Interactive Self-Study Module: Diffusion and Reaction in Porous Catalysts


This module uses screencasts and interactive simulations to explain how diffusion can affect the rate of catalytic reactions in porous catalysts. Your retention of material in this module will increase if you write down reasons for your answers to ConcepTests, questions in screencasts, and questions to answer before using interactive simulations, and you try to solve the example problems before watching the screencast solutions. We suggest using the learning resources in the following order:

  1. Attempt to answer the multiple choice ConcepTest and solve the example problem before watching the screencasts or working with the simulations.
  2. Watch the screencasts that describe the reaction rates, concentration gradients, and effectiveness factors.
  3. Review the important equations.
  4. Use the interactive simulation to further understand the behavior of reaction in porous catalysts.
  5. Try to solve the example problems before watching the solutions in the screencasts.
  6. Answer the ConcepTests.
  7. Look at the list of key points, but only after you try to list the key points yourself.
  • The rates of catalytic reactions in porous catalysts are often limited by the rates of diffusion of reactants into the pores.
  • This module is intended for a course in kinetics/reactor design.
Before studying this module, you should:
  • be able to explain diffusion.
After studying this module, you should be able to:
  • Calculate the Thiele modulus and effectiveness factor for a catalyst pellet.
  • Explain what a Thiele modulus represents and what an effectiveness factor represents.
  • Explain what the concentration profile looks like in a catalyst pellet for fast and slow reactions (or for slow and fast diffusivities).
  • Calculate the rate of reaction in the pellet, given a concentration profile in a catalyst pellet.