Three-Way Catalyst

Three-Way Catalyst

Catalysts which can convert hydrocarbons, CO and NOx in parallel are known as 3-way catalysts. They are used in all types of gasoline engines (e.g. motorcycles, stationary engines, sport boats, small engines). The conversion of the pollutants into CO2, water and nitrogen takes place on the precious metal coating of the catalyst.

A decisive factor for the effectiveness of the HeraPur® catalyst is the right fuel-air ratio (lambda =1). If there is too much air in the exhaust (referred to as "lean exhaust"), the conversion of nitrogen oxides does not function correctly. If there is too little air available ("rich exhaust"), the catalytic combustion of the hydrocarbons and CO is incomplete.

If the catalyst is to work as efficiently as possible, it is necessary that it functions as soon as possible after the motor has started. This is indicated by the so-called light off temperature – from this point the catalyst is active. It also plays a role in the ageing behavior of the catalyst. As a result of deposits from motor oils and extreme temperature loadings this starting temperature drifts to higher levels and the catalyst ages.

3-way catalysts of Heraeus combine several advantageous properties. For one thing, special additives make Palladium-rich coatings possible which perform to the required standard but at lower costs compared with Platinum or Rhodium coatings. At the same time only the smallest quantities of precious metals are necessary, which reduces costs considerably. The precious metals are specially stabilized in order to minimize thermal and other ageing effects. Depending on the intended application, the compositions of our coatings are adapted and tailor-made to meet the customer' s wishes. This results in very efficient catalyst coatings.

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