for these units ideally contain naphthenes, aromatics, and paraffins in predominantly the six to eight carbon atom range.
The most common type of naphtha is derived directly from crude distillation and
is called straight run naphtha. In addition to straight run, naphthas can be derived
from other processes that catalytically or thermally crack heavier hydrocarbons to
naphtha range hydrocarbons. For example, cracked feedstocks may be derived
from fluid catalytic cracking (FCC) units, hydrocracking units, cokers, and
visbreaking units. Naphthas can also be synthetically derived from a FischerTropsch process.
Characterization
Naphthas are characterized by their boiling point curves and component compositions. Distillation values for the initial boiling point (IBP), the mid-boiling point,
and the endpoint (EP) as shown in Fig. 2 are often used to classify the naphtha as
light or heavy. Straight run naphtha from crude distillation with a boiling range of
150–400
F (65–200
C) would be classified as heavy naphtha.
Table 1 shows the composition for typical naphtha that contains 55.4 wt.% total
paraffins, 30.7 wt.% total naphthenes, 0.1 wt.% total olefins, and 13.9 wt.% total
aromatics. Naphthas are classified as lean or rich based on their compositions.
A lean feed has a high concentration of paraffins and relatively low
concentrations of naphthenes and aromatics, whereas a rich feed has a low
paraffin concentration and relatively high concentrations of naphthenes plus
aromatics.
The heaviness (distillation endpoint) and type (lean or rich) are indicators of the
difficulty in reforming the naphtha. For example, light-lean naphtha with an
endpoint of 320
F (160
C) and 65 wt.% paraffins is more difficult to reform
than a heavy-rich naphtha with an endpoint of 370
F (188
C) and 60 wt.%
naphthenes plus aromatics.
150
200
250
300
350
400
IBP 10
30
50
70
90
EP
Percent Over
Temperature, °F
Fig. 2 ASTM D-86
distillation curve for naphtha
(Huebner et al. 1999)
Catalytic Reforming in Petroleum Processing
233
The most common type of naphtha is derived directly from crude distillation and
is called straight run naphtha. In addition to straight run, naphthas can be derived
from other processes that catalytically or thermally crack heavier hydrocarbons to
naphtha range hydrocarbons. For example, cracked feedstocks may be derived
from fluid catalytic cracking (FCC) units, hydrocracking units, cokers, and
visbreaking units. Naphthas can also be synthetically derived from a FischerTropsch process.
Characterization
Naphthas are characterized by their boiling point curves and component compositions. Distillation values for the initial boiling point (IBP), the mid-boiling point,
and the endpoint (EP) as shown in Fig. 2 are often used to classify the naphtha as
light or heavy. Straight run naphtha from crude distillation with a boiling range of
150–400
F (65–200
C) would be classified as heavy naphtha.
Table 1 shows the composition for typical naphtha that contains 55.4 wt.% total
paraffins, 30.7 wt.% total naphthenes, 0.1 wt.% total olefins, and 13.9 wt.% total
aromatics. Naphthas are classified as lean or rich based on their compositions.
A lean feed has a high concentration of paraffins and relatively low
concentrations of naphthenes and aromatics, whereas a rich feed has a low
paraffin concentration and relatively high concentrations of naphthenes plus
aromatics.
The heaviness (distillation endpoint) and type (lean or rich) are indicators of the
difficulty in reforming the naphtha. For example, light-lean naphtha with an
endpoint of 320
F (160
C) and 65 wt.% paraffins is more difficult to reform
than a heavy-rich naphtha with an endpoint of 370
F (188
C) and 60 wt.%
naphthenes plus aromatics.
150
200
250
300
350
400
IBP 10
30
50
70
90
EP
Percent Over
Temperature, °F
Fig. 2 ASTM D-86
distillation curve for naphtha
(Huebner et al. 1999)
Catalytic Reforming in Petroleum Processing
233