Development of Three-Way Catalyst with the Simultaneous Function of HC-Trapping and Ni-Free H2S Control 2007-01-1059
H2S, which causes the rotten egg odor, has been the one of gaseous components in interest and suppressed by the use of NiO as a scavenger since the start of automotive catalysts application to gasoline emission control in 1970s. Ni-free H2S suppression has been one of topics in gasoline emission control, because the controversial NiO is not permitted in some regions. It was found that some zeolites had unique H2S trapping capability from the powder screening works for the alternative H2S scavenger to NiO.
By combining the well-known property of HC-trapping ability of zeolites, zeolite-containing three-way catalysts were developed to suppress H2S as well as cold-start HC emission for gasoline engine powered vehicle.
The newly developed catalyst showed equivalent H2S suppression ability to the conventional NiO-containing catalyst at engine and vehicle test cycles that consisted of sulfur storage and release steps. Zeolite type was selected with respect to H2S trapping capability and thermal stability. The catalyst containing zeolite decreased the cold-start emissions that were ascribed to the improved HC trapping and TWC performance of the zeolite-containing catalyst.