碳纳米管合成中双金属催化剂的逐步浸渍

IF 4.8 2区 化学 Q2 CHEMISTRY, PHYSICAL
Eunsu Yang , Jinwon Choi , Gihan Kwon , Taejin Kim , Jaegeun Lee
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引用次数: 0

摘要

负载型双金属催化剂在碳纳米管合成中得到了广泛的应用,但浸渍工艺对催化剂的影响尚不清楚。在这里,我们研究了金属浸渍的顺序如何影响碳纳米管的合成。采用共浸渍法和阶梯浸渍法在氧化铝载体上制备了钴钼(co- mo)双金属催化剂,并比较了两种催化剂在相同条件下的碳纳米管合成性能。阶梯式浸渍催化剂的产碳率高于共浸渍催化剂。值得注意的是,先浸渍Mo后浸渍Co的产率最高,尽管BET表面积最小。同步加速器x射线衍射和可见/紫外拉曼光谱分析表明,该催化剂仅含有具有MoO4结构的Al2(MoO4)3。x射线光电子能谱澄清了表面化学性质:碳纳米管生产率最高的催化剂将Mo完全暴露为Al2(MoO4)3和CoMoO4中的Mo6 +,而其他催化剂则同时含有Mo4+和Mo6+。已知像Al2(MoO4)3这样的MoOx物种在碳纳米管合成过程中抑制Co烧结,延缓催化剂失活并提高碳收率。碳产率与CoMoO4含量呈反比关系。这是由于CoMoO4形成过程中催化活性Co的消耗,减少了碳纳米管生长的活性位点。ICP-OES进一步证实了阶梯式催化剂具有较高的Co和Mo负载,有助于提高催化剂的性能。CoMoO4的形成程度强烈依赖于金属的引入顺序。通过考虑载体零电荷点与金属前驱体溶液pH值之间的关系,可以说明这一趋势。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Stepwise impregnation of bimetallic catalysts for carbon nanotube synthesis
Supported bimetallic catalysts are widely used for carbon nanotube (CNT) synthesis, yet the effects of impregnation procedure remain underexplored. Here, we investigated how the sequence of metal impregnation affects CNT synthesis. We prepared cobalt-molybdenum (Co-Mo) bimetallic catalysts on alumina supports via co- and stepwise impregnation, then compared their CNT synthesis performance under identical conditions. Stepwise-impregnated catalysts exhibited higher carbon yields than those prepared by co-impregnation. Notably, impregnating Mo after Co achieved the highest yield despite the lowest BET surface area. Synchrotron X-ray diffraction and visible/UV-Raman spectroscopy revealed that only this catalyst contained Al2(MoO4)3 with a MoO4 structure. X-ray photoelectron spectroscopy clarified the surface chemistry: the catalyst with the highest CNT productivity exposed Mo entirely as Mo6 + in Al2(MoO4)3 and CoMoO4, whereas the others contained both Mo4+ and Mo6+. The MoOx species like Al2(MoO4)3 is known to suppress Co sintering during CNT synthesis, delaying catalyst deactivation and enhancing the carbon yield. Moreover, an inverse relationship was observed between carbon yield and the CoMoO4 content. This is attributed to the consumption of catalytically active Co during CoMoO4 formation, which reduces active sites for CNT growth. ICP-OES further confirmed higher Co and Mo loadings for stepwise catalysts, contributing to superior catalyst performance. The extent of CoMoO4 formation strongly depended on the metal introduction sequence. This trend is illustrated by considering the relationship between the point of zero charge of support and the pH of the metal precursor solutions.
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来源期刊
Applied Catalysis A: General
Applied Catalysis A: General 化学-环境科学
CiteScore
9.00
自引率
5.50%
发文量
415
审稿时长
24 days
期刊介绍: Applied Catalysis A: General publishes original papers on all aspects of catalysis of basic and practical interest to chemical scientists in both industrial and academic fields, with an emphasis onnew understanding of catalysts and catalytic reactions, new catalytic materials, new techniques, and new processes, especially those that have potential practical implications. Papers that report results of a thorough study or optimization of systems or processes that are well understood, widely studied, or minor variations of known ones are discouraged. Authors should include statements in a separate section "Justification for Publication" of how the manuscript fits the scope of the journal in the cover letter to the editors. Submissions without such justification will be rejected without review.
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