The inert gas stripping method has been used to determine the C4 relative volatility in DMF and salt added DMF respectively at infinite dilution. The result showed that salt added DMF was better in separating C4. Through the model calculation of the first extractive distillation tower

the amount of solvent was reduced by 10.5 % and the heat duty decreased by 17.5 % on the reboiler

by 8.0 % on the condenser with salt added DMF

compared with DMF without salt. The idea of adding salt in solvent provided an important reference for separating non - polar system by extractive distillation.