Spent Catalysts from Dewaxing Operations - Spent Hydroprocessing Catalysts - page 260

100 and 400 ◦ C. It has been noted that some catalyst testing was done in the IS mode, e.g., in
the presence of N 2 as carrier gas.
Among zeolites, a high selectivity was achieved using the medium pore size ZSM-5 zeolite.
Bendoraitis et al. [579] observed that the ZSM-5 zeolite and Pt/mordenite exhibited the shape
selective properties. The latter had larger pores than ZSM-5 zeolite. The pour points of lube
base oil were similar over both catalysts, whereas viscosity index over ZSM-5 catalyst was
higher than that over Pt-mordenite [579] . A modification of the ZSM-5 zeolite was tested by
Chen and Garwood [580] for dewaxing a middle distillate fuel. In this case, the zeolite was
exchanged with Zn/CH 4 Cl solution to obtain 0.9 wt.% of Zn. The activity of this catalyst was
in the range of that of the Ni/kieselguhr catalyst [581] . In view of the similarity of the process,
the observations made during dewaxing of the middle distillate feeds may also be relevant for
dewaxing of VGO and DAO.
A series of non-zeolitic catalysts was patented by Gillespie et al. [582-584] . The catalyst
development was based on the observation that catalysts containing lanthanide series and
platinum-group components provide a superior performance and stability during HIS of the
full boiling range of n-paraffins to i-paraffins. In this case, the catalyst comprised the
tungstated support zirconium oxide, a lanthanide element, and/or yttrium as the first
component, and a second component being a metal from platinum-group. The first component
consisted of a single lanthanide-series element or yttrium, while the second component of a
single platinum-group metal. Preferably, the first component was ytterbium, holmium, yttrium,
cerium, europium, or their mixtures, whereas the second component was Pt. The catalysts
contained the inorganic-oxide binder, such as alumina. Another solid-acid HIS catalyst
patented by Gillespie [583] consisted of the sulfated ZrO 2 as well as a group III A component,
and Pt. The catalyst was active for the conversion of a paraffinic feed to an iso-paraffin rich
product with the significantly enhanced cold flow properties. The catalyst comprising of the
support of the tungstated zirconia, at least one lanthanide element, preferably ytterbium or
holmium and Pt, was active for the selective upgrading a paraffinic feed to iso-paraffins rich
product [584] . Other suitable supports included HfO 2 ,TiO 2 , and SnO 2 . Another catalyst
consisted comprised a combination of the sulfated ZrO 2 support with one lanthanide element
or yttrium component, and the Pt deposited Al 2 O 3. This was very active catalyst for HIS as
well. In this case, the Al 2 O 3 was used as the binder [585] .
Vigorous research activities in the development of novel HIS catalysts by several research
groups should be noted. This research has been carried out in line with a growing interest in
synthetic fuels from Fischer-Tropsch synthesis. Detailed accounts of these studies will be
given by de Klerk and Furimsky [586] . A cursory account is only given in this topic to indicate
fundamental differences between the structure of conventional hydroprocessing catalysts and
catalysts comprising novel phases.