Research On Automotive Exhaust Catalyst Of Nano Rare Earth Peroskite-type

The La_0．6 Sr_0．4 Ni_1-xCu_xO₃(x=0．0～1．0) perovskite-type catalysts were synthesisedby Sol-Gel method using citric acid as the chelating agent and the precursors werecalcined at 650℃,750℃,850℃under the atmosphere of air. The experimentalprocess and the samples were characterized via X-ray diffraction (XRD), scanningelectron microscope (SEM), the specific surface area mensuration(BET), ThermoGravimetric Analysis(DTA-TG), temperature-programmed reduction of H₂ technique(H₂-TPR) and X-ray Photoelectron Spectroscopy(XPS).The conditions of preparationcraft, structures and surface morphologies technology, reducibility and the superficialelement chemistry conditions have been studied.The perovskite-type oxides La_0．6 Sr_0．4 Ni_1-xCu_xO₃(x=0．0～1．0) powder samples havebeen synthesized successfully The XRD results showed that all the powdersamples(x=0．6) were perovskite-type compounds and there were neither simple metaloxides nor any other secondary phases The La_0．6 Sr_0．4 Ni_1-xCu_xO₃(x=0．6) samples wererhombohedral perovskite-type lattice and have fairly good structural stability. With theincrease of x, the main diffraction peaks of XRD shifted to high angles, whichrepresented a distortion to large size of the crystal cell. Through by SEM the powdercould be identified as porous structure. the specific surface area mensurationobservation showed that the specific surface area was greater over 10m²/g . Thethermal decomposition process has been studied by TG-DTA technique. Smooth TGcurves were obtained at about 650℃, which indicated perovskite structure wereformed.. The samples was examined by H₂-TPR and the result showed that there werethree types of Oxygen species in the structure. The results of XPS showed that therewere two types of Oxygen in the structure and three types of chemistry states insurface texture.and there were two types of chemical states of Nikel and only one typesof chemical states of Copper on the sample surface.The best dehydration temperature of the Sol should be at 70℃～80℃, The drytemperature of the Gel had been raised to 200℃～250℃, the samples' blowout wasprevented effectively while calcinations ; The proper calcinations temperature shouldbe at 700℃～800℃. The experiment proved that It could be obtained thatsingle-phased, uniform perovskite-type catalysts with nanometer particle size bymonophase and ctric acite complexing sol-gel process with high stability andrepeatability. Especially, calcinations temperature was low and required equipment wassimple.