Page 350 - Elements of Chemical Reaction Engineering Ebook

Chap. 6 Questions and Problems 32 1
In1 each of the questions and problems below, rather than just drawing a box
around :your answer, write a sentence or two describing how you solved the problem,
the assumptions you made, the reasonableness of your answer, what you learned, and
any other facts that you want to include.
P6-1 (a) Make up and solve an original problem to illustrate the principles of this
chapter. See Problem P4-1 for guidelines.
(b) Write a question based on teh material in this chapter that q-tical thinking.
Explain why your question quim critical thinking. IHint: See prehce p. n.1
(c) choose a FAQ from Chapter 6 to be eliminated and say why it should be elimin&ed.
(a) Listen to the audios on the CD and pick one and say why it was the
most helpful.
(e) Which example on the CD ROM Lecture notes for Chapter 6 was least helpful?
P6-2 (a) What if you could vary the temperature in Example 6-_1? What tempera-
ture and CSTR space-time would you use to maximize YD for an entering
concentration of A of 1 mol/dm3? What temperature would you choose?
(b) What if the reactions in Example 6-3 were carried out in a CSTR instead
of a PBR? What would be the corresponding optimum conversion and
space-time, tLpt ?
(c) What if you varied the catalyst particle size in Example 6-6? Would it
increase or decrease SXT ? [Hint: Use a form of Equation (S6-18) and
make a plot of SXT versus a.]
(d) What feed conditions and reactors or combination of reactors shown in
Figure 6-3 would you use to
(1) maximize the overall selectivity in Example 6-8? Start by plot-
ting SCF as a function of OB in a 10-dm3 PFR;
(2) maximize the yield of YFA with and the overall selectivity of & ?
(e) What if you could vary the ratio of hydrogen to mesitylene in the feed
(0.2 < OH < 5) in Example 6-6. What is the effect of OH on topt ? Plot
the optimum yield of xylene as a function of QH. Plot the selectivity 5,
as a function of BH. Suppose that the reactions could be run at different
temperatures. What would be the effect of the ratio of k, to k2 on topt and
on the selectivity SXT and the yield?
(f) Repeat part (d) for Example 6-7.
(8) How would pressure drop affect the results shown in Figure E6-8.1;'
P6-3B The hydrogenation of 0-cresol 2-methylphenol (MP) is carried out over a
Ni-catalyst [Znd. Eng. Chem. Res., 28, 693 (1989)l to form 2-methylcyclo~hex-
anone (ON), which then reacts to form two stereoisomers, cis- (cs-OL) and
trans (tr-OL)-2-methylcyclohexanol. The equilibrium compositions (on a
hydrogen-free basis) are shown in Figure P6-3.
(a) Plot (sketch) the selectivities of ON to cs-OL and of tr-OL to cs-OL as a
function of temperature in the range 100 to 300°C.
(b) Estimate the heat of reaction for the isomerization
tr-OL cs-OL
(c) Plot (sketch) the yields of MP to tr-OL and of MP to ON as functions of
temperature assuming a stoichiometric feed.
P6-4, (a) What reaction schemes and conditions would you use to maximize the '
selectivity parameters S for the following parallel reactions:
A + c ._j D r,, = 800e(-2~=T)C~CC
A+C ---+ U, ru = 10e(-3002T)CACc

where D is the desired product and U, is the undesired product?