Page 337 - Elements of Chemical Reaction Engineering Ebook

308 Multiple Reactions Chap. 6

gas-phase and there is volume change, we use molar flow rates, 5, as vari-
ables. The total molar flow rate for n species is

n
FT = Fj (6-30)
J=1
For q reactions occurring in the gas phase, where N different species are
present, we have the following set of algebraic equations:

4
FN
F10- F1 = -r,V = VC -Til = V* fl CTo, ..., - CTo) (6-31)
i= 1 FT

We can use an equation solver in POLYMATH or similar to solve Equa-
tions (6-31) through (6-33).

Example 67 HydrodealkyyEation of Mesitylene in a CSTR

For the multiple reactions and conditions described in Example 6-6, calculate the
conversion of hydrogen and mesitylene along with the exiting concentrations of
mesitylene, hydrogen, and xylene in a CSTR.

Solution
1. Mole balances:
Hydrogen: FHo - FH'= (- rlH + -r2H 1 V (E6-7. I)

Mesitylene: FMO - FM = -rlMV (E6-7.2)

Xylene: Fx= (r,,+r*x)V (E6-7.3 1
Toluene: FT = r2TV (E6- 7.4)

Methane: FMe = (IlMe + r2Me 1 V (E6-7.5)

2. Rate laws:
Reaction 1: -r,H = -rlM = rlX = rlMe = k,Ck2CM (E6-7.6)

112
Reaction 2: - r2* = - r2x = r2* = rZMe = k,C, Cx (E6-7.7)