Waste polypropylene has been subjected to pyrolysis followed by in-situ aromatization in a specially designed semi batch reactor at the temperature ranging from 500 - 800 degrees C. The molecules of interest are valuable aromatics benzene, toluene, ethyl benzene and xylene (BTEX) which appeared highest amount in the liquid mixture. The catalyst used is commercial ZSM-5 (30:1). The catalytic pyrolysis of PP is studied in a semi batch reactor in two different phases, keeping the catalyst in the liquid phase (L-type) and liquid and vapor phase/multiphase (M-type), respectively. The BTEX yield is enhanced significantly using multiphase catalytic pyrolysis of polypropylene. The catalytic performance of ZSM-5 catalyst for PP pyrolysis is evaluated with respect to target aromatics BTEX. The thermal pyrolysis of PP produced maximum liquid yield of 80.56 wt. % at a temperature of 700 degrees C. The commercial catalysts ZSM-5 produced highest liquid yield of 86.3 wt. % for liquid phase (L-type) pyrolysis. The BTEX yield is significantly increased from 30.9 wt.% for thermal pyrolysis to 53.09 wt. % for catalytic multiphase/M-type pyrolysis. Almost 72 % increase in BTEX yield is recorded for catalytic multiphase/M-type pyrolysis in comparison to thermal process. The pyrolysis oil is analyzed using GC-FID, carbon residue test and other fuel testing methods to examine the suitability of its end use and aromatic content.