Accurate Measurements of NH3 Differential Adsorption Heat Unveil Structural Sensitivity of Brønsted Acid and Brønsted/Lewis Acid Synergy in Zeolites,The Journal of Physical Chemistry Letters

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Accurate Measurements of NH3 Differential Adsorption Heat Unveil Structural Sensitivity of Brønsted Acid and Brønsted/Lewis Acid Synergy in Zeolites
The Journal of Physical Chemistry Letters ( IF 4.8 ) Pub Date : 2024-01-18 , DOI: 10.1021/acs.jpclett.3c03336
Zhenxuan Yuan ₁ , Yunxing Bai ₁ , Ke Gong ₁ , Weixin Huang ₁

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Differential adsorption heats of NH₃ on a series of zeolites, including MOR, MFI, FER, and BEA, are accurately measured to probe their acidity using flow-pulse adsorption microcalorimetry. Initial adsorption heats of NH₃ at Brønsted acid sites (BAS) vary between 105 to 136 kJ/mol, depending on framework aluminum amounts and topography structures of zeolites. A Brønsted/Lewis acid synergy between BAS and proximate tricoordinated framework-associated aluminum species is identified to generate super acid sites with initial adsorption heats of NH₃ around 150 kJ/mol, but occurs only in the MFI zeolites and sensitively depends on the Si/Al ratio. These accurate data of NH₃ differential adsorption heats unveil structural sensitivity of BAS and Brønsted/Lewis acid synergy in zeolites and provide experimental benchmark data for fundamental understanding of acidity and acid-catalysis of zeolites.

中文翻译：

NH3 差异吸附热的精确测量揭示了沸石中布朗斯台德酸和布朗斯台德/路易斯酸协同作用的结构敏感性

使用流量脉冲吸附微量热法精确测量 NH ₃在一系列沸石（包括 MOR、MFI、FER 和 BEA）上的微分吸附热，以探测其酸度。 NH ₃在布朗斯台德酸位点 (BAS) 的初始吸附热在 105 至 136 kJ/mol 之间变化，具体取决于骨架铝量和沸石的形貌结构。确定 BAS 和近似三配位骨架相关铝物质之间的布朗斯台德/路易斯酸协同作用可产生超酸位点，NH ₃的初始吸附热约为 150 kJ/mol，但仅发生在 MFI 沸石中，并且敏感地取决于 Si/铝比。这些准确的NH ₃差吸附热数据揭示了沸石中BAS和布朗斯台德/路易斯酸协同作用的结构敏感性，并为沸石酸度和酸催化的基本理解提供了实验基准数据。

更新日期：2024-01-18

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