Biomedical Engineering Reference
In-Depth Information
9.9.
Dehydration of alcohol over alumina
e
silica catalyst can be employed to produce
alkenes. The dehydration of
n
-butanol was investigated by J.F. Maurer (PhD thesis,
University of Michigan). The data shown in
Fig. P9.9
were obtained at 750
Fin
a modified differential reactor. The feed consisted of pure butanol.
(a)
Suggest a mechanism and rate-controlling step that is consistent with the data
(b)
Evaluate the rate law parameters.
9.10.
The catalytic dehydration of methanol (M) to form dimethyl ether (DME) and water
(W) was carried out over an ion exchange catalyst (K. Klusacek, Collection Czech.
Chem. Commun.
, 49, 170, 1984). The packed bed was initially filled with nitrogen gas
(N) and at
t
0, a feed of pure methanol vapor entered the reactor at 413 K,
100 kPa, and 0.2
¼
10
6
m
3
/s. The following partial pressure data were recorded at
the exit to the differential reactor containing 1.0 g of catalyst in 4.5
10
6
m
3
of
reactor volume.
t
, s
0
10
50
100
150
200
300
P
N
, kPa
100
50
10
2
0
0
0
P
M
, kPa
0
2
15
23
25
26
26
P
W
, kPa
0
10
15
30
35
37
37
P
DME
, kPa
0
38
60
45
40
37
37
9.11.
In the decomposition of N
2
O on Pt, if N
2
O is weakly adsorbed and O
2
is moderately
adsorbed, what form of rate law would be expected based on an LHHW mechanism?
Explain briefly.
9.12.
Rate laws for the decomposition of PH
3
(A) on the surface of Mo (as catalyst) in the
temperature range 843
e
918 K are as follows:
Pressure
p
A
, kPa
Rate law
w
r
A
¼
kp
A
0
10
3
8
r
A
¼
kp
A
/(
a
þ
bp
A
)
10
2
2.6
r
A
¼
constant
Interpret these results in terms of an LHHW mechanism.
9.13.
Consider the following overall reaction:
1
2
A
2
þ
B
/
C
þ
D
The mechanism has the following features:
(i)
Molecules of A
2
dissociatively adsorb on two type 1 sites (one A atom on each
site).
(ii)
Molecules of B adsorb on type 2 sites.
(iii)
The rate-determining step is the surface reaction between adsorbed A and
adsorbed B.
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