H3PW12O40/CNTs吸附-分解NOx及微波作用效果

将碳纳米管(CNTs)载体分别经混酸与硝酸蒸气预处理并在不同温度下煅烧, 然后分别采用浸渍法及机械研磨法负载磷钨酸(HPW), 制备出HPW/CNTs催化剂, 对比考察了上述催化剂对NOx的吸附与分解效果. 在空速为10000 h-1、 吸附温度为200℃的条件下, 用0.5 g催化剂对1696 mg/m3的NOx进行吸附实验, 结果表明, 以硝酸蒸气预处理且经300℃煅烧后的CNTs为载体, 采用机械研磨负载法制备的催化剂HPW/CNTs对NOx的吸附率与吸附能力最高, 分别为54%与16.6 mg NOx/(g\5h). 对吸附NOx后的催化剂体系进行了催化分解NOx的程序升温脱附-质谱(TPD-MS)研究, 结果表明, 所吸附的NOx在快速升温过程中发生分解, 在此过程中有氧产生, 分解产物包括N2, O2及N2O. 采用电阻炉快速加热与微波辐射2种方式分别对吸附的NOx进行催化分解, 结果表明, 微波功率为700 W时, NOx分解为N2的收率为33.3%, 高于电阻炉以150℃/min快速升温的N2收率. 使用过的催化剂通水蒸气后可实现再生, 对再生后的催化剂进行循环使用研究, 结果表明, 再生后的催化剂吸附与催化分解NOx的性能未有明显下降.

NOx Adsorption and Decomposition over H3PW12O40/CNTs and the Effect of Microwave Irradiation

A series of HPW/CNTs catalysts was prepared by impregnation and mechanical grinding methods.For this purpose,CNTs was pretreated separately by nitric acid vapor,mixture of nitric acid and sulphuric acid,and subsequently calcined.The performances of catalysts on NOx adsorption-decomposition were studied.The 0.5 g catalyst was used to adsorb 1696 mg/m3 NOx under the space velocity of 1000 h-1 at 200 ℃,and the results showed that the catalyst prepared by mechanical grinding methods supporting HPW on CNTs pretreated by nitric acid vapor and calcined at 300 ℃ had the highest NOx adsorption efficiency and capacity of 54% and 16.6 mg NOx/(g\5h).Temperature-programmed desorption-mass spectroscopy(TPD-MS) was carried out on the catalyst adsorbed NOx,and the result showed that N2,O2 and N2O were formed during rapid heating,among which O2 was observed for the first time.Two modes of decomposition were adopted,one is by electric oven at a ramping rate of 150 ℃/min,and the other,by microwave oven.Compared to the mode of the former,the latter has higher N2 yield with a N2 yield upto 33.3% corresponding to the power of microwave oven being 700 W.The catalyst used can be reused by water vapor reactivation,and the recycling results showed that there were no significant performance degradation on NOx adsorption and catalytic decomposition.