Catalytic activity of biomass-supported Pd nanoparticles: Influence of the biological component in catalytic efficacy and potential application in ‘green’ synthesis of fine chemicals and pharmaceuticals

K Deplanche,J.A Bennett,I.P Mikheenko,J Omajali,A.S Wells,R.E Meadows,J Wood,L.E Macaskie

doi:10.1016/j.apcatb.2013.09.045

K Deplanche, J.A Bennett + Show 6 more

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https://doi.org/10.1016/j.apcatb.2013.09.045

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Abstract

Five gram negative and two gram positive bacterial strains known for their heavy metal tolerance or ability to reduce metal ions were coated with Pd(0) nanoparticles (NPs) via reduction of soluble Pd(II) ions under H2 following an initial uptake of PdCl42- without added electron donor ('biosorption'), where the gram negative strains had a ~5-fold greater capacity for Pd(II). Cupriavidis metallidurans accumulated Pd(II) exceptionally; the possibility of reduction to Pd(0) via an endogenous electron donor was not discounted. The initial rate of subsequent H2-mediated Pd(II) reduction correlated with the Pd(II) removed during biosorption (r2=0.9). TEM showed strain-specific variations of Pd-NPs. At a 1:3 loading of Pd:biomass the cell surfaces of Escherichia coli and Desulfovibrio desulfuricans showed uniform coverage with small NPs with the other strains showing larger aggregates. NPs made by the gram positive cells appeared larger than their gram negative counterparts. At a loading of 1:19 all were active catalysts in Cr(VI) reduction and in two Heck coupling reactions. BioPdE. coli and bioPdD. desulfuricans and bioPdA. oxydans were consistently the best and worst catalysts respectively. BioPdE. coli was further tested as a process catalyst according to industrial protocols in Heck and Suzuki coupling reactions. Laboratory and industrial tests (coupling of phenyl iodide and ethyl acrylate) gave 75% and 78% conversion to ethyl cinnamate, respectively. The biomaterial catalysed Heck and Suzuki reactions using bromoacetophenone and 4-bromoanisole (Heck) and 4-chloroanisole (Suzuki) but not 3-chlorotoluene. In accordance with known chemical catalysis the catalytic efficacy was related to electron-withdrawing substituents on the phenyl ring, with more than 90% conversion (Suzuki) using 4-bromobenzotrifluoride.

Highlights

Due to their often unequalled catalytic properties, platinum group metals (PGMs) are widely used in many catalytic processes of the petrochemical and chemical manufacturing industries
In this study an E. coli, D. desulfuricans, a Micrococcus sp. and S. oneidensis showing hydrogenase-mediated metal reduction [4,6,50,51,52] were tested for their ability to reduce Pd(II)
M. luteus, A. oxydans and C. metallidurans often show high tolerance to a large number of metallic ions [53,54,55,56,57,58,59,60] and actinides [61] by mechanisms which include efflux systems, biosequestration and/or bioprecipitation [54,56,57] prompting their inclusion in the study

Summary

Introduction

Due to their often unequalled catalytic properties, platinum group metals (PGMs) are widely used in many catalytic processes of the petrochemical and chemical manufacturing industries. Devices for the automotive industry, PGM demand and market price have increased concurrently. The use of petrochemicals for ’platform’ chemical synthesis is of concern due to the dual effects of dwindling oil supplies and the environmental impact of CO2. The development of efficient, cost-effective recycling and green chemistry technologies is a first step towards the conservation and sustainable use of resources. Due to limited global resources and the high market value of PGM, their recovery often takes priority over environmental concerns, for example more than 14 tonnes CO2 is generated per kilo of Pt produced from primary sources [1]. Traditional PGM recycling methods (electrochemical recovery, solvent extraction) are energy-demanding or rely on the use of aggressive chemicals [2,3]

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