(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. Today’s. . lecture. Interstage. Cooling. Noble Prize 2007. ID: 628278
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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
Slide2Today’s lecture
Interstage
Cooling
Noble Prize 2007Catalytic Steps
2
Slide33
Slide4Catalysts 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
Slide5Catalysts affect both Selectivity and Yield
Different reaction Paths
5
Slide6Different shapes and
sizes
of
catalyst.
6
Slide7Catalytic packed-bed
reactor
, schematic.
7
Slide8Steps in a Catalytic Reaction
8
Slide9Active SiteReactions 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
Slide10The 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
10
Slide11Adsorption
11
Slide12More Catalysis
12
Slide13Langmuir Adsorption Isotherm
Increasing T
Slope=k
A
More Catalysis
13
Slide14The Surface Reaction Step
14
Slide15The Surface Reaction Step
15
Slide16The Surface Reaction Step
16
Slide17The Surface Reaction Step
17
Slide18The Surface Reaction Step
18
Slide19Desorption from surface
Vacant and occupied sites
19
Slide20Steps in a Catalytic Reaction
Adsorption on Surface
Surface Reaction
Single Site
Dual Site
Desorption from Surface
20
Slide21The Rate Limiting Step:Which Step Has the Largest Resistance?
Electrical analog to heterogeneous reactions
21
Slide22Collecting information for catalytic reactor design
22
Slide23Octane NumbersCatalytic Reforming
Normal Pentane Octane Number = 62
Iso
-Pentane Octane Number = 95
23
Slide2424
Slide2525
Slide26Steps in a Catalytic Reaction
Adsorption on Surface
Surface Reaction
Single Site
Dual Site
Desorption from Surface
26
Slide27Steps in a Catalytic Reaction
Adsorption on Surface
Surface
Reaction
Dual
Site
27
Slide28Steps in a Catalytic Reaction
Surface Reaction Eley-Rideal
Desorption
form Surface
28
Slide29End of Lecture 23
29
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