Research into Eliminating Particulate from Diesel Engine Exhaust over Zeolite Covered with Catalysts of Perovskite-Type Oxides

The soot and NOx coming from diesel emissions can be considered as a dangerous pollutant, and have been causing serious environmental and health problems. To meet the increasingly stringent legislation for soot emission, the catalytic technology was used to eliminate soot emission from diesel exhausts. The catalysts, the perovskite-type oxides impregnated over zeolite supports (HTS, HZSM-5, RPSA, ZRP), were synthesized by lower-temperature citric acid-ligated impregnation method. The catalyst samples were characterized by XRD and SEM. The XRD patterns show that the perovskite-type oxides (ABO₃) were loaded on zeolite supports because of the characteristic diffraction peaks of ABO₃ structure at 32.5°, 47°, and 57.7°. The SEM images show that the perovskite-type oxides were spread equably on zeolite surface. The catalytic activity of the samples for diesel particle oxidation with a NO-O₂ mixture was investigated by temperature-programmed reaction. The catalytic activity of the catalysts varied with the sort of zeolite supports (HTS, HZSM-5, RPSA, ZRP). In LaMnO₃/HZSM-5 catalyst, the partial substitution of La³⁺ at A-site by alkali Cs⁺ enhanced the catalytic activity for the oxidation of particle, and the Tm and Sco₂ were 438°C and 87.28%.