Selective catalyst reduction (SCR) using cordierite honeycomb substrate is generally used as a DeNOx catalyst for diesel engines exhaust in both on-road and commercial off-highway vehicles to meet today’s worldwide emission regulations. Worldwide NOx emission regulations will become stricter, as represented by CARB2027 and EuroVII. Technologies which can achieve further lower NOx emissions are required.
Recently, several technologies, like increased SCR catalyst loading amount on honeycomb substrates, and additional SCR catalyst volume in positions closer to the engine are being considered to achieve ultra-low NOx emissions. However, undesirable pressure drop increase and enlarging after treatment systems will be caused by adopting these technologies. Therefore, optimization of the material and honeycomb cell structure for SCR is inevitable to achieve ultra-low NOx emissions, while minimizing any system drawbacks.
Since the SCR catalyst generally being used in the market today is coated on the honeycomb wall, the main approaches of improving DeNOx performance are making the wall thin and increasing the cell density. In addition to these, NGK has developed a high porosity cordierite substrate that allows the catalyst to fill into the wall [SAE 2014-01-1528] [1]. This time, NGK succeeded in improving performance of conventional thin wall and high cell density substrates by further improving high porosity material toward future regulations.
In this paper, performance of both high and conventional porosity on thin wall, high cell density substrates have been compared under different catalyst loading amount conditions, the standard catalyst amount for the current regulations, and a higher amount for future, tighter, regulations. DeNOx performance, pressure drop, and light-off property has been evaluated. In addition, mechanical strength and thermal resistance has been also evaluated to assess concerns on high porosity material. With these results, we will show how this innovation will bring benefits to future after treatment systems.