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2.2.1. Naphtha feeds 
The feed of the naphtha isomerization unit depends a lot on the refinery. It can be either the 
hydrotreated naphtha from the crude oil distillation, either light naphtha cut from reforming 
unit. A typical isomerization naphtha feed contains principally C
5
and C
6
paraffins. It contains 
also between 0 and 3% of C
4
paraffins and other hydrocarbons such as benzene, naphtenes, 
olefins and C
7+
.

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The following table indicates the typical properties of an isomerization naphtha feed: 
Compound Quantity 
Isopentane 
n-Pentane 
Cyclopentane 
2.2-Dimethylbutane 
2.2-Dimethylbutane 
2-Methylpentane 
3-Methylpentane 
n-Hexane 
Methylcyclopentane 
Cyclohexane 
Benzene 
C
7+ 
20 % wt. 
29 % wt. 
1 % wt. 
0.3 % wt. 
1.5 % wt. 
11 % wt. 
8.2 % wt. 
19.5 % wt. 
5 % wt. 
1.5 % wt. 
2 % wt. 
1 % wt. 
Table B-2-1: Typical properties of isomerisation naphtha feed 
Isomerization naphtha feed boiling point is generally comprised between 70 °C and 80 °C. 
2.2.2. Hydrogen 
Hydrogen is necessary in order to avoid a coke deposit on the catalyst. Moreover, the quantity 
of hydrogen must be high enough to hydrogenate benzene and to favorize isomerization 
reactions. 
2.2.3. Catalyst 
Metallic platinum on chlorinated alumina based catalyst, that must be used in inert conditions 
and with continuous chlorine injection is the current isomerization catalyst. 
 
2.2.4. Dryers molecular sieves 
 
Synthetic zeolite containing sodium and calcium is used as dryer. 
 
2.3. Products characteristics 
High-octane isomerate product is the principal product from this process. By-product is the 
fuel gas produced at the head of the stabilization column and washed with caustic soda before 
being sent to the fuel gas network. 
2.4. Normal operations