The role of alumina in the supported Mo/HBeta–Al₂O₃ catalyst for olefin metathesis: A high-resolution solid-state NMR and electron microscopy study

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• 作者：Xiujie Li ; Weiping Zhang ; Shenglin Liu ; Longya Xu ; Xiuwen Han ; Xinhe Bao
• 关键词：Olefin metathesis ; Mo/HBeta&#x2013 ; Al₂O₃ catalyst ; Solid-state NMR ; ²⁷Al MQ MAS NMR ; Hyperpolarized ¹²⁹Xe NMR ; Electron microscopy
• 刊名：Journal of Catalysis
• 出版年：2007
• 期刊代码：97_00219517
• 类别：ce
• 出版时间：15 August 2007
• 卷：250
• 期：1
• 页码：55-66
• 文件大小：677 K

摘要

High-resolution solid-state MAS NMR; hyperpolarized ¹²⁹Xe NMR, SEM, and TEM; XRD; and N₂ adsorption were used to investigate the role of alumina in the Mo/HBeta–Al₂O₃ catalyst. XRD and N₂ adsorption showed that introduction of alumina into the support may protect the HBeta framework from destruction. Quantitative ²⁹Si MAS, ²⁷Al MAS, and MQ MAS NMR spectra demonstrated that dealumination occurs preferentially at specific T-sites in the Mo/HBeta catalyst; however, the framework aluminum in HBeta zeolites remains at the same crystallographic sites after the addition of alumina. Hyperpolarized ¹²⁹Xe NMR, HRTEM, and SEM images indicate that Mo species are readily dispersed in alumina rather than in HBeta zeolites. The preferential migration of Mo species into the alumina pores may preserve the integrity of the HBeta zeolite framework and result in the moderate distribution of Mo species and acidity in the composite support. These may be correlated with the high performance of Mo/HBeta–Al₂O₃ catalysts in the metathesis of ethene and butene-2 to propene.