Page 304 - Elements of Chemical Reaction Engineering 3rd Edition

276 Collection and Analysis of Rate Data Chap. 5

P5-16B Mixtures of hydrocarbons (e.g., petroleum feedstocks) that undergo cracking
reactions or hydrodemethylation can sometimes be lumped as just one reac-
tant or as two or more reactants, In many cases it is difficult to distinguish
lumping as a single reactant with second-order kinetics from lumping as two
reactants each with first-order kinetics [Znd. Eng. Chem. Process Des. Dev.,
19, 197 (1980)l. To distinguish between these two cases, the initial reactant
concentration must be varied in more than one run and conversions greater
than 92% should be sought in taking the data.
From the batch reactor data below, determine whether first-order kinet-
ics for lumping as two reactants A and B or second-order kinetics for lumping
one reactant D best describes the system. Experimental conditions are such
that one can neglect volume change.
Mechanism I Mechanism I1

Two specie$ One species
kD
kA D __+ products
A --+ products
kB
B ---+ products
C(t) = C,(t) + CBW c(t) = cD(t)

Only the total concentration of the lumped reactant, C(t), can be monitored as
a function of time, For two-parameter lumping, estimates of the initial con-
centrations are C,, = 0.008 kmol/m3 and C,, = 0.006 kmol/m3.

t (SI 0 10 20 30 40 60 80
Concentration 1 0.014 0.0115 0.0097 0.0084 0.0074 0.0060 0.0051
(kmol/m3 )

Where would you place additional data points?
P5-17D Prepare a detailed experimental plan to learn the rate law for
(a) The hydrogenation of cyclopentane on a Pt/Al,O, catalyst.
(b) The liquid-phase production of methyl bromide from an aqueous solution
of methyl amine and bromine cyanide.
(c) The acid-catalyzed production of ethylene glycol from an aqueous solu-
tion of ethylene oxide.
P5-18, The irreversible liquid-phase reaction
A+B+C
is carried out in a batch reactor. The following data were collected during the
course of the reaction:

t (min) 0.0 2.0 4.0 6.0
C, (moVdm3) 2.00 1.31 0.95 0.73