Processing of Primary Fischer-Tropsch Products - University of Alberta

In the case of zeolites, the acidity depends also on the silica/alumina ratio
as well as on the zeolite structure and the degree of exchange of sodium ions
with protons. In mixed zeolite amorphous silica/alumina carriers the amorphous
phase can either act simply as a binder at low level or at higher levels can also
contribute to the activity.
6.3.3 Metal components
Most commonly the metals used in hydrocracking catalysts are a
combination of group VIA (molybdenum, ttmgsten) and group VIIIA (cobalt,
nickel). These metals are sulphided prior to use and kept in a sulphided state
during the hydrocracking operation by sulphur compounds in the feed in the case
of refinery feeds or by adding sulphur containing compounds in the case of
sulphur free feeds, like FT derived feeds.
From hydrogenation studies it was found that the optimum ratio of the
metals is:
Mvin/(Mvm + Mvi) = --0,25, where MvIII is Co or Ni and MvI is Mo or W.
The hydrogenation activity of the various couples decrease in the order:
Ni-W > Ni-Mo > Co-Mo > Co-W.
The hydrogenation activity is also function of the metal loading and
dispersion. The required metal loading will depend on the desired balance
between the cracking/isomerisation and hydrogenation functions.
The noble metal content of hydrocracking catalysts is generally around
0.5% or less. For non-noble metal the loadings are 3-8% nickel or cobalt oxides
and 10-30% for molybdenum or tungsten oxides.
6.4 Hydroprocessing flow sheet options to produce diesel
The FT syncrude upgrading may be designed in a number of
configurations. These can be selected by process synthesis optimisation
depending on the desired product slate [77]. Four of the possible process
configurations are described in Table 6 and shown in Fig. 6.
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