Cerium – The Mystery Ingredient in Car Catalysts

Most of us think of platinum, palladium and rhodium in connection with automotive catalysts. There is more to their chemistry, however. At the recent conference of the International Precious Metals Institute (IPMI), Dr. Stefan Steinlechner of the Chair of Nonferrous Metallurgy at the University of Leoben, Austria, reported about a new method of recovering cerium from spent automotive catalysts which they developed for a partner company. Why is Cerium in car catalysts, and why is it such a challenge to recover it? Tech Metals Insider spoke with Dr. Steinlechner to find out.

“Cerium is a component in what is called the ‘washcoat’ of the catalyst. Purpose of the washcoat is to increase the surface area of the catalyst, and – in the case of cerium – to serve as a storage for oxygen. Cerium increases the durability of a catalyst In case of incomplete combustion cycles in the engine.”

According to Steinlechner’s findings, cerium is not the only rare earth element in automotive catalysts but by far the most prominent. The exact chemistry of each type of catalyst is a secret closely guarded by its respective manufacturer. Despite recent price drops for most rare earth elements, this group of materials is now on the “watch list” of many consumers and producers alike, who have become aware of the price sensitivities involved.

For comparison, Steinlechner pointed out that an average automotive catalyst, which may weigh anywhere between 500g and 2,500g in a standard car, will contain just 0.2-0.3% of precious metals but between 3 and 5% cerium.

“Conventional pyro metallurgical recycling processes will leave behind rare earth elements in their slag fraction where they are lost. Our hydrometallurgical process will remove them from the surface of the catalyst inward, which makes recovery easier.” Steinlechner adds that cerium is also used in larger amounts as a polishing agent in the glass industry where residues are more concentrated, and therefore have been recycled for some time already.

“Almost 50% of the world’s cerium usage is in automotive catalysts today. While China has only about 30-35% of the world’s resources of cerium, 95% originates from there”, explains Steinlechner. Increasing the recycling rate from automotive catalysts and elsewhere has become a crucial step to add stability to the future supply of this rare earth metal.

By Bodo Albrecht