Search Results

There is a need for an efficient, durable technology to reduce NOx emissions from oxidative exhaust streams such as those produced by compression-ignition, direct-injection (CIDI) diesel or lean-burn gasoline engines. A partnership formed between the DOE Office of Advanced Automotive Technology, Pacific Northwest National Laboratory, Oak Ridge National Laboratory and the USCAR Low Emission Technologies Research and Development Partnership is evaluating the effectiveness of a non-thermal plasma in conjunction with catalytic materials to mediate NOx and particulate emissions from diesel fueled light duty (CIDI) engines. Preliminary studies showed that plasma-catalyst systems could reduce up to 70% of NOx emissions at an equivalent cost of 3.5% of the input fuel in simulated diesel exhaust. These studies also showed that the type and concentration of hydrocarbon play a key role in both the plasma gas phase chemistry and the catalyst surface chemistry.

NOx emissions from a heavy-duty diesel engine were reduced by more than 90% and 80% utilizing a full-scale ethanol-SCR system for space velocities of 21000/h and 57000/h respectively. These results were achieved for catalyst temperatures between 360 and 400°C and for C1:NOx ratios of 4-6. The SCR process appears to rapidly convert ethanol to acetaldehyde, which subsequently slipped past the catalyst at appreciable levels at a space velocity of 57000/h. Ammonia and N2O were produced during conversion; the concentrations of each were higher for the low space velocity condition. However, the concentration of N2O did not exceed 10 ppm. In contrast to other catalyst technologies, NOx reduction appeared to be enhanced by initial catalyst aging, with the presumed mechanism being sulfate accumulation within the catalyst. A concept for utilizing ethanol (distilled from an E-diesel fuel) as the SCR reductant was demonstrated.