Research Of Catalytic Oxidation Of NO Over La-based Perovskite-type Oxide

Effective control of vehicle exhaust emissions is an important way to reduceatmospheric haze pollution. Lean-combustion technology is becoming a maintechnology for vehicle engine because of its fuel economy and CO2emissionsreduction. However the O2and NOxconcentrations of lean-burn engine exhaustemissions are high, traditional three-way catalyst (carbon monoxide, hydrocarbonsand nitrogen oxides while catalytic elimination) in this condition can not eliminateNOxeffectively. Selective catalytic reduction (SCR) and NOxstorage and reduction(NSR) both with Pt, Pd and other precious metals currently as active components arethe most promising lean NOxcontrol technologies, While the price of these noblemetals is expensive and sulfur resistance is poor. Development of more affordable andefficient lean NOxconversion catalyst becomes the key of vehicle exhaust controltechnology.In this paper, a series of La-based perovskite oxides was synthesized by citricacid sol-gel method. Effects of preparation parameters, A-and B-doped on the NOcatalytic oxidation were investigated. The crystal phase, surface area and redoxproperties were characterized by XRD, BET and H2-TPR. The results showed thatLaCoO3and LaMnO3possessed preferable NO catalytic oxidation. Ce-substituted ofA and Fe-substituted of B simultaneously enhanced low temperature activity and SO2resistance. Among all the catalysts, La0.8Ce0.2CoO3achieved77%NO oxidationconversion at300℃under Vsp=60000h-1. Ce-substituted enhanced the lattice oxygenof LaCoO3and then improved NO catalytic oxidation. In the presence of SO2,Fe-substituted delayed sulfur poisoning of Co, thereby improving SO2resistance ofcatalysts. Meanwhile this article investigated the influences of operating conditions onactivity of La0.8Ce0.2CoO3NO catalytic oxidation. A reaction kinetic equation wasalso established.In order to overcome low surface area, low SO2resistance of La0.8Ce0.2CoO3. This paper also studied La1-xCexCoO3supported catalysts with CeO2、TiO2、Fe2O3assupports for NO catalytic oxidation. The results indicated that, CeO2was the bestsupport, La0.8Ce0.2CoO3/CeO2supported catalyst owned significant NO oxidationactivity compared to La0.8Ce0.2CoO3and achieved85%NO conversion at250℃. SO2resistance raised simultaneously and maintained activity for10hours in the presenceof SO2, SO2adsorbed on the active sites of Ce firstly, the active component Co beganto be influenced only when SO2adsorbent was saturated. XRD, BET and otherH2-TPR revealed that La0.8Ce0.2CoO3distributed uniformly on the support, the surfacearea of the supported perovskite catalysts increased significantly compared tounsupported ones, as well as redox ability.