Development of Low Temperature Active Three Way Catalyst 2019-01-1293
Today, technologies to increase fuel efficiency, such as the realization of increased engine combustion efficiency and the downsizing and turbocharging of the engine, are increasingly being applied in order to reduce automotive CO2 emissions. However, these technologies reduce the temperature of the exhaust gas supplied to the three-way catalyst. Three-way catalysts tend not to display their purification performance at engine start, when the catalyst temperature is low. Early warm-up of the catalyst is important to increasing purification performance.
It was considered that reduction of the thermal mass of the catalyst, which would boost the temperature rise performance of the unit, would be a key factor in realizing an early warm-up of the catalyst. 1) Reducing the weight of the substrate, and 2) Reducing the amount of washcoat are effective methods in reducing the thermal mass of a catalyst. Of these, Honda has already studied reduction of the weight of the substrate. If the amount of washcoat is simply reduced on an existing catalyst, while temperature rise performance will increase, the exhaust gas purification performance of the catalyst will decline after aging. This is a result of the fact that reduction of the amount of washcoat reduces the catalyst’s reactivity, thermal durability, and resistance to phosphorus poisoning.
Focusing on catalyst reactivity and thermal durability, the research discussed in this paper modified the alumina, OSC, and other materials and evaluated its temperature rise and purification performance in a vehicle. As a result, it was possible to improve both temperature rise performance and purification performance, and realize a reduction of approximately 20% in emissions. It was also verified that these technologies are able to comply with the US LEV3 and SULEV30 standards.