英国伦敦大学学院Marc-Olivier Coppens团队报道了外表面扩散势垒对Pt/β催化正戊烷异构化反应的影响。 相关研究成果于2021年4月15日发表在《德国应用化学》。

沸石晶体的外表面含有运输障碍，阻碍分子的吸收和依赖它的过程，如催化和分离等。然而，表面障碍在这类过程中的潜在主导作用才刚刚出现。

该文中，研究人员开发了一种通用的策略来量化表面势垒对沸石催化的影响。以Pt/β催化正戊烷异构化为模型反应体系。首先，采用SiO2化学液相沉积法对β沸石进行表面改性，以控制其表面势垒。SiO2的沉积对β晶体物理性质改变很小，但Brnsted酸中心明显减少。

用零长柱（ZLC）法测量了正戊烷在SiO2沉积后的表观扩散系数，结果表明正戊烷在SiO2沉积后的表观扩散系数增加了一倍以上，表明表面势垒减弱。在固定床反应器中进行了催化性能测试，结果表明，SiO2沉积后的表观催化活性提高了51-131%。

研究结果直接证明了减少表面势垒是改善沸石催化剂性能的有效途径。

附：英文原文

Title: Effect of External Surface Diffusion Barriers on Pt/Beta Catalyzed Isomerization of n‐Pentane

Author: Shen Hu, Junru Liu, Guanghua Ye, Xinggui Zhou, Marc-Olivier Coppens, Weikang Yuan

Issue&Volume: 2021-04-15

Abstract: Zeolite crystals contain transport barriers on their external surface that hinder molecular uptake and processes that depend on it, such as catalysis and separations. However, the potentially dominant role of surface barriers in such processes is only emerging. In this work, we have developed a generalizable strategy to quantify the effect of surface barriers on zeolite catalysis. Isomerization of  n  ‐pentane, catalyzed by Pt/Beta, is taken as a model reaction system. Firstly, the surface modification by chemical liquid deposition of SiO  2  was carried out to control the surface barriers on zeolite Beta crystals. The deposition of SiO  2  leads to a very slight change in the physical properties of Beta crystals, but an obvious reduction in Brnsted acid sites. Diffusion measurements by the zero‐length column (ZLC) method show that the apparent diffusivity of  n  ‐pentane can be more than doubled after SiO  2  deposition, indicating that the surface barriers have been weakened. Catalytic performance was tested in a fixed‐bed reactor, showing that the apparent catalytic activity improved by 51–131% after SiO  2  deposition. These results provide direct proof that reducing surface barriers can be an effective route to improve zeolite catalyst performance deteriorated by transport limitations.

DOI: 10.1002/anie.202104859

Source: https://onlinelibrary.wiley.com/doi/10.1002/anie.202104859