Lecture 27 - University of Michiganelements/5e/powerpoints/2013lectures/Lec... · 2019. 8. 7. ·...

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 27

Web Lecture 27 Class Lecture 23

 How Reaction Rate Varies with: 1.  Temperature 2.  Catalyst Particle Size 3.  Eternal Flow Rate

  For A.  Reaction Rate Limited Reactors B.  Internal Diffusion Limited Reactions C.  External Rate Limited Reactions

And all 9 combinations of numbers and letters, Eq. 1A, 1B, 1C, 2A, 2B, 2C and 3A, 3B and 3C.

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Internal Diffusion How will we know these trends discussed in the last slide:

1.  Solve the diffusion and reaction equation for catalyst particle for concentration gradient

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CA =CA0λ

Sinh  Θ1λ( )Sinh Θ1

2. Find the true rate of reaction as a function of the external and internal surface reactions.

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Internal Diffusion

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D ~ T1.75

kr ~ e−E RT

− "rA =3R

Dekr kr =

3R

De  kr  

− "rA =~ D0.875e−E 2RT

=

Surface Reaction

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−rA = krCA = k1 expER1T1−1T

"

#$

%

&'

"

#$$

%

&''

− "rA

U

− "rA

dp

− "rA

T

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and − rA = −knCAn

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The Thiele modulus for this first order reaction is

For a first-order reaction, Equation (15-19) becomes

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Figure E15-1.1 Damaged cartilage. (Figure courtesy of Newsweek, September 3, 2001.) 22

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Diffusion of O2 around collagen

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A0

A

CC ,

Lz == ψλ

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