南京大学王伟团队报道了单沸石纳米颗粒的程序升温脱附。相关研究成果于2024年11月20日发表在《美国化学会杂志》。

沸石是各种化学过程中必不可少的固体酸催化剂。程序升温脱附（TPD）是通过测量大块样品中探针的脱附动力学，来表征沸石酸度的最成熟的技术之一。然而，由于样品量大（～0.1g），表观解吸动力学不可避免地与传质和热传导混合，因此传统的TPD很难提供沸石的固有酸性能。

该文中，研究人员开发了一种光学显微镜方法，通过原位监测加热过程中，探针分子脱附导致的个体散射强度降低，来测量单个沸石纳米颗粒的TPD光谱，称为oTPD。

样品量的显著减少对oTPD光谱做出了贡献，揭示了比表观值低～300°C的固有解吸温度，并且峰宽从～150°C大大变窄到～15°C。将同一个体的oTPD和显微拉曼光谱相关联，进一步揭示了酸度和硅岛含量之间的线性关系。

该项研究为测量单一沸石纳米颗粒的固有酸性质，和解吸动力学提供了前所未有的能力，对更好地理解结构-酸度关系，和设计更好的沸石催化剂具有重要意义。

附：英文原文

Title: Temperature-Programmed Desorption of Single Zeolite Nanoparticles

Author: Xuannuo Yi, Shasha Liu, Taotao Zhao, Xiangke Guo, Kai Zhou, Weiping Ding, Wei Wang

Issue&Volume: November 20, 2024

Abstract: Zeolites are essential solid acid catalysts in various chemical processes. Temperature-programmed desorption (TPD) is one of the most established techniques used to characterize the acidity of zeolites by measuring the desorption kinetics of probes from bulk samples. However, conventional TPD can hardly deliver the intrinsic acid properties of zeolites because the apparent desorption kinetics are inevitably mixed with mass transfer and thermal conduction due to the large sample amount (～0.1 g). Herein, we developed an optical microscopy approach to measure the TPD spectra of single zeolite nanoparticles, termed oTPD, by in situ monitoring of the reduced scattering intensity of individuals as a result of the desorption of probe molecules during heating. A significantly reduced sample amount contributed to the oTPD spectrum, revealing an intrinsic desorption temperature of ～300 °C lower than the apparent value and also a greatly narrowed peak width from ～150 to ～15 °C. Correlating oTPD and micro-Raman spectra of the very same individuals further uncovered a linear dependence between the acidity and the content of silicon islands. This study provided unprecedented capabilities for measuring the intrinsic acid properties and the desorption kinetics of single zeolite nanoparticles, with implications for better understanding the structure–acidity relationship and for designing better zeolite catalysts.

DOI: 10.1021/jacs.4c09274

Source: https://pubs.acs.org/doi/abs/10.1021/jacs.4c09274