Hydroprocessing of Petroleum - Spent Hydroprocessing Catalysts - page 32

Figure 3.6: Typical shapes of commercial hydroprocessing catalysts [From ref. 75 . Reprinted
with permission].
pore radius, the tolerance to metals abruptly decreases, whereas the decrease in activity was
less pronounced.
In an effort to enhance the overall catalyst utilization and to improve the reactor performance,
various shapes and sizes of catalyst particles have been developed. Typical shapes of particles
are shown in Fig. 3.6 [75] . In the case of fixed bed reactors, the development of pressure drops
can be diminished by selecting an optimal shape of particles. In this regard, the method of
catalyst loading, i.e., dense versus sock, is also important as it is evidenced by Fig. 3.7 [91] .
The shape and size of particles as the method of loading may play an important role if the in
situ regeneration of spent catalyst bed is considered.
3.3.3 Improved Hydroprocessing Catalysts
Catalysts used in petroleum refining processes deactivate with time during the operation. The
rate of deactivation and catalyst life depends primarily on the catalyst structure, operating
severity and feedstock quality. For a given feedstock, the operating severity can be reduced and
the life of the catalyst can be extended if more active and stable catalysts are used in the
process. Therefore, the development of better catalysts is one of the alternatives to minimize
the utilization of fresh catalysts and generation of spent catalysts. In this regard, numerous
attempts to improve catalyst performance reported in the scientific literature have been noted.
These improvements together with better catalyst loading procedures and improved feed
distribution in reactors have increased run-lengths significantly and reduced spent catalyst
waste generation.