1. 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. Lecture 23

2. Today’s lecture Interstage Cooling Noble Prize 2007 Catalytic Steps 2

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. 3

4. Catalysts affect both Selectivity and Yield Different reaction Paths 4

5. Different shapes and sizes of catalyst. 5

6. Catalytic packed-bed reactor, schematic. 6

7. Steps in a Catalytic Reaction 7

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. 8

9. The Adsorption Step Vacant and occupied sites For the system shown, the total concentration of sites is C t = C v + C A.S + C B.S 9

10. Adsorption 10

11. More Catalysis 11

12. Langmuir Adsorption Isotherm Increasing T Slope=k A More Catalysis 12

13. The Surface Reaction Step 13

14. The Surface Reaction Step 14

15. The Surface Reaction Step 15

16. The Surface Reaction Step 16

17. The Surface Reaction Step 17

18. Desorption from surface Vacant and occupied sites 18

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

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

21. Collecting information for catalytic reactor design 21

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

23. 23

24. Steps in a Catalytic Reaction Adsorption on Surface Surface Reaction Single Site Dual Site Desorption from Surface 24

25. Steps in a Catalytic Reaction Adsorption on Surface Surface ReactionDual Site 25

26. Steps in a Catalytic Reaction Surface Reaction Eley-Rideal Desorption form Surface 26

27. End of Lecture 23 27