Multi-stage process for demetalation and desulfurization of petroleum oils

DETAILED DESCRIPTION OF THE INVENTION The hydrocarbon feed to the process of this invention can be a whole crude.
However, since the high metal and sulfur components of a crude oil tend to be concentrated in the higher boiling fractions, the present process more commonly will be applied to a bottoms fraction of a petroleum oil, i.
e.
, one which is obtained by atmospheric distillation of a crude petroleum oil to remove lower boiling materials such as naphtha and furnace oil, or by vacuum distillation of an atmospheric residue to remove gas oil.
Typical residues to which the present invention is applicable will normally be substantially composed of residual hydrocarbons boiling about 650.
degree.
F.
and containing a substantial quantity of asphaltic materials.
Thus, the charge stock can be one having an initial or 5 percent boiling point somewhat below 650.
degree.
F.
, provided that a substantial proportion, for example, about 70 or 80 percent by volume, of its hydrocarbon components boils above 650.
degree.
F.
A hydrocarbon stock having a 50 percent boiling point of about 900.
degree.
F.
and which contains asphaltic materials, 4% by weight sulfur and 51 ppm nickel and vanadium is illustrative of such charge stock.
Typical process conditions may be defined as contacting a metal and/or sulfur and/or CCR contaminant containing charge stock with this invention's catalyst under a hydrogen pressure of about 500 to 3000 psig at 600.
degree.
to 850.
degree.
F.
temperature, and 0.
1 to 5 LHSV (i.
e.
, 0.
1 to 5 volumes of charge stock per volume of catalyst per hour).
The hydrogen gas which is used during the hydro-demetalation, hydrodesulfurization, and CCR removal is circulated at a rate between about 1,000 and 15,000 s.
c.
f.
/bbl.
of feed and preferably between about 3,000 and 8,000 s.
c.
f.
/bb.
The hydrogen purity may vary from about 60 to 100 percent.
If the hydrogen is recycled, which is customary, it is desirable to provide for bleeding off a portion of the recycle gas and to add makeup hydrogen in order to maintain the hydrogen purity within the range specified