Abstract
This thesis comprises of the analysis of a commercial three way catalyst (TWC), as well as the discovery, development and analysis of a novel environmental pollution control catalyst for the abatement of automobile exhaust gases (namely CO by oxidation, HC (propane) by oxidation and NOX by reduction. All work was undertaken in collaboration with Blackthorn Autocatalysts, Chichester, West Sussex. The commercial TWC work comprised of two parts: (i) catalytic poisoning effects on the commercial TWC by metal compounds used in lead replacement petrol on activity of CO oxidation and HC oxidation. (ii) platinum group metal losses from the commercial TWC during laboratory simulation of an automobile exhaust gas during normal driving conditions. Here the author finds that (i) is more significant than (ii). The work on the novel catalyst also comprises of two parts: (i) The activity of a Keggin-type catalyst of the form [AlO4Al12(OH)24(H2O)12]7+ was compared to that of the TWC with respect to CO oxidation, HC oxidation and NOX reduction with varying Fe3+/Al3+ and Au3+/Fe3+/Al3+ substitutions. Comparisons of various preparative methods are made. Selected catalysts are characterised and probed in depth. (ii) A spinel-type catalyst of the form %Au/CoXFe3-XO4 was selected and activity with respect to CO oxidation, HC oxidation and NOX reduction with varying values of x and Au3+ loadings were compared to the TWC. It was characterised in full. Fe substituted Keggins-type catalysts proved to compare favourably with a commercial TWC in HC oxidation, but no CO oxidation and proved to be thermally unstable at the high temperatures experienced by TWCs. 1% Au containing cobalt-ferrite spinel-type catalysts of the form COXFe3-XO4 were x = 1.5 proved to compare very favourable when compared to the commercial TWC. Achieving lower LOTs for CO and HC oxidation under stoichiometric conditions. It was also found to be very active in NOX reduction under net reducing conditions. These Au/CoXFe3-XO4 catalysts were readily supported on pre-calcined Fecralloy at a level of 0.2 wt%, but more work is required to achieve higher loadings and higher activities. The application of such materials to the catalysis of environmental pollution control could be significant.