NMR Study on the Acidity of TS-1 Zeolite |
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Authors: | Jianqin Zhuang Zhimin Yan Xiumei Liu Xianchun Liu Xiuwen Han Xinhe Bao Ulrich Mueller |
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Affiliation: | (1) State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian, 116023, China;(2) BASF Aktiengesellschaft, Chemicals Research & Engineering, Zeolite Catalysis, GCC/Z-M 301, D-67056 Ludwigshafen, Germany |
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Abstract: | The acidic properties of TS-1 and Silicalite-1 zeolites have been investigated by the solid-state MAS NMR technique capable of in situ sample pretreatment. As shown by a combination of the 31P MAS NMR and 1H MAS NMR techniques with trimethylphosphine, not only Brønsted acid sites but also Lewis acid sites exist in the TS-1 zeolites. Moreover, TS-1 zeolite is more acidic compared with Silicalite-1. The 1H, 29Si MAS NMR spectra and the resonance related to Brønsted acid species in the 31P MAS NMR spectra demonstrate clearly that the presence of titanium in the framework results in the formation of a new hydroxy group, titanols, which is more acidic than silanols of Silicalite-1. The 31P MAS NMR measurements also illustrate convincingly the existence of at least two different Lewis acid species on the TS-1 zeolites. The conversion of propylene oxide into methoxypropanol catalyzed by TS-1 or Silicalite-1 zeolite in methanol solution as a test reaction has also been described. With the increase of titanium in zeolite, TS-1 appears to have a higher activity during the reaction of propylene oxide to methoxypropanol. |
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Keywords: | TS-1 zeolite solid-state MAS NMR acidity |
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