Size, Shape and Support Effects on the Catalytic Activity of Immobilized Nanoparticles release_pxpfrmm4pzcknocdbfqbuhwzna

Abstract

Abstract: A brief overview of this PhD thesis, The emergence of nanotechnology has stimulated both fundamental and industrially relevant studies of the catalytic activity of noble metal nanoparticles. Palladium, ruthenium and gold are well known catalysts when used in nanoparticle- based systems. This body of work endeavoured to investigate the catalytic activity of these noble metal nanoparticles through three studies as a briefly overviewed below. Study 1: Palladium is a well-known catalyst, even in bulk phases, but its high cost had driven industry towards its use in nanoparticle- based systems well before nanotechnology had attracted the attention of the media. Palladium nanoparticles often show remarkable catalytic activity and selectivity, particularly for the hydrogenation of some unsaturated hydrocarbons, such as alkenes, alkynes and unsaturated carbonyl compounds. The nature of supports can affect the catalytic activity and selectivity of metal-support interaction. Natural polymeric supports, such as wool, can be suitable for new generation of composite materials incorporating nanosized metal nanoparticles and have the added advantage of being "environmentally friendly". Catalytic hydrogenation of cyclohexene to cyclohexane by palladium nanoparticles immobilized on wool was demonstrated by using a Parr high pressure hydrogenation set-up. The efficiency of the process was explored over loading rates from 1.6% to 2.6% of palladium nanoparticles (by weight) with a variety of particle sizes. Optimization of the reaction conditions including, stirring rate, amounts of reactants, gas pressure and target temperature, led to series of catalytic activity tests carried out for 5 or 24 hours (each) at 400psi H2 and 40 oC using a stirring rate 750 rpm. Product mixtures were analysed using gas chromatography (GC-FID) to determine conversions. Samples S1 and S2 proved to be the most active catalysts because the average Pd particle size was around ~5 nm and the particles were more accessible for the reactant (i.e., Pd [...]
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