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摘要: 用溶胶-凝胶法制备了不同组成的Mg-Co和Mg-Mn-Co复合氧化物,用于催化分解N2O。在较高活性的Mg-Mn-Co表面浸渍K2CO3溶液,制备K改性催化剂。用X射线衍射(XRD)、N2物理吸附(BET)、扫描电镜(SEM)、H2程序升温还原(H2-TPR)、O2程序升温脱附(O2-TPD)等技术表征催化剂结构,考察了复合氧化物的组成、K负载量等制备参数对催化剂活性的影响。结果表明,加入助剂K显著提高了催化剂活性,其中,0.02 K/MgMn0.2Co1.8O4活性较高,有氧无水、有氧有水气氛400℃连续反应50 h,N2O转化率分别保持97%和60%。有水-无水气氛交替实验表明,有水反应后再进行无水实验,K改性催化剂的稳定性较好。
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关键词:
- N2O催化分解 /
- Mg-Co复合氧化物 /
- Mg-Mn-Co复合氧化物 /
- K改性催化剂 /
- 催化性能
Abstract: Mg-Co and Mg-Mn-Co composite oxides with different compositions were prepared by sol-gel method for N2O catalytic decomposition in the presence of oxygen. Of Mg-Mn-Co catalysts, the one with higher activity was impregnated by K2CO3 solution to make K-modified catalyst. These catalysts were characterized by X-ray diffraction(XRD), nitrogen physisorption (BET), scanning electron microscopy(SEM), temperature-programmed reduction of hydrogen(H2-TPR), and temperature-programmed desorption of oxygen(O2-TPD). The effect of preparation parameters such as compositions and potassium loadings on their catalytic activity has been investigated. The results show that K-modified catalysts exhibit better activity and higher resistance towards water in contrast to un-modified catalyst due to the weakness of surface metal-oxygen bonds. Among these catalysts, 0.02K/MgMn0.2Co1.8O4 is the most active, over which 97% and 60% conversions of N2O can be reached at 400℃ after continuous running for 50 h under the atmosphere of oxygen-alone and oxygen-steam together, respectively. When the steam is switched off, the catalytic activity of 0.02K/MgMn0.2Co1.8O4 can be restored to large extent, indicating the good water-resistance of K-modified catalyst. -
表 1 Mg-Co复合氧化物的晶粒粒径和比表面积
Table 1 Crystallite size and BET surface area of Mg-Co composite oxides
Catalyst Crystallite size
d/nmaBET surface area
A/(m2·g-1)Co3O4 113.4 4.0 Mg0.2Co2.8O4 85.0 8.4 Mg0.4Co2.6O4 66.1 13.0 Mg0.6Co2.4O4 104.4 18.8 Mg0.8Co2.2O4 74.1 16.8 MgCo2O4 58.8 20.1 acalculated by Scherrer equation on the basis of (311) crystallographic plane data in XRD patterns 表 2 Mg-Mn-Co复合氧化物的晶粒粒径和比表面积
Table 2 Crystallite size and BET Surface area of Mg-Mn-Co composite oxides
Catalyst Crystallite size
d/nmaBET surface area
A/(m2·g-1)MgCo2O4 58.8 20.1 MgMn0.2Co1.8O4 17.6 75.0 MgMn0.4Co1.6O4 7.8 77.7 MgMn0.6Co1.4O4 8.6 81.0 MgMn0.8Co1.2O4 16.0 72.4 MgMnCoO4 11.9 73.3 a calculated by Scherrer equation on the basis of (311) crystallographic plane data in XRD patterns 表 3 K/MgMn0.2Co1.8O4催化剂的晶粒粒径和比表面积
Table 3 Crystallite size and BET surface area of K/MgMn0.2Co1.8O4 catalysts
Catalyst Crystallite size
d/nmaBET surface area
A/(m2·g-1)MgMn0.2Co1.8O4 17.6 75.0 0.01K/MgMn0.2Co1.8O4 21.2 60.8 0.02K/MgMn0.2Co1.8O4 33.6 54.6 0.03K/MgMn0.2Co1.8O4 25.4 45.7 0.04K/MgMn0.2Co1.8O4 24.7 56.8 0.05K/MgMn0.2Co1.8O4 27.0 44.9 a calculated by Scherrer equation on the basis of (311) crystallographic plane data in XRD patterns -
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