Preparation And Characterization Of Catalysts For Both Denitrification And Desulfurization With CO As Reducing Agent

FCC flue gas contains large amounts of harmful substances, such asNO_x, SO₂, CO, CO₂and so on. If these substances are emitted into theatmosphere, great damage would be caused to the environment. SO₂andNO_xare main sources of acid rain and photochemical smogs, theyendanger the ecological balance and human health, and are not conduciveto the sustainable development of China’s economy and society.Therefore, effective ways to control these harmful substances are needed.SCR technology has been applied in the real industry and dry Flue Gassynchronization catalytic desulfurization and denitrification is apromising new technology. Catalysts and reducing agents are key factorsin the methods mentioned above. Hexaaluminate catalysts which havegood high temperature stability and high catalytic activity are consideredto be promising catalysts. Transitional metal ion modified ZSM-5zeolitecatalysts have good catalytic activity and are widely used catalysts. Touse CO which comes from FCC fuel gas as reducing agent can not onlyachieve the effect of desulfurization and denitrification, but also get rid of itself.In the thesis, the co-precipitation methods were employed to preparea range of different transit metal-doped hexaaluminate catalysts. Theimpregnation methods were employed to prepare a range of transit metalcontaining ZSM-5zeolite catalysts. The catalysts were characterized byXRD, BET, H2-TPR and TG-DSC. The catalytic desulfurization anddenitrification performance was evaluated through the catalystmicro-reactor and the flue gas analyzer.The catalysts LaBA_l11O_19-δ（B=Mn, Fe, Ni, Cu, Zn, Ce, Co and Mg）and LaMnFeAl10O19-δwere prepared by co-precipitation. The structureand catalytic denitrification activities of the substituted hexaaluminatecatalysts are investigated. The results showed that the LaFeAl₁₁O_19-δcatalyst showed good catalytic denitrification activity. The catalyticactivity of LaMnFeAl10O19-δcatalyst was better than that of bothLaFeAl₁₁O_19-δcatalyst and LaMnAl₁₁O_19-δcatalyst. More Fe ions weredoped based on the LaMnFeAl₁₀O_19-δcatalyst, but excessive Fe ions couldnot enter the hexaaluminate lattice better, and the catalytic activitydecreased.The denitrification and sulfur tolerance property of theLaBAl₁₁O_19-δ（B=Fe, Cu, Ce and Mn） catalysts and LaMnFeAl₁₀O_19-δcatalyst were investigated. The results showed that the denitrificationactivity of each catalyst decreased comparing to that before SO₂was added. The denitrification and sulfur tolerance property ofLaMnFeAl10O19-δcatalyst was better than that of both LaMnAl₁₁O_19-δcatalyst and LaFeAl₁₁O_19-δcatalyst.The LaFeMAl₁₀O_19-δ（M=Mn, Cu, Ni, Mg） catalysts,LaFexCu1-xAl₁₁O_19-δcatalysts, LaCeMAl10O19-δ（M=Cu, Ni, Fe, Mg, Mn）catalysts, LaCexFe1-xAl₁₁O_19-δcatalysts and LaCexCu1-xAl₁₁O_19-δcatalystswere prepared and the denitrification and sulfur tolerance property of thecatalysts mentioned above were investigated. The results showed thatHexaaluminate catalysts doped with different metal ions showed differentdenitrification and sulfur tolerance properties, and the molar proportion ofmetal ions could also affect the catalytic activity. LaFe0.6Cu0.4Al₁₁O_19-δcatalyst showed good denitrification and sulfur tolerance property.The simultaneous desulfurization and denitrification activities ofLaFeAl₁₁O_19-δcatalyst, LaFe0.6Cu0.4Al₁₁O_19-δcatalyst andLaCe0.2Fe0.8Al₁₁O_19-δcatalyst were investigated. The results showed thatthe catalytic denitration activity of LaFeAl₁₁O_19-δcatalyst andLaFe0.6Cu0.4Al₁₁O_19-δcatalyst was stronger than their desulfurizationactivity, while LaCe0.2Fe0.8Al₁₁O_19-δcatalyst showed better desulfurizationactivity than denitration activity.ZSM-5zeolite did not have denitrification activity until certainamounts of transit metal ions were loaded.70%Fe/ZSM-5had the bestcatalytic denitration activity in the x%（mass fraction） Fe/ZSM-5zeolite catalysts.70%Fe/ZSM-5catalyst showed better desulfurization activitythan denitrification activity. When2%O₂was added, the denitration anddesulfurization activities of70%Fe/ZSM-5catalyst decreased, but itsdesulfurization activity is still better than its denitration activity.