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The state of nickel in spent Fluid Catalytic Cracking catalysts

Paper ID Volume ID Publish Year Pages File Format Full-Text
39444 45823 2014 11 PDF Available
Title
The state of nickel in spent Fluid Catalytic Cracking catalysts
Abstract

•The speciation of Ni in spent Fluid Catalytic Cracking catalysts is studied.•Carefully performed XRD analyses reliably detect NiO at the 1000 ppmw level.•NiO is not detected even after contamination of the order of 15,000 ppmw of Ni.•Ni disperses on the alumina binder forming NixAl2O3+x layers (x < 0.2)•Spent FCC catalysts can be classified as a non-hazardous waste.

The speciation of Ni in spent Fluid Catalytic Cracking catalysts is studied. Carefully performed XRD analyses with NiO/SiO2 samples used as calibration standards, demonstrate that the presence of NiO as a separate phase is reliably detected also for NiO concentration close to 0.1 wt% (1000 ppmw). Actually, both on real spent FCC catalysts (ECAT's) and on artificially contaminated industrial FCC catalysts, NiO is not detectable as a separate phase, even after contamination of the order of 15,000 ppmw of Ni. SEM–EDS experiments provide evidence of a largely preferential location of Ni on alumina particles present in the FCC catalyst mixture, thus acting as “nickel traps”. XRD, UV–vis and TPR data confirm that Ni deposits on alumina particles forming a hardly reducible surface and subsurface layer, giving rise to a solid whose composition is NixAl2O3+x with x << 0.25. As a result of this, the formation of extended Ni metal particles in the raiser reactor is avoided, being their unwanted dehydrogenation activity essentially eliminated. The absence of bulk NiO in the spent FCC catalysts (at least when Ni content is in the range 2000–10,000 ppmw) allows the classification of this material as a non-hazardous waste.

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Keywords
Nickel speciation; Catalyst for FCC; Fluid Catalytic Cracking catalyst; Spent catalyst; Refinery waste; Nickel speciation; Non-dangerous waste
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Publisher
Database: Elsevier - ScienceDirect
Journal: Applied Catalysis A: General - Volume 486, 22 September 2014, Pages 176–186
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Catalysis
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Price was $35.95
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