低温SCR脱硝催化剂过渡金属氧化物改性及硫中毒失活机制研究

Deactivation by SO_2 of Transition Metal Oxides Modified Low-temperature SCR Catalyst for NO_x Reduction with NH_3

以浸渍法制备MnOx-CeOx/ACF催化剂.在110-230℃温度范围内,MnOx-CeOx/ACF催化剂具有较好地低温选择性催化还原脱除NOx的活性.结果表明,该催化剂在150℃和230℃的脱硝效率分别达到80%和90%.加入Fe、Cu和V等过渡金属氧化物对MnOx-CeOx/ACF催化剂进行改性.该类过渡金属氧化物的加入对MnOx-CeOx/ACF的活性具有抑制作用.相比于MnOx-CeOx/ACF以及Cu和V改性的催化剂,Fe改性催化剂在一定时期内具有良好的抗SO2性能.在SO2存在下,Fe改性催化剂在初始6h内其脱硝效率保持在75%以上.X射线光电子能谱（XPS）和傅立叶转换红外光谱（FTIR）分析结果表明,催化剂失活包括两部分机制,一是形成硫酸铵盐,可粘附在催化剂表面使催化剂失活;另外一个机制是作为活性成分的锰铈等金属氧化物被SO2硫化形成金属硫酸盐.

MnO,-CeOx/ACF catalyst was prepared by impregnation method, which exhibited high activity for low-temperature selective catalytic reduction of NO, over the temperature range 110-230℃. Experiments results indicated that the catalyst yielded 80% NO conversion at 150℃ and 90% at 230℃. The Oxides of Fe, Cu and V were added to the catalysts based on MnOx-CeOx/ACF. The additions of these transition metal oxides had a negative effect on the activity of the catalysts. Compared with MnOx-CeOx/ACF and Cu and V modified catalysts, NO conversion for Fe-MnO,-CeOx/ACF catalyst leveled off at nearly 75% in the first 6 h in the presence of SO2 , Two mechanisms of catalyst deactivation by SO2 were discovered by the methods of X-ray photoelectron spectrum （XPS） and Fourier transform infrared spectra （FTIR）, indicating that the catalysts were covered by ammonium sulfates and the metal oxides, acting as active components, were also sulfated by SO2 to form metal sulfates.