HZSM-5 Zeolites with Different SiO2/Al2O3 Ratios. Characterization and NH3 Desorption Kinetics
HZSM-5 Zeolites with Different SiO2/Al2O3 Ratios. Characterization and NH3 Desorption Kinetics
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DOI：
10.1021/ie4039532
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发表时间：
2014-10-08
影响因子：
4.2
通讯作者：
de Lasa, Hugo
中科院分区：
文献类型：
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作者：
Al-Dughaither, Abdullah S.;de Lasa, Hugo
该文章报道了 SiO2/Al2O3 比例（30、80 和 280）对 HZSM-S 沸石性能的影响 XRD 图案显示，低 SiO2/Al2O3 比例沸石的 XRD 峰强度在低 2 theta 角处降低 N-2 吸附和解吸等温线显示出滞后现象，微孔和中孔都可能导致 颗粒网络。 NLDFT 圆柱模型证实了这一特性。沸石孔隙骨架中有5.5埃的微孔。此外，比表面积孔体积和孔径的破坏表明，SiO2/Al2O3 比例的变化不会影响 HZSM-S 的结构性能。 NH3-TPD 显示弱酸位点和强酸位点。吡啶-FTIR 还证实，在 HZSM-S 中，磨损酸度包含路易斯和氢键位点，而强酸度主要涉及布朗斯台德和氢键位点。事实证明，弱酸与强酸位点的比率以及通过 NH3 解吸动力学和数值回归进行的测量可以确定强酸位点和弱酸位点的活化能。还发现，动力学解吸速率常数的变化与用 NH3-TPD 和 Prridine-FTIR 观察到的弱酸位点和强酸位点的变化一致。
The article reports the influnce of the SiO2/Al2O3 ratio (30, 80, and 280) on HZSM-S zeolite properties XRD patterns show a decrease in the XRD peak intensity at low 2 theta angles for low SiO2/Al2O3 ratio zeolites N-2 adsoption and desorption isotherms display hysterisis with both cmicroores and mesopores likely contributing to the patciles network. The NLDFT cylindrical model confirms the charactersitic. 5.5 angstrom micropores in the zeolite pore framework. Furthermore specific surface area pore volume, and pore size distruped demonstrate that changes in the SiO2/Al2O3 ratio do not influence HZSM-S structural properties. NH3-TPD shown both weak and strong acid sites. Pyridine-FTIR also confirms that, in HZSM-S the wear acidity encompasses Lewis and hydrogen-bonded sites while the strong acidity manly involves the Bronsted and sites. It is proven that the ratio of weak to strong acid sties and measure by NH3 desorption kinetics and numerical regression allow the establishment of energies of activation for both strong and weak acid sites. It is also found that the kinetic desorption rate constants vary in agreement with the changes in weak and strong acid sites as observed with NH3-TPD and Prridine-FTIR.