The effects of excess manganese in nano-size lanthanum manganite perovskite on enhancement of trichloroethylene oxidation activity
The effects of excess manganese in nano-size lanthanum manganite perovskite on enhancement of trichloroethylene oxidation activity
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DOI：
10.1016/j.cej.2012.11.005
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发表时间：
2013-01-15
影响因子：
15.1
通讯作者：
Mortazavi, Yadollah
中科院分区：
文献类型：
--
作者：
Maghsoodi, Sarah;Towfighi, Jafar;Mortazavi, Yadollah
研究了钙钛矿型LaMn1+xO3+δ中过量锰对空气中三氯乙烯（TCE，一种含氯挥发性有机化合物）氧化增强的影响。通过微波辅助“凝胶燃烧”法合成了各种LaMn1+xO3+δ（x = 0.0 - 0.4）纳米催化剂，并在空气中600℃下煅烧。样品的XRD图谱证实了钙钛矿结构的形成，SEM显微照片显示出具有宽尺寸分布的海绵状团聚纳米颗粒，且其结构中存在大孔隙。TEM显微照片表明存在12 - 30 nm的纳米颗粒，可能是高度分散的无定形和/或细小的MnOx微晶，这些在XRD图谱中无法检测到。TPR结果表明，LaMnO1+xO3+δ催化剂的氧过量程度随锰过量而增加。对于LaMn1.2O3+δ催化剂，观察到其BET表面积提高了2.5倍，且三氯乙烯氧化活性最高。与LaMnO3+δ相比，LaMn1.2O3+δ上三氯乙烯氧化的T - 50和T - 90分别降低了150℃和174℃。催化剂在反应条件下暴露后BET表面积的损失可能是观察到的初始失活的原因。XPS光谱显示在初始失活过程中形成了LaOCl。关于三氯乙烯的简单零级动力学表达式对LaMn1+xO3+δ催化剂上三氯乙烯转化率的变化提供了相当好的拟合。（C）2012 Elsevier B.V.保留所有权利。
The effects of excess manganese in LaMn1+xO3+delta perovskite on enhancement of trichloroethylene (TCE) oxidation, as a chlorinated volatile organic compound (CVOC), in air are studied. Various LaMn1+xO3+delta (x = 0.0-0.4) nanocatalysts were synthesized by a microwave-assisted "gel combustion" method and calcined at 600 degrees C in air. XRD patterns of the samples confirm formation of perovskite structure and SEM micrographs exhibit spongy agglomerated nanoparticles with a wide size distribution and presence of large pores in their structure. TEM micrographs show the presence of 12-30 nm nanoparticles of possibly highly dispersed amorphous and/or fine crystallites of MnOx, which are not detectable in XRD patterns. TPR results indicate that the oxygen overstoichiometry of LaMnO1+xO3+delta catalysts increases with excess Mn. Enhancement of BET surface area of the catalyst samples as much as 2.5-fold and the maximum TCE oxidation activity are observed for the LaMn1.2O3+delta catalyst. As compared to LaMnO3+delta, T-50 and T-90 of TCE oxidation on LaMn1.2O3+delta are decreased by 150 and 174 degrees C, respectively. Loss of BET surface areas of the catalysts after exposure to reaction conditions may be responsible for the observed initial deactivation. XPS spectra show the formation of LaOCl during the initial deactivation. Simple zero-order kinetics expression with respect to TCE, provides fairly good fits for the evolution of the TCE conversion on LaMn1+xO3+delta catalysts. (C) 2012 Elsevier B.V. All rights reserved.