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首页> 外文期刊>Chemical engineering journal >Effects of excess manganese in lanthanum manganite perovskite on lowering oxidation light-off temperature for automotive exhaust gas pollutants
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Effects of excess manganese in lanthanum manganite perovskite on lowering oxidation light-off temperature for automotive exhaust gas pollutants

机译：钙锰酸镧锰中过量锰对降低汽车尾气污染物氧化起燃温度的影响

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The effects of excess manganese on enhancement of oxidation activity of LaMn_(1+x)O_(3+δ) perovskite for CO and propane removal from a synthetic automotive exhaust gas are reported. Various LaMn_(1+x)O_(3+δ) (x = 0.05-0.4) perovskite-type nanocatalysts were prepared by a microwave-assisted "gel combustion" method and calcined at 700℃ in air. Scanning electron microscopy (SEM) of the samples demonstrates highly porous and frothy particles. More than twice enhancement in the BET surface area of the catalyst samples is observed for the LaMn_1.2O_(3+δ) catalyst, as compared to LaMnO_3. X-ray powder diffraction (XRD) analyses show only the perovskite structure for the catalysts. H_2-, CO-, and C_3H_8- temperature programmed reductions (TPR) indicate that the excess manganese oxides in LaMn_(1+x)O_(3+δ) significantly enhance the reducibility of the catalysts. The manganese oxides may be in the form of a separate phase of amorphous and/or small crystallites. Redox titration test results show that, as the amount of Mn in the structure increases, the average oxidation state of manganese reduces resulting in lowering cation vacancies. The light off temperature for CO and propane oxidation on LaMn_1.2O_(3+δ) is decreased by 57 and 38℃, respectively as compared to those of LaMnO_3 perovskite. LaMn_1.2O_(3+δ) is stable under harsh conditions of the pollutants oxidation.
机译：报道了过量锰对增强LaMn_（1 + x）O_（3 +δ）钙钛矿对CO的氧化活性和从合成汽车尾气中去除丙烷的影响。通过微波辅助“凝胶燃烧”法制备了各种LaMn_（1 + x）O_（3 +δ）（x = 0.05-0.4）钙钛矿型纳米催化剂，并在空气中于700℃煅烧。样品的扫描电子显微镜（SEM）显示出高度多孔和泡沫状的颗粒。与LaMnO_3相比，对于LaMn_1.2O_（3 +δ）催化剂，观察到催化剂样品的BET表面积增加了两倍以上。 X射线粉末衍射（XRD）分析仅显示催化剂的钙钛矿结构。 H_2-，CO-和C_3H_8-程序升温还原（TPR）表明LaMn_（1 + x）O_（3 +δ）中过量的锰氧化物显着提高了催化剂的还原性。锰氧化物可以是无定形和/或小微晶的分离相的形式。氧化还原滴定测试结果表明，随着结构中Mn含量的增加，锰的平均氧化态降低，从而导致阳离子空位降低。与LaMnO_3钙钛矿相比，LaMn_1.2O_（3 +δ）上CO和丙烷氧化的起燃温度分别降低了57和38℃。 LaMn_1.2O_（3 +δ）在苛刻的污染物氧化条件下是稳定的。

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