کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
10245133 | 47713 | 2005 | 9 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
In situ monitoring of n-butene conversion on H-ferrierite by 1H, 2H, and 13C MAS NMR: kinetics of a double-bond-shift reaction, hydrogen exchange, and the 13C-label scrambling
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
مهندسی شیمی
کاتالیزور
پیش نمایش صفحه اول مقاله
![عکس صفحه اول مقاله: In situ monitoring of n-butene conversion on H-ferrierite by 1H, 2H, and 13C MAS NMR: kinetics of a double-bond-shift reaction, hydrogen exchange, and the 13C-label scrambling In situ monitoring of n-butene conversion on H-ferrierite by 1H, 2H, and 13C MAS NMR: kinetics of a double-bond-shift reaction, hydrogen exchange, and the 13C-label scrambling](/preview/png/10245133.png)
چکیده انگلیسی
Kinetics of a double-bond-shift reaction, hydrogen exchange, and 13C-label scrambling were monitored in situ by 2H, 1H, and 13C MAS NMR for n-but-1-ene adsorbed on the zeolite ferrierite under batch reactor conditions at 290-373 K. A double-bond-shift reaction, the fastest among the three reactions studied, can be monitored provided that 97% of Brønsted acid sites are substituted by Na cations. The activation energy for this reaction was found to be 9.8 kcalâmolâ1. Hydrogen exchange with protons from the zeolite is observed for both methene and methyl groups of n-but-2-ene, formed from the initial n-but-1-ene. The terminal olefinic CH2 group of n-but-1-ene is involved in the exchange, providing the pathway for the exchange into the methyl group of the n-but-2-ene, mainly observed in the spectrum in accordance with thermodynamic equilibrium between n-but-1-ene and n-but-2-ene. This offers similar apparent activation energies of about 7 kcalâmolâ1 for the exchange into methene and methyl groups of n-but-2-ene. The 13C-label scrambling in n-but-2-ene is indicative of sec-butyl cation formation from the olefin in the zeolite framework, which can be formed as a small quantity of transient species not detectable by NMR but providing the label scrambling. The apparent activation energy for the 13C-label scrambling was found to be 21 ± 2 kcalâmolâ1, which is three times higher compared with the activation energy for the label scrambling in sec-butyl cation in a superacidic solution.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Journal of Catalysis - Volume 229, Issue 1, 1 January 2005, Pages 243-251
Journal: Journal of Catalysis - Volume 229, Issue 1, 1 January 2005, Pages 243-251
نویسندگان
Alexander G. Stepanov, Sergei S. Arzumanov, Mikhail V. Luzgin, Horst Ernst, Dieter Freude,