Octane and

p

-xylene are common components in crude gasoline

so their separation process is very important in petroleum industry. The azeotrope and near azeotrope are often separated by extractive distillation in industry

which can realize the recovery and utilization of resources. In this work

the vapor–liquid equilibrium experiment was used to obtain the vapor–liquid equilibrium properties of the difficult separation system

and on this basis

the solvent extraction mechanism was studied. The mechanism of solvent separation plays a guiding role in selecting suitable solvents for industrial separation. The interaction energy

bond length and charge density distribution of

p

-xylene with solvent are calculated by quantum chemistry method. The quantum chemistry calculation results and experiment results showed that

N

-formylmorpholine is the best solvent among the alternative solvents in the work. This work provides an effective and complete solvent screening process from phase equilibrium experiments to quantum chemical calculation. An extractive distillation simulation process with

N

-formylmorpholine as solvent is designed to separate octane and

p

-xylene. In addition

the feasibility and effectiveness of the intensified vapor recompression assisted extraction distillation are also discussed. In the extractive distillation process

the vapor recompression-assisted extraction distillatio

n process is globally optimal. Compared with basic process

the total annual cost can be reduced by 43.2%. This study provides theoretical guidance for extractive distillation separation technology and solvent selection.