Environmental Engineering Reference
In-Depth Information
Table 5.6: Analysis of spent hydroprocessing catalysts (as received) [From ref.
337
. Reprinted with
permission].
Analysis (wt.%)
Catalyst
1
2
3
4
Carbon
7
.
4
15
.
0
7.7
56
.
3
Hydrogen
1
.
2
3
.
3
0.8
1
.
1
Nitrogen
0
.
40
0
.
14
0.14
0
.
30
Sulfur
7
.
13
12
.
9
6.2
4
.
60
Iron
0
.
08
7
.
0
0.05
0
.
49
Vanadium
0
8
.
6
34 ppm
2
.
7
Nickel
2
.
7
3
.
9
64 ppm
1
.
2
H/C
1
.
9
1
.
5
1.2
0
.
2
the NiMo/Al
2
O
3
catalyst 2 was used for upgrading an atmospheric residue using a fixed bed
reactor. The extrudate form of the CoMo/Al
2
O
3
catalyst 3 was used in a commercial
hydrodesulfurization (HDS) unit. The NiMo/Al
2
O
3
catalyst 4 was obtained from a fixed bed
reactor after upgrading of a heavy feed. This catalyst was received as a lump weighing about
4 kg. It is believed that at the end of operation, the catalyst was deactivated to such an extent
that the fixed bed essentially fused. Therefore, a chisel and hammer had to be used to produce
particles (minus 20mesh) for evaluation. These particles were non-extractable by hot THF in a
Soxhlet apparatus.
According to
Table 5.5 [337]
, catalyst 1 is classified as hazardous solid because for this
catalyst, the concentration of As in the leachate was about 10 times greater than allowed by
regulatory levels. Most likely, arsenic originated from the distillate feed during the continuous
operation lasting more than two years. For other spent catalysts, the content of the trace metals
were lower than regulatory limits. However, high concentrations of the active metals (e.g., Mo,
Ni, and Co) in leachates also suggest that these catalysts should be handled as hazardous solids
in spite of the fact that they are not included among the NPDWS in
Table 5.1 [296]
. Again,
there is no reason to believe that this will not change in a future.
5.3 Pretreatment of Spent Catalysts for Disposal
Spent catalyst wastes could be disposed of into a landfill only if it could be proven with
certainty that the landfill met non-hazardous criteria. In the USA, the disposal and treatment of
spent refinery catalysts is governed by the RCRA, which holds not only the approved
dump-site owner liable, but the owner of the buried waste as well. This environmental
responsibility continues for the life of the dump-site. Spent catalysts sent to landfills should be
