Effect of preparation method on the performance of Fe-Ag/Al2O3 catalyst in the selective catalytic reduction of NO with propene
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摘要: 前期研究表明Fe-Ag/Al2O3/CM催化剂具有较好的选择催化还原脱硝与抗水抗硫性能。为此,本文考察了制备工艺对其丙烯选择性催化还原脱硝性能的影响。先后选取了3种活性组分负载方式,即物理研磨法、直接浸渍法和溶胶-凝胶-浸渍法。结果发现,三组催化剂都具有很好的抗H2O和SO2的能力,但就最大脱硝效率而言,溶胶-凝胶-浸渍法(100%)优于物理研磨法(62%)和直接浸渍法(58%)。多种表征测试结果表明,影响催化剂性能的主要影响因素为比表面积和铁银之间的相互作用。对于溶胶-凝胶-浸渍法制得的催化剂样品,第一载体堇青石与第二载体Al2O3共同作用,既能保证很高的比表面积,同时有利于Fe和Ag离子之间的相互作用,形成了AgFeO2双金属氧化物活性成分,还原性最强。对于物理研磨法,催化剂呈粉末状,虽然比表面积最大,但Fe和Ag以氧化物形态(Ag2O和Fe3O4)和少许的单质Ag形式存在,两种金属相互作用弱、还原性差。对于直接浸渍法,由于缺少第二载体Al2O3的分散作用,Fe和Ag以各自氧化物呈方块晶体在催化剂表面团聚,比表面积最小,催化活性最低。
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关键词:
- 选择性催化脱硝 /
- 丙烷 /
- Fe-Ag/Al2O3 /
- 制备工艺 /
- 溶胶-凝胶-浸渍
Abstract: Previous works demonstrated that the Fe-Ag/Al2O3 catalyst could efficiently reduce NO into N2 by propene with a good resistance towards H2O and SO2. In this work, the effect of preparation method on the performance of Fe-Ag/Al2O3 catalyst in the selective catalytic reduction (SCR) of NO with propene was investigated. Three typical methods, viz., physical grinding (PG), direct impregnation (DI) and sol-gel-impregnation (SGI), were comparatively used to load the active components on the supports. The results indicate that all the catalysts prepared by these three methods display good tolerance towards water vapor and SO2. However, they are rather different in the denitration efficiency; the maximum NO removal efficiency of the catalysts prepared by three methods follows the order of SGI (100%) > PG (62%) > DI (58%). Various characterization results reveal that the catalytic performance of Fe-Ag/Al2O3/CM was mainly related to the porous surface and Fe-Ag interaction. By using the SGI approach, the primary support of cordierite and the secondary support of Al2O3 work together to achieve a large surface area and an intense interaction between Fe and Ag on the resultant DP-Fe/Ag/Al2O3/CM catalyst, forming the bimetal AgFeO2 oxide and displaying the best reducibility. In terms of the PG method, the prepared GR-Fe/Ag/Al2O3 catalyst is powdery and shows the largest surface area; however, without cordierite serving as the monolithic support, Ag2O and Fe3O4 exist as separate oxides together with a hint of elemental Ag. As a result, the GR-Fe/Ag/Al2O3 catalyst shows poor reducibility due to the lack of porous surface to facilitate the Fe-Ag interaction. In contrast, the DP-Fe/Ag/CM catalyst prepared using the DI method shows rather poor dispersion of Fe and Ag due to the absence of the secondary support of Al2O3; in fact, individual Ag2O and Fe3O4 agglomerate on the catalyst surface and no AgFeO2 species is detected. Therefore, the DP-Fe/Ag/CM catalyst, with the surface area of only 1/4 of that for Fe-Ag/Al2O3/CM-SGI, exhibits the poorest activity in the SCR of NO by propene.-
Key words:
- selective catalytic reduction of NO /
- C3H6 /
- Fe-Ag/Al2O /
- preparation methods /
- sol-gel-impregnation
1) #: 共同第一作者 -
表 1 催化剂的微孔隙特性
Table 1 Textural properties of various catalysts
Catalyst ABET/(m2·g−1) νp/(cm3·g−1) dp/nm GR-Fe/Ag/Al2O3 37 0.058 20.9 DP-Fe/Ag/CM 5 0.026 10.2 DP-Fe/Ag/Al2O3/ CM 23 0.054 9.23 -
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