超声改性的CuO/Al2O3-MgO催化剂结构 及其超低浓度甲烷催化燃烧性能

采用普通浸渍和超声改性的方法分别制备了CuO/Al₂O₃-MgO催化剂,用于超低浓度甲烷的催化燃烧,并利用SEM、XRD、XPS、H₂-TPR等技术对催化剂进行表征,研究了超声改性作用对催化剂的结构和性能的影响.结果表明,与普通浸渍法制备的催化剂相比,在超声改性的CuO/Al₂O₃-MgO催化剂上,甲烷的转化率得到提高,燃烧特征温度降低.随着超声时间的延长和超声功率的增加,催化剂的催化活性均呈现先增大后减小的趋势;催化剂制备的最佳超声工况为功率150 W、时间20 min.超声改性可使催化剂的比表面积和孔容积增大,表面催化活性较高的Cu⁺浓度增加,活性组分CuO由晶相向非晶相转变、分散度增大,晶粒粒径变小、分布更均匀;这使得甲烷催化燃烧的表观活化能下降、催化剂活性得到增强.

Structure of CuO/Al2O3-MgO catalyst modified by ultrasound assisted dispersion and its catalytic performance in the combustion of lean methane

CuO/Al₂O₃-MgO catalyst was prepared by ultrasound assisted dispersion and used in the catalytic combustion of lean methane. The CuO/Al₂O₃-MgO catalyst was characterized by SEM, XRD, XPS, and H₂-TPR and the effect of ultrasonic modification on the structure and catalytic performance was investigated. The results showed that the activity of the CuO/Al₂O₃-MgO catalyst prepared by ultrasonic treatment is much higher than that prepared by the conventional impregnation method. The catalytic activity of CuO/Al₂O₃-MgO is related to both the ultrasonic time and power; the optimum ultrasonic time and power are 20 min and 150 W, respectively. Compared with the conventional impregnation, the ultrasonic modification is propitious to get a catalyst with higher surface area and pore volume, smaller particles, and higher dispersion of active Cu species. Moreover, the ultrasonic modification may promote the formation of Cu⁺ on the catalyst surface and improve the low temperature reducibility. All these can depress the activation energy and enhance the activity of the CuO/Al₂O₃-MgO catalyst in methane oxidation.