Synthesis and characterization of divalent cobalt-substituted mesoporous aluminophosphate molecular sieves and their application as novel heterogeneous catalysts for the oxidation of cycloalkanes
Synthesis and characterization of divalent cobalt-substituted mesoporous aluminophosphate molecular sieves and their application as novel heterogeneous catalysts for the oxidation of cycloalkanes
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DOI：
10.1016/j.jcat.2005.04.036
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发表时间：
2005-07
影响因子：
7.3
通讯作者：
P. Selvam;S. Mohapatra
中科院分区：
文献类型：
--
作者：
P. Selvam;S. Mohapatra
水热合成了热稳定的二价钴取代的六方介孔磷酸铝分子筛CoHMA，并通过多种分析和光谱技术对其进行了系统的表征。XRD、TEM、艾德、ICP-AES、TGA-DTA、N2吸附、DR-UV-维斯、XANES和NH3-TPD研究表明二价钴在介孔磷酸铝基质的四面体骨架中具有类质同晶取代。此外，热处理前后CoHMA的蓝色进一步证实了二价钴在基质中的四面体环境。结果表明，CoHMA催化剂在温和的反应条件下，对环烷烃环己烷、环辛烷和环十二烷的氧化表现出优异的活性。与迄今为止报道的许多其他钴基多相催化剂不同，CoHMA在煅烧或任何其他合成后处理时没有显示出钴的任何移位或偏析。在这项研究中，CoHMA的性能也进行了比较，含钴的微孔磷酸铝，即CoAPO-5与AFI拓扑结构，以及与微孔和介孔类似物的钴硅酸盐分子筛具有MFI或MCM-41结构。
Thermally stable divalent cobalt-substituted hexagonal mesoporous aluminophosphate, CoHMA molecular sieves were hydrothermally synthesized and systematically characterized by several analytical and spectroscopic techniques. XRD, TEM, ED, ICP-AES, TGA-DTA, N2sorption, DR-UV–vis, XANES, and NH3-TPD studies showed isomorphous substitution of divalent cobalt in a tetrahedral framework of a mesoporous aluminophosphate matrix. Furthermore, the blue color of CoHMA, before and after thermal treatment, further confirmed the tetrahedral environment of divalent cobalt in the matrix. As a result, the CoHMA catalyst showed excellent activity for the oxidation of cycloalkanes, that is, cyclohexane, cyclooctane and cyclododecane, under mild reaction conditions. Unlike the many other cobalt-based heterogeneous catalysts reported so far, CoHMA does not show any dislodgement or segregation of cobalt with calcination or any other postsynthesis treatments. In this study, the performance of CoHMA was also compared with the cobalt-containing microporous aluminophosphate, that is, CoAPO-5 with AFI topology, as well as with both microporous and mesoporous analogues of cobalt silicate molecular sieves that have MFI or MCM-41 structures.