A high-resolution MAS NMR study on the potential catalysts Mo/HBeta for olefin metathesis: The interaction of Mo species with HBeta zeolite |
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Authors: | Xiujie Li Weiping Zhang Shenglin Liu Xiuwen Han Longya Xu Xinhe Bao |
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Institution: | State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China |
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Abstract: | The interfacial interaction of Mo species with the HBeta zeolite was studied by multinuclear MAS NMR, XRD and N2 adsorption. As proved by the quantitative 27Al MAS NMR, this interaction is so strong as to dealuminate the framework of HBeta, and leads to a new peak appearing at ?14 ppm, which indicates the formation of crystalline Al2(MoO4)3. This can also be detected by XRD measurements when the Mo loading is as high as 9.0 wt.%. The corresponding quantitative 29Si and 1H MAS NMR spectra show that the amount of silanols and Brønsted acidic sites decrease obviously with increasing Mo loading. This also reveals an interaction between Mo species and HBeta support through an oxygen bridge resulting from condensation with the hydroxyls on the support. At higher Mo loadings, the interaction is so strong that it results in an extraction of aluminum from the zeolite framework, and subsequently appearance of Al2(MoO4)3 and loss of Brønsted acidic sites. These can be correlated to the low catalytic activity of Mo/HBeta in metathesis of ethylene and 2-butylene to propylene. |
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Keywords: | MAS NMR Mo/HBeta catalyst HBeta zeolite Interaction Olefin metathesis reaction Ethylene 2-Butylene Propylene |
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