Development of highly efficient double-substituted perovskite catalysts for abatement of diesel soot emissions

Abstract

Strontium-substituted LaCoO₃ and double-substituted La_0.9Sr_0.1CoO₃ by Cu, Fe and Ni perovskite catalysts were prepared via citric acid sol–gel method. The precursors were calcined at 750 °C in stagnant air. The precursor of the catalyst showing the best activity for soot oxidation was also reactively calcined in a flowing reactive mixture of 4.6 % CO in air at 750 °C. The catalysts were characterized by N₂-sorption, XRD, FTIR and SEM. The substitution of Sr in LaCoO₃ enhanced the activity of the catalyst. Further, increase in the activities of the catalysts was observed for double substitution of Cu, Ni and Fe in La_0.9Sr_0.1CoO₃. The catalyst formulation La_0.9Sr_0.1Co_0.5Fe_0.5O₃, calcined in air (Cat-5A) and reactively calcined (Cat-5B), showed higher activities than other four optimized catalysts composition calcined in air. Cat-5B exhibited the best activity resulting in total soot combustion at the lowest temperature of 325 °C. The best performance of Cat-5B was associated with its partially reduced perovskite phase as a result of reactive calcination leading to lattice vacancies and defects. Cat-5B has good thermal stability found in a repeated cycles of soot combustion experiments.