Convective diffusion overview

This chapter treated, the fixed-bed reactor, a tubular reactor packed with, catalyst pellets. We started with a general overview of the transport and reactio.n events that take place in. the fixed-bed reactor transport by convection in the fluid diffusion inside the catalyst pores. and adsorption, reaction and desorption on the catalyst surface. We summarized the transport properties of the catalyst particles, and described bulk and Knudsen diffusion phenomena. 

We do not intend in this chapter to present an extensive analysis of mass transfer concepts but, rather, to summarize the basics of mass transfer as required in the design and analysis of polymer processing operations. In this regard, we give only an extensive overview of the estimation techniques for the diffusivity, solubility, and permeability of solvents in polymers. The laws of diffusional mass transfer, as well as the relationships for convective mass transfer, remain the same as applied to any material. The books by Perry and Chilton (1973), Reid et al. (1977), and Brandmp and Immergut (1989) provide an extensive overview of experimental data and formulas for the calculation of diffusivity, solubility, and permeability of various polymer systems. 

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