Question

Consider the following homogeneous isothermal liquid-phase parallel reactions carried out in three reactor configurations (having identical volumes and same operating temperatures), as shown in the figure. A + B → D Rate of formation of D: 𝑟𝐷 = 𝑘1𝐶𝐴𝐶𝐵 A + B → U Rate of formation of U: 𝑟𝑈 = 𝑘2𝐶𝐴^2𝐶𝐵 where D is the desired product and U is the undesired product. The inlet concentrations of A and B are the same in all three configurations (𝐶𝐴0 = 𝐶𝐵0 = 1 mol L −1 ). The total molar feed flow rate of A (𝐹𝐴0) and that of B (𝐹𝐵0) are the same in all three configurations (𝐹𝐴0 = 𝐹𝐵0 = 10 mol min−1 ). In configuration I, 𝐹𝐴0 is equally distributed among all the inlets. Similarly, in configuration III, 𝐹𝐵0 is equally distributed among all the inlets. Assuming plug flow behavior, at steady state, which one of the following statements is CORRECT?

• A. Configuration I and Configuration III give the same selectivity of the desired product.
• B. Configuration I gives the highest selectivity of the desired product.
• C. Configuration II gives the highest selectivity of the desired product.
• D. Configuration III gives the highest selectivity of the desired product.

Official answer: Configuration I gives the highest selectivity of the desired product.