Low-Level NOX Sensor for Diesel Emissions Systems

To meet the environmental regulations mandated by governments world-wide, the diesel vehicle industry requires improved NOX sensors capable of quantifying total NOX (NO and NO2) at low ppm levels. Furthermore, regulations dictate a sharp decline in NOX emissions from both mobile and stationary sources, impacting a wide range of applications, including heavy duty diesel trucks and passenger cars. Currently, only one sensor is commercially available, and it lacks the low concentration accuracy and fast response time to meet these growing needs. NexTech Materials has developed a new NOX sensing technology that leverages a unique electro-catalytic effect to rapidly and selectively measure NOX in diesel exhaust streams at concentrations as low as 1 ppm and with response time less than 200 milliseconds. Additionally, NexTech has demonstrated the potential for tuning its sensor to also detect ammonia emissions, enabling quantification of both NOX and ammonia in a single sensor device. In the Phase I project, NexTech improved the response magnitude, long- term stability, and dual ammonia sensing capability of its baseline sensor through materials formulation and sensor design modifications. A prototype package and controller was designed and fabricated to support product demonstrations which generated tremendous interest among diesel vehicle manufacturers and Tier-1 automotive suppliers. In Phase II, NexTech will build upon the core technology improvements developed in Phase I, focusing on further improving ppm-level NOX sensitivity, dual NOX and ammonia sensing, and long-term stability. Guided by input from target OEM customers, the dual NOX/NH3 sensors will be evaluated under a comprehensive set of test conditions and fully packaged prototype sensors will be provided to customers for engine evaluation. Commercial Applications and Other Benefits Successful completion of this project will result in a sensor with improved performance and lower cost than commercially available NOX sensors, enabling lower emissions and improved competitive pricing to vehicle manufacturers. Additionally, the low ppm accuracy will have applicability in off-road and industrial applications, which are becoming increasingly regulated. The dual ammonia sensing capability offers further benefit in exhaust systems employing selective catalytic reduction (SCR) abatement systems, in which ammonia slip into the exhaust stream is a common issue. Accurate quantification of both NOX and ammonia will allow exhaust system developers to operate SCR systems more effectively, enabling significantly reduced NOX emissions over traditional approaches.