Environmental and Safety Aspects of Spent Hydroprocessing Catalysts - Spent Hydroprocessing Catalysts - page 106

Table 5.2: Constituents of potentially hazardous solids [From ref. 306 . Reprinted with permission].
Compounds of Be, V, hexavalent Cr, Co, Ni, Cu, Zn, As, Se, Te, Ag, Cd, Sn, Sb,
Ba, Hg, Pb, and Ta
Inorganic acids
Inorganic sulfides
Inorganic fluorine compounds, excluding CaF 2
Inorganic cyanides
Phenols
Ethers
Aromatic compounds; polycyclic and heterocyclic
Organic nitrogen compounds, especially aromatic and aliphatic amines
Organic sulfur compounds
Substances of an explosive character
Organohalogen compounds
concern for spent catalysts that were not properly de-oiled and dried. Such cases of spent
catalysts cannot be completely ruled out. The complete list of regulated organic compounds,
given by Vallerot, was part of the groups in Table 5.2 [298] . Inorganic acids (e.g., sulfuric)
require attention during a prolonged exposure of spent catalyst to air and water, such as in
landfills.
For hydroprocessing catalysts, the major inorganic constituents that are added to the catalysts
during operation include V and Ni. Depending on the origin of the feed, other contaminant
metals, such as As, Fe, Ti, Ca, Na, clays, etc., may also be added. Details of the composition of
organic and inorganic deposits in spent hydroprocessing catalysts were presented in the
Chapter 4 on catalyst deactivation. It should be noted that the metals that are part of the spent
catalysts (e.g., V, Ni, Co, Mo, W, Fe, etc.) are not included among the NPDWS constituents in
Table 5.1 [296] . In spite of this, all necessary precautions have to be taken to prevent release of
these metals to ground water and, thus, to avoid future liabilities.
The performance of hydroprocessing catalysts can be improved by modifying -Al 2 O 3 support
with various additives. In this regard, the catalysts modification, using fluoride and phosphate
compounds, resulted in a significant enhancement in the activity and stability of catalyst. All
handling stages of spent hydroprocessing catalysts must take into consideration the presence
of the fluoride and phosphate species. So far, little attention has been paid to the release of
fluorine and phosphorus containing compounds in spite of their hazardous nature. It is
desirable that such compounds are added to the list of toxic emissions if their release from
spent catalysts can be confirmed.
Hazardous characteristics of spent hydroprocessing catalysts are listed in Table 5.3 [16,306] .
The RCRA characteristic hazardous waste is defined in 40 CFR 261 subpart C as one that fails