Hydroprocessing of Petroleum - Spent Hydroprocessing Catalysts - page 17

CHAPTER 3
Hydroprocessing of Petroleum
As the most advanced hydrogen addition method, hydroprocessing has been an essential
process for conversion of various petroleum fractions and residues to commercial fuels and
other products. Depending on the origin of the feed, wide ranges of operating conditions have
been employed in commercial hydroprocessing units. To suit processing requirements, refiner
may choose from among reactors employing different types of beds, e.g., fixed bed, moving
bed, ebullated bed and slurry bed. An efficient hydrogen transfer to reactant molecules cannot
be facilitated without the presence of an active catalyst. The design of catalytic reactors,
particularly their internals, may have a pronounced effect on the operation. A high performance
of hydroprocessing units requires an optimal matching of the type of feed with that of catalyst
and reactor. This ensures that the rate of catalyst deactivation is kept at a minimum.
3.1 Feeds for Hydroprocessing
Most, if not all, spent catalysts generated during hydroprocessing of the feeds derived from
petroleum require special management procedures. One may also include in this category of
the feeds synthetic crude obtained from heavy oils and tar sands. Non-petroleum feeds include
those derived from bio crude, oil shale and coal-derived liquids. There is little known about the
generation of spent catalysts during hydroprocessing of these materials on a commercial scale.
There has been decades of commercial experience in the production of synthetic crude via
Fischer-Tropsch (FT) synthesis. The upgrading of this crude to commercial products is
conducted under conditions approaching those applied during hydroprocessing of petroleum
feeds, although some fundamental differences in operating parameters should be noted. The
procedures used for handling spent catalysts from this source are similar as well. Nevertheless,
the following discussion is focusing primarily on the feeds of petroleum origin. Because of the
extensive information on various aspects of hydroprocessing feeds readily available in the
literature, only a general and brief account of their properties is given. A significant difference
between the operating conditions applied during hydroprocessing of the metals free feeds and
those containing metals and asphaltenes should be noted.
The properties of several distillate feeds and an atmospheric residue are shown in Table 3.1
[44] . It was indicated earlier that the severity of hydroprocessing depends on the properties of
the feed and it always increases from light feeds towards heavy feeds. For example, for feeds
in Table 3.1 , the severity will increase in the following order: kerosine > gas oil > atmospheric
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