lec20_04272007_w - 10.37 Chemical and Biological Reaction...

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10.37 Chemical and Biological Reaction Engineering, Spring 2007 Prof. K. Dane Wittrup Lecture 20: Reaction and Diffusion in Porous Catalyst This lecture covers: Effective diffusivity, internal and overall effectiveness factor, Thiele modulus, and apparent reaction rates Reaction & Diffusion -Diffusion in a porous solid phase Ex. Precious metals on ceramic supports or drug/nutrient delivery through tissues -Derive steady state material balance accounting for diffusion and reaction in a spherical geometry -Thiele modulus ( φ ) R r [S] 0 = surface concentration of a growth substrate (ex. glucose and O 2 ) Figure 1. Sphere of Cells Assume pseudo-homogeneous medium and Fick’s Law describes diffusion [ ] dS Flux D dr =− , where # [] molecules Flux area time = and 2 length D time = n s ns rk C −= max s s s s VC r KC + Cite as: K. Dane Wittrup, course materials for 10.37 Chemical and Biological Reaction Engineering, Spring 2007. MIT OpenCourseWare (http://ocw.mit.edu), Massachusetts Institute of Technology. Downloaded on [DD Month YYYY].
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n=0 n=1 C s -r s Figure 2. Rate of reaction versus species concentration max st 1o r d e r s ss s s VC CK r K ⇒≈ ± max 0 th order s rV ²
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This note was uploaded on 11/27/2011 for the course CHEMICAL E 10.302 taught by Professor Clarkcolton during the Fall '04 term at MIT.

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lec20_04272007_w - 10.37 Chemical and Biological Reaction...

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