کد مقاله | کد نشریه | سال انتشار | مقاله انگلیسی | نسخه تمام متن |
---|---|---|---|---|
7832357 | 1503293 | 2006 | 6 صفحه PDF | دانلود رایگان |
عنوان انگلیسی مقاله ISI
Modification of the structure and properties of SAPO-11 using rare earths
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کلمات کلیدی
موضوعات مرتبط
مهندسی و علوم پایه
شیمی
شیمی تئوریک و عملی
پیش نمایش صفحه اول مقاله
![عکس صفحه اول مقاله: Modification of the structure and properties of SAPO-11 using rare earths Modification of the structure and properties of SAPO-11 using rare earths](/preview/png/7832357.png)
چکیده انگلیسی
Silicoaluminophosphate (SAPO)-11 molecular sieve was modified by rare earth La and Ce using impregnating and ion-exchanging methods. The RE-modified SAPO-11 samples were characterized by X-ray diffraction (XRD), Brunauer-Emmett- Teller (BET), pore-size distribution (PSD), in-situ Fourier transform infrared spectroscopy (FTIR), and temperature-programmed desorption of ammonia (NH3-TPD), and compared with the unmodified SAPO-11 sample. The XRD patterns indicated that after RE modification, especially for the La-exchanged sample, the composition of molecular sieve was changed and the crystallinity decreased. The normalized surface area (NSA) of ion-exchanged samples proved that the unsubstituted metal oxides accumulated inside the SAPO-11 pores. Because of the RE cations that were loaded onto the surface of molecular sieve, which could be regarded as the Lewis acid sites, there was an increase in the amount of Lewis acid sites and a decrease in the Brønsted acid/Lewis acid (B/L) ratio. The ability of RE cations to acquire electrons was weaker than that of Al3+; therefore, the bond strength of bridged hydroxyl decreased after modification. The total acidity of SAPO-11 decreased after RE modification.
ناشر
Database: Elsevier - ScienceDirect (ساینس دایرکت)
Journal: Acta Physico-Chimica Sinica - Volume 22, Issue 12, December 2006, Pages 1495-1500
Journal: Acta Physico-Chimica Sinica - Volume 22, Issue 12, December 2006, Pages 1495-1500
نویسندگان
Yuewei Zhang, Meiqing Shen, Xiaodong Wu, Duan Weng, Zhihua Zhang, Ran Tian, Kebin Chi,