Development of a Methodology to Generate On-Board Diagnostic Threshold Selective Catalytic Reduction Catalysts for Heavy-Duty Diesel Applications

摘要

The On-Board Diagnostic (OBD) system of a vehicle monitors the engine and exhaust emission control components that can affect the emissions performance of the vehicle. When the Malfunction Indicator Lamp (MIL), also known as the "Check Engine" light, is illuminated, at least one emission related problem has been detected, and the driver is notified that vehicle service is needed. For heavy-duty diesel engine and medium-duty diesel vehicle applications, the California Air Resource Board (CARB) has mandated that heavy-duty OBD be implemented for all on-highway engines offered for sale in California, beginning with model year (MY) 2010. OBD monitoring requirements increase in stringency over a phase-in period between 2010 and 2016. Urea based selective catalyst reduction (SCR) technology is the primary technology to meet the US2010 diesel NO_x emissions standards in North America. Satisfying the OBD regulations requires the consistent generation of degraded SCR catalysts which are used to calibrate and validate OBD catalyst monitors to the required threshold. Unfortunately, current methods for the generation of such "threshold" parts are time consuming and subject to considerable variability, resulting in a significant test costs and inefficiency. The objective of this work was to develop a method to consistently age zeolite SCR catalysts to a targeted NO_x level. The approach utilized the SwRI FOCAS HGTR diesel burner technology to create a method that incorporated real time performance monitoring, embedded in a thermal aging cycle, allowing aging to be discontinued at precise levels of degradation.