Lean-Burn Natural Gas Engine Exhaust Remediation Using Nanostructured Catalysts and Coatings

Abstract

We have developed nanocrystalline catalytic systems with excellent thermal stability that reduce NO, CH4 and CO emissions from exhaust streams containing excess oxygen. Magnesium oxide, yttrium oxide and samarium oxide catalysts were synthesized using a controlled wet-chemical precipitation technique. This process produces nanocrystalline, high surface area metal oxide powders that can be easily coated onto monoliths and substrates. Greater than 50% conversion of NO to N2 was achieved in excess O2 at high space velocities with the nanocrystalline oxide catalysts. Nanostructured barium hexaaluminate coated with manganese oxide was used to aid in the complete oxidation of CO and CH4. The nanocrystalline oxide systems have superior hydrothermal stability compared to noble metal and zeolitic catalysts. Presence of water vapor in the feed stream resulted in only a slight loss of activity for the nanocrystalline Y2O3 system, the full activity of which was restored upon removal of water from the feed stream.