are crucial to reduce the effect of coke buildup and to lengthen the catalyst cycle
length. SR reformers make use of catalysts that contain platinum modified by
rhenium or, to a lesser extent, iridium. These modifiers act by either hydrogenating
the coke to a less graphitic species (Augustine et al. 1989) or by cracking the coke
precursors (Sorrentino et al. 1984). Rhenium or iridium significantly enhances the
life of the catalyst over older catalysts that only contained Pt. Pt-Re catalysts have
been improved by increasing the ratio of Re to Pt which provides additional catalyst
stability. All SR catalysts are sulfided to minimize metal-catalyzed hydrogenolysis
reactions that produce light gases and reduce gasoline yield.
The support is most often gamma alumina, although there have been some uses
of eta alumina (Mills et al. 1953). The supports are typically extrudates in cylindrical form with diameters that range from 1.6 mm (1/16 in.) to 2.1 mm (1/12 in.).
Since the reactors are fixed in an SR unit, different catalysts can be loaded in
different positions. The use of two catalysts in an SR unit – one catalyst in the front
reactors and another catalyst in the back reactors to provide maximum yield,
activity, and stability – was commercialized in 1994 (Weiszmann 1986).
New-generation SR catalysts are further improving C 5 + reformate yields by the
addition of promoters to attenuate metal cracking, by modification of the support
density, by optimization of the Pt/Re ratio, and by improvement of manufacturing
procedures (Moser et al. 1996; Lapinski et al. 2006).
Catalysts for Cyclic Units
Cyclic reforming units have fixed beds, but there is an additional swing reactor that
is substituted in any reactor position to allow regeneration of each reactor on an
ongoing basis. The catalysts types that have been used in cyclic reforming include
Pt, Pt-Re, Pt-Ir, and Pt-Sn on chlorided alumina. Because the reactors can be
regenerated one after another, lower stability Pt-only catalysts are still being used
by some refiners in their cyclic units.
Catalysts for CCR Process Units
In moving bed continuous regeneration units (Weiszmann 1986), the catalyst flows
through the reactors and is regenerated continually in a separate regeneration vessel
that is part of the reactor-regenerator loop. Process conditions are much more
severe, thus shortening catalyst life and requiring regeneration cycles of only a
few days. The catalysts types found best for this service are Pt-Sn on chlorided
alumina. These catalysts increase the liquid, aromatic, and hydrogen yields by
reducing the activity of the platinum for hydrogenolysis or metal-catalyzed cracking reactions. These components also provide some stabilization of the catalyst
relative to Pt alone.
New proprietary catalysts have been developed that utilize additional promoter
elements that modify both the acid and metal functions to increase yields, lower
248
M.P. Lapinski et al.
length. SR reformers make use of catalysts that contain platinum modified by
rhenium or, to a lesser extent, iridium. These modifiers act by either hydrogenating
the coke to a less graphitic species (Augustine et al. 1989) or by cracking the coke
precursors (Sorrentino et al. 1984). Rhenium or iridium significantly enhances the
life of the catalyst over older catalysts that only contained Pt. Pt-Re catalysts have
been improved by increasing the ratio of Re to Pt which provides additional catalyst
stability. All SR catalysts are sulfided to minimize metal-catalyzed hydrogenolysis
reactions that produce light gases and reduce gasoline yield.
The support is most often gamma alumina, although there have been some uses
of eta alumina (Mills et al. 1953). The supports are typically extrudates in cylindrical form with diameters that range from 1.6 mm (1/16 in.) to 2.1 mm (1/12 in.).
Since the reactors are fixed in an SR unit, different catalysts can be loaded in
different positions. The use of two catalysts in an SR unit – one catalyst in the front
reactors and another catalyst in the back reactors to provide maximum yield,
activity, and stability – was commercialized in 1994 (Weiszmann 1986).
New-generation SR catalysts are further improving C 5 + reformate yields by the
addition of promoters to attenuate metal cracking, by modification of the support
density, by optimization of the Pt/Re ratio, and by improvement of manufacturing
procedures (Moser et al. 1996; Lapinski et al. 2006).
Catalysts for Cyclic Units
Cyclic reforming units have fixed beds, but there is an additional swing reactor that
is substituted in any reactor position to allow regeneration of each reactor on an
ongoing basis. The catalysts types that have been used in cyclic reforming include
Pt, Pt-Re, Pt-Ir, and Pt-Sn on chlorided alumina. Because the reactors can be
regenerated one after another, lower stability Pt-only catalysts are still being used
by some refiners in their cyclic units.
Catalysts for CCR Process Units
In moving bed continuous regeneration units (Weiszmann 1986), the catalyst flows
through the reactors and is regenerated continually in a separate regeneration vessel
that is part of the reactor-regenerator loop. Process conditions are much more
severe, thus shortening catalyst life and requiring regeneration cycles of only a
few days. The catalysts types found best for this service are Pt-Sn on chlorided
alumina. These catalysts increase the liquid, aromatic, and hydrogen yields by
reducing the activity of the platinum for hydrogenolysis or metal-catalyzed cracking reactions. These components also provide some stabilization of the catalyst
relative to Pt alone.
New proprietary catalysts have been developed that utilize additional promoter
elements that modify both the acid and metal functions to increase yields, lower
248
M.P. Lapinski et al.