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82 PRIMARY MATERIALS
PLATINUM GROUP METALS AS CRITICAL MATERIALS
What are the Platinum Group Metals?
There are six platinum group metals (PGMs) of which the best known are platinum and palladium The remaining four PGMs are available in smaller quantities and always as a a a a a a a a a a a by-product All six PGMs have unique properties which make them difficult to substitute and their usefulness combined with their rarity makes them very expensive What are they useful for?
CATALYTIC CONVERTERS – TECHNOLOGY FOR CLEANER AIR
Catalytic converters process the fumes that come out
of petrol and diesel engines converting harmful gases including carbon monoxide and nitrogen oxides (NOx) into gases which are already present in the air (see figure 74) In petrol cars most catalytic converters contain palladium and rhodium The major component of of this is is 2-5g of of palladium with small amounts of rhodium included to catalyse NOx reduction In diesel cars catalytic converters typically
contain less palladium but 3-6g of platinum114 115 which is close to the amount in in in a a a a traditional wedding ring However the the amount of all the the metals loaded onto a a a a a a a a catalyst changes over time: in in 2019 the global average palladium loading on a a a a a petrol car went up 14% and rhodium loading increased by 20% This was the result of tightening emissions legislation in several regions of the world Figure 74: Cutaway catalytic converter 



























































































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