Process to recover metals from spent catalyst

Details Process to recover metals from spent catalyst Process to recover metals from spent catalyst

1999-05-06

2001-01-30

Bos, Steven (Department: 1754)

Chemistry of inorganic compounds

Treating mixture to obtain metal containing compound

Group vib metal

C423S063000, C423S053000, C423S056000, C423S067000, C423S068000

Reexamination Certificate

active

06180072

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a process for recovering products from spent catalyst, in particular for recovering and reclaiming metals, oils, and fuel-rich alumina product from petroleum processing catalysts.
BACKGROUND OF THE INVENTION
Petroleum hydrocarbons (oils) in and on spent catalyst feeds are known to inhibit metal reclaiming economics. The oils present on the catalysts block the catalyst pores and require more severe conditions to oxidize surface metals via hydrometallurgical oxidation. In addition, oils lead to undesirable organic contamination in leaching processes and recovered products. Methods commonly used to deoil catalyst, such as thermal deoiling or roasting, are unsatisfactory, leading to alumina reactions with metals at high temperatures and ultimately reduced metal yields.
Metals targeted for reclaiming are commonly recovered following removal of in-use generated petroleum coke. Coking of hydrotreating catalyst does not limit the metals recovery, but may impact processing kinetics due to catalyst pore plugging. The coke may impact reaction kinetics in hydrotreating by lowering diffusion rates due to catalyst pore plugging. Removal of the coke is costly and requires high temperature processing of 400° C. to 800° C. At the higher temperatures, the reaction is fairly rapid, making the process impossible to do in a gradual, controlled manner. Further, the process, which is exothermic at the surface of the catalyst, thermally stresses the catalyst surface and converts metals to less soluble species such as spinels. Therefore, a low temperature, controlled process is desirable.
To meet present day standards as a total reclaimer, oil must be recovered as a commercial product. The oil cannot be rendered as a waste stream in the deoiling process. In conventional high temperature treatments the oil is burned off with the coke, emitting carbon dioxide, carbon monoxide, and sulfur and nitrogen oxide byproducts. A more robust reclamation process minimizes air emissions and provides for recovery of the oil as a value-added product.
Metals present on the catalyst are present as a range of sulfides located in a variety of surface geologies. Some of the metal sulfides are readily oxidized in air at ambient temperatures, but other metal sulfides may require elevated temperatures and oxygen pressures to oxidize.
SUMMARY OF THE INVENTION
The present invention relates to an integrated process for the treatment of catalysts comprising alumina-containing carriers and metals(s) to recover said metal(s) therefrom, which process comprises the steps of:
a) collecting one or more catalyst, said one or more catalyst containing one or more metal as metal sulfide wherein said at least one of said one or more metal sulfide is selected from a molybdenum sulfide, a vanadium sulfide, a tungsten sulfide, and combinations thereof;
b) deoiling said one or more catalyst;
c) leaching said one or more catalyst in an atmospheric leach in the presence of air or oxygen at a pH greater than 9 for a time sufficient to convert in the range of about 50-70% of said one or more metal sulfide to soluble metal and sulfur species, thereby forming a first leached slurry comprising a first liquid stream containing soluble metal and sulfur species and a first solid;
d) separating said first leached slurry into said first liquid stream and said first solid;
e) leaching said first solid in a pressure leach process in the presence of air or oxygen at a pH greater than 9 for a time sufficient to convert greater than about 90%, based upon the metal sulfides present on the one or more catalyst before step (c), of said one or more metal sulfide to soluble metal and sulfur species, thereby forming a second leached slurry comprising a second liquid stream containing soluble metal and sulfur species and a second solid;
f) separating said second leached slurry into said second liquid stream and said second solid;
g) collecting said first liquid stream and said second liquid stream to form a combined liquid stream;
h) oxidizing said combined liquid stream;
i) contacting the oxidized liquid stream with an organic solvent containing an extractant effective to transfer soluble metal species into the organic, thereby creating a metal species containing organic phase and a substantially metals-free aqueous liquid containing sulfate;
j) recovering said substantially metals-free aqueous liquid containing sulfate;
k) stripping the soluble metal species from the organic phase in the presence of an aqueous ammonia solution, thereby forming an aqueous phase containing metal species;
l) adjusting the pH of the aqueous phase to selectively precipitate at least one metal as at least one ammonium metal salt; and
m) separating said at least one ammonium metal salt from said aqueous phase and recovering said at least one ammonium metal salt.


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