Regeneration - Spent Hydroprocessing Catalysts - page 176

various industrial operations, have also been used for oxidative regeneration of spent
hydroprocessing catalysts [446] .
Significant improvements in the control of temperature and overall regeneration were achieved
by introducing processes in which the regeneration is conducted with the spent catalyst in a
continuous motion. The improved control of the process parameters which resulted in
significant enhancement in the catalyst activity recovery, as it is demonstrated in Fig. 6.33
[448] . Thus, at least four utilization-regeneration cycles could be achieved using the off-site
regeneration. Worldwide, there are three major companies namely, Porocel (previously CRI),
EURECAT, and TRICAT that offer off-site catalyst regeneration services [7,453] . Each of
these companies employs different regeneration technologies. Porocel uses fluidized bed
combined with moving belt [454] , Eurecat uses rotatory kiln [455] , and TRICAT uses a
fluidized bed [456] in their regenerators.
Presulfiding services after regeneration are also offered by these companies. In the case of
some new generation diesel hydrotreating catalysts with high metals (Mo and Co or Ni)
loading, additional chemical treatments of decoked catalysts with oxygen containing chelating
agents are done to redisperse the metals [457,458] . Recently, Albemarle has introduced
REACT technology that enables the activity of regenerated STARS catalyst to be recovered to
over 90% when compared with fresh catalyst. It is claimed that Albemarle's REACT
technology redistributes the metals and reconfigures the actives sites to the type II formation of
the original STARS catalysts [458,113] . Criterion Catalyst Company has developed a similar
revitalization technique for regeneration of their CENTINEL catalysts. Recovery of the
activity levels very close to that of fresh catalyst activity has been reported in the revitalization
technology [459,460] . In this regard, the best-known and most established commercial
processes include the belt regeneration process developed by the Catalyst Recovery
International (currently Porocel) [459] and a cylindrical drum arranged to rotate slowly on a
horizontal axis, which has been developed and used commercially by EUROCAT
[452,453,461] .
A brief description of the strategy adopted by EUROCAT is given to illustrate the necessity of
a preliminary spent catalyst evaluation prior to regeneration [462] . This strategy relies on the
extensive database of the laboratory results and the results from commercial operation. This
database may be used to predict the regeneration difficulty after the spent catalyst evaluation
on a laboratory scale. For this purpose, a composite sample is split into three sub-samples for
laboratory regeneration under different conditions. This is followed by the analysis of carbon
and sulfur content as well as surface area. The regenerated samples are sulfided before
performing a dynamic oxygen chemisorption, which is an indication of the level of catalyst
recovery. A typical information obtained from these evaluations is shown in Fig. 6.22
[366-368] showing the effect of temperature on the carbon and sulfur content as well as that
on the dynamic oxygen chemisorption and surface area of regenerated catalyst, respectively.