Naphtha isomerization operating conditions

The objectives of the catalytic reforming of naphtha are to increase the naphtha octane number (petroleum refination) or to produce aromatic hydrocarbons (petrochemistry). Bifunctional catalysts that promote hydrocarbon dehydrogenation, isomerization, cracking and dehydrocyclization are used to accomplish such purposes. Together with these reactions, a carbon deposition which deactivates the catalyst takes place. This deactivation limits the industrial operation to a time which depends on the operational conditions. As this time may be very long, to study catalyst stability in laboratory, accelerated deactivation tests are required. The knowledge of the influence of operational conditions on coke deposition and on its nature, may help in the efforts to avoid its formation. 

The maximum production of isohexanes is considered the practical parameter of choice upon which refiners base their selection of operating conditions in light naphtha isomerization. 

In the isomerization of naphtha" using aluminum chloride, the Research octane number in a once-through operation is increased from 65 to 80. Further increase in octane number occurs with recycling (91 at 2 1 recycle ratio), but the economy of recycling is doubtful because of difficulties with fractionation. When processing mixed hexanes" operating conditions are... 

An alternate course, which was not pursued, would be to operate the reformer at less severe conditions where naphthene conversions are high but where isomerization and hydrocracking are less. The resultant reformate could be extracted with raffinate going to a naphtha cracker for olefin production while the extract is hydrodealkylated. 

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