Plastics have become a vital ingredient in the world. Due to their non-biodegradability and low life time, their huge wastes made environmental problems in the world. Chemical recycling of them plastics could be a promising method to overcome this problem. Waste plastics can be converted to feed-stocks or valuable liquid fuels by chemical recycling method. Current study focuses on catalytic conversion of mixed HDPE/LDPE/PP to hydrocarbon liquids and gases over a silico-alumina catalyst using a laboratory semi batch reactor operating isothermally at ambient pressure. Effect of catalyst percentage and reaction temperature on kinetics of the reaction is investigated in the current study. The liquid samples were analyzed using GC/FID to find out their composition. A kinetic model at optimum reaction conditions has been developed and activation energy determined. The model equation gives a suitable match with experimental results.