1. Consider the following parallel reactions occurring in a liquid-phase reactor:
(1) A → D (Desired) with rD = 0.5CA2
(2) A → U (Undesired) with rU = 1.2CA
Calculate the instantaneous selectivity (SD/U) when the concentration of A is 2.0 mol/dm3.
2. You are managing parallel reactions where ED = 50,000 J/mol and EU = 80,000 J/mol.
(a) To maximize the production of D relative to U, should you operate at a high or low temperature?
(b) Justify your answer using the selectivity-temperature relationship.
3. Consider:
(1) A + B → D
rD = k1CA2CB
(2) A + B → U
rU = k2CACB2
To maximize SD/U, should you use a CSTR or a PFR?
Should B be fed all at once or slowly?
4. The following gas-phase reactions are carried out isothermally in a PFR:
(1) A → D
rD = k1CA
(2) A → U
rU = k2CA2
The feed is pure A at CA0 = 0.5 mol/dm3. At the operating temperature, k1 = 0.2 min-1 and k2 = 0.8
dm3/mol⋅min. Calculate the instantaneous selectivity SD/U at the reactor inlet and at 50% conversion.
5. Two parallel reactions have the following rate constants:
kD=1010exp(−10000/T)
kU=1015exp(−15000/T)
Calculate the temperature (in Kelvin) at which the instantaneous selectivity SD/U is exactly 1
(assuming reaction orders are identical).
6. A reaction A + B → D is 0.5 order in A and 2.0 order in B. The side reaction A + B → U is 1.5 order
in A and 1.0 order in B.
(a) Write the expression for SD/U.
(b) Suggest the best reactor type and feeding scheme to maximize D.
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