使用瞬态 XAS 检测基于 MoS2 的加氢处理催化剂活性位点的可逆 SO 交换的微小水平：金属负载、促进、温度和含氧反应物的影响,ACS Catalysis

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使用瞬态 XAS 检测基于 MoS2 的加氢处理催化剂活性位点的可逆 SO 交换的微小水平：金属负载、促进、温度和含氧反应物的影响
ACS Catalysis ( IF 11.3 ) Pub Date : 2021-12-23 , DOI: 10.1021/acscatal.1c04767
Abhijeet Gaur _{1,

2} , Matthias Stehle ₂ , Marc-André Serrer _{1,

2} , Magnus Zingler Stummann ₃ , Camille La Fontaine ₄ , Valérie Briois ₄ , Jan-Dierk Grunwaldt _{1,

2} , Martin Høj ₃

Affiliation

将调制激发光谱 (MES) 与时间分辨 X 射线吸收光谱 (XAS) 结合应用于非促进和共同促进的 Mo 基加氢处理催化剂（即Mo 和 CoMo 催化剂），以研究在H ₂ S 和 H ₂ O影响下的活性位点组成。在 400 至 500 °C 的温度下，使用具有不同 Co/Mo 金属负载量的催化剂进行了交替富硫和富水条件下的瞬态实验，以研究相关效应这些因素对活性位点稳定性的影响。对于这两种类型的催化剂，解调的Mo K-edge光谱的特征与MoS ₂和MoO的差异光谱相匹配_{3 个}参考文献表明在 H ₂ O/H ₂ S 循环过程中存在可逆的氧化-硫化过程。在金属负载量增加的 CoMo 催化剂的情况下，Mo K- 和 Co K- 边缘的瞬态 XAS 显示硫化 Mo 和 Co 位点的 SO 交换水平微弱，尽管 26% 至 47% 的 Co 被束缚为稳定的 CoAl ₂ O ₄，它不会形成大量硫化物。因此，即使在存在多个 Co 相（氧化物和硫化物）和相对于 Mo 原子总数而言活性位点数量较少的情况下，瞬态 XAS 也可以成功地检测到活性 Co 和 Mo 位点上发生的变化。此外，解调光谱的幅度比较表明，随着温度的升高，Mo原子更容易发生SO交换，而Co促进则稳定了硫化钼。与 1-丙醇相比，使用 1-丙醇进行的 MES 耦合 XAS 实验以评估在另一种含氧反应物存在下的 SO 交换程度，揭示了与 1-丙醇相比，水对这些硫化钼位点的亲和力更高。

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Using Transient XAS to Detect Minute Levels of Reversible S-O Exchange at the Active Sites of MoS2-Based Hydrotreating Catalysts: Effect of Metal Loading, Promotion, Temperature, and Oxygenate Reactant

Modulation excitation spectroscopy (MES) coupled with time-resolved X-ray absorption spectroscopy (XAS) was applied to unpromoted and Co-promoted Mo-based hydrotreating catalysts (i.e., Mo and CoMo catalysts) for investigating the minute as well as instantaneous differences in active site composition under the influence of H₂S and H₂O. Transient experiments during alternating sulfur- and water-rich conditions were performed at temperatures between 400 and 500 °C using catalysts with varying Co/Mo metal loadings to study the correlative effect of these factors on the stability of the active sites. For both types of catalysts, the features of the demodulated Mo K-edge spectrum matching the difference spectra of the MoS₂ and MoO₃ references indicate a reversible oxidation–sulfidation process during H₂O/H₂S cycling. In the case of CoMo catalysts with increasing metal loadings, transient XAS at the Mo K- as well as Co K-edge revealed minute levels of S-O exchange at both sulfided Mo and Co sites, although 26 to 47% of the Co was bound as stable CoAl₂O₄, which does not form a bulk sulfide. Thus, even in the presence of multiple Co phases (oxide and sulfide) and a low number of active sites relative to the total number of Mo atoms, transient XAS can successfully detect the changes occurring over both the active Co and Mo sites. Furthermore, the comparison of the amplitude of the demodulated spectra showed that Mo atoms are more prone to S-O exchange with increasing temperature, while Co promotion stabilized the molybdenum sulfide. MES-coupled XAS experiments with 1-propanol performed to evaluate the degree of S-O exchange in the presence of another oxygenate reactant revealed the higher affinity of water toward these sulfided Mo sites as compared to 1-propanol.

更新日期：2022-01-07

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