Low and non-PGM materials for use in three-way catalytic converters in the treatment of gasoline exhaust

• Main Author: Watson, David Robert
• Published: Cardiff University 2015
• Subjects: 541; QD Chemistry
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.681275

The aftertreatment of vehicular exhaust has been a silent revolution in public health, however catalysts continue to be dependent on resources that are expensive, difficult to extract from the crust and are extremely expensive. This thesis sets out to address the problem of tightening legislation and the increasing scarcity of precious resources by taking steps away from the dependence on platinum group metals, either by reduction of their use or elimination. In Chapter 3 of this thesis, mechanochemical synthesis of perovskites was carried out with Ag doped LaMnO3 as well as a novel reactive grind process whereby nitrates were mixed in pestle and mortar and reacted with NaOH before being calcined. A reduced 3FI statistical design was carried out to determine the important variables in high energy ball mill synthesis and the interaction between these variables. In Chapter 4, Pt and Pd catalysts were synthesised via novel physical grind with acetylacetonate salt precursors along with base metal dopants (Co, Fe) and a combustion stage to produce highly dispersed and highly active catalysts with high activity in lean exhaust mixtures. The effects of weight loading of the base metals were investigated,focusing on the influence on particle size and activity. These catalysts showed moderate activity for exhaust aftertreatment reactions. Additionally Pt catalysts were synthesised in a variety of ways from a modified impregnation procedure utilising toluene to produce better dispersed metallic nanoparticles on the surface of a hydrophobic material such as SiC, SnO2, Si3N4 and BN,the SiC catalysts showed good activity towards both CO oxidation and propane oxidation as well as displaying the features of a WGS reaction and CO2 activation.