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Thesis (M.S.)—University of Nebraska—Lincoln, 1972. Department of Chemical Engineering.


Copyright 1972, the author. Used by permission.


Flow reactors are often best suited for kinetic analysis. A tubular reactor with catalyst deposited on the wall is an attractive design, as it overcomes some of the above mentioned problems. First, it is possible to determine the catalyst surface area precisely. Secondly, since the heat effects associated with the reaction appear only at the wall, isothermal conditions are much easier to maintain. Finally, the geometry of the apparatus is relatively simple, thus allowing the possibility of accurate mathematical modeling.

Katz showed how such a system can be effectively used to study reaction kinetics. In his study he proposes to obtain flow-averaged concentrations at various residence times and subsequently make some precise calculations to get a plot of instantaneous reaction rates vs. concentration at which the reaction is proceeding. Chun later worked on Katz’ method by simulating such a reactor on a digital computer and showed the method worked quite efficiently. She also developed methods to take care of experimental errors that might be introduced in the determination of flow-averaged reactant concentrations.

Such systems or similar systems have been used by others for different purposes. In all these studies the authors, in the interest of mathematical convenience, have neglected diffusion in the axial direction as compared to convective transport due to bulk flow. The purpose of the present work is to check the validity of this assumption.

In the present work, the tubular reactor was simulated on a digital computer by solving numerically the appropriate partial differential equation and boundary conditions. In particular, flow-averaged concentrations were obtained for varying reaction rates for first and second order reactions, for a) neglecting axial diffusion b) including axial diffusion.

It was observed that this assumption can be used for most practical purposes, since a significant difference in flow-averaged concentrations is noticed at very low Peclet numbers.

Advisor: Richard E. Gilbert