Mn离子掺杂对K_2Mn_xAl_(12-x)O_(19-δ)催化剂结构及其甲烷燃烧性能的影响

Effect of Mn doping to substitute Al on the structure and methane combustion activity of hexaaluminates catalysts K_2Mn_xAl_(12-x)O_(19-δ)

采用反相微乳液-金属醇盐水解法制备了K作为镜面阳离子,锰离子作为活性组分的一系列六铝酸盐催化剂K2MnxAl12-xO19-δ(x=0、1.0、1.5、2.0、2.5、3.0)。通过X射线衍射、差热-热重和程序升温还原等实验技术及甲烷燃烧,对催化剂的结构和性质进行了考察。主要考察了不同Mn离子的掺杂量对催化剂结构及对甲烷催化燃烧活性的影响。结果表明,K作为镜面阳离子,不但可以形成完整的六铝酸盐,而且所制备的催化剂具有较高的催化活性。不同的Mn离子掺杂对于催化剂的特性有较大的影响。当Mn的掺杂量在六铝酸盐K2MnxAl12-xO19-δ结构式中为x=1时,制备的催化剂K2MnAl11O19-δ具有较高的催化活性,起燃温度Tl0%为458℃,至676℃甲烷完全转化,Mn掺杂量增多导致晶体结构中出现钙钛矿杂质。

A series of K and Mn modified lanthanum hexaaluminates,K2MnxAl（12-x）O19-δ（x=0, 1.0, 1.5, 2. 0, 2.5, 3.0） as new catalysts for combustion of methane, were prepared by means of reverse microemulsion-hydrolysis of metal alkoxide and high temperature calcination. The structure and properties of the catalysts were characterized by XRD, DTA-TG, TPR and methane catalytic combustion reaction. Effect of Mn doping to substitute A1 on the structure and methane combustion activity of K2MnxAl（12-x）O19-δ catalysts was investigated. The results showed that the catalyst with good crystallinity was obtained after calcination in oxygen at 1200℃. At the same time all catalysts have high catalytic activity. The introduction of different content of Mn ion show great effect on the properties of catalysts. The K2MnxAl（12-x）O19-δ catalyst has higher activity with T10% at 458℃ and T90% at 676℃. Increased of Mn ions in precursor resulted in the formation of perovskite phase in the samples.