Evaluation of SCR Catalyst Technology on Diesel Particulate Filters

Selective Catalytic Reduction (SCR) catalysts have been demonstrated as effective for controlling NOx emissions from diesel engines, maintaining high NOx conversion even after the extended high temperature exposure encountered in systems with active filter regenerations. As future diesel emission regulations are expected to be further reduced, packaging a large volume of SCR catalysts in diesel exhaust systems, along with DOC and particulate filter catalysts, will be challenging. One method to reduce the total volume of catalysts in diesel exhaust systems is to combine the SCR and DPF catalysts by coating SCR catalyst technology on particulate filters. In this work, engine evaluation of SCR coated filters has been conducted to determine the viability of the technology. Steady-state engine evaluations demonstrated that high NOx conversions can be achieved for SCR coated filters after high temperature oven aging. The effect of soot loading on back pressure as well as the time for soot regeneration was investigated for SCR coated filters and compared to conventional oxidative catalyst coatings. Hydrocarbon, CO, and NOx emission performance during a filter regeneration condition has also been evaluated. The SCR coated filter technology has also been demonstrated on several filter materials.