Platinum Metals Rev., 1977, 21, (4), 121
Catalysts for Automobile Emission Control
While the hydrocarbons and carbon monoxide emitted from automobile exhausts can now be catalytically oxidised very satisfactorily a number of different approaches are still being pursued for the control of nitrogen oxides. In a recent paper J. C. Schlatter and K. C. Taylor of General Motors Research Laboratories report work carried out on the addition of platinum and palladium to rhodium catalysts to improve their oxidising capacity when used for the simultaneous control of all three pollutants (J. Catalysis, 1977, 49, (1), 42-50). It was found that an improvement could be achieved in the laboratory and initial associated disadvantages were later avoided.
The results obtained using laboratory feedstream are not always substantiated when engine exhaust tests are carried out and these have still to be done. It is however reported that for enhanced performance the platinum or palladium, should not be deposited on the same support beads as the rhodium. The two sets of beads can then be separately positioned, with the rhodium catalyst in the front of the catalytic bed. In this way each material is in the environment most suited to its catalytic purpose.