Environmental Engineering Reference
In-Depth Information
Table 6.6: Porosity of fresh, spent, and regenerated catalysts [From ref.
402
. Reprinted with
permission].
Pore volume (mL/cm
3
)
Pore size and run no.
Surface area
Run time (h)
m
2
/g
Loss (%)
L
p
= 0.00567 cm
f
0
.
557
253
-
1
u
0
.
272
178
30
1
r
0
.
537
232
8
30
2
u
0
.
159
107
58
2
r
0
.
530
229
9
70
3
u
0
.
152
44
83
3
r
0
.
465
211
17
140
L
p
= 0.0294 cm
1
u
0
.
229
147
42
1
r
0
.
538
230
9
15
2
u
0
.
222
136
46
2
r
0
.
509
253
0
50
3
u
0
.
174
93
63
3
r
0
.
518
220
13
90
surface area. The catalysts were used for hydroprocessing of an atmospheric residue derived
from the conventional crude containing less than 20 ppm of metals. The loss of surface area
and pore volume with the duration of operation was quite evident. However, even after 140 h
on stream, more than 80% recovery of surface area and pore volume could be achieved on
regeneration. In the case of the NiMo/Al
2
O
3
extrudate catalyst, the aged catalyst suffered a
large loss in 70 to 140 A diameter pore region
[403]
. Most of the pore volume could be
recovered on regeneration. The lower recovery of surface area and pore volume was achieved
for higher metal content feeds
[404]
.
Diffusivity measurements can provide important information, particularly when they are
performed on fresh, spent, and regenerated catalysts. In the study of Johnson et al.
[405]
, the
diffusivity was determined by contacting the catalysts with the solution of coronene in
cyclohexane. The diffusivity increased on regeneration of catalyst but it did not reach that of
the fresh catalyst. The loss in diffusivity did not correlate with the catalyst activity recovery
[404]
. The former was more pronounced than the loss in activity.
6.2.4.2 Activity of Regenerated Catalysts
Figure 6.22 [367,368]
shows the effect of temperature on the surface area and dynamic O
2
chemisorption (DOC) of the regenerated catalysts. The latter is usually performed on the
regenerated-presulfided catalysts and is an indication of the catalyst activity recovery.
