The production of pyrolysis oil from polypropylene plastic waste was examined over molybdenum modified alumina-silica catalysts (Mo/Al-Si). The reactions were carried out with 1 L of batch reactor under atmospheric pressure at 430 °C. The pyrolysis oil yield was in the order, 10% Mo/Al-Si > 5% Mo/Al-Si > the absence of catalyst. The 10% Mo/Al-Si was highest activity due to the stronger acidity facilitating the pyrolysis reaction. It accelerated the reaction to produce the pyrolysis oil at lower temperature. Comparison of the pyrolysis oil properties to the standards of the diesel fuel from Thai Department of Energy Business shows that the color and the distillation were within standards. Moreover, the results reveal that the kind of raw material affected the product yield of pyrolysis process.