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Unformatted text preview: 1 + k 2 ) p A p B dF B /dV =  r 1  r 2 =  ( k 1 + k 2 ) p A p B dF R /dV = r 1 = k 1 p A p B dF S /dV = r 2 = k 2 p A p B A expression for the selectivity (S), defined as the ratio of F D to F U , can be derived by combining the last two equations and integrating: k 2 dF D = k 1 dF U S = F R / F S = k 1 / k 2 = 21.53 Note: solving for the fractional conversion of propylene requires integration of the material balance on A. Let x = 1  F A / F A i . Then F B = F B i  F A i x = F A i (4  x), F R + F S = F A i x, and F T = F A i (5  x). Assuming that the ideal gas law is valid, p A = R T C A = R T C T ( F A / F T ) = P T (1  x) / (5  x) and p B = P T (4  x) / (5  x). Substituting into the material balance yields F A i dx / dV = (k 1 + k 2 ) P T 2 (1  x) (4  x) / (5  x) 2 [ (k 1 + k 2 ) P T 2 V / F A i ] = (1/3) ln (1  x/4)  (16/3) ln (1  x) + x Solving by trial and error yields: x = 0.464...
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This note was uploaded on 04/29/2008 for the course CHE 4151 taught by Professor J during the Spring '08 term at FIT.
 Spring '08
 J
 pH, Reaction

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