The rational synthesis and catalytic testing of heterogeneous multimetallic nanoparticles for the hydrogenation of CO2

Crawley, James 2023. The rational synthesis and catalytic testing of heterogeneous multimetallic nanoparticles for the hydrogenation of CO2. MPhil Thesis, Cardiff University. Item availability restricted.

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Abstract

It has been documented for over a century that metal surfaces can act as catalysts for many different reactions, such as the Fe-based catalyst used in the Haber-Bosch ammonia synthesis. For many decades, metal nanoparticles, defined as particles less than 100 nm in diameter, have become widely used as catalysts for many industrially important reactions, including hydrogenations, dehydrogenations, oxidations, reductions, and more. The nanoscopic size of a metallic nanoparticle results in extremely high surface area to volume ratios, which in turn results in a large number of catalytic sites per quantity of material used. Since catalyst design focuses on the highest activity and selectivity towards the desired product using the least material possible, metal nanoparticles have become an attractive choice. Multimetallic nanoparticles, which include more than one metal, have become increasingly popular over the past two decades. Synergistic effects between metals have been reported by many research teams. A wide array of publications have indicated a superior catalytic activity and selectivity towards the desired product when adding a second, or even a third metal, to a nanoparticle catalyst, when compared to monometallic catalysts. When designing a multimetallic nanoparticle catalyst for application in an industrial reaction, there are many factors to consider. Particle size, shape, morphology, structure, and molar ratio between metals are all highly important. Small alterations to even one of these factors can have a dramatic impact on catalytic performance. Many traditional synthesis methods still commonly used today, such as wet and incipient wetness impregnation, are crude processes that afford poor control over these factors. This is especially an issue in the design of multimetallic nanoparticles, which are more complex than monometallic nanoparticles. A highly rational synthetic procedure known as Strong Electrostatic Adsorption (SEA), developed by John Regalbuto, has been investigated in the synthesis of supported multimetallic Pd-containing nanoparticles as catalysts for the hydrogenation of CO2 to methanol. Methanol is a highly important industrial chemical – 53 million tonnes were consumed in 2011 alone – and this process is important for CO2 capture. The SEA method involves altering the pH of the solution to induce a charge on the supporting material, maximising electrostatic interaction between the supporting material and the metal precursors to yield small nanoparticles around 1 nm in diameter.

Item Type:	Thesis (MPhil)
Date Type:	Completion
Status:	Unpublished
Schools:	Chemistry
Funders:	C2C WP2
Date of First Compliant Deposit:	5 March 2024
Last Modified:	06 Mar 2024 09:10
URI:	https://orca.cardiff.ac.uk/id/eprint/166891

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