Mild hydrocracking of heavy hydrocarbon feedstocks employing silica-alumina catalysts

A catalyst comprising 2.0 to 6.0 wt.% of an oxide of a Group VIII metal, 12.0 to 25.0 wt.% of an oxide of molybdenum and 0 to 3.0 wt.% of an oxide of phosphorus, supported on a porous alumina support containing 4.0 to 30 wt.% of silica can be used in a mild hydrocracking process for the hydrodemetallation (HDM), hydrodesulphurization (HDS) and hydroconversion (HC) of hydrocarbon feedstocks, such as residuum feedstocks which provides increased conversion of the hydrocarbons boiling above 540 DEG C into hydrocarbons boiling below 540 DEG C, and increased yields of middle distillates. The catalyst has a molybdenum gradient (MbG) of 1.0 to 10.0, MbG being defined by the ratio and a specific pore diameter distribution.n