Improvement in the coating homogeneity in electrosynthesized Rh structured catalysts for the partial oxidation of methane
Improvement in the coating homogeneity in electrosynthesized Rh structured catalysts for the partial oxidation of methane
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DOI：
10.1016/j.cattod.2014.10.003
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发表时间：
2015-05-15
期刊：
影响因子：
5.3
通讯作者：
Vaccari, Angelo
中科院分区：
文献类型：
--
作者：
Benito, Patricia;Monti, Marco;Vaccari, Angelo
采用碱性电解法在泡沫铁铬合金表面沉积Rh/Mg/Al和Rh/Al氢氧化物，以改善沉积膜的均匀性和组成，从而提高焙烧法制备的结构化催化剂在甲烷催化部分氧化制合成气反应中的性能。这项工作的重点是通过将电接触点的数量从1点增加到3点来降低开孔泡沫圆柱体内的电流梯度，以促进氢氧化物的更均匀沉淀。电化学和催化测试以及SEM/EDS和mu-XRFIXRD分析允许将电接触点的数量与材料性能的影响相关联。最后，在铂片上进行合成，研究了支撑体的电性能和形状对膜组成的影响，采用3个接触点的结构，由于在支撑体附近产生碱性介质的硝酸盐和水分子的还原得到了增强，因此获得了更均匀的泡沫表面涂层。层厚度高达5-15 μ m的沉积，然而，连续沉淀的膜的组成接近预期的一个和一个层富含铝和铑（外层）是不可避免的。涂层的改进使得在-1.1 V下制备3000 s的样品的性能增强。因此，在煅烧和催化测试期间在-1.2V下持续2000 s制备的样品中外层的低粘附性可能是催化性能意外降低的原因。通过在Pt板上进行合成，观察到相同的顺序沉淀，表明载体的电性质对此现象不起关键作用。(C)2014爱思唯尔有限公司版权所有。
The precipitation of Rh/Mg/Al and Rh/Al hydroxides on the surface of FeCrAlloy foams by a base electrogeneration method was investigated to improve the properties of the deposited film (homogeneity and composition) and therefore the performances of the structured catalysts, obtained by calcination, in the Catalytic Partial Oxidation of CH4 to syngas. The work focussed on decreasing current gradients within open-cell foam cylinders by increasing the number of electrical contacts from 1 to 3 points to promote a more homogeneous precipitation of the hydroxides. Electrochemical and catalytic tests as well as SEM/EDS and mu-XRFIXRD analyses allowed to correlate the effect of the number of electrical contact points with materials properties. Lastly, syntheses were performed on Pt plates to study the effect of the electrical behaviour and shape of the support on the composition of the film.A more homogeneous coating of the foam surface was achieved by adopting a configuration with 3 contact points since the reduction of nitrates and water molecules that generates the basic media in the vicinity of the support was enhanced. Layer thicknesses up to 5-15 mu m were deposited; however, the sequential precipitation of a film with composition closer to the expected one and a layer enriched in Al and Rh (outer layer) was not avoided. The improvement in the coating gave rise to enhanced performances for a sample prepared at -1.1 V for 3000 s. Contrarily, the low adherence of the outer layer in a sample prepared at -1.2 V for 2000 s during both calcination and catalytic tests may be responsible of the unexpected decrease in catalytic performances. The same sequential precipitation was observed by performing the syntheses on Pt plates, showing that the electrical nature the support did not play a key role on this phenomenon. (C) 2014 Elsevier B.V. All rights reserved.