Journal of Supercritical Fluids, Vol.138, 207-214, 2018
Extraction of palladium from alumina-supported catalyst in supercritical CO2 using functional fluorinated polymers
The use of functional CO2-philic polymers in supercritical carbon dioxide (scCO(2)) for a greener method of extracting Pd from spent catalysts has been investigated. Three fluorinated polymers bearing complexing units (a thiol-terminated poly(1,1,2,2-tetrahydroperfluorodecyl acrylate) homopolymer PFDA-SH, a poly(1,1,2,2-tetrahydroperfluorodecyl acrylate-co-diphenylphosphinostyrene) gradient copolymer P(FDA-co-DPPS), and a thiolterminated gradient copolymer P(FDA-co-DPPS)-SH) were synthesized and successfully used to extract palladium from commercial Pd/Al2O3 supported catalysts (beads and pellets with 0.5 wt.% and 5 wt.% Pd loading, respectively). These non-destructive extractions were carried out in scCO(2) under mild conditions (40 degrees C and 25 MPa). Inductively coupled plasma atomic emission spectroscopy (ICP-AES) analysis on the Pd/Al2O3 catalysts before and after extraction confirmed the removal of palladium from the catalytic supports. Up to 40% of palladium was extracted from the commercial supported catalysts with full recovery of the original alumina support.
Keywords:Supercritical carbon dioxide;Palladium extraction;Fluorinated polymers;Spent catalyst;Green solvent