New Nissan Catalytic Converter Trims Exotic Metals Use by Half
For over a quarter century, catalytic converters have remained one of the most effective yet costliest ways to trim vehicle tailpipe emissions. Next week, Nissan will introduce a new variation on the theme that dramatically reduces the amount of the pricey metals like rhodium and platinum required to make them work when it rolls out the latest version of its Cube in the Japanese market. Currently, automakers are using about half of the world's rhodium and up to 80 percent of its platinum reserves as active scrubber elements that coat the substrates in conventional converters. Developed as part of its alliance with Renault, this new variation is both far less expensive to produce and far more efficient when it comes to reducing oxides of nitrogen (NOx) and non-methane hydrocarbon levels.
The reason why current converters require relatively greater amounts of rhodium and platinum is that their high internal temperatures cause these metals to cluster on the substrate. This, in turn, reduces the amount of functioning surface area and ultimately limits their cleaning properties. According to Masanori Nakamura, manager of the Nissan Research Center, his group attacked the problem in a way that revisited the design basics of converters: "Nissan engineers approached the problem from a physical perspective rather than a chemical perspective in order to achieve the breakthrough."
The key difference in the Nissan converter is that the precious metals on its substrate are separated by a "wall material" that prevents clustering in a way that Nakamura did not elaborate on -- save for likening it to "eggs protected in a bird's nest." However the process is accomplished, the net result is that less of these catalyzing elements are required to effectively get the job done. While the new Cube will see the first use of this ultra-low precious metal technology, it's also destined to appear on other Nissan and Renault vehicles with gasoline and/or diesel engines, and can be adapted to other non-automotive applications.