Structural features of La1-xCexNiO3 mixed oxides and performance for the dry reforming of methane
Structural features of La1-xCexNiO3 mixed oxides and performance for the dry reforming of methane
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DOI：
10.1016/j.apcata.2006.06.010
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发表时间：
2006-09-01
影响因子：
5.5
通讯作者：
Fierro, J. L. G.
中科院分区：
文献类型：
--
作者：
Lima, S. M.;Assaf, J. M.;Fierro, J. L. G.
采用柠檬酸盐法制备了La_（1-x）Ce_xNiO_3（x = 0，0.05，0.4和0.7）复合氧化物，并将其还原活化后用于甲烷二氧化碳重整制合成气反应。采用热重分析（TGA）、X射线衍射（XRD）、比表面积测定、X射线光电子能谱（XPS）、程序升温还原（TPR）、透射电镜（TEM）和程序升温氧化（TPO）等手段对产物进行了表征。LaNiO3钙钛矿对甲烷重整具有活性，但随着时间的推移而缓慢失活。然而，用四价金属阳离子（Ce）取代A位点金属离子导致催化活性增加。此外，Ce的插入增加了催化剂相对于重整反应的稳定性。La0.95Ce0.05NiO3催化剂的活性最高，在1023 K时CO2转化率为62%。XRD和TPR分析证实，在高Cc含量下，CeO2以CeO2相的形式出现，干扰了钙钛矿结构的形成，生成NiO和La2NiO4。由于氧化铈的低溶解度，其在低Ce含量区域中插入钙钛矿结构中也是可能的。掺入的这种低量的铈不仅负责钙钛矿在其通过还原活化后的催化性能的增强，而且还负责碳形成的抑制。(C)2006 Elsevier B.V.保留所有权利。
Mixed oxides La1-xCexNiO3 (x = 0, 0.05, 0.4 and 0.7) have been prepared by the citrate method and tested, after reduction activation, in the CO2 reforming of methane reaction into synthesis gas. The compounds were characterized by thermogravimetric analysis (TGA), X-ray diffraction (XRD), specific surface area measurements, X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), transmission electron microscopy (TEM) and temperature-programmed oxidation (TPO). The LaNiO3 perovskite exhibited activity to methane reforming, but suffered a slow deactivation with time-on-stream. Nevertheless, substitution of the A site metal ion with a tetravalent metal cation (Ce) led to an increase in catalytic activity. Moreover, the insertion of Ce increased the stability of the catalysts with respect to the reforming reaction. The La0.95Ce0.05NiO3 catalyst showed the highest activity, with CO2 conversion of 62% at 1023 K. The XRD and TPR analyses confirmed that at high Cc contents, ceria appears as segregated CeO2 Phase and interferes with the rate of perovskite structure formation, so that NiO and La2NiO4 are produced. As a consequence of the low solubility of cerium oxide, its insertion in the perovskite structure is also possible in the low Ce-content regions. This low amount of cerium incorporated is responsible not only for the enhancement of catalytic performance of the perovskite after its activation by reduction, but also for the inhibition of carbon formation. (C) 2006 Elsevier B.V. All rights reserved.