Thermal stability of Pd-containing LaAlO3 perovskite as a modern TWC

TWC activity and thermal stability of LaAlO3-based Pd catalysts were investigated under simulated gasoline engine exhaust conditions. The LaAlO3-based catalysts revealed a stronger thermal stability than the conventional Al2O3-based ones. Pd-substituted for Al in the LaAlO3 perovskite structure exhibits a stronger thermal stability than that impregnated on the LaAlO3 surface. The increased electron density around Pd induced by the electron donation from the more electronegative La may enhance the thermal stability of PdO by suppressing the decomposition of PdO. The strong interaction between Pd and La appears also contributing to the improvement of the TOFs for the TWC reactions over the Pd-substituted LaAlO3 (i.e., LaAlPdO3) catalyst, as evidenced by CO-chemisorption, TGA, XPS, XANES, H-2-TPR, DRIFT and TPD studies. CO and C3H6 oxidation reactions over the LaAlO3-based Pd catalysts are strongly structure-sensitive, while those over the Al2O3-based Pd catalysts are weakly structure-sensitive. The NO reduction and H-2 oxidation reactions are strongly structure-sensitive over all the Pd-containing catalysts examined. (C) 2015 Elsevier Inc. All rights reserved.