Development of Sustainable Solid-Supported Strong Acid Catalysts

Abstract

The United Nations sustainability goal twelve is to ensure responsible consumption and production. This includes the environmentally sound management of hazardous wastes, by preventing or minimizing the generation of hazardous wastes and eliminating or reducing the transboundary movements of hazardous waste. Heterogeneous acid catalysts have the potential to reduce or eliminate sources of acid waste from the industrial manufacturing of fine chemicals. This is achieved through physical separation and recycling of catalyst or through continuous synthesis over an immobilised catalyst. However, many potential heterogeneous acid catalysts have drawbacks that reduce their attractiveness over conventional homogeneous acid catalysts, such as cost or stability.

Organofunctionalised silicas are a group of chemicals that show promise in the application of heterogeneous acid catalysts. These are generally acid functionalised alkyl silanes, which are supported onto mesoporous silica, through covalent siloxane linkers. However, these have proven to be vulnerable to hydrolysis of the siloxane bond, leading to leaching of the alkylsilane into the reaction mixture and loss of catalytic performance. One proposed method of overcoming this limitation, is through materials known as dipodal silanes. These materials contain two silicon atoms and can form double the number of siloxane bonds, giving a potential 10,000 fold increase to the resistance to hydrolysis.

As current research into dipodal silanes has been limited to unfunctionalized alkyl silanes for use as hydrophobic coatings. This thesis contains our work in developing a successful synthesis of two different acid functionalised dipodal silanes. The analysis of mesoporous silica coated with these silanes, covering the quantity of supported silane, stability to hydrolysis and functionality as acid catalysts. As well as the development of an example plug-flow reaction, using these novel materials to proving their effectiveness in these conditions, with comparisons to commercially available competitors.

Date of Award	12 Nov 2025
Original language	English
Awarding Institution	University of Bath
Supervisor	Matthew Davidson (Supervisor) & Alfred Hill (Supervisor)