OVERVIEW

The presence of large molecules indicates a significant complexity of the reactions occurring during hydroprocessing of heavy feeds. Because of the increasing involvement of asphaltenic molecules, the complexity increases from VGO/HGO toward VR and topped heavy crude. In every case, the primary objective is the conversion of large molecules to distillates. This may be accomplished via HCR of resins and asphaltenes simultaneously with the conversion of porphyrin structures. Therefore, for heavy asphaltenic feeds, a high rate of the HDAs is required to achieve a desirable rate of HDM. Thus, the removal of most of the metals cannot be achieved before asphaltenes are depolymerized to smaller entities.

In the case of VGO, HGO and DAO feeds, a high level of HYD of aromatics, i.e., a high rate of HDAr, must be achieved, when the feed preparation for FCC is the objective. Moreover, for such feeds even traces of metals and asphaltenes as well as nitrogen have to be removed to prevent poisoning of FCC catalyst, unless a more advanced process, i.e., RFCC, is used. In the case of catalytic dewaxing of these feeds, catalyst must possess an adequate HCR activity and selectivity to ensure a high yield of middle distillates and lube base oil fractions. For dewaxing catalysts, hydroisomerization of ra-paraffins to isoparaffins becomes an important catalytic functionality to ensure low freezing point and pour point of the final products. In addition, to be suitable for preparation of lubricants, lube base oil must exhibit good viscosity behavior. For this purpose,...