Alternative Recovery and Valorization of Metals from Exhausted Catalytic Converters in a New Smart Polymetallic Catalyst

Abstract

A new metals‐polymeric composite, Metx‐EPS (I), was prepared to be used as catalyst in water or in two‐phase aqueous conditions. The metals source was an exhausted catalytic converter that was grinded and treated with an acidic solution at room temperature. After filtration, the solution was concentrated, neutralized and added to a broth of Klebsiella oxytoca DSM 29614 to produce (I) where metals are embedded in a peculiar polysaccharide structure (EPS). The composite was easily recovered from the fermentation broth and purified. The process protocol was verified many times and was shown to be reproducible satisfactorily. The % recovery of metals, originally present in the converter, was good as determined by atomic absorption. The morphology and the chemical state of main metals in (I) were investigated by X‐ray absorption spectroscopy methods (XANES and EXAFS). No metallic alloy seems to be evident. The catalytic activity and a possible synergic effect due to the presence of the different metals was valuated in the hydrogenation of some substrates, valuable precursors for the production of fine chemicals.

A Biogenerated Polymetallic Catalyst from Society's Wastes

“…The presence of metals bounded to capsular EPS and valence and structural information of metal cations in the Met x -EPS complex at the atomic scale were confirmed by x-ray absorption spectroscopy methods XANES and EXAFS [8]. It is known that, in the XANES spectrum, an increase of oxidation state results in a shift of each absorption feature to higher energies [4,12].…”

“…As already described in more detail [8], Met x -EPS (I) was characterized by FT-IR and by the xray absorption spectroscopy methods XANES and EXAFS. The IR spectrum (Appendix, Fig.…”

Sustainable Synthesis of Aryl and Heteroaryl Aldehydes

“…First, we studied the carbonylation reaction on 2‐iodo‐5‐ethylthiophene ( II b ) catalyzed by 1.7 % (Pd‐EPS) or by (Met x ‐EPS). These are heterogeneous biogenerated species, previously obtained by some of us, during citrate fermentation of Klebsiella oxytoca DSM 29614 in the presence of a palladium salt, in the case of (Pd‐EPS) [35,36] (see SI), or of different metals recovered from an exhausted catalytic converter, in the case of (Met x ‐EPS) [38,39] (see SI). Both these catalysts, had given very interesting results in the aqueous biphasic hydrogenation of different unsaturated substrates and in the hydrodehalogenation of 1260 Aroclor [35–40] .…”

“…These are heterogeneous biogenerated species, previously obtained by some of us, during citrate fermentation of Klebsiella oxytoca DSM 29614 in the presence of a palladium salt, in the case of (Pd‐EPS) [35,36] (see SI), or of different metals recovered from an exhausted catalytic converter, in the case of (Met x ‐EPS) [38,39] (see SI). Both these catalysts, had given very interesting results in the aqueous biphasic hydrogenation of different unsaturated substrates and in the hydrodehalogenation of 1260 Aroclor [35–40] . In particular, in (Met x ‐EPS), which contains different metals such as Al, Ce, W and the platinum‐group metals Pd, Pt and Rh (1.9 % Pd, 1.0 % Pt and 0.25 % Rh) (see SI), the co‐presence of these noble transition metals could influence the catalysis by a synergic effect, leading to different activity and selectivity with respect to single metal species [38–40] .…”

“…Methylenbenzo[d] [1,3]dioxole was received from Endura S.p.A. (Italy), triethylsilane from AlzChem Group AG (Germany), 5 % Pd/C (50 % wet) and γ-Al 2 O 3 from Chimet S.p.A. (Italy). 1.7 % Pd-EPS, [35] Met x -EPS, [38,39] and 0.3 % Pd/Al 2 O 3 [40] were prepared following reported procedures. CPME was received from IMCD Italia SpA.…”