Page 358 - Elements of Chemical Reaction Engineering Ebook

Chap. 6 Questions and Problems 329
mend to maximize the formation of C6H4(CH3)* (i.e. Cs)? [Hint: Plot the
overall selectivity as a function of reactor volume.]
(b) How would your answer change if you were to maximize the overall
selectivity to C, to C9, i.e. S89 ? To C, to C,?
(c) What do you think the point of this problem to be?
Make a plot of the mole fraction of each component as a function of
conversion of pentamethylbenzene. Make a plot of the mole fraction of each
component as a function of plug-flow .reactor volume. Discuss any optimiza-
tion that could be done.
P6-17B Review the oxidation of formaldehyde to formic acid reactions over a van-
dium titanium oxide catalyst [Znd. Eng. Chem. Res., 28, 387 (1 989)] shown in
the ODE solver algorithm in the Summary.
(a) Plot the species concentrations as a function of distance down the PFR for
an entering flow rate of 100 dm3/min at 5 atm and 140°C. The feed is 66.'7%
HCHO and 33.3% 0,. Note any maximum in species concentrations.
(b) Plot the yield of overall HCOOH yield and overall selectivity of HCOH
to CO, of HCOOCH, to CH30H and of HCOOH to HCOOCH, as a
function of the OO2. Suggest some conditions to best produce forrnic
acid. 'Write a paragraph describing ,what you find.
(c) Compare your plot in part (a) with a similar plot when pressure drop is
taken into account with rx = 0.002 dm-3.
(d) Suppose that E, = 10,000 cal/mol, E2 = 30,000 cal/mol, E, = 20,000
callmol, and E4 = 10,OOO cal/mol, what temperature would you recom-
mend for a 1000-dm3 PFR?
P6-18, The liquefaction of Kentucky Coal No. 9 was carried out in a slurry reactor
[D. D. Gertenbach, R. M. Baldwin, and.R. L. Bain, Ind. Eng. Chem. Process
Des. Dev., 21, 490 (1982)l. The coal particles, which were less than 2:OO
mesh, were dissolved in a -250°C vacuum cut of recycle oil saturated with
hydrogen at 400°C. Consider the reaction sequence

coal (C) .- k, preasphaltines (P)

\ Jk3 k4
asphaltines (A) k5 > oils (0)
which is a modified version of the one given by Gertenbach et al. All reac-
tions are first order. Calculate the molar flow rate of each species as a func-
tion of space-time in
(a) A plug-flow reactor.
(b) A 3-m3 CSTR.
(c) What is the point of this problem?

Additional information:
Entering concentration of coal: 2 km01/m3
Entering flow rate: 10 dm3/min
At 400°F. k, = 0.12 min-l, k, = 0.046 min-I, k, = 0.020 min-I, k4 = 0.034
min-1, k, = 0.04 min-1.
A liquid feed to a well-mixed reactor consists of 0.4 g mol/dm3 of A and the
same molar concentration of E The product C is formed from A by two different
reaction mechanisms: either by direct transformation or through intermediate
B. The intermediate B is also formed from E Together with C, which remains
in solution, an insoluble gas D is formed. which SeDarates in the reactor.