New Catalysts from Spent Catalysts - Spent Hydroprocessing Catalysts - page 245

9.1.3 Spent Catalysts in Slurry Bed Hydrocracking
The processes employing slurry bed reactors have been developed with the aim to offset the
costs of operation associated with a large catalyst inventory required for upgrading
problematic feeds via catalytic route. Thus, rather than to use commercial catalysts, these
processes employ low-cost solids which contain catalytically active transition metals such as
Fe, Ni, V, etc. Such solids are either disposed from industrial operations (e.g., red mud from
aluminum production, a high Ni and Cu content solid from nickel and copper production, steel
making, etc.) or they are occurring naturally. Therefore, their cost represents only a fraction of
that of commercial hydroprocessing catalysts. The best-known processes operating in a slurry
mode include Hydrocracking-Deasphalting-Hydrgenation (HDH) process developed by
Venezuelan INTEVEP [537] and German Veba Combi Cracking (VCC) process developed by
VEBA [538] . They were operated on a demonstration scale (150 barrels per day) and a
commercial scale, respectively. Apparently, both processes are suitable for hydrocracking
heavy feeds the metal content of which exceeds 1000 ppm of V + Ni (e.g., Boscan).
Apparently, there is a number of other slurry bed hydrocracking processes in various stages of
development. In this regard, the updated information was published elsewhere [539] .
It was disclosed by Beret et al. [540] that fines of the spent catalyst could be used in a process
for upgrading heavy petroleum feed. The process comprised a two-stage system. The fines
introduced into the first stage had coke-suppressing and demetalizing activity. The effluent
from the first stage was directly passed and processed under hydrocracking conditions in the
second stage.
In a crushed form, spent hydroprocessing catalysts exhibited a high activity during
hydrocracking of vacuum residue in a slurry bed reactor [541] . This is not surprising, because
in a powder form of catalyst, diffusion problems encountered during hydrocracking of heavy
petroleum feeds are almost completely avoided. During slurry bed hydrocracking, active
metals in spent-crushed catalysts (e.g., Ni, Co, Mo, and Fe) are rapidly converted to
corresponding sulfides in situ. This results in the enhancement of hydrogen activation on the
surface of catalyst particles. As a consequence, active hydrogen converts coke precursors to
volatile products before they are converted to coke. Even a heavily deactivated crushed
catalyst (without decoking) can be successfully used in the slurry bed reactors. This was
confirmed by Matsumura et al. [542] who used a spent catalyst containing 9.6 wt.% V,
6.0 wt.% Ni, and 12.9 wt.% carbon. In spite of the heavy contamination, the catalyst exhibited
a good activity during upgrading of vacuum residue. The results published by Sakabe and Yagi
[408] support the observations made in these studies [541,542] .
It was indicated earlier that the metals loaded extracts from rejuvenation of spent
hydroprocessing catalysts may be co-slurried with a heavy feed and as such act as catalysts.
Apparently, this option for the utilization of metals from spent catalysts has not yet been
explored.