Oxidation of soot with modified silver catalysts

Thesis

As the demand for motor vehicles has soared dramatically with the emergence of rapidly developing countries, the need for regulating vehicle emissions and pollutants is increasingly more important. With the newest regulations for diesel particulate emissions soon to be enforced, there is a great need to catalytically convert soot particles from the exhaust into relatively less polluting carbon dioxide.

Here a supported silver catalyst is reported for the soot oxidation reaction. The silver catalyst is protected and supported using various capping agents and metal oxides, and modified using various synthetic methods. The catalysts are then tested with soot using thermogravimetric analysis (TGA) at a reaction temperature up to 700oC.

In order for a better design and modification of the silver catalyst, an improved understanding of the interaction between silver nanoclusters and the metal oxide support must be established.

XPS and UV/VIS spectroscopy are amongst the techniques used to probe the metal/metal oxide interaction. It is shown that the surface plasmon resonance of silver can be perturbed by the metal oxide support, modifying its band structure. It is also extremely important for the catalyst to be thermally stable up to 600°C for it to be employable in an exhaust system. In-situ XRD can be used to investigate the thermal stability of both the silver and metal oxide species in an oxidising environment. The phase changes, if any, of either species under heating can also provide a better understanding of the metal/metal oxide interaction and ultimately the soot combustion mechanism.

It has been demonstrated that different catalyst surfaces can have different catalytic performances. By altering the morphology of the support, preferential growth of one surface can be achieved, thereby modifying the catalytic performance for soot combustion.

Authors: Lau, A

• DOI: 10.5287/ora-mq6zqx8dm
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: Morphology Modification; Heterogeneous Catalyst; Soot Combustion; Meta;-Support Interaction; Size Effect
• Subjects: Chemistry