Example - Series Rxns

Example - Series Rxns - dichlorobenzene respectively....

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1 CHE 4151 Jennings EXAMPLE H Series Reactions Mono- and dichlorobenzene are both valuable commercial products. They may be formed by reaction of benzene liquid with chlorine gas: C 6 H 6 + Cl 2 )) ) C 6 H 5 Cl + HCl C 6 H 5 Cl + Cl 2 )) ) C 6 H 4 Cl 2 + HCl At 55 o C, the values of the specific rate constants for the two reactions are k 1 = 82.2 and k 2 = 6.0 L / mol-hr. a) Write material balances for a batch reactor. The initial concentration of benzene is 11.2 mol / L. Assume that all the chlorine gas added is absorbed by the liquid phase and that its concentration is constant at 0.089 mol / L. At what time does the maximum concentration of monochlorobenzene occur ? b) Calculate the concentrations of mono- and dichlorobenzene in the reactor at the time calculated in part (a). ANSWER : a) Let B, C, M, and D represent benzene, chlorine, monochlorobenzene, and
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Unformatted text preview: dichlorobenzene respectively. Material balances for a constant volume batch reactor may be written as d C d t B = - k 1 C B C C d C d t M = k 1 C B C C - k 2 C M C C d C d t D = k 2 C M C C If the concentration of chlorine is assumed to remain constant, the equations may be integrated sequentially to yield C B = C B,0 e-a t C M = a b a-C B,0 M e-a t - e-b t M C D = C B,0 - ( b - a )-1 C B,0 [ b e-a t - a e-b t ] where a = k 1 C C = 7.298 hr-1 and b = k 2 C C = 0.534 hr-1 . The maximum concentration of M will occur when dC M /dt = 0. Differentiation yields t MAX = ( b - a )-1 ln ( b / a ) = 0.3866 hr b) At t = 0.3866 hr = 23.20 min, C M = 9.111 mol / L , C D = 1.423 mol / L Note : S = C M / C D = 6.40...
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Example - Series Rxns - dichlorobenzene respectively....

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