改性介孔Al_2O_3负载锰基催化剂的结构及其催化氧化与抗硫性能

Structure,Catalytic Oxidation Performance,and Sulfur Resistance of Mn-Based Catalysts Supported on Modified Mesoporous Al_2O_3

采用分步浸渍法分别制备了LaCeZr和YCeZr组合助剂改性的介孔Al2O3负载的Mn基系列氧化物催化剂,用X射线衍射、氮气吸附-脱附、X射线吸收精细结构、X射线光电子能谱和程序升温还原等方法对催化剂进行了表征,探讨了催化剂中Mn物种的存在形式及其还原性能,并与样品催化CO和C3H8的氧化活性相关联.结果表明,样品中Mn物种主要以Mn3O4形式存在,该物种在不同样品中与载体的作用强弱不同,从而表现出不同的还原性能和催化活性.助剂改性有效抑制了Mn-Al之间的相互作用,提高了Mn–O键的活动度,从而提高了催化剂的氧化活性.相比于YCeZr助剂,LaCeZr助剂改性更大程度上提高了Mn物种的还原性,因而大大提高了催化剂的氧化性能.650oC焙烧的LaCeZr组合助剂改性的介孔Al2O3负载的Mn氧化物催化剂,在0.035%SO2存在的条件下对CO的氧化活性并未下降,对C3H8的氧化活性下降幅度也较小,表现出优越的抗硫性能和氧化性能.

The manganese oxide catalysts supported on mesoporous Al2O3 modified by LaCeZr or YCeZr were prepared by successive im- pregnation. The structure of the catalysts was characterized by X-ray diffraction, N2 adsorption-desorption, X-ray absorption fine structure, X-ray photoelectron spectroscopy, and temperature-programmed reduction by H2. The state of manganese species and their reducibility were investigated and correlated with the CO and C3H8 oxidation performance of the catalysts. The results demonstrate that the manganese species mainly exist as Mn3O4 crystallites, which interact with the support Al2O3. The different interaction strength determines the reducibility and catalytic properties of the catalysts. The promoters LaCeZr or YCeZr effectively inhibit the interaction between Mn and Al oxides, increasing the mobility of Mn-O bond and the catalytic activity of the corresponding catalysts. Compared with YCeZr, the promoter LaCeZr improves the reducibility of MnOx to a larger extent, enhancing the activity more obviously. The catalysts modified by LaCeZr calcined at 650℃ exhibits high oxidation performance and sulfur resistance. In the presence of 0.035% SO2 in the feed, the CO oxidation activity of the catalyst can be well maintained, and the C3H8 oxidation activity decreases only a little.