Metal Reclamation from Spent Hydroprocessing Catalysts - Spent Hydroprocessing Catalysts - page 266

CHAPTER 11
Metal Reclamation from Spent
Hydroprocessing Catalysts
Considering stringent environmental and safety regulations (e.g., unlimited liability), metal
recovery from spent catalysts is more attractive an option than landfilling. Previous chapters
indicated that spent catalysts, discarded as solid wastes from the hydroprocessing units of
petroleum refining industries, contain alumina and metals, such as Mo, Ni, Co, and V, in
appreciable concentrations [9,13,27,121] . These metals are highly valuable and are used
extensively in the steel industry and in the manufacture of special alloys. These metals are
usually manufactured from the ores and minerals containing them. Spent hydroprocessing
catalysts could be used as a cheap source for these valuable metals. This will result in
recycling and reutilization of the waste catalysts. Consequently, environmental problems
associated with handling of spent catalysts can be eliminated. In view of the environmental
and economic benefits, increasing attention has been paid to the development of processes for
recovering metals and other valuable materials from spent non-regenerable hydroprocessing
catalysts. This is supported by a growing number of articles appearing in scientific and
technical literature.
Several methods, such as chlorination, acid leaching, alkali leaching, bioleaching, roasting
with soda salts, etc., have been studied. The detailed accounts of these studies have been given
in both open and patent literature. Focus has been on recovery of Mo, Ni, V, and Co from the
spent hydroprocessing catalysts. Several companies have also been established for large-scale
reclamation of metals and metal compounds from spent hydroprocessing catalysts. Table 11.1
[608] lists pure compounds which can be isolated from spent catalysts using various
reclamation methods. In the following sections, the information available in the literature both
on the laboratory studies and industrial scale processes for recovery of metals from spent
hydroprocessing catalysts are reviewed.
11.1 Laboratory Studies on Metal Recovery from Spent
Hydroprocessing Catalysts
Most of the studies on recovery of metals from spent hydroprocessing catalysts involve
leaching with the solutions of both inorganic and organic agents. Leaching with the aid of
microorganism, i.e., bioleaching has been attracting attention as well. The dissolution of
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