In chemical-reaction engineering, special measures of product distribution are sometimes used when multiple reactions occur. Two of these are yield Y_j and selectivity S_j∕k. We adopt the following definitions:

For any particular application, yield and selectivity can be related to component rates and reaction coordinates. For two-reaction schemes the two reaction coordinates can be found from Y_j and S_j∕k, allowing the usual material-balance equations to be written.
Consider the gas-phase reactions:

A + B → C (I)                A + C → D (II)

Here, C is the desired product, and D is the undesired by-product. If the feed to a steady-flow reactor contains 10 kmol·h⁻¹ of A and 15 kmol·h⁻¹ of B, and if Y_C = 0.40 and S_C/D = 2.0, determine complete product rates and the product composition (mole fractions), using reaction coordinates.

Transcribed Image Text:

moles formed of desired product j moles of j that would be formed with no side reactions and with complete consumption of the limiting reactant species moles formed of desired product j Sj/k = moles formed of undesired product k