Although diesel engines are more fuel efficient than their gasoline counterparts, increases in fuel economy are still needed. Coincidentally, environmental policies now require significant decreases in tailpipe NOx, HC, CO, CO2 and PM emissions from diesel engines. To meet the fuel economy demand, low temperature combustion (LTC) engines have been developed. Although the relatively low temperature of conventional diesel engine exhaust is already a challenge for emissions control, especially during cold start and under idling conditions, low temperature combustion engines have 40 to 70C lower exhaust temperatures which means lower catalyst activity. These advanced combustion engines produce lower NOx and particulate matter (soot) emissions than current diesel engine technologies, but emit higher levels of other pollutants, specifically CO and hydrocarbons (HCs). The lower temperature exhaust combined with higher levels of CO and HCs are especially problematic. As a result, the LTC engine may have better fuel economy, but produce significantly higher emissions, as today?s catalytic converter technology is inefficient at such low temperatures. A solution is clearly a more active catalyst technology. This is simple to state, yet difficult to achieve.
A novel approach to achieving catalyst activity control has been proposed in response to the joint National Science Foundation and Department of Energy solicitation on Advanced Combustion Engines. The joint Agency award is made through the NSF Chemical, Bioengineering, Environmental and Transport Systems Division and its Catalysis & Biocatalysis Program to Professors William Epling, Michael P. Harold, Dan Luss, Lars Grabow, and Vemuri Balakotaiah from the University of Houston (UH) and James Parks from the Oak Ridge National Laboratory (ORNL). The team will use their extensive background knowledge in this area to tailor design catalysts, specifically by optimizing the catalyst composition along the length and diameter of the catalytic converter to take advantage of pollutant concentration and temperature profiles that exist under normal operation. This will ultimately lead to lower temperatures required to achieve high pollutant conversions. Understanding and exploiting the temperature and concentration profiles is a technique still in its infancy, and this novel approach can enhance efficiency for not only exhaust emissions catalysts, but for virtually all catalytic systems.
The research team from UH and ORNL is uniquely poised to meet the challenge, through research spanning the molecular to engine level, and with expertise in engine exhaust emissions catalyst synthesis and characterization, reaction modeling and engineering, and combustion and vehicle testing, in state-of-the-art facilities spanning high performance computer clusters, advanced catalyst characterization, bench-scale catalytic reactors and fully-instrumented engines. By simulating the reactions at the molecular level, novel material combinations will be discovered. Lab-scale studies will allow measurement of gas concentration and temperature profiles along the catalyst bed. These measurements will be used to build a computer model of the system, which will in turn be used to predict the optimal catalyst composition along the bed. These predictions will be used to synthesize new catalyst designs to be tested at the lab and engine scale. The results will ultimately be shared with major catalyst manufacturers for their review.
A major emphasis of the proposed research is the education and training of graduate and undergraduate students. The students will be using advanced theoretical, computational and experimental tools, training them to become capable chemical engineering researchers. The research will provide the students with a perspective in applying engineering tools to solve environmental problems. The students will also participate in research at the UH Texas Center for Emissions and Fuel Research, where they will have the opportunity to work alongside engineers and industrial collaborators who are developing and testing new technologies on full-scale engines. This project will include junior-level undergraduate students, with targeted recruiting of underrepresented groups. Each undergraduate researcher will be assigned an individual project that is appropriate for their skill level and knowledge. Each will have a graduate student mentor to assist with supervision and advising, also providing the graduate student with supervisory skills training. Ultimately, it will provide graduate students with training for industrial and academic careers and provide undergraduate students with research experience and motivate them to pursue graduate studies. The data will also be posted on the Cross-Cut Lean Exhaust Emissions Reduction Simulations (CLEERS) group website database, accessed by industry, academic and national lab colleagues to better understand new catalyst technologies and develop and tune in-house models.
