News Release

SwRI technology reduces heavy-duty diesel emissions to meet stringent CARB 2027 NOx requirements

CAT-DEF™ technology findings presented at WCX™ 2022

Reports and Proceedings

Southwest Research Institute


image: CAT-DEF™ technology is a catalyst- and surfactant-modified diesel exhaust fluid solution developed by Southwest Research Institute. SwRI engineers used this diesel exhaust system with urea injector and static mixer to conduct deposit testing. Cat-DEF technology can help automotive manufacturers meet emissions requirements and can be added to older and current diesel engines. view more 

Credit: Southwest Research Institute

SAN ANTONIO — May 4, 2022 — Southwest Research Institute (SwRI®) demonstrated the effectiveness of its patented and award-winning CAT-DEF™ technology during the WCX™ World Congress Experience in Detroit, which took place April 5-7. The internally funded advancement successfully reduced heavy-duty diesel engine nitrogen oxide (NOx) emissions to meet the California Air Resources Board (CARB) 2027 standards.

CAT-DEF, which stands for Catalyzed Diesel Exhaust Fluid, is an SwRI-developed catalyst- and surfactant-modified diesel exhaust fluid (DEF) solution. Today’s diesel engines use selective catalytic reduction (SCR), an advanced emissions control system, to abate NOx emissions. DEF is injected into the exhaust stream and ideally decomposes to form ammonia, which reacts with NOx on the SCR catalyst to form N2 and H2O.

Although the current process is relatively efficient at temperatures greater than 250°C, at temperatures below 250°C, urea-derived deposits form within the aftertreatment system. These deposits severely limit low-temperature NOx conversion and increase fuel consumption as high-temperature engine operations are required to remove the deposits.

SwRI’s novel technology decreases NOx and carbon dioxide emissions for diesel engines by significantly reducing undesirable deposit formation in exhaust systems.

“Although DEF technology has been utilized for more than a decade, the highest emissions control efficiencies could never be realized due to DEF’s tendency to create potentially harmful deposits in the exhaust system, particularly when the engine is operated at low loads and temperatures,” said Dr. Charles E. Roberts Jr., director of SwRI’s Commercial Vehicle Systems Department. “A combination of surface-active agents and heterogenous catalysts blended into CAT-DEF reduces deposits by 90% with potential reductions up to 98%.”


Using internal funding, SwRI engineers studied the technology’s effectiveness for reducing NOx emissions at the new standards set by CARB—known for enacting stricter standards than the Environmental Protection Agency—through a head-to-head comparison of diesel engines operated with and without CAT-DEF.

“We demonstrated that using CAT-DEF allowed an engine to meet or exceed upcoming CARB 2027 NOx requirements, while using standard DEF did not meet the new standard,” said SwRI Research Scientist Dr. Grant Seuser, one of CAT-DEF’s principal investigators, who alongside his fellow researchers shared their findings during a session on system integration and durability at WCX. “Our findings show that DEF can now be utilized over a much broader range of engine operation, decreasing overall NOx emissions.”

SwRI’s CAT-DEF technology is currently available to license. The novel innovation is backwards compatible and can be used in existing engines as a deposit reduction solution. For future applications, which will be required to meet more stringent regulatory requirements, the award-winning CAT-DEF solution competes with higher-cost engine hardware modifications currently being considered by the diesel engine industry and DEF manufacturers.

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