Albemarle’s ATIS-2L, introduced in the 2000s, providing higher activity and
conversion for C 5 /C 6 applications.
Chlorided Alumina-Type Catalysts
Chlorided alumina, the highest-activity paraffin isomerization catalyst available,
increases the octane of a typical light-naphtha stream from about 70 to as high as
86 RON in a once-through paraffin isomerization unit as depicted in Fig. 1. Higher
product octane, up to 93 RON, can be obtained by recycling low-octane hydrocarbons
back to the reactors for further upgrade. The C 5 + yield from chlorided alumina catalysts
is generally the highest from any commercial catalyst because of high catalyst selectivity and low operating temperature. Because chlorided alumina systems are not
economically regenerable either within the process unit or ex situ, eventual reloading
may be required, depending upon contaminant levels contained in the feed and process
gas streams. While the average life of a catalyst load is 5 years, there are catalyst loads
operating well beyond 20 years with diligent care and operations monitoring.
Nevertheless, the chlorided alumina system is often the most economical choice
because of its inherent high activity. In addition, only chlorided alumina catalysts
have enough activity to economically and effectively isomerize butanes. Approximately 85 % of the installed isomerization processes today employ chlorided
alumina-type catalysts.
Zeolitic-Type Catalysts
Zeolitic isomerization catalysts, such as UOP’s HS-10 Hysomer™ catalyst, operate
at higher temperatures than chlorided alumina catalysts. Almost no new process
units employ this technology due to unfavorable economics. The maximum product
octane that can be achieved is limited by the unfavorable equilibrium at these
conditions. Yields are also lower as a result of the higher operating temperature
and the less selective characteristics of zeolitic catalysts. A typical octane upgrade
for a once-through zeolitic isomerization unit is from 70 to about 79 RON. Higher
product octanes (86–88) can be obtained in a recycle operation, such as in a UOP
TIP™ unit (Total Isomerization Process) as depicted in Fig. 1. A TIP unit uses a
multi-vessel vapor-phase adsorption process (IsoSiv™ process) to separate normal
paraffins so they can be recycled to the reactor.
The most attractive benefit of zeolitic isomerization catalysts is that they are not
permanently deactivated by water or other oxygenates and are fully regenerable.
Consequently, zeolitic catalysts have often been used when revamping other process units, such as hydrotreaters or reformers to isomerization service. Sulfur can be
present in the feedstock with catalysts such as the HS-10 catalyst, but performance
is debited to some extent. Sulfur suppresses the platinum function as it does in any
platinum-containing catalyst. Although isomerization activity is maintained, a net
C 5 + product yield loss results. Feed hydrotreating is not an absolute requirement
Isomerization in Petroleum Processing
489
conversion for C 5 /C 6 applications.
Chlorided Alumina-Type Catalysts
Chlorided alumina, the highest-activity paraffin isomerization catalyst available,
increases the octane of a typical light-naphtha stream from about 70 to as high as
86 RON in a once-through paraffin isomerization unit as depicted in Fig. 1. Higher
product octane, up to 93 RON, can be obtained by recycling low-octane hydrocarbons
back to the reactors for further upgrade. The C 5 + yield from chlorided alumina catalysts
is generally the highest from any commercial catalyst because of high catalyst selectivity and low operating temperature. Because chlorided alumina systems are not
economically regenerable either within the process unit or ex situ, eventual reloading
may be required, depending upon contaminant levels contained in the feed and process
gas streams. While the average life of a catalyst load is 5 years, there are catalyst loads
operating well beyond 20 years with diligent care and operations monitoring.
Nevertheless, the chlorided alumina system is often the most economical choice
because of its inherent high activity. In addition, only chlorided alumina catalysts
have enough activity to economically and effectively isomerize butanes. Approximately 85 % of the installed isomerization processes today employ chlorided
alumina-type catalysts.
Zeolitic-Type Catalysts
Zeolitic isomerization catalysts, such as UOP’s HS-10 Hysomer™ catalyst, operate
at higher temperatures than chlorided alumina catalysts. Almost no new process
units employ this technology due to unfavorable economics. The maximum product
octane that can be achieved is limited by the unfavorable equilibrium at these
conditions. Yields are also lower as a result of the higher operating temperature
and the less selective characteristics of zeolitic catalysts. A typical octane upgrade
for a once-through zeolitic isomerization unit is from 70 to about 79 RON. Higher
product octanes (86–88) can be obtained in a recycle operation, such as in a UOP
TIP™ unit (Total Isomerization Process) as depicted in Fig. 1. A TIP unit uses a
multi-vessel vapor-phase adsorption process (IsoSiv™ process) to separate normal
paraffins so they can be recycled to the reactor.
The most attractive benefit of zeolitic isomerization catalysts is that they are not
permanently deactivated by water or other oxygenates and are fully regenerable.
Consequently, zeolitic catalysts have often been used when revamping other process units, such as hydrotreaters or reformers to isomerization service. Sulfur can be
present in the feedstock with catalysts such as the HS-10 catalyst, but performance
is debited to some extent. Sulfur suppresses the platinum function as it does in any
platinum-containing catalyst. Although isomerization activity is maintained, a net
C 5 + product yield loss results. Feed hydrotreating is not an absolute requirement
Isomerization in Petroleum Processing
489