieve very low sulfur levels. In this study reactivities, reaction pathways and reaction kinetics of benzothiophene and hindered dibenzothiophenes were studied. The focus was on 4,6-DMDBT and 4-MDBT which are considered as most refractory sulfur compounds to be desulfurized. CoMo/Al2O3 and Phosphorus modified CoMo/Al2O 3 were synthesized by wet impregnation method. Catalysts were characterized by BET surface area and pore volume and by X-ray Diffraction. Reaction studies were carried out in a batch autoclave reactor system. CoMo/Al2O 3 catalysts were prepared to achieve selective HDS properties and to enhance the favorable reaction pathway. The phosphorus modified CoMo/Al 2O3 shows higher conversion as compared to unmodified catalysts. The reaction pathway study showed that the simultaneous Hydrodesulfurization (HDS) of DBT in a simultaneous reaction were influenced due to the presence of 4-MDBT and 4,6-DMDBT, the conversion of DBT was higher for the latter case. Simultaneous HDS of DBT also influenced the Direct desulfurization/Hydrogenation (DDS/HYD) ratio which was higher when DBT was desulfurized with 4,6-DMDBT. |
