不同前驱体制备的Al/K碳烟燃烧催化剂的催化性能

以Al(NO3)3(或Al2O3)和KNO3(或KOH)为原料,采用直接涂抹法,制取不同比例的Al/K碳烟催化剂。通过程序升温氧化(TPO)研究了焙烧温度、老化时间对催化剂催化活性的影响,同时用XRD对催化剂的成分进行分析。结果表明,Al/K摩尔比为3∶1、1∶1和3∶1的Al2O3/KNO3,Al(NO3)3/KNO3和Al2O3/KOH催化活性都较高。但是,高温焙烧或老化时,由于降低催化剂的比表面积导致催化剂催化活性明显降低;Al2O3/KOH经过焙烧形成K2Al2O4,故表现出较好的催化活性,但是吸水能力较强。

Catalytic Activity of Al/K Catalysts Prepared by Different Precursors for Soot Combustion

Using Al(NO3)3(or Al2O3),KNO3(or KOH) as raw materials,the Al/K catalysts with different Al∶K molar rations were prepared by direct coating method.The effects of the calcination temperature and high temperature aging on the catalytic activities of the catalysts were studied by temperature programmed oxidation(TPO).The catalyst compositions were characterized by XRD.The results showed that the catalysts calcined at 600 ℃ would result in the best catalytic activities at Al∶K molar ratios of 3∶1,1∶1 and 3∶1 for Al2O3/KNO3,Al(NO3)3/KNO3 and Al2O3/KOH catalyst systems,respectively.However,the calcination at high temperature or long time aging would considerably deteriorate the catalytic activity because of specific surface loss.It was also found that Al2O3/KOH combination could form K2Al2O4 which posses a good catalytic activity and a high moisture absorption capability.This study result confirms that the usage of Al2O3 foam filter would impose no harmful effect on the soot oxidation catalysts containing K element.