Mazda Develops New Catalyst Material Structure for Autos That Reduces Precious Metal Requirements
01 October 2007
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| Mazda’s new catalyst structure. Click to enlarge. |
Mazda Motor Corporation has developed a new catalyst structure for automotive exhaust systems that substantially reduces the amount of precious metals such as platinum and palladium that are required.
The new development enables Mazda to reduce the amount of platinum and palladium used in automotive three-way catalysts by 70 to 90%. It does not result in any changes in the performance of purifying gas emissions and maintains the high durability of conventional catalysts.
In conventional catalysts, the precious metals that promote the chemical reactions that treat exhaust gases are adhered to a base material. Exposure to exhaust gas heat causes the precious metal to agglomerate into larger particles. This reduces the catalyst’s effective surface area and catalytic activity, which requires the use of a significant amount of precious metals to counter and maintain an efficient purification performance.
Mazda developed a new catalyst using its proprietary catalyst material structure and precious metal particles that are less than 5 nanometers (nm) in diameter. This is the first time that a catalyst material has been achieved that features single, nanosized precious metal particles embedded in fixed positions.
As a result, there is no agglomeration of the precious metal particles, and the amount of high-priced precious metals used in three-way catalytic converters can be reduced by 70 to 90%. Moreover, the new catalyst material will maintain the same level of purifying efficiency, with minimal deterioration over time even under the harshest operating conditions.
A related article covering Daihatsu's variation on this theme appeared on GCC almost two years ago.
http://www.greencarcongress.com/2005/11/daihatsu_introd.html
Reducing the cost of three-way catalysts is the obvious application and, essential if rapidly emerging economies are to tighten their own emissions standards more rapidly.
Cost reduction is even more important in the case of the lean NOx traps used for small diesels and stratified GDI engines - lean operation in part load saves a lot of fuel. Up to now, these have required large amounts of precious metals, one reason why LNTs have rarely been used up to now. However, it's not immediately clear if the washcoat matrix material used here will also work for the NOx adsorption material, e.g. barium oxide. Also, LNTs will always require ultra-low levels of fuel sulfur to minimize catalyst poisoning.
Posted by: Rafael Seidl | 01 October 2007 at 04:03 AM
The use of nanostructures to enhance the efficency of use of precious metal catalysis is vital to the future of cheap fuel cells.
Posted by: Ben | 01 October 2007 at 07:35 AM
Hopefully the described deposition techniques will not (substantially) offset the cost reductions achieved through using less precious metal.
If the cost reduction is commensurate with the material reduction, retrofitting off-road vehicles (lawn mowers, atvs, blowers, even motorcycles) with three way catalysts should be reasonably inexpensive.
It may even be reasonable to mandate stricter emission stanards for trains, class 8 tucks, and other hdvs.
Such emission reductions (via catlayst retrofit) should be considered low hanging fruit, imho (assuming lower price levels for cats).
Posted by: GreenPlease | 01 October 2007 at 08:19 AM
Hopefully the described deposition techniques will not (substantially) offset the cost reductions achieved through using less precious metal.
If the cost reduction is commensurate with the material reduction, retrofitting off-road vehicles (lawn mowers, atvs, blowers, even motorcycles) with three way catalysts should be reasonably inexpensive.
It may even be reasonable to mandate stricter emission stanards for trains, class 8 tucks, and other hdvs.
Such emission reductions (via catlayst retrofit) should be considered low hanging fruit, imho (assuming lower price levels for cats).
Posted by: GreenPlease | 01 October 2007 at 08:31 AM
@ GreenPlease -
I can't access the source link provided in the article, so I don't know if Mazda - or rather, its monolith supplier - is using a non-standard manufacturing process to implement this.
The usual process is to simply dunk the ceramic monolith in a washcoat bath containing both the washcoat matrix and the dispersed precious metals. I think all they did was switch to a different matrix material that reduces the mobility of the catalytically active sites at high temperatures. Of course, only the ones that end up on the exposed surface of the washcoat actually do anything at all.
Even greater reductions in precious metal usage would require a two-stage process in which the pure washcoat matrix is applied first and the precious metals deposited exclusively on the matrix surface second. They'd have to be kept well dispersed in the bath somehow, though.
Posted by: Rafael Seidl | 01 October 2007 at 02:05 PM
Greenpease -- For the past few years, most motorcycles have been delivered with catalytic converters, and the number of models with them is increasing every year. Granted, I don't think there is a Harley on the road with the stock exhaust, but that's a different problem. (And one that would be easily fixed with a little enforcement, there are already federal laws in place regarding tampering with emissions equipment, and the necessary noise laws are already on the books in most states.)
Posted by: rob | 01 October 2007 at 03:36 PM