Sustainable catalysts for sustainable fuel production

Whitelegge, James 2024. Sustainable catalysts for sustainable fuel production. PhD Thesis, Cardiff Univeristy. Item availability restricted.

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Abstract

The Guerbet reaction has a long industrial history for the generation of useful long chain alcohols, it has received renewed interest in recent years due to the potential for sustainable fuel production. Several isomers of butanol have desirable gasoline-like properties and can be used as a replacement transportation fuel. Biorenewable ethanol can be coupled using the metal catalysed Guerbet reaction to produce biobutanol. The homogeneous catalysts used for this are typically based upon the platinum group metals ruthenium and iridium equipped with phosphorus donating species. This thesis aims to reduce the reliance upon these rare, expensive, or difficult to handle species as catalysts for the Guerbet. Taking inspiration from the work of Gusev and co-workers, Sulfur was identified as an alternative for phosphorus. The catalytic activity of a range of SS-, SN- and SNS-donor ligands on ruthenium were explored. The pyridine-based ruthenium SNS-pincer complexes emerged as an exceptionally active catalytic system for the Guerbet synthesis of n-butanol from ethanol. A range of these compounds was then prepared and tested for catalysis, with the structure-activity properties of these complexes investigated. A fully phosphorus free form of the highly active ruthenium SNS-complexes based upon the Ru(dmso)4Cl2 species was prepared. This complex demonstrated notable activity to the Guerbet reaction as one of the most active fully phosphorus-free catalysts ever reported. A series of NMR spectroscopy experiments were then performed which have supported a proposed mechanism. Copper was then explored as an alternative for the platinum group metals typically used as catalysts for the Guerbet synthesis of isobutanol from ethanol and methanol. A range of simple copper salts were explored, and a conditions optimisation was performed which has led to the development of a copper catalytic system which performed similarly to some of the manganese systems in the literature. The application of amines and an investigation of homogeneity or heterogeneity suggested that the active species is not homogeneous.

Item Type:	Thesis (PhD)
Date Type:	Completion
Status:	Unpublished
Schools:	Chemistry
Date of First Compliant Deposit:	12 September 2024
Last Modified:	13 Sep 2024 09:53
URI:	https://orca.cardiff.ac.uk/id/eprint/172052

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