A mixture of postconsumer polyolefin waste (PE/PP) was pyrolyzed over cracking catalysts using a fluidizing reaction system similar to the fluid catalytic cracking (FCC) process operating isothermally at ambient pressure. Experiments carried Out with various catalysts gave good yields of valuable hydrocarbons with differing selectivity in the final products dependent on reaction conditions. Greater product selectivity was observed with a commercial FCC equilibrium catalyst (Ecat-F1) with more than 50 wt % olefins products in the C-3-C-6 range. A kinetic model based on a lumping reaction scheme for the observed products and catalyst coking deactivations has been investigated. The model gave a good representation of experiment results. Moreover, this model provides the benefits of lumping product selectivity, in each reaction step, in relation to the performance of the FCC equilibrium catalyst used, the effect of reaction temperature, and the particle size selected. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114:193-203, 2009