微波热解制备g-Fe2O3催化剂及其SCR脱硝性能

以FeSO₄·7H₂OFe(NO₃)₃·9H₂O]为铁源,采用新型微波热解法制备γ-Fe₂O₃a-Fe₂O₃]催化剂样品,通过XRD、N₂等温吸附-脱附、压汞法等实验手段对催化剂样品晶相、微观孔结构等进行表征;考察两种催化剂样品的NH₃-SCR脱硝性能,通过归一化处理得到两种催化剂在不同温度下的本征脱硝反应速率,同时对比研究了γ-Fe₂O₃与钒系催化剂的脱硝活性;研究氨氮比、氧浓度等运行参数对γ-Fe₂O₃催化剂NH₃-SCR脱硝性能的影响规律,并对其抗硫抗水性能进行考察.结果表明:采用新型微波热解法可得到纯度较高的γ-Fe₂O₃催化剂,其介孔分布合理且大孔数量丰富;同时γ-Fe₂O₃催化剂表现出优于a-Fe₂O₃催化剂的脱硝性能,400℃时最大NO_x转化率达到96%,300、325、350℃下单位面积脱硝速率达到a-Fe₂O₃催化剂的3倍左右;γ-Fe₂O₃催化剂具备优良的抗硫抗水性能,其最佳氨氮比为1、最佳氧体积分数为3.5%.

Microwave-assisted preparation of g-Fe2O3 as SCR catalysts

γ-Fe₂O₃ and a-Fe₂O₃ catalysts were prepared respectively via a novel microwave pyrolysis method using FeSO₄·7H₂O and Fe(NO₃)₃·9H₂O as ferrous source. Crystalline phase and microstructure of catalysts were characterized by X-ray diffraction(XRD), mercury intrusion porosimetry(MIP), N₂ adsorption-desorption and NH₃-SCR activity of different catalysts were investigated. SCR reaction rates over the catalysts at different temperatures were obtained by unitary processing, and SCR activities over γ-Fe₂O₃ and vanadium-based catalysts were compared. The effects of O₂ concentration, molar ratio of NH₃/NO, SO₂, and H₂O on SCR activity of γ-Fe₂O₃ catalyst were also studied. Pure γ-Fe₂O₃ catalyst could be obtained via this novel microwave pyrolysis method, and showed higher crystallinity than a-Fe₂O₃ catalyst. γ-Fe₂O₃ catalyst had broader pore size distribution as well as appropriate ratios of mesopores and macropores. Meanwhile, γ-Fe₂O₃ catalyst exhibited better SCR activity than a-Fe₂O₃ catalyst. The highest NO_x conversion of γ-Fe₂O₃ catalyst was up to 96% at 400℃ and SCR reaction rates normalized by surface area were three times higher than that of a-Fe₂O₃ catalyst at 300, 325 and 350℃, respectively. The optimum molar ratio of NH₃/NO and O₂ concentration for selective catalytic reduction over γ-Fe₂O₃ catalyst were recommended to be 1 and 3.5% (vol), respectively.