Mg掺杂改性γ-Fe_2O_3催化剂NH_3-SCR脱硝特性

采用共沉淀-微波热解法制备一系列不同Mg掺杂比的Fe_(1-x)Mg_xO_z(x=0,0.1,0.2,0.3)催化剂,研究Mg掺杂对γ-Fe_2O_3催化剂SCR脱硝活性的影响,并借助XRD,N_2吸附-脱附、SEM和EDS等手段对催化剂进行表征。Mg的最佳掺杂比为0.2,且Fe_(0.8)Mg_(0.2)O_z催化剂在325℃时脱硝效率可达99.1%,同时活性温度窗口为250~350℃。Fe_(0.8)Mg_(0.2)O_z催化剂主要活性组分为γ-Fe_2O_3,其中Mg以无定型状态存在,能够与晶格中的Fe相互作用形成良好的固溶体,其较大的比表面积(44.00 m~2/g)、比孔容(0.19 cm~3/g)为反应气体在催化剂表面吸附与活化提供了丰富的表面活性位;合理的孔结构分布、良好的孔间连通性则利于传质的快速进行。Fe_(0.8_Mg_(0.2)O_z催化剂最佳O_2体积分数为3%,推荐NH_3/NO为1;催化剂表面氧化能力的提高及反应物的快速吸附、活化有利于NH3-SCR反应的进行。

Structural properties of Mg doped γ-Fe2O3 catalysts and their activities in the selective catalytic reduction with NH3

A series of magnetic iron-magnesium mixed oxide catalysts (Fe1xMgxOz,where x=0,0.1,0.2,0.3) were synthesized via a novel co-precipitation method with microwave thermal treatment and their activities were tested on a quartz fixed-bed reactor.Physical properties of the catalysts were characterized by X-ray diffraction (XRD),N2-adsorption-desorption,Scanning Electron Microscope (SEM) and Energy Dispersive Spectrometer (EDS).Fe0.8Mg0.2O z with a wide temperature window of 250 ℃ to 350 ℃ was validated as the proper SCR catalyst,and the maximum NOxconversion of 99.1% was achieved at 325 ℃.Activity was strongly influenced by the γFe2O3 crystalline phase,magnesium existed in an amorphous phase and interacted with iron oxide intensively to form solid solution.Optimum pore diameter distribution,appropriate surface area (44.00 m2/g),pore volume (0.19 cm3/g) and abundant lattice oxygen could be guaranteed in Fe0.8Mg0.2O zcatalyst,which was good for the diffusion process and enhanced the activity.The optimum O2 concentration of Fe0.8Mg0.2Oz catalyst was 3%,and recommended NH3/NO was 1.The improvement of oxidation ability on the surface of the catalyst and the rapid adsorption and activation of reactants were both in favor of NH3-SCR reaction.