Abstract:

With rice husk as silicon source, silica was firstly prepared by the direct calcination method, and then the Fe₂O₃/SiO₂ catalyst was prepared by co-impregnation method with the silica as the carrier. As a comparison, the Fe₂O₃/C-SiO₂ catalyst supported on commercial silica was prepared by the same method. Both catalysts were used in catalyzing H₂O₂ to pre-oxidize NO. The effects of different operating conditions (loading, catalysis temperature, vaporization temperature of H₂O₂, flow rate of H₂O₂ and vapor concentration) on the pre-oxidation of NO were systematically investigated. In addition, the physicochemical properties of the catalysts were characterized and attempts were made to correlate them with their catalytic performance. The experimental results indicated that a NO oxidation efficiency of 73% could be achieved when the loading was 50%, catalysis temperature was 140℃, vaporization temperature of H₂O₂ was 120℃, and the flow rate of H₂O₂ was 2.5mL/h. Under the same experiment conditions, the NO pre-oxidation efficiency of Fe₂O₃/SiO₂ catalyst was about 20% higher than that of Fe₂O₃/C-SiO₂ catalyst. TPR result showed that the carrier could lower the reduction temperature of active components and further reduce their agglomeration. The catalyst has a stable crystal structure, and good mechanical strength and thermal stability. ESR and XPS results indicated that the catalytic performance of Fe₂O₃/SiO₂ catalyst was better than that of Fe₂O₃/C-SiO₂ catalyst, which better catalyzed the decomposition of H₂O₂ to produce ·OH.

Key words: rice husk, silica, iron-based catalyst, gas phase H₂O₂, denitrification

摘要：

以稻壳为硅源，采用直接煅烧法制备白炭黑，以其为载体，采用共浸渍法制备Fe₂O₃/SiO₂催化剂；并采用同样方法以商用二氧化硅为载体制备Fe₂O₃/C-SiO₂催化剂，将二者用于催化H₂O₂预氧化NO的实验。探究不同工况（负载量、催化温度、H₂O₂汽化温度、H₂O₂流量和水汽浓度）对NO预氧化的影响，并对催化剂进行表征，分析其物理化学性质对催化性能的影响。结果表明，在负载量为50%、催化温度为140℃、H₂O₂汽化温度为120℃、H₂O₂流量为2.5mL/h时，达到最佳工况，NO氧化度能达到73%；在相同实验条件下Fe₂O₃/SiO₂催化剂的预氧化效果要比Fe₂O₃/C-SiO₂催化剂高20%左右。TPR结果表明载体可以降低活性组分的还原温度，减少活性组分的团聚；催化剂的晶相结构稳定，机械强度及热稳定性良好；ESR和XPS结果显示Fe₂O₃/SiO₂催化剂的催化性能优于Fe₂O₃/C-SiO₂催化剂，能够更好地催化分解H₂O₂产生·OH。

关键词: 稻壳, 二氧化硅, 铁基催化剂, 气相双氧水, 脱硝