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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! ′
( Why ?? ) L11-7
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
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.
- Fall '13