Analysis of HC and CO Pollutants in Relation to the Physical Properties of Noble Metal Catalysts under Varying Engine Conditions

This study explores the environmental implications of automobile emissions in relation to the sourcing and performance of platinum group metals used in catalytic converters. Platinum group metals such as platinum, palladium and rhodium are critical components in emission control technologies, but are sourced through energy-intensive mining processes that themselves have significant environmental footprints. The combustion of fossil fuels in vehicles contributes heavily to air pollution, releasing hydrocarbons and carbon monoxide, especially under varying engine loads and speeds. Catalytic converters, coated with noble metal catalysts, mitigate these pollutants. However, their performance is influenced by the structural properties and degradation of the catalyst over time. Using a fresh catalytic converter embedded with noble metal catalysts, emissions were analysed on a research engine test bench. Results showed that usage alters catalyst surface area, pore structure, and noble metal content, affecting conversion efficiency. Emissions of HC and CO were notably higher at low engine loads and speed conditions common in urban environments, highlighting both the role and limitations of noble metal catalysts in emission control. This study links the environmental costs of mining noble group metals with their downstream benefits in reducing vehicular emissions, offering a broader perspective on the lifecycle impact of clean air technologies. Major Findings: Hydrocarbon and carbon monoxide emissions are higher at low engine load and speed due to incomplete combustion, subsequently decreasing as load and speed increase. Driving conditions in cities are characterised by lower speeds, which contribute to higher pollution levels. Analysis of a fresh catalytic converter showed notable alterations in pore structure and surface area during operation, such as relating to engine conditions, catalyst degeneration and emission levels.