Estimation of Cumene Cracking Reaction-Diffusion Model Parameters: Uniqueness and Parametric Sensitivity Analysis

Abstract

The pulse response of cumene cracking over ZSM5 extrudates has been measured using a Jetloop recycle reactor. A model assuming first order irreversible reaction with constant macro-pore diffusivity and linear adsorption was used to describe the response curves of the reactants and products. The model parameters adsorption, diffusion and reaction rate are in general highly correlated. Relationships for regions of parameter insensitivity and correlation functions between dependent parameters are given. With the aid of independent measurement of adsorption, a sensitivity analysis and a similarity analysis between equations, it was possible to reduce the 7 parameter model into a 2 parameter model for conditions of strong diffusion limitation observed in these experiments. Although good model fits could be achieved, a high degree of uncertainty in the parameter estimates remained, which reflects the high correlation of the physical parameters. Comparison with steady state results shows that the transient diffusivity for cumene is approximately equal to the Knudsen diffusivity, but an order of magnitude lower than the steady state diffusivity. The transient Thiele modulus for cumene was an order of magnitude higher than the steady state value.