The acid properties of H-ZSM-5 as studied by NH3-TPD and 27Al-MAS-NMR spectroscopy
The acid properties of H-ZSM-5 as studied by NH3-TPD and 27Al-MAS-NMR spectroscopy
复制标题
DOI：
10.1016/j.apcata.2007.06.003
复制
发表时间：
2007-09-10
影响因子：
5.5
通讯作者：
Simon, Ulrich
中科院分区：
文献类型：
--
作者：
Rodriguez-Gonzalez, Luz;Hermes, Florian;Simon, Ulrich
用氨程序升温脱附（NH_3-TPD）法研究了不同SiO_2/Al_2O_3比（30，50，80，150，280和1000）的H-ZSM-5分子筛的酸性。采用不同的预处理方法以及氨解吸后不同曲线拟合方法的比较来区分不同的吸附位点。应用27 Al-MAS-NMR光谱以区分骨架（AlF）与骨架外铝（AIEF）。这两种技术都表明，当考虑铝含量时，布朗斯台德酸中心的浓度低于预期。由假定氨的自由再吸附的理论模型确定的布朗斯台德酸中心的强度被发现在Δ H = 129-161 U mol（-1）的范围内，并且显示酸强度的变化小于a = 12 U mol（-1）。(c)2007 Elsevier B. V.保留所有权利。
The acid properties of H-ZSM-5 zeolites with different SiO2/Al2O3 ratios (30, 50, 80, 150, 280 and 1000) were examined by means of the temperature programmed desorption of ammonia (NH3-TPD). Different pretreatments together with a comparison of different curve-fitting methods after desorption of ammonia were used to differentiate between different adsorption sites. 27 Al-MAS-NMR spectroscopy was applied to distinguish the framework (AlF) from the extra-framework aluminum (AIEF). Both techniques reveal that the concentration of Bronsted acid sites is lower than expected when considering the aluminum content. The strength of the Bronsted acid sites, determined by a theoretical model assuming the free readsorption of ammonia, is found to be in the range of Delta H = 129-161 U mol(-1) and shows variations in the acid strength to be less than a = 12 U mol(-1). (c) 2007 Elsevier B.V. All rights reserved.