The synergic effect between Mo species and acid sites in Mo/HMCM-22 catalysts for methane aromatization.
The synergic effect between Mo species and acid sites in Mo/HMCM-22 catalysts for methane aromatization.
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DOI：
10.1039/b502794b
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发表时间：
2005-08
期刊：
影响因子：
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通讯作者：
Ding Ma;Qingjun Zhu;Zili Wu;Danhong Zhou;Yuying Shu;Q. Xin;Yide Xu;X. Bao
中科院分区：
文献类型：
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作者：
Ding Ma;Qingjun Zhu;Zili Wu;Danhong Zhou;Yuying Shu;Q. Xin;Yide Xu;X. Bao
研究了甲烷芳构化反应工作催化剂的前驱体Mo/HMCM-22催化剂的酸性质，以及Mo物种与酸中心的协同作用。结果表明，钼的引入改变了HMCM-22的布朗斯特和刘易斯酸性。我们建议的Mo物种的单体形成的交换Mo物种与布朗斯台德酸网站。另一方面，配位不饱和位点（CUS）被认为是负责新检测到的刘易斯酸位点的形成。通过计算机模拟，结合实验结果，推测甲烷的有效活化是在MCM-22分子筛12个MR超笼中的Mo物种上完成的，而同一孔道系统中的Brønsted酸中心对苯的生成起着关键作用.与Mo/HZSM-5相比，Mo/HMCM-22催化剂的反应活性曲线呈现出明显的火山型特征，这是由于MCM-22分子筛独特的孔道结构和Mo物种与酸中心的协同作用所致。
The acid properties of Mo/HMCM-22 catalyst, which is the precursor form of the working catalyst for methane aromatization reaction, and the synergic effect between Mo species and acid sites were studied and characterized by various characterization techniques. It is concluded that Brønsted and Lewis acidities of HMCM-22 are modified due to the introduction of molybdenum. We suggest a monomer of Mo species is formed by the exchange of Mo species with the Brønsted acid sites. On the other hand, coordinate unsaturated sites (CUS) are suggested to be responsible for the formation of newly detected Lewis acid sites. Computer modelling is established and coupling with experimental results, it is then speculated that the effective activation of methane is properly accomplished on Mo species accommodated in the 12 MR supercages of MCM-22 zeolite whereas the Brønsted acid sites in the same channel system play a key role for the formation of benzene. A much more pronounced volcano-typed reactivity curve of the Mo/HMCM-22 catalysts, as compared with that of the Mo/HZSM-5, with respect to Mo loading is found and this can be well understood due to the unique channel structure of MCM-22 zeolite and synergic effect between Mo species and acid sites.