Study Of Catalytic Properties Of La_1-yK_yCo_1-xFe_xO₃ For Reducing NO By Soot Under Lean Burn

Motor vehicle pollution has become one of the major air pollutants with the social development, accelerated urbanization and increase of vehicle fleet, which presents a great challenge to human survival and development. Lean burn can effectively reduce emissions of hydrocarbons and carbon monoxide but seldom nitrogen oxides. Therefore, the development of a catalyst that can remove carbon particles and nitric oxide simultaneously under Lean Burn is of great significance.Here we investigated the effect of substitution B site of catalyst LaCoO3 by Fe on its activity. It was showed that LaCoO3 exhibit the highest activity and conversed 19.19% NO into N₂ when the amount of introduced Fe was 0.2.Moreover the effect of substitution A site of the obtained catalyst LaCo_0.8Fe_0.2O₃ by K on its adsorption and activity. The catalyst can transform 26.83% NO to N2 at utmost. When the amount of introduced K was 0.1.The substitution by K in LaCo_0.8Fe_0.2O₃ could enhance the adsorption strength of reactant molecules on the surface and accelerate the reaction, which was caused by the increase of Co²⁺. In contrast too much K ion in the catalyst reduced Co²⁺ dramatically, resulting in decreased absorption intensity although adsorption sites were more than before.In addition the evaluation of the functions of oxygen during the reaction of NO-O₂-Soot was carried out by varying the concentration of oxygen in the system.It was found that oxygen played two important roles in the process. On one hand oxygen helped the formation nitrate or other nitrogen and oxygen intermediates from NO on the catalyst surface. On the other hand oxygen can oxidize soot into carbon monoxide which reduced the nitrogen-oxygen intermediates mentioned above into nitrogen.