Effect of Mn doping to substitute Al on the structure and methane combustion activity of hexaaluminates catalysts K2MnxAl12-xO19-δ
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摘要: 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。Abstract: A series of K and Mn modified lanthanum hexaaluminates, K2MnxAl12-xO19-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 microemulsionhydrolysis 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 Al on the structure and methane combustion activity of K2MnxAl12-xO19-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 K2MnAl11O19-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.
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Key words:
- hexaaluminate /
- catalytic combustion /
- methane /
- substitute /
- activity
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