Multiple Reaction Conversion Notes

25 mol c2h6 05 mol co2 if we did not know the

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Unformatted text preview: ct along (1) & (2): 1 mol CH4 -> 0.25 mol C2H6 + 0.5 mol CO2. If we did not know the reaction equations we might be tempted to calculate: SC= = nC= / (nC= + nCO2) = 0.25 / 0.75 = 1/3. But we reacted equal amounts of CH4 along both pathways: shouldn’t SC= = 0.5 ?! “atom selectivity”: S j ,i = ChE ChE 400 - Reactive Process Engineering Selectivity: one last slide… dN B ν A ⋅ dN A ν B Also called “instantaneous” selectivity in batch reactors… ′ SB = …or “local” selectivity in (plug) flow reactors: ′ SB = And for once we can also use concentrations! ′ SB = ( Why ?? ) L11-7 L11- ′ SB = “differential” selectivity: dN B ν A ⋅ = dN A ν B Example reaction: A -> B -> C Let’s look at a reactant, which can form a desired product D, and an undesired side-product U in parallel reactions. A U Total Cost Reactor Cost Separations Cost 0 L11-8 L11- Two problems: • “repair” of low S generally not possible • undesired side-product usually needs to be...
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This note was uploaded on 10/31/2013 for the course CHE E440 taught by Professor Baier during the Fall '13 term at Columbia.

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