Understanding Bio-induced Selectivity in Nanoparticle Catalyst Manufacture

Lead Research Organisation: University of Birmingham
Department Name: Chemical Engineering

Abstract

This project proposes to make highly selective nano-particulate catalysts using a novel method ('biocasting') for a set of defined catalytic reactions and to develop understanding of how to control the catalyst manufacturing process to achieve the desired selectivity which is not readily achieved using chemical manufacturing alone.. Controlled growth of metal nanoparticles in various naturally occurring and modified bacteria will be used to produce the required catalysts supported on cell surfaces.Previous work, has demonstrated that bacteria can be used as a catalyst support for nanoparticulate metals, including platinum and palladium. The process involves reducing the metal enzymatically from a salt solution over a bacterial culture, with templating and stabilisation achieved using biochemical components at the living/nonliving interface, followed by post-processing, which kills the bacterial cells but retains the special catalytic properties of nanoparticles. Such materials have been shown to provide selectivity towards desirable products in catalytic reactions including double bond isomerisation and selective hydrogenation, but at present there is a lack of understanding of why this superior selectivity occurs. One factor may be the crystal structure, including the ratios of edge to terrace and corner atoms which influence the adsorption of reactants upon the catalyst surface. Another effect is the rate of diffusion of reactants to the metal surface. This proposal will develop understanding of why the nanoparticles give rise to superior catalytic selectivity, and thus will enable the rational design and production of nanoparticles for given applications. The present proposal will seek to clean the biotemplated metal particles using chemical and electrochemical methods in order to control the metal cluster morphology, and to block selectively certain active sites on the catalyst using Bi, Pb, sulphur or bacterially derived agents incorporated at the synthesis stage. By switching on or off active sites in this way and associated characterization and testing of the catalysts, it will be possible to identify which types of sites are associated with favourable selectivity in chemical transformations.The produced catalysts will be characterized using a range of techniques which will elucidate information about the nanoparticle size, shape, cluster structure, redox behaviour, electrochemical and spectroscopic behaviour (SERS, XPS, XRD, TPD, DRIFTS and CV). Catalytic selectivity will be studied in a range of selective hydrogenation and double bond isomerisation reactions. The ultimate goal is to replace Lindlar catalysts based on lead modified palladium and other transition metals with more environmentally benign alternatives; previous studies in ours and collaborators' laboratories have shown that the precious metal can be supplemented with cheap metals such as Fe and can even be sourced as such mixtures from waste and scrap for economic manufacture.Current methods for nanoparticle manufacture are not 'clean' and/or not scalable. The major advantage of biomanufacturing is its scalability; we have routinely grown several kilos of the bacteria at the 600 litre scale in our pilot plant. As part of this project we will make Bio-Pd preparations at the 30-100 litre scale (batch cultures), checking the small-scale and large-scale NP products for conserved properties, and also stock aliquots for shelf-life evaluation.

Publications

10 25 50

 
Description A range of biogenic catalysts were prepared at Biosciences in Birmingham. These have undergone further cleaning and characterisation at Chemistry in Cardiff. Catalyst testing was carried out in Birmingham. A summary of findings of testing biogenic catalysts in the liquid phase is given below.

Summary of findings in liquid phase catalysis: The selectivity towards1,4-butynediol hydrogenation of both a standard 5 wt% Pt on graphite supported catalyst and a biogenic Pt analogue is reported. In both cases, it is determined using cyclic voltammetry that step sites afford the greatest extent of hydrogenation and that deliberate blocking of such sites gives rise to significant selectivity in favour of the 1,4-butenediol product. For the 5 wt% Pt/graphite catalyst, irreversible adsorption of bismuth was used as the step site blocking agent. In the case of the biogenic Pt nanoparticles synthesised within the bacterium Escherichia coli, residual molecular organic fragments, left over after chemical cleaning and subsequent separation from the bacterial support, were observed to have accumulated preferentially at defect sites. This phenomenon facilitated an increase in selectivity towards alkenic products of up to 1.4 during hydrogenation of the alkyne. When biogenic nanoparticles of platinum supported upon bacterial biomass were also investigated, they too were found to be active and selective although selectivity towards 1,4-butenediol was optimised only after the particles were chemically cleaned and separated from the biomass. Selectively-poisoned 5% Pt on graphite (0.5 monolayers), although highly selective, gave half the reaction rate of the "cleaned" (most biomass removed from the Pt) biogenic platinum nanoparticles (20% and 45% conversion of starting material respectively after 2 h) but the latter exhibited less selectivity for butenediol (0.7 and 0.9 respectively). It is proposed therefore that such biogenic materials may potentially act in a similar manner to Lindlar-type catalysts, used extensively in organic synthesis for selective hydrogenation of alkynes, in which an additive partially poisons metal sites but without the associated hazards of toxic heavy metals such as lead being present.
Exploitation Route The techniques developed under this project could potentially lead to:

• Manufacture of catalysts from waste materials such as scrap catalytic converters and electronic waste.

• Reduction of waste of raw materials in chemical manufacture through use of highly selective catalysts.

• Recovery of metals from catalysts for further recycling using microwaving or sonication.

• Improved manufacturing through selective production of desirable chemicals, whilst reducing the amount of waste produced.
The project is subject to a collaboration agreement between the Universities of Cardiff and Birmingham. Alta Innovations, the Technology Transfer company serving University of Birmingham University, will help to connect academic expertise and intellectual property to help solve industry-based problems. The Tech Transfer Offices of Birmingham & Cardiff have had 'hands-on' experience in working collaboratively towards a common goal via a previous Royal Society award. Deplanche/Macaskie have filed a patent application (BioAu catalysts) superior performance for selective oxidation reactions, and similarly patents would be applied for to protect the intellectual property generated under this project.
Sectors Agriculture, Food and Drink,Chemicals,Education

URL http://www.roadstoriches.co.uk/
 
Description The findings have indicated that potentially toxic chemicals used in catalysis such as lead in Lindlar catalysts could potentially be replaced by less harmful materials via biogenic preparation routes. Bacterial cells such as E.coli and D. desulfuricans showed an ability to accumulate small nanoparticles of metals such as palladium. Such catalysts were shown to have good selectivity in reactions such as Heck and Suzuki coupling reactions, which are commonly used industrial reactions. This method of producing catalysts could facilitate the recovery of spend metals from scrap sources such as car catalytic converters and electronics waste, as well as low grade road dust containing metals expelled from catalytic converters of vehicles. The type of bacterial strain could also influence the catalytic performance. The above advantages have been demonstrated through publications, conferences and public engagement workshops. They could potentially be used by industry, e.g. Macaskie and Wood are collaborating with C-Tech Innovation to exploit novel catalytic processes. A post-doc from an associated project, Dr Angela Murray, has formed a spin-out company Roads to Riches, who are exploiting the recycling of road dust to make value added catalysts.
First Year Of Impact 2012
Sector Chemicals,Education
Impact Types Societal,Economic

 
Description Use of Microwave Injury to Predispose Bacteria to Make Highly Active Catalytic Nanoparticles
Amount £20,000 (GBP)
Organisation University of Birmingham 
Department University of Birmingham EPSRC Follow On Fund
Sector Academic/University
Country United Kingdom
Start 11/2013 
End 03/2014