Umeno, T., Hanzawa, M., Hayashi, Y., and Hori, M., "Development of New Lean NOx Trap Technology with High Sulfur Resistance," SAE Technical Paper 2014-01-1526, 2014, doi:10.4271/2014-01-1526.
In this study several NOx storage materials have been investigated to see their NOx storage properties. And sulfur release properties of these materials have been also investigated. Based on these findings, new LNT catalyst was developed. In this new LNT catalyst Barium is supported on one basic material, and Strontium is coated in the whole catalyst with high dispersion. And it shows higher NOx storage performance against conventional LNT one even though 10g/L of sulfur was introduced to the catalysts.According to analysis results of new LNT catalyst after sulfur poisoning, it was found that sulfur was mainly adsorbed on Strontium selectively, and then it formed sulfate compound as SrSO4. On the other hand, another sulfate compounds could be hardly observed. And regarding Barium on basic material some analysis measurement said that it has not only better NOx storage function, but also better sulfur release function. The assumption why new LNT catalyst has high sulfur resistance is that Strontium works like scavenger effect against sulfur, therefore it enables to keep higher NOx storage performance by Barium even if it contains much sulfur amount in the catalyst.