Platinum, environmental impact

The criteria for selection of a suitable oxidation catalyst for heavy-duty ethanol-fiielled vehicles in city traffic involve aspects such as regulated emissions (CO, NOx, hydrocarbons and particulates), emissions of unbumed ethanol, formation of acetaldehyde, acetic acid, and nitrogen dioxide. The oxidation of nitric oxide to nitrogen dioxide can be a problem when using highly active precious metal catalysts. This is especially the case when using platinum as active material (Pettersson et ai, 1994). NO2 is more toxic than NO and should be minimized at street levels. The catalyst with the highest activity for ethanol conversion is not necessarily the best choice if the minimum environmental impact is the objective. 

M. Schuster, M. Schwarzer, G. Risse, Determination of palladium in environmental samples, in F. Alt, F. Zereini (eds), Anthropogenic Platinum-group Element Emissions. Their Impact on Man and Environment, Springer, Berlin, 2000, pp. 173 D182. 

Akatsuka, K., McLaren, J.W. Preconcentration/separation methods for the determination of trace platinum in environmental samples by ICP-MS. In Zereini, F., Alt, F. (eds.) Anthropogenic platinum-group element emissions. Their impact on men and environment, pp. 123-131. Springer, Berlin (2000)... 

Zlschka M, Wegschelder W (2000) Reliability of and measurement uncertainty for the determination of Au, Pd, Pt and Rh for ICP-MS in environmentally relevant samples. In Zereini F, Alt F (eds) Anthropogenic platinum-group element emissions their impact on man and environment. Springer, Berlin, pp 201-214... 

The platinum-group metals Rh, Pd and Pt play a vital role in keeping the environment devoid of pollutants originating from vehicle exhausts. They are present in catalytic converters (which we discuss in detail in Section 25.8) where they catalyse the conversion of hydrocarbon wastes, CO and NO. (see Box 15.7) to CO2, H2O and N2. In 2008, the manufacture of catalytic converters used 81% of the rhodium, 47% of palladium and 44% of platinum consumed worldwide. The growth rate of environmental catalyst manufacture by companies such as Johnson Matthey in the UK is driven by legislative measures for the control of exhaust emissions. Regulations in force in the US and Europe have had a major impact on the levels of emissions and have improved the quality of urban air. Tighter control of vehicle emissions has now been introduced in most parts of Asia. 

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