with zeolitic catalysts, but it is necessary to get the optimum performance from the
catalyst. Approximately 30 zeolitic-type units still operate today.
Sulfated Metal Oxide-Type Catalysts
Sulfated metal oxide catalysts, which have been described as solid superacids,
exhibit high activity for paraffin isomerization reaction (Gosling et al. 1998)
when compared to zeolitic-type catalysts. These metal oxides form the basis of a
more recent generation of isomerization catalysts that have been actively discussed
in the scientific literature. These catalysts are most commonly tin oxide (SnO 2 ),
zirconium oxide (ZrO 2 ), titanium oxide (TiO 2 ), tungstated zirconia, or ferric oxide
(Fe 2 O 3 ) that has been sulfated by reaction with sulfuric acid or ammonium sulfate.
Sulfated alumina is not an active catalyst for hydrocarbon reactions.
A typical metal oxide catalyst, such as UOP’s PI-244 Par-Isom™ catalyst, has a
considerably higher activity than that of traditional zeolitic-type catalysts, and this
activity advantage is equivalent to about 80
C lower reaction temperature. The
lower reaction temperature allows for a product with a significantly higher product
octane, about 82 RON for a typical feed, four numbers higher than that of a zeolitic
catalyst. Similar to zeolitic catalysts, the PI-244 catalyst is not permanently
deactivated by water or oxygenates in the feedstock. These catalysts are also fully
regenerable using a simple oxidation procedure that is comparable to the one used
for zeolitic catalysts. The high activity of the PI-244 catalyst makes it an ideal choice
for new units where the full performance advantage of chlorided alumina catalysts is
not required or where the refiner is concerned about contaminants in the feedstock.
The performance of well-established commercial isomerization catalysts such as
UOP HS-10 (zeolitic), UOP LPI-100 (an older-generation sulfated zirconia catalyst),
UOP PI-244 (modified sulfated zirconia), and UOP I-82 (chlorided alumina) catalysts
is compared in Fig. 6, which illustrates the octane number improvement over zeolitic
catalysts for all the catalysts as a function of average reactor bed temperature. This
ranking illustrates the activity advantage for the chlorided alumina-type catalyst over
the zeolitic-type catalysts, an advantage that translates directly to octane improvement.
This is particularly true for fixed volume systems, when considering reloading existing
process units. Likewise, this ranking shows the performance benefit of the first- and
second-generation sulfated zirconia-type catalysts over zeolitic. It should be noted that
for unconstrained new unit designs, additional catalyst volume can be added to attain
lower temperature operation and higher octane. Comparisons of chlorided alumina
(I-82) and sulfated zirconia (PI-244) catalysts are provided in the following sections.
Process Options
Two process options are commercially available via either chlorided alumina-type
catalyst (e.g., the Penex process with I-82) or sulfated zirconia catalyst (e.g., the
Par-Isom process with PI-244). Both provide excellent upgrading of light naphtha
490
D. Sullivan et al.
catalyst. Approximately 30 zeolitic-type units still operate today.
Sulfated Metal Oxide-Type Catalysts
Sulfated metal oxide catalysts, which have been described as solid superacids,
exhibit high activity for paraffin isomerization reaction (Gosling et al. 1998)
when compared to zeolitic-type catalysts. These metal oxides form the basis of a
more recent generation of isomerization catalysts that have been actively discussed
in the scientific literature. These catalysts are most commonly tin oxide (SnO 2 ),
zirconium oxide (ZrO 2 ), titanium oxide (TiO 2 ), tungstated zirconia, or ferric oxide
(Fe 2 O 3 ) that has been sulfated by reaction with sulfuric acid or ammonium sulfate.
Sulfated alumina is not an active catalyst for hydrocarbon reactions.
A typical metal oxide catalyst, such as UOP’s PI-244 Par-Isom™ catalyst, has a
considerably higher activity than that of traditional zeolitic-type catalysts, and this
activity advantage is equivalent to about 80
C lower reaction temperature. The
lower reaction temperature allows for a product with a significantly higher product
octane, about 82 RON for a typical feed, four numbers higher than that of a zeolitic
catalyst. Similar to zeolitic catalysts, the PI-244 catalyst is not permanently
deactivated by water or oxygenates in the feedstock. These catalysts are also fully
regenerable using a simple oxidation procedure that is comparable to the one used
for zeolitic catalysts. The high activity of the PI-244 catalyst makes it an ideal choice
for new units where the full performance advantage of chlorided alumina catalysts is
not required or where the refiner is concerned about contaminants in the feedstock.
The performance of well-established commercial isomerization catalysts such as
UOP HS-10 (zeolitic), UOP LPI-100 (an older-generation sulfated zirconia catalyst),
UOP PI-244 (modified sulfated zirconia), and UOP I-82 (chlorided alumina) catalysts
is compared in Fig. 6, which illustrates the octane number improvement over zeolitic
catalysts for all the catalysts as a function of average reactor bed temperature. This
ranking illustrates the activity advantage for the chlorided alumina-type catalyst over
the zeolitic-type catalysts, an advantage that translates directly to octane improvement.
This is particularly true for fixed volume systems, when considering reloading existing
process units. Likewise, this ranking shows the performance benefit of the first- and
second-generation sulfated zirconia-type catalysts over zeolitic. It should be noted that
for unconstrained new unit designs, additional catalyst volume can be added to attain
lower temperature operation and higher octane. Comparisons of chlorided alumina
(I-82) and sulfated zirconia (PI-244) catalysts are provided in the following sections.
Process Options
Two process options are commercially available via either chlorided alumina-type
catalyst (e.g., the Penex process with I-82) or sulfated zirconia catalyst (e.g., the
Par-Isom process with PI-244). Both provide excellent upgrading of light naphtha
490
D. Sullivan et al.