A mechanism-oriented kinetic model has been developed with a small CPU requirement which allows the model to be incorporated into a reactor simulation with fluid dynamics and heat and mass transfer. The model achieves a small CPU requirement by lumping radicals with similar reactivity together A 42-lump subset of the 10(5) or more radicals is used to describe all the elementary reactions with a high degree of accuracy. Structure/reactivity relationships are utilized to provide rate constants for these elementary steps. The model predictions are compared to the results of full mechanistic simulations and the reaction of pure and synthetic mixtures of model compounds.