Reactor simulation of benzene ethylation and ethane dehydrogenation catalyzed by ZSM-5: a multiscale approach

Abstract

Rate expressions are vital for analysis, design and operation of chemical reactors. However, due to a simplified picture of the underlying physical processes, empirical power-law (PL) fits, and Langmuir–Hinshelwood (LH) expressions may not be reliable when extrapolated to conditions which were not included in the parameterization process. In the present work the extrapolation ability of LH and PL models are evaluated for the zeolite catalyzed alkylation of benzene with ethene. For this purpose, extrapolated data are compared to results obtained from a detailed continuum model based on a multiscale approach (Hansen et al., J. Phys. Chem. C, 113 (2009) 235–246). It is demonstrated that extrapolation is in particular questionable if the gas phase composition is outside the fitting range. A second purpose of the present work is the extension of our continuum model to include the dehydrogenation of ethane. The parameters describing adsorption and diffusion are obtained from Monte Carlo and molecular dynamics simulations, respectively. Reaction rate constants are derived from quantum chemical calculations and transition state theory. We have used the extended continuum model in the design equation of a fixed bed reactor and simulated the dehydroalkylation activity for different input conditions. Furthermore, the benefit from removing hydrogen from the reaction mixture using a membrane reactor is discussed.