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Lecture 23

Lecture 23. Chemical Reaction Engineering (CRE) is the field that studies the rates and mechanisms of chemical reactions and the design of the reactors in which they take place. Today’s lecture. Interstage Cooling Noble Prize 2007 Catalytic Steps. Catalysts and Catalysis.

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Lecture 23

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  1. Lecture 23 Chemical Reaction Engineering (CRE) is the field that studies the rates and mechanisms of chemical reactions and the design of the reactors in which they take place.

  2. Today’slecture • Interstage Cooling • Noble Prize 2007 • Catalytic Steps

  3. Catalysts and Catalysis • A Catalyst is a substance that affects the rate of chemical reaction but emerges from the process unchanged. • Catalysis is the occurrence, study, and use of catalysts and catalytic processes. Approximately 1/3 of the GNP of materials produced in the U.S. involves a catalytic process.

  4. Catalysts affect both Selectivity and Yield Different reaction Paths

  5. Different shapes and sizes of catalyst.

  6. Catalyticpacked-bedreactor, schematic.

  7. Steps in a Catalytic Reaction

  8. Active Site • Reactions are not catalyzed over the entire surface but only at certain active sites or centers that result from unsaturated atoms in the surface. • An active site is a point on the surface that can form strong chemical bonds with an adsorbed atom or molecule.

  9. The Adsorption Step Vacant and occupied sites For the system shown, the total concentration of sites is Ct = Cv + CA.S + CB.S

  10. Adsorption

  11. More Catalysis

  12. More Catalysis Increasing T Langmuir Adsorption Isotherm Slope=kA

  13. The Surface Reaction Step

  14. The Surface Reaction Step

  15. The Surface Reaction Step

  16. The Surface Reaction Step

  17. The Surface Reaction Step

  18. Desorption from surface Vacant and occupied sites

  19. Steps in a CatalyticReaction Adsorption on Surface Surface Reaction Single Site Desorption from Surface Dual Site

  20. The Rate Limiting Step:Which Step Has the Largest Resistance? Electrical analog to heterogeneous reactions

  21. Collecting information for catalytic reactor design

  22. Octane Numbers • Catalytic Reforming • Normal Pentane Octane Number = 62 • Iso-Pentane Octane Number = 95

  23. Steps in a CatalyticReaction Adsorption on Surface Surface Reaction Single Site Desorption from Surface Dual Site

  24. Steps in a CatalyticReaction Surface Reaction Dual Site Adsorption on Surface

  25. Steps in a CatalyticReaction Surface Reaction Eley-Rideal Desorption form Surface

  26. End of Lecture 23

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