Abstract
<jats:title>Abstract</jats:title> <jats:p>This study proposes and investigates a three-cut fractionation scheme for hydrotreated naphtha aimed at improving the efficiency of downstream C₅–C₆ isomerization and enhancing the octane characteristics of the Euro-5 gasoline pool. Unlike the conventional two-cut configuration, the proposed scheme enables selective recovery of an isopentane-rich stream while simultaneously producing a light naphtha fraction compositionally optimized for subsequent skeletal isomerization. The study was performed using steady-state Aspen HYSYS simulations combined with detailed hydrocarbon compositional analysis based on ASTM D6729 gas chromatography. The implementation of the three-cut splitter was found to cause significant redistribution of hydrocarbons among the product streams. The Σ(i/n) ratio in the light naphtha fraction decreased from 1.09 to 0.76, indicating an increase in normal paraffin content and the formation of more favorable thermodynamic conditions for downstream isomerization processes. Simultaneously, the ΣC₅ content in light naphtha decreased from 56.99 to 25.68 wt.%, whereas the proportion of ΣC₆⁺ hydrocarbons increased to 74.18 wt.%. The ΣC₅ content in the dedicated isopentane-rich stream reached 91.48 wt.%, with isopentane concentration accounting for 70.48 wt.%. At the same time, the research octane number (RON) of light naphtha increased from 65.2 to 68.1, while the motor octane number (MON) increased from 61.5 to 65.6. The obtained results confirm that selective three-cut fractionation represents an effective tool for compositional re-engineering of hydrotreated naphtha streams, providing enhanced isomerization efficiency, improved antiknock properties of gasoline components, and compliance with Euro-5 fuel specifications without increasing process severity or energy consumption.</jats:p>