The aim of this research was to study the pyrolysis of used lubricating oil on spent FCC catalyst in a batch microreactor of 250 ml. The experiment was carried out under various condition by the follow variables : reaction temperature of 410 - 450 oC, reaction time of 30 - 60 min, initial hydrogen pressure of 1 - 5 bars, amount of spent FCC catalyst ranging from 1 - 5 % by weight and weight of raw material was 20 g. The two level factorial experimental design was performed to investigate the effect of variables on oil yield to determine the optimum condition. The product oil was analyzed by Simulate Distillation Gas Chromatography (DGC). The optimum conditions of pyrolysis of used lubricating oil were reaction temperature of 430 OC, reaction time of 60 min, initial hydrogen pressured of 5 bars by using 4 percent by weight of spent FCC catalyst. The product was present in 72.94 percent by weight of oil yield, 23.86 percent by weight of gas yield, and 3.24 percent by weight of solid yield and composed of naphtha, kerosene, light gas oil, gas oil and long residue (33.08, 11.46, 16.65, 2.70 and 9.05 percent by weight respectively). It was found that the product consist of an aromatic hydrocarbon in main structure. Comparing the structure oil product with benzene (octane 95) was similar.
