Page 334 - Elements of Chemical Reaction Engineering Ebook

Sec. 6.3 Algorithm for Solution to Complex Reactions 305
The hydrodealkylation of mesitylene is to be carried out isothwmally at
150bOR and 35 atm in a packed-bed reactor in which the feed is 66.7 mol% hydro-
gen and 33.3 mol% mesitylene. The volumetric feed rate is 476 ft3/h and the reactor
volume (Le., V = W/p,) is 238 ft3.
The rate laws for reactions 1 and 2 are, respectively,
-rlM = klcMCO,' (E6-6.3)

rzT =1 k2cXe (&I-6.4)

where the subscripts are: M = mesitylene, X =I rn-xylene, T = toluene, Me =
metilane, and W = hydrogen (H2).
At 1500"R the specific reaction rates are:

Reaction 1: k, = 55.20 (ft3/lb rnol)O.5 /h
Reaction 2 k, = 30.20 (ft3/lb mo1)05 /h

The bulk density of the catalyst has been included in the specific reaction rate (Le.,
k, =I k; p* ).
Plot the concentrations of hydrogen, mesitylene, and xylene as a function of
space-time. Calculate the space-time where the production of xylene is a maximum
(i.e.,, zap, 1.

Solution
Reactionl: M+H + X+Me @ti-6.1)
Reaction2 X+H d T+Me (E%;-6.2)

1. Mole balances:

Hydrogen: (Eitii-6.5)

Mesitylene: (Eh-6.6)

dFX
=
Xylene,: - rlX + r2x (E6-6.7)
dV
Toluene: (E6-6.8)

Methane: (E6-6.9)

2!. Rate'laws: