Nanocomposites for nitrogen oxide emissions control in lean-burn engines

摘要

(cont.) reducing agent than propane in the SCR of NO. Pt-Rh/CuO/A1₂O₃ nanocomposites capable of adsorbing SO₂ in oxygen-rich environment as metal sulfates and releasing SO₂ in reducing atmosphere were synthesized with sequential precipitation technique. These CuO-based sorbents possessed excellent SO₂ adsorption capacity and superior regenerability by CO compared to those produced by the impregnation method due to higher surface area and dispersion of Cu species. A gram of sorbent with 30 wt% Cu could adsorb over 50 mg of SO2 before SO₂ breakthrough was observed. The rate of SO₂ desorption from the CuO/A1₂O₃ sorbents could be enhanced through the incorporation of noble metals. With the use of 0.1 wt% Pt, the CuO/A1₂O₃ sorbent with 30 wt% Cu could be regenerated twice as quickly. Also, on average only 8 ppm of SO₂ were detected downstream of this sorbent over each adsorption cycle at 400⁰C. The excellent sorbent regeneration was attributed to better CO adsorption and lower sulfate decomposition temperature as a result of Pt addition. The nature of sulfur deactivation of these sorbents was highly dependent on the composition of noble metals used. By employing both Rh and Pt, sorbent regeneration rate and stability could be optimized. Rh/CuO-MgO/A1₂O₃ nanocomposites capable of adsorbing NOx and SO₂ in oxygen-rich environment and releasing N₂ and SO₂ in reducing atmosphere were successfully prepared by sequential precipitation ...