The present investigation focuses on the separation of phenanthrene (a polyaromatic hydrocarbon) from n-tetradecane (model diesel composition) via pervaporation using a fabricated aromatic polyimide membrane. The experiments demonstrate preferential permeation of the polyaromatic for all films within the studied experimental range. The influence of operating temperature, membrane pretreatment time, membrane composition, and membrane thickness on the pervaporative performance were investigated. Statistical software Design Expert 7.1.4 was used to derive the regression equation describing the effect of the above mentioned factors on the pervaporation separation index. These factors are optimized using response surface methodology. The highest value of pervaporation separation index obtained is 1.5277 kg m(-2)h(-1) and the corresponding optimized condition is: operating temperature 493 K, pretreatment time 16.55 h with a membrane composition of 2.76 wt% of phenanthrene in polyamic acid and thickness 53.22 mu m. POLYM. ENG. SCI., 57:392-402, 2017. (c) 2016 Society of Plastics Engineers