The dynamic behavior of a fixed‐bed catalytic reactor

Abstract

Abstract The dynamic behavior of a fixed‐bed catalytic reactor was studied under isothermal conditions by means of frequency response analysis. The investigation was conducted over a range of nonreacting and reacting conditions by using the hydrogen‐oxygen combination over supported platinum as the reaction system. The kinetics of the surface catalysis of this reaction were investigated separately and then were incorporated into the analysis of frequency response data under reaction conditions. A method was developed whereby nonlinear chemical reaction effects appearing in the frequency response measurements could be separated from hydrodynamic factors for a plug flow reactor. Use is made of the describing function technique, often used to approximate nonlinear servomechanism response, to accomplish this. It is shown by this method that Peclet numbers measured for the reacting system agree with those measured in the absence of reaction. Based on the semitheoretical value of 2 for the Peclet group at high Reynolds numbers, a value of 0.73 sq. cm./min. was determined for the effective diffusion coefficient of hydrogen at 100°C. within the porous catalyst particles. Analysis of frequency response data in which this diffusion is not accounted for leads to Peclet numbers which are unreasonable in view of previously reported results.