Zn-Promoted H-ZSM-5 for Endothermic Reforming of n-Hexane at High Pressures
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- 作者：Yu-Hao Yeh ; Shiyu Zhu ; Patrick Staiber ; Raul F. Lobo ; Raymond J. Gorte
- 刊名：Industrial & Engineering Chemistry Research
- 出版年：2016
- 出版时间：April 13, 2016
- 年：2016
- 卷：55
- 期：14
- 页码：3930-3938
- 全文大小：432K
- 年卷期：0
- ISSN：1520-5045
文摘
The addition of Zn to H-ZSM-5 zeolites was studied for application to endothermic reforming in hypersonic aircraft engines. Temperature-programmed-desorption (TPD)/thermogravimetric-analysis (TGA) measurements with 2-propanamine on two H(Zn)-ZSM-5 samples showed that at low ion-exchange levels, less than 0.5 Zn/Al, each Zn cation displaces one Brønsted-acid site. Although rates for n-hexane conversion at 633 and 823 K and at a pressure of 137 bar decreased with the loss of Brønsted sites, Zn promotion greatly increased the production of H2 and the formation of small aromatic molecules. FTIR of adsorbed acetonitrile-d3 and calorimetric measurements of adsorbed CO at 195 K indicate that the exchanged Zn cations form Lewis-acid centers. A model in which the Zn cations, acting as Lewis-acid centers, polarize intermediates formed at Brønsted sites is presented as a way of understanding the observations.