Effect of different RuO2 contents on selective catalytic oxidation of ammonia over RuO2-Fe2O3 catalysts
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摘要: 采用溶胶-凝胶法（sol-gel）制备了一系列具有不同RuO2含量的RuO2-Fe2O3催化剂，并将其应用于氨选择性催化氧化（NH3-SCO）研究中。结果表明，所有RuO2-Fe2O3催化剂都表现出较好的低温活性，且RuO2含量对催化剂的NH3催化氧化活性影响显著。此外，利用BET、XRD、H2-TPR和DRIFTS等表征手段研究了催化剂的物理化学性质和催化活性之间的关系。结果表明，RuO2的加入增大了催化剂的比表面积。RuO2与Fe2O3之间存在的协同效应提高了催化剂的氧化还原能力，从而提高了催化剂的氨氧化活性。同时，RuO2含量对催化剂表面酸性影响很大，且催化剂表面主要存在Lewis酸性位点。Abstract: A series of RuO2-Fe2O3 catalysts varied in RuO2 loading were prepared by sol-gel method and used for selective catalytic oxidation of ammonia to nitrogen. The results indicated that all the RuO2-Fe2O3 catalysts showed an excellent low-temperature catalytic activity and the RuO2 loading played a key role in catalytic activity of ammonia oxidation. Moreover, the characterizations of BET, XRD, H2-TPR and DRIFTS were employed to investigate the relation between the physicochemical property of catalysts and catalytic activity. The research results elucidated that the introduction of RuO2 increased the surface area. The synergistic effect between RuO2 and Fe2O3 enhanced the redox property and the catalytic activity of ammonia oxidation. Meanwhile, the RuO2 loading gave the significant effect on surface acidity of catalysts. Lewis acid sites were predominant on the catalyst surface.
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图 1 RuO2含量对RuO2-Fe2O3催化剂SCO催化性能的影响
Figure 1 Influence of RuO2 loading of RuO2-Fe2O3 catalysts on SCO catalytic performance
(a): NH3 conversion; (b): N2 selectivity; (c): NO yield; (d): NO2 yield; (e): N2O yield
图 2 纯的Fe2O3和RuO2-Fe2O3催化剂的XRD谱图
Figure 2 XRD patterns of pure Fe2O3 and RuO2-Fe2O3 catalysts
图 3 不同催化剂的N2吸脱附曲线(a)和孔径分布图(b)
Figure 3 (a) N2 adsorption-desorption isotherms and (b) pore-size distribution of different catalysts
图 6 250 ℃时NH3在不同催化剂表面吸附变化的原位漫反射红外光谱谱图
Figure 6 In situ DRIFTS of different catalysts exposed to NH3 for various times at 250 ℃
(a): Fe2O3; (b): 0.5%RuO2-Fe2O3; (c): 1%RuO2-Fe2O3; (d): 1.5%RuO2-Fe2O3; (e): 2%RuO2-Fe2O3
表 1 不同催化剂的孔结构参数
Table 1 Pore structural parameters of different samples
Sample ABET
/(m2·g-1)Pore volume
v/(cm3·g-1)Fe2O3 14.3 0.15 0.5%RuO2-Fe2O3 16.0 0.16 1%RuO2-Fe2O3 14.2 0.13 1.5%RuO2-Fe2O3 15.6 0.14 2%RuO2-Fe2O3 19.1 0.16 
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