Automobile catalytic converters are comprised of precious metals and it is on the surface of these metals that the reaction takes place which turns harmful emission gases into harmless ones. A key focus in catalyst technology has been how to expose as much surface area as possible and to avoid deterioration due to agglomeration. Conventionally, precious metal particles are adhered to a base material. However, heat from the exhaust gas causes the particles to collect together and agglomerate to form larger particles. This reduces the surface area of precious metals and deteriorates their performance as catalysts. To counter this effect, large amounts of precious metals must be used in conventional catalytic converters.
Mazda took advantage of single nanotechnology* to realize a new and unique catalyst structure in which precious metal particles are individually embedded in to the base material.
* Single nanotechnology: a technology to control finer materials structures than nanotechnoloty
The new catalyst has two main features.
- It inhibits the thermal deterioration caused by the agglomeration of precious metal particles
- It offers a significant improvement in oxygen absorption and release rates for enhanced emissions clearingpurification
With these features, the amount of precious metals needed to ensure the same level of effectiveness is reduced by 70 to 90 percent compared to previous products. At the same time, the performance of the catalytic converter is almost unaffected by harsh driving styles.
This technology has significantly reduced the amount of expensive precious metals such as platinum, palladium and rhodium needed for three-way catalysts to effectively clean purify gasoline engine exhaust emissions.
Previously, Mazda's platinum group metal (PGM) single-nanocatalyst technology was suitable for use only in underfloor convertors. Improving properties such as its heat resistance and low-temperature purification performance, has enabled its use in convertors connected directly to the engine where conditions are much severe.
In addition to fixing the PGM in the support material, the support material itself is fixed in extremely heat-resistant oxide ceramic suppressing the tendency of the catalyst to agglomerate (clump together) leading to a deterioration in performance. This makes possible its use in directly connected convertors. It also leads to a significant reduction in the use of precious resources, such as rare metals and rare earth materials which are used in the support materials.
This technology was first introduced with the facelifted Demio featuring SKYACTIV-G 1.3 in July 2011, and has been progressively introduced to SKYACTIV engine models since that time. It is also suitable as a catalyst in diesel particulate filters which remove soot from diesel engines and is employed in Mazda's new generation clean diesel engine SKYACTIV-D.
PGM Single Nano Size Particle Catalyst Technology