lec17_04132007_g - 10.37 Chemical and Biological Reaction...

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10.37 Chemical and Biological Reaction Engineering, Spring 2007 Prof. William H. Green Lecture 17: Mass Transfer Resistances This lecture covers: External diffusion effects, non-porous packed beds and monoliths, and immobilized cells Table 1. Homogeneous vs. Heterogeneous Catalysis Homogeneous vs. Heterogeneous Catalysis acids,bases radicals organometallics enzymes better mixing, uniformity transport limitations immobilized enzymes metals solid acids, bases metal oxides, zeolites, clays, silica multiphase systems reuse catalyst easily product purity 1. New rate law on surface 2. Model the transport and mixing (,,) fluid i ixyz N C Volume = (,) on surface sites on surface j surface jxy N N θ = 1 jv a c a n c y θθ += " ,, 11 () rxn rxn N fluid N suface fluid ii n n i m m nm A rr C r V C ν νθ == ⎛⎞ =+ ⎜⎟ ⎝⎠ ∑∑ mol sv o l mol sa r e a QSSA for surface species: "" , (,) 0 jj m m C =≈ QSSA f C = At surface flows j d dt = 0 " j avagadro sites area rN N + δ A P A Catalyst surface Figure 1.
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lec17_04132007_g - 10.37 Chemical and Biological Reaction...

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