Modern refining configurations may also include processes which convert
low-quality products to gasoline precursors, enhancing the gasoline’s octane rating.
These include the alkylation and isomerization processes (see the relevant chapters). Others which are less common are the oxygenated precursors (discussed in the
chapter “▶ Introduction to Crude Oil and Petroleum Processing”).
Catalytic Reforming
This is a process which converts a relatively low octane straight run naphtha into a
high-octane liquid reformate which is a major precursor for finished gasoline. This
process also produces a high-purity hydrogen stream; this makes the process one of
the most important in a modern-day refinery configuration.
Briefly, the straight run heavy naphtha is heated and is passed over beds of
platinum/rhenium catalyst contained in (usually) three or four separate reactor
vessels. A recycle hydrogen stream accompanies the feed through these reactors,
and the reaction temperature is controlled by heaters between each reactor. The
principal reaction is the dehydrogenation of the naphthenes in the feed to their
respective aromatic homologues. In so doing the excess hydrogen molecules are
released as a hydrogen by-product. Other reactions also occur which enhance the
octane rating of the debutanized reformate liquid product. Among these are some
isomerization and, to some extent, some hydrocracking. Details of this process are
given in the chapter “▶ Catalytic Reforming in Petroleum Processing.”
Some typical properties of the debutanized reformate are given in Table 2. The
feed to the catalytic reformer in this case includes the straight run naphtha (SRN)
from the crude unit and the naphtha streams from gas oil hydrotreaters and a
thermal cracker. This feed stream was also hydrotreated before entering the catalytic reformer (Table 2).
Naphtha from a Fluid Catalytic Cracking Unit
The naphtha from the FCCU is always a prime precursor for gasoline blends. There
are usually two naphtha streams which are the debutanized overhead distillate from
the cracker’s main fractionator. This distillate is fractionated to produce a light
naphtha and the heavy naphtha. As can be seen from the chapter “▶ Fluid Catalytic
Cracking (FCC) in Petroleum Refining,” the fluid catalytic cracker is a very flexible
unit with respect to the feedstock that it can process. As a matter of fact, the only
real constraints on the process are high metals and Conradson carbon contents of
the feed. Even these constraints are reduced with the improved catalysts now
available and some modification to the conventional process (see the topic in
chapter “▶ Upgrading the Bottom of the Barrel” on deep oil cracking). The effect
of the feedstock quality however is confined mostly to the severity of cracking and
the resulting yields of the cracked products. The qualities of the streams from the
main fractionator can be and usually are constant. Table 3 shows the properties of
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D.S.J. Jones and S.A. Treese
low-quality products to gasoline precursors, enhancing the gasoline’s octane rating.
These include the alkylation and isomerization processes (see the relevant chapters). Others which are less common are the oxygenated precursors (discussed in the
chapter “▶ Introduction to Crude Oil and Petroleum Processing”).
Catalytic Reforming
This is a process which converts a relatively low octane straight run naphtha into a
high-octane liquid reformate which is a major precursor for finished gasoline. This
process also produces a high-purity hydrogen stream; this makes the process one of
the most important in a modern-day refinery configuration.
Briefly, the straight run heavy naphtha is heated and is passed over beds of
platinum/rhenium catalyst contained in (usually) three or four separate reactor
vessels. A recycle hydrogen stream accompanies the feed through these reactors,
and the reaction temperature is controlled by heaters between each reactor. The
principal reaction is the dehydrogenation of the naphthenes in the feed to their
respective aromatic homologues. In so doing the excess hydrogen molecules are
released as a hydrogen by-product. Other reactions also occur which enhance the
octane rating of the debutanized reformate liquid product. Among these are some
isomerization and, to some extent, some hydrocracking. Details of this process are
given in the chapter “▶ Catalytic Reforming in Petroleum Processing.”
Some typical properties of the debutanized reformate are given in Table 2. The
feed to the catalytic reformer in this case includes the straight run naphtha (SRN)
from the crude unit and the naphtha streams from gas oil hydrotreaters and a
thermal cracker. This feed stream was also hydrotreated before entering the catalytic reformer (Table 2).
Naphtha from a Fluid Catalytic Cracking Unit
The naphtha from the FCCU is always a prime precursor for gasoline blends. There
are usually two naphtha streams which are the debutanized overhead distillate from
the cracker’s main fractionator. This distillate is fractionated to produce a light
naphtha and the heavy naphtha. As can be seen from the chapter “▶ Fluid Catalytic
Cracking (FCC) in Petroleum Refining,” the fluid catalytic cracker is a very flexible
unit with respect to the feedstock that it can process. As a matter of fact, the only
real constraints on the process are high metals and Conradson carbon contents of
the feed. Even these constraints are reduced with the improved catalysts now
available and some modification to the conventional process (see the topic in
chapter “▶ Upgrading the Bottom of the Barrel” on deep oil cracking). The effect
of the feedstock quality however is confined mostly to the severity of cracking and
the resulting yields of the cracked products. The qualities of the streams from the
main fractionator can be and usually are constant. Table 3 shows the properties of
62
D.S.J. Jones and S.A. Treese