Heterogeneous reactions external diffusion effects

External Diffusion Effects on Heterogeneous Reactions Chap. 11... 

The DVD-ROM contains PDF files of the last live chapters from the fourth edition of the Elements of Chemical Reaction Engineering, which is mostly graduate material. These chapters, which were omitted from this book but are included on the DVD-ROM are DVD Chapter 10. Catalyst Decay DVD Chapter 11, External Diffusion Effects on Heterogeneous Reactions DVD Chapter 12. Diffusion and Reaction DVD Chapter 13, Distribution of Residence Times for Reactors DVD Chapter 14. Models for Non Ideal Reactors and a new chapter. DVD Chapter 15, Radial and Axial Temperature Variations in a Tubular Reactor. 

The catalytic behavior of enzymes in immobilized form may dramatically differ from that of soluble homogeneous enzymes. In particular, mass transport effects (the transport of a substrate to the catalyst and diffusion of reaction products away from the catalyst matrix) may result in the reduction of the overall activity. Mass transport effects are usually divided into two categories - external and internal. External effects stem from the fact that substrates must be transported from the bulk solution to the surface of an immobilized enzyme. Internal diffusional limitations occur when a substrate penetrates inside the immobilized enzyme particle, such as porous carriers, polymeric microspheres, membranes, etc. The classical treatment of mass transfer in heterogeneous catalysis has been successfully applied to immobilized enzymes I27l There are several simple experimental criteria or tests that allow one to determine whether a reaction is limited by external diffusion. For example, if a reaction is completely limited by external diffusion, the rate of the process should not depend on pH or enzyme concentration. At the same time the rate of reaction will depend on the stirring in the batch reactor or on the flow rate of a substrate in the column reactor. 

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