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利用菱铁矿的热分解特性,在空气中不同温度下(400、500、600、700、800℃)煅烧天然菱铁矿制备具有纳米尺寸形貌特征的α-Fe_2O_3,作为NH_3选择性催化还原(NH_3-SCR)脱硝的催化剂.采用X射线衍射(XRD)、程序升温脱附(NH_3-TPD)、X射线光电子能谱(XPS)、紫外-可见漫反射吸收光谱(UV-Vis DRS)等手段对催化剂结构进行表征,并利用气固相催化反应系统对催化剂的NH_3-SCR脱硝活性和N_2选择性进行评价,同时考察其抗水抗硫及稳定性.结果表明,天然菱铁矿于空气中500℃煅烧相变为α-Fe_2O_3,具有最低的晶体尺寸(约10 nm)、最高的比表面积(39.68 m~2·g~(-1))和最优的脱硝活性;500℃煅烧菱铁矿制备的催化剂在250~400℃温度窗口内脱硝效率达到100%,并能保持较高的N_2选择性,这主要归因于其具有的纳米多孔结构特性和较大的比表面积,以及表面丰富的酸性位点和吸附态氧.当同时存在5%H_2O和0.04%SO_2时,α-Fe_2O_3在250~400℃区间的脱硝效率高于88%,且在300℃下持续反应360 min,脱硝效率维持在75%以上,表明500℃煅烧菱铁矿制备的催化剂具有良好的抗水抗硫和稳定性.
Based on the thermal decomposition characteristics of siderite, α-Fe 2 O 3 with nano-sized topography was prepared by calcining natural siderite at different temperatures (400, 500, 600, 700 and 800 ℃) in air as selective catalytic reduction of NH 3 (NH 3 -TPD), X-ray photoelectron spectroscopy (XPS), UV-Vis DRS and so on, were studied by means of X-ray diffraction (XRD) Means to characterize the structure of the catalyst and to evaluate the NH3-SCR denitrification activity and N2 selectivity of the catalyst by using a gas-solid catalytic reaction system, and to study the water and sulfur resistance and stability of the catalyst. The results show that natural siderite in the air Calcined at 500 ℃ to α-Fe 2 O 3 with the lowest crystal size (about 10 nm) and the highest specific surface area (39.68 m 2 · g -1) and the best denitrification activity. The catalyst prepared in iron ore has a denitrification efficiency of 100% in the temperature range of 250-400 ℃ and can maintain a high N 2 selectivity, which is mainly attributed to its nano-porous structure and large specific surface area, as well as the surface Abundant acidic sites and adsorbed oxygen, when both 5% H 2 O and 0.04% SO 2 are present , the denitrification efficiency of α-Fe 2 O 3 in the range of 250-400 ℃ is higher than 88%, and the reaction is continued at 300 ℃ for 360 min. The denitrification efficiency is maintained above 75%, indicating that the catalyst prepared at 500 ℃ calcined siderite has good resistance Water resistance to sulfur and stability.