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基于Ce-Ti复合金属氧化物催化剂的选择性催化还原NO_x研究
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摘要
氨选择性催化还原技术被认为是最为有效的去除氮氧化物的方法,而合成低毒性高活性且温度窗口较广的催化剂是脱硝领域备受关注的热点。本文采用浸渍及共沉淀的方法在铈钛金属氧化物催化剂的基础上,成功地制备出不同比例的钼铈钛及铈钛铝复合金属氧化物脱硝催化剂,结合比表面积、X-射线光电子能谱、氢气程序升温还原等表征手段以及原位红外分析技术对催化剂的催化活性和物理化学性质进行分析,并对其反应机理进行了探讨。结果表明:通过浸渍法制备的2.5%Mo-Ce-Ti催化剂在200-440℃温度范围内表现出80%以上的脱硝效率,Mo的掺杂提高了催化剂表面的NH4+和吸附态NH3的数量,从而促进了催化活性。而通过浸渍法和共沉淀法制备的铈钛铝催化剂中,当Al:Ti比例为1:3时,催化剂的比表面积最大、催化活性最佳,Al的掺杂增加了催化剂表面吸附氧含量及活性位点,从而提高了该催化剂的脱硝性能。并借助原位红外光谱谱图分析了两种催化剂的反应机理及途径。
Ammonia Selective catalytic reduction(NH3-SCR) is considered as the most effective technology for removal of NOx.Therefore,researches on how to synthesis catalysts with low toxicity,high activity and a wide temperature window have become focus on denitration.Different molar ratios of Mo and Al doped Ce-Ti catalysts have been prepared by impregnation and co-precipitation method.Activity and physical chemical properties of catalysts were investigated through Brunauer-Emmertt-Teller(BET),X-ray Photoelectron Spectroscopy(XPS),H2-Temperature Program(H2-TPR),and In situ FTIR characterization.The NOx conversion of 2.5%Mo-Ce-Ti was above 80% in the temperature range of 200-440℃.the Mo doping to Ce-Ti increased the amount of NH4+ and adsorbed NO2 on catalyst surface,and thus promoted the NH3-SCR activity.The largest BET and highest activity of Ce-Al1-Ti3 contributed to an increase of surface oxygen and activity sites,which facilitated to the reaction.The reaction mechanisms were investigated by in situ FTIR.
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