Spent fluid catalytic cracking catalyst secondary resource
Used petroleum-refinery fluid catalytic cracking (FCC) catalyst, a heterogeneous alumina/silica-rich secondary resource that may contain rare earths and accumulated metals. It is distinct from fresh catalyst, spent hydrocracking or hydrotreating catalyst, automotive catalyst, constituent elements and mineral species. The selected evidence concerns one Valero FCC feed and filtered microbial culture supernatant; it does not confer criticality on all FCC wastes.
Microbial & Biochemical Mechanisms (1)
Rare-earth leaching with Gluconobacter oxydans spent medium
bioleaching
Microbial
Associated Organisms:
Gluconobacter oxydans (NCBITaxon:442)
Cell-free spent medium from Gluconobacter oxydans NRRL B58 released a reported approximately 49% of the total acid-digestible rare-earth inventory from one spent FCC feed. The observation supports laboratory biolixiviant leaching; it is neither an element-specific yield nor isolated rare-earth product recovery.
Experimental Context & Analytical Limits:
Reed et al. obtained spent FCC catalyst from Valero, Houston, with average particle size 80-90 micrometres and reported 55-60% Al2O3 and 35-40% SiO2. Table 1 shows a lanthanum-dominated REE inventory, determined by repeated HCl/HNO3 digestion at 125 degrees C and ICP-MS. B58 obtained from USDA NRRL was grown for four days in modified Pikovskaya medium (Pkm), 30 degrees C, 150 rpm. Comparator PkmT cultures contained added tryptone and were grown at 20 degrees C, so this comparison changes both medium composition and growth temperature. The supernatant was centrifuged at 10000 x g for 20 minutes and sterilized through a 0.22-micrometre filter. Triply autoclaved FCC feed at 1.5% w/v was leached in 50 mL tubes for 24 hours at 30 degrees C and 150 rpm, in triplicate. Leachates were filtered through 0.22-micrometre filters and analyzed by ICP-MS. Sterile medium and 10, 30 and 90 mM gluconic acid in medium were comparators. This is a laboratory tube experiment using industrially sourced waste.
Reed et al. obtained spent FCC catalyst from Valero, Houston, with average particle size 80-90 micrometres and reported 55-60% Al2O3 and 35-40% SiO2. Table 1 shows a lanthanum-dominated REE inventory, determined by repeated HCl/HNO3 digestion at 125 degrees C and ICP-MS. B58 obtained from USDA NRRL was grown for four days in modified Pikovskaya medium (Pkm), 30 degrees C, 150 rpm. Comparator PkmT cultures contained added tryptone and were grown at 20 degrees C, so this comparison changes both medium composition and growth temperature. The supernatant was centrifuged at 10000 x g for 20 minutes and sterilized through a 0.22-micrometre filter. Triply autoclaved FCC feed at 1.5% w/v was leached in 50 mL tubes for 24 hours at 30 degrees C and 150 rpm, in triplicate. Leachates were filtered through 0.22-micrometre filters and analyzed by ICP-MS. Sterile medium and 10, 30 and 90 mM gluconic acid in medium were comparators. This is a laboratory tube experiment using industrially sourced waste.
Curated Evidence Points:
Support
Source:
reed_2016
Sections 2.5, 2.7, 3.2 and 3.4, Figures 3 and 5 report approximately 49% total REE leaching with B58 Pkm supernatant, versus near-baseline sterile-medium controls. Figure 5 reports roughly 24%, 36% and 45% with 10, 30 and 90 mM abiotic gluconic acid. Bars describe total-REE percentages relative to the characterized feed, with standard deviations from triplicate experiments; they are not lanthanum or cerium yields. The PkmT treatment in Figure 3 is about 33% for B58 versus about 49% in Pkm. PkmT and Pkm cultures were grown at 20 and 30 degrees C, respectively, before both supernatants were used for leaching at 30 degrees C. The lower PkmT value cannot isolate a tryptone effect because medium and preculture temperature changed together.
Partial
Source:
reed_2016
Section 3.6 gives initial pH 2.3 for the B58 supernatant containing 12.5 mM gluconic acid, versus 3.2, 2.9 and 2.5 for the three chemical controls. Their unmatched acidity prevents assigning the difference to a unique microbial ligand effect. Gluconic and 2-ketogluconic acids were measured, but the proposed 2,5-diketogluconic acid was not verified because its standard was unavailable. No specific enzyme mechanism is established. FCC assays used bacterial supernatants only; whole-cell/fungal and biosorption findings from phosphor experiments must not be transferred to FCC. No purified product, complete mass balance, economic feasibility or industrial deployment was demonstrated.
Sources & References
-
reed_2016: Reed et al. (2016). Bioleaching of rare earth elements from waste phosphors and cracking catalysts. Hydrometallurgy 166:34-40. DOI 10.1016/j.hydromet.2016.08.006; accepted manuscript INL/JOU-16-37735, Sections 2.1-2.7, 3.2-3.6, Table 1 and Figures 3,5 (PDF pp.6-10,15-22).
https://www.osti.gov/servlets/purl/1357607 (accessed 2026-10-11) -
ncbi_gluconobacter: NCBI Taxonomy 442: Gluconobacter oxydans, species; this identifier does not authenticate NRRL B58 strain provenance.
https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=442 (accessed 2026-10-11)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-11T09:26:04.458978+00:00 |
Codex (GPT-6; Codex) | CREATE | Created the distinct secondary-resource identity and source-scoped laboratory evidence, preserving control, measurement, scale and source-consistency limitations. |
2026-10-11T09:35:34.405602+00:00 |
Codex (GPT-6; Codex) | EDIT | Address independent review: expose the Pkm 30-degree-C versus PkmT 20-degree-C preculture-temperature confound, distinguishing their common 30-degree-C leach from microbial growth conditions. |
Record source: data/records/spent-fluid-catalytic-cracking-catalyst.yaml