CHE3044F, 2013
TUTORIAL 10
page 1
CHE3044F, 2013 : Reactor Design 1 : TUTORIAL 10 1. (adapted from Fogler, P5-10). The gas phase decomposition A −→ B + 2C is carried out in a constant volume batch reactor. Runs 1 to 5 are were carried out at 100◦ C while run 6 was carried out at 110◦ C. run Initial concentration, CA0 mol.L−1 1 0.0250 2 0.0133 3 0.010 4 0.050 5 0.075 6 0.025
Half-life, t1/2 (min) 4.10 7.70 9.80 1.96 1.30 2.00
(a) Using the data in the table determine the reaction order and the reaction rate constant (b) What is the activation energy for this reaction. 2. (adapted from Fogler, P5-16). The thermal decomposition of isopropyl-isocyanate was studied in a differential packed bed reactor. From the data in the table determine the reaction rate equation parameters (rate constant, reaction order and activation energy) run 1 2 3 4 5 6
Rate mol.s −1 L−1 4.9 × 10−4 1.1 × 10−4 2.4 × 10−3 2.2 × 10−2 1.18 × 10−1 1.82 × 10−2
Concentration mol.L−1 0.20 0.02 0.05 0.08 0.10 0.06
Temperature K 700 750 800 850 900 950
3. The presence of a substance C seems to increase the rate of reaction of A and B in the reaction A + B −→ R We suspect that C acts catalytically by combining with one of the reactants to form an intermediate, which then acts further. From the data given in the table, suggest a mechanism and rate equation for this reaction. CA 1 3 4 2 2 1
CB 3 1 4 2 4 2
CC 0.02 0.02 0.04 0.01 0.03 0.05
rR 9 5 32 6 20 12
CHE3044F, 2013
TUTORIAL 10
page 2
4. Pure gaseous A at about 3 atm and 30◦ C (120 mmol/L) is fed into a 1 L mixed flow reactor at various flow rates. There it decomposes (A −→ 3R), and the exit concentration of A is measured for each flow rate. From the data in the table, find the rate equation that represents the kinetics of this reaction. Assume that A alone affects the reaction rate. ν0 L/min CA mmol/L
0.06 30
0.48 60
1.5 80
8.1 105
5. When oxygen is bubbled through a high temperature batch of A-containing liquid material, A oxidises slowly to give a slowly decomposing intermediate X and a final product R. The following results are measured. t, [min] CA , [mol/m3 ] CR , [mol/m3 ] 0 100 0 0.1 95.8 1.4 2.5 35 26 5 12 41 7.5 4 52 10 1.5 60 20 negligible 80 ∞ 0 100 We have no way of analysing for X. However, we are safe in assuming that at any time CA + CR + CX = CA0 . What can we say about the mechanism and the kinetics of this oxidation. (Hint : plot the data and examine the plot).
CHE3044F, 2013
TUTORIAL 10
page 3
6. (Exam, 2011, Question 2). ABC Research Labs have studied the oxidation of sodium sulphite (Na2 S), species A, to sodium thiosulphate (Na2 S2 O3 ), species R, in a batch reactor. The intermediate concentrations (Na2 S2 ), species T and (Na2 SO3 ), species S, were carefully measured. The results are shown in the concentration versus time plot. After a very long reaction time, the concentration of species S and T are zero.
(a) Explain why this reaction network is able to describe these results. k1
S
k4
k2
A k3
T
(4)
R k5
(b) Develop the rate law for each species in this network assuming first order reactions. (4) (c) Using the data given in the figure, evaluate all the rate constants in the reaction network (Hint : What happens to the network when the concentrations of one or some the products are low) (12)
CHE3044F, 2013
TUTORIAL 10
page 4
7. (Final Exam, 2012, Questionb 4). Chemical A is reacted to R and S in a plug flow reactor using a feed of pure A. The following concentration profiles are obtained. These are the only reaction products that are detected.
(a) Propose a reaction scheme from these data.
(6)
(b) Evaluate the reaction rate parameters for all proposed reactions assuming that they are first order. (8) (c) What is the size of the PFR that will produce 100 mol.min−1 of R when operated at the maximum yield of R. (4) 8. (Final Exam, 2012, Questionb 4). The gas phase reaction between A and B to produce R has been measured in a 1 L CSTR. A + B −→ R The volumetric flow rate to the reactor in all cases was 1 L.mi n−1 and consisted of only A and B. The pressure of the reaction system is 4 atm. The concentration of R in the exit gas has been measured at the following conditions Feed mole fraction, yA0 CR [mmol.L−1 ] Temperature, ◦ C
0.01 0.405 200
0.02 1.06 200
0.5 70.8 200
0.5 78.2 250
Determine the rate law consistent with these data.
