Mn掺杂对LaFeMn_xAl_(11-x)O_(19)结构及其催化甲烷燃烧的影响

采用溶胶-凝胶法制备了同时掺杂Fe和Mn系列的六铝酸盐催化剂LaFeMnxAl11-xO19(x=0,0.5,1,2,3,4,5),通过X射线衍射、BET比表面积测定、扫描电子显微镜、X射线光电子能谱和程序升温还原技术对催化剂的结构进行了表征,考察了Mn掺杂量对催化剂结构及甲烷催化燃烧活性的影响。实验结果表明,LaFeMnxAl11-xO19催化剂在1 200℃焙烧后可形成完整的六铝酸盐晶型,同时具有较高的催化性能和高温稳定性。当Fe含量不变时,Mn掺杂量对催化剂的活性有较大的影响,掺杂Mn使催化剂的活性明显提高,但掺杂过量Mn后催化剂的活性又有所降低。其中LaFeMnAl10O19催化剂具有较大的比表面积(16.3m2/g)和较高的催化活性,起燃温度T10为497℃,完全转化温度为T90为701℃。

Effects of Mn Doping on Structure of LaFeMnxAl11-xO19 and Catalytic Combustion of Methane on the Catalyst

A series of Mn and Fe doped LaFeMnxAl11-xO19(x=0,0.5,1,2,3,4,5) catalysts for catalytic combustion of methane were prepared by the sol-gel method and succeeded calcination.The catalysts were characterized by means of XRD,BET,SEM,XPS and TPR.Effects of Mn doping on structures of LaFeMnxAl11-xO19 catalysts and their activities in catalytic combustion of methane were investigated.The catalysts with good form of crystalline hexa-aluminate can be obtained by calcination at 1 200 ℃ for 4 h.Its catalytic activity and stability in catalytic combustion of methane are high.Activity of the catalysts firstly rises and then drops with increase of Mn doping amount.Synergism between Fe and Mn is observed.LaFeMnAl10O19 catalyst possesses relatively large specific surface area(16.3 m2/g) and shows high activity.Methane conversions on LaFeMnAl10O19 catalyst are 10% at 497 ℃ and 90% at 701 ℃ separately.