Regenerable sulfur traps for on-board vehicle applications

Abstract

Provided are improved regenerable SOtrap formulations for on-board vehicle applications. The regenerable sulfur trap formulations reduce the rate of sulfur poisoning of a downstream nitrogen storage reduction (NSR) catalyst trap in exhaust gas cleaning systems for combustion engines by adsorbing SOas metal sulfate under lean exhaust conditions and desorbing the accumulated SOunder rich exhaust conditions. The regenerable sulfur oxides trap catalyst compositions include a metal (M) oxide, wherein M is selected from Cu, Fe, Mn, Ag, Co and combinations thereof and a metal (M)-La—Zr oxide, wherein M is selected from Cu, Fe, Mn, Ag, Co and combinations thereof. In addition, provided are improved exhaust gas cleaning systems and methods for treating exhaust gas from a combustion source that include a hydrogen generation system, a regenerable sulfur oxides trap, and a regenerable nitrogen storage reduction (NSR) catalyst trap. The improved exhaust gas cleaning systems and methods allow for the sulfur released from the sulfur trap to pass through the nitrogen oxide trap with no or little poisoning of NOstorage and reduction sites, which significantly improves NSR catalyst trap lifetime and performance to meet future emissions standards. The disclosed exhaust gas cleaning systems are suitable for use in internal combustion engines (e.g., diesel, gasoline, CNG) which operate with lean air/fuel ratios over most of the operating period.