Applied Catalysis B: Environmental, Vol.199, 108-122, 2016
Selective hydrogenation using palladium bioinorganic catalyst
Palladium bioinorganic catalyst (bio-Pd) was manufactured using bacteria (Desulfovibrio desulfuricans and Escherichia coli) via the reduction of Pd(II) to bio-scaffolded Pd(0) nanoparticles (NPs). The formed Pd NPs were examined using electron microscopy and X-ray powder diffraction methods: a loading of 5 wt% Pd showed an average particle size of 4 nm. The catalytic activities of the prepared bio-Pd NPs on both bacteria were compared in two hydrogenation reactions with that of a conventionally supported Pd catalyst (Pd/Al2O3). Concentration profiles of the different hydrogenation products were fitted using a Langmuir-Hinshelwood expression. In 2-pentyne hydrogenation, 5 wt% Pd-E.coli achieved 100% of 2-pentyne conyersion in 20 mins and produced 10.1 +/- 0.7 x 10(-2) mol L-1 of desired cis-2-pentene; in contrast 5 wt% Pd/Al2O3 yielded 6.5 +/- 0.4 x 10(-2) mol L-1 of cis-2-pentene after 40 mins. In the solyent-free hydrogenation of soybean oil, the use of 5 wt% Pd-E.coli yielded cis-C18:1 of 1.03 +/- 0.04 mol L-1 and trans C18:1 of 0.26 +/- 0.03 mol L-1 (similar to 50% less of the latter than 5 wt% Pd/Al2O3) after 5 h. Similar results were obtained using bio-Pd-E.coli and bio-Pd-D.desuifuncans. Bio-Pd was concluded to have the advantage of a lower cis-trans isomerisation in hydrogenation of alkyne/alkenes. Hence bionianufacturing is an environmentally attractive, scalable and facile alternative to conventional heterogeneous catalyst for application in industrial hydrogenation processes. D. desulfuricans is inconvenient to grow at scale but wastes of E. coli are produced from various industrial processes. 'Second life' (i.e. recycled from a pilot scale biohydrogen production process) E. coli cells were used to make bio-Pd catalysts. Although bio-Pd-secondlife gave a slower conversion rate of 2-pentyne and soybean oil compared to bio-Pd from purpose-grown cells it showed a higher selectivity to the cis-isomer product. (C) 2016 The Authors. Published by Elsevier B.V.