Direct decomposition of methane over SBA-15 supported Ni, Co and Fe based bimetallic catalysts
Direct decomposition of methane over SBA-15 supported Ni, Co and Fe based bimetallic catalysts
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DOI：
10.1016/j.apsusc.2015.01.032
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发表时间：
2015-03
影响因子：
6.7
通讯作者：
M. Pudukudy;Z. Yaakob;Zubair Shamsul Akmal
中科院分区：
文献类型：
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作者：
M. Pudukudy;Z. Yaakob;Zubair Shamsul Akmal
甲烷的热催化分解是制备无COx氢气和碳纳米材料的替代途径。本文采用湿浸渍法合成了一系列以介孔SBA-15为载体的Ni、Co和Fe基催化剂，并对其结构、织构和还原性能进行了表征，并成功地用于甲烷裂解反应。小角X射线衍射图和透射电子显微镜（TEM）图像清楚地显示了金属氧化物颗粒在SBA-15表面的精细分散，而不影响其介孔织构。氮吸附分析表明，减少比表面积和孔体积的SBA-15，金属负载后，由于部分填充的六边形介孔的金属物种。甲烷分解实验的结果表明，即使在300分钟的运行时间（TOS）之后，所有的催化剂在700 °C下对于反应都是高度活性和稳定的。而NiCo/SBA-15催化剂在30 min内的最大氢产率为1.56%。CoFe/SBA-15催化剂具有较高的催化稳定性，在反应过程中氢气产率为51%。催化剂的催化稳定性归因于催化剂中形成的镍合金。此外，沉积的碳被发现是在一组新的空心多壁纳米管的形式与开放的尖端，表明一个基地的增长机制，这证实了SBA-15负载的催化剂的选择性形成开放的尖端碳纳米管。拉曼光谱和热重分析结果表明，在该催化剂上沉积的碳纳米管具有较高的石墨化度和氧化稳定性。
Thermocatalytic decomposition of methane is an alternative route for the production of COx-free hydrogen and carbon nanomaterials. In this work, a set of novel Ni, Co and Fe based bimetallic catalysts supported over mesoporous SBA-15 was synthesized by a facile wet impregnation route, characterized for their structural, textural and reduction properties and were successfully used for the methane decomposition. The fine dispersion of metal oxide particles on the surface of SBA-15, without affecting its mesoporous texture was clearly shown in the low angle X-ray diffraction patterns and the transmission electron microscopy (TEM) images. The nitrogen sorption analysis showed the reduced specific surface area and pore volume of SBA-15, after metal loading due to the partial filling of hexagonal mesopores by metal species. The results of methane decomposition experiments indicated that all of the bimetallic catalysts were highly active and stable for the reaction at 700 °C even after 300 min of time on stream (TOS). However, a maximum hydrogen yield of ∼56% was observed for the NiCo/SBA-15 catalyst within 30 min of TOS. A high catalytic stability was shown by the CoFe/SBA-15 catalyst with 51% of hydrogen yield during the course of reaction. The catalytic stability of the bimetallic catalysts was attributed to the formation of bimetallic alloys. Moreover, the deposited carbons were found to be in the form of a new set of hollow multi-walled nanotubes with open tips, indicating a base growth mechanism, which confirm the selectivity of SBA-15 supported bimetallic catalysts for the formation of open tip carbon nanotubes. The Raman spectroscopic and thermogravimetric analysis of the deposited carbon nanotubes over the bimetallic catalysts indicated their higher graphitization degree and oxidation stability.