Study of Zn and Ga Exchange in H-[Fe]ZSM-5 and H-[B]ZSM-5 Zeolites

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• 作者：Yu-Hao YehRaymond J. Gorte
• 刊名：Industrial & Engineering Chemistry Research
• 出版年：2016
• 出版时间：December 21, 2016
• 年：2016
• 卷：55
• 期：50
• 页码：12795-12805
• 全文大小：609K
• ISSN：1520-5045

文摘

The catalytic properties of H-[Fe]ZSM-5 and H-[B]ZSM-5 were explored after addition of Zn or Ga. TPD–TGA of 2-propanamine adsorbed on Zn- and Ga-exchanged H-[Fe]ZSM-5 showed a decrease in Brønsted-acid site densities and the formation of new dehydrogenation sites, similar to what is observed following exchange in H-[Al]ZSM-5 and in amorphous silica–alumina. Exchanged Zn cations in [Fe]ZSM-5 also exhibited Lewis-acid character, as demonstrated by the appearance of a υ(CN) stretch at 2310 cm^–1 upon adsorption of CD₃CN. By contrast, the sites in H-[B]ZSM-5 were not capable of protonating 2-propanamine, did not form dehydrogenation sites when Zn or Ga were added, and showed no evidence for sites with Lewis-acid character from the FTIR spectroscopy of CD₃CN. Neither H(Zn)-[Fe]ZSM-5 nor H(Zn)-[B]ZSM-5 catalyzed reactions of n-hexane at 773 K, but the TPD–TGA of adsorbed propene on H(Zn)-[Fe]ZSM-5 showed strong interactions between the Zn and olefins that might be responsible for the dehydrocyclization of light alkanes in Zn-exchanged, Al-containing zeolites.