Titanium-doped nanocomposite of Al2O3 and ZrO2–TiO2 as a support with high sulfur durability for NOx storage-reduction catalyst

A nanocomposite of Al2O3 and a ZrO2–TiO2 solid solution (AZT) doped with Ti (Ti–AZT) was synthesized as a support for a NOx storage-reduction (NSR) catalyst in order to achieve sulfur durability. Ti–AZT maintained the original structure of AZT after the Ti doping step and exhibited lower basicity. Energy dispersive X-ray spectroscopy revealed that the Ti concentration on the Al2O3 particles was more than 10 at.% on average for a sample containing 3.3 at.% of doped titanium. Doped titanium was homogeneously distributed on the surface without the formation of discrete TiO2 particles. SO2-temperature programmed desorption at less than 823 K indicated that the catalyst containing Ti–AZT had larger sulfur desorption than that containing AZT. After sulfur aging tests, the Ti–AZT catalyst provided a large amount of NOx storage. The improved sulfur durability in the NSR catalyst resulted from the presence of TiO2 as a Al2O3–TiO2 solid solution in Ti–AZT.