Effect of sulfur in gasoline on NOx conversion properties of lean NOx catalysts

摘要

Effects of sulfur in gasoline on exhaust emissions were studied on vehicles equipped with different types of lean NOx catalysts, where all catalysts were incorporated basic oxides as NOx adsorbents. Some of newly launched vehicles were found to have enough performance to keep the NOx abatement by the vehicle chassis dynamometer using a regular gasoline (sulfur level 30 wt-ppm). To compare these lean NOx catalysts' own performances and characteristics, the under-floor catalysts were sampled and characterized before and after the 10,000 km run. Poisoning experiments by synthetic exhaust gas reactor with SO_2 were demonstrated to reproduce almost the same NOx performance as for the 10,000 km aged catalysts. The Na and K containing catalysts exhibited to have the advantage of anti-sulfur ability (probably, easier sulfur desorption) as compared with the Ba catalyst. NOx and sulfate storage and regeneration mechanism under the lean/rich modulation were discussed.