Number and Brønsted Acid Strength of Bridging OH Groups with Different Stretching Frequencies in Zeolite β Analyzed by Ammonia IRMS-TPD Measurement and DFT Calculations
Number and Brønsted Acid Strength of Bridging OH Groups with Different Stretching Frequencies in Zeolite β Analyzed by Ammonia IRMS-TPD Measurement and DFT Calculations
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通过氨 IRMS-TPD 测量和 DFT 计算分析 β 型沸石中不同拉伸频率的桥接 OH 基团的数量和布朗斯台德酸强度
DOI：
10.1016/j.cattod.2013.08.006
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
Miki Niwa
中科院分区：
文献类型：
--
作者：
Naonobu Katada;Hiroyasu Tamagawa;Miki Niwa
用氨红外/质谱（IRMS）程序升温脱附（TPD）法测定了β沸石中以OH伸缩频率为基准分为三部分的桥连OH数目和表征酸强度的氨脱附焓。另一方面，优化的结构，波数和氨脱附能（Edes）的所有几何可能的酸位位于晶体学上的非等效位置在一个晶体结构的援助，计算密度泛函理论（DFT）。计算的波数主要分为三个部分。AlOHSi单元中的H与该单元周围的氧原子之间的相互作用被建议降低OH频率。各部分的伸缩振动数、平均Edes和波数与实测值一致。
The number and ammonia desorption enthalpy, as a measure of acid strength, of bridging OH groups divided into three portions based on the OH stretching frequency in zeolite β were measured by means of a method of ammonia infrared/mass spectroscopy (IRMS) temperature-programmed desorption (TPD). On the other hand, the optimized structures, wavenumbers and ammonia desorption energies (Edes) of all the geometrically possible acid sites located at crystallographically non-equivalent positions in a BEA structure were calculated with an aid of density functional theory (DFT). The calculated wavenumbers could be classified mainly into three portions. The interaction between H in the AlOHSi unit and oxygen atoms surrounding the unit is suggested to lower the OH frequency. The number, averagedEdesand wavenumber of stretching vibration of each portion were in agreement with the observed values.