Upcoming directives for emission limits on heavy-duty diesel vehicles (HDDV) in the USA, the EU, and in Japan will set high standards in performance of emission control systems to reduce pollutants, especially of NOx and PM. This is true for conversion performance as well as durability of these systems. Homogeneous SCR catalyst has been on the road in Europe and the US for many years by now with good performance in emission conversion as well as in on-road durability [5, 6, 7].
This paper reports the results of mechanical durability testing of homogeneous SCR catalyst. The work has been part of the qualification for the upcoming implementation for EURO4 as well as US07 into the production phase.
Much of durability data that has been published by now, does address specifically passenger car and light duty applications. Requirements, as spelled out by OEMs of the heavy-duty industry have been derived of different boundary conditions. Examples include different vibration levels, different temperature profiles, and significantly longer service life. In order to address these requirements, customized test procedures needed to be developed.
This paper presents results of evaluations in regard to mechanical fatigue of homogeneous SCR catalysts. Changes in mechanical strength of fresh as well as aged catalyst material were evaluated. The application of this data in regard to converter lifetime provides an indication of the high durability of homogeneous SCR catalyst in service.