Selective Hydrogenation Catalyst Made Via Heat-Processing of Biogenic Pd Nanoparticles and Novel ‘green’ Catalyst for Heck Coupling Using Waste Sulfidogenic Bacteria

A heterogeneous Pd catalyst, biologically-mineralized palladium nanoparticles (bio-Pd), was synthesized using sulfidogenic bacteria which reduced soluble Pd(II) to catalytically-active Pd-nanoparticles (NPs). Heat treatment (processing) of bio-Pd (5 or 20 wt% on the cells) made by Desulfovibrio desulfuricans evolved supported Pdcatalyst comprising Pd-NPs held on large spherical hollow structures. The rate of hydrogenation of 2-butyne1,4-diol was similar to 5-fold slower than for a commercial catalyst (similar to twice that of native bio-Pd), but with high selectivity to the alkene, fulfilling a key industrial criterion. In the Heck reaction, while bio-Pd showed a comparable reaction rate in ethyl cinnamate synthesis to that achieved by commercial Pd/C, heat-treated bio-Pd had negligible activity. D. desulfuricans bio-Pd was replaced by bio-Pd made using a consortium of waste acidophilic sulfidogenic bacteria (CAS) supplied from an unrelated primary remediation process. This gave comparable activity to commercial 5 wt% Pd/C in ethyl cinnamate synthesis, signposting an economic, scalable route to catalyst manufacture.