Study On Properties Of Cordierite Loading Iron Oxide Used For Selective Catalytic Reduction Of NO_x

Atmospheric pollution caused by nitrogen oxides is NO and NO₂,nitrogen oxides harm as follow: The first, the formation of photochemical smog. The second, It is very easy to combinat with the blood. The third, damaging the ozone lager in the stratospheric. The fourth, it can produce toxic greater nitric acid or nitrate aerosols, formation of acid rain. Atmospheric nitrogen oxides content evaluation is to determine the quality of the human environment or one of the important indicators. In more than ten years, the effective reduction of NO_x has become one of the greatest challenges in the fields of global environmental protection and catalysis. So we shoud study effective catalyst to reduce NO_x Mixed metal oxides are one of the catalysts that wipe NO_x off. Because of its special crystal structure and high oxidation-reduction catalytic activity, it will be applied prospect.Theγ-Al₂O₃ sol-solution containing CeO₂ and La₂O₃ were coated on porous cordierite substrate. A serial of cordierite-based complex oxides of Fe was prepared by impregnation and their catalytic activity in selective catalytic reduction were systematically investigated using method of temperature progress while urea as reductant. The catalytic reactions were conducted in fixed-bed fluxion reactor. Influence of washcoat content and baking temperature on cordierite special surface area was analyzed.The results showed that special surface area of catalyst containing La₂O₃ and BaO are much higher than that of catalyst containing no La₂O₃ and BaO. Thermal stability and catalytic performance are improved by the addition of alkaline-earth metal oxide and transition metal oxide .The result showed that Fe-Ce-Mn has higher activity when their quantity are 6wt%,4wt%,3wt% and temperature is 300℃, and it makes the efficiency of the NO_x reduction exceed up to 80 percent. The research result indicates that catalytic activity relates with not only species of the active component but also the loaded amount,velocity and calcinate temperature. The catalytic activity also bears on the quality of carrier,the decentralization extent of active components,harmony performance among the active components.The structure,reduction property,surface morphology and surface elements of the catalysts were analyzed by XRD,SEM,BET,TPR,XPS methods. The addition of Ce and Mn obviously improves the activity of catalyst for methane combustion. The addition of Ce improves the thermal stability of Fe₂O₃ ,which increases the thermal stability of the catalyst. The surfacial elements of the catalysts existed in the form of oxides. The addition of Ce enhanced the dispersion of Fe on the support so that the surface active species were increased and the catalytic activity is enhanced. Meanwhile the added Mn also lowered the reaction activation energy, made the active Fe species more reducible, accelerated its reduction rate, and the catalytical activity was improved.