Silicon microfabricated reactor for operando XAS/DRIFTS studies of heterogeneous catalytic reactions
Silicon microfabricated reactor for operando XAS/DRIFTS studies of heterogeneous catalytic reactions
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用于多相催化反应原位 XAS/DRIFTS 研究的硅微加工反应器
DOI：
10.1039/d0cy01608j
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发表时间：
2020
影响因子：
5
通讯作者：
Venezia B
中科院分区：
文献类型：
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作者：
Venezia B
Operando x射线吸收光谱（XAS）、漫反射红外傅立叶变换光谱（DRIFTS）和质谱（MS）提供了催化剂结构、表面反应机理和活性关系的补充信息。这些技术的强大组合一直是设计和制造合适的光谱操作反应器的推动力，这些反应器可以减轻传统反应细胞固有的局限性，并促进动力学机制下的实验。微反应器由于其塞流式操作，无死体积，可忽略的质量和传热阻力，最近成为有效的光谱操作细胞。在这里，我们提出了一种新型的微型反应器，可以用于operando XAS和DRIFTS研究。该反应器具有玻璃-硅-玻璃三明治状结构，反应通道（3000 μm × 600 μm；宽度×深度）填充催化剂床（约25 mg），并侧向放置x射线光束，而红外光束从顶部照射催化剂床。反应器出口与MS连接，用于对反应器流出物进行连续监测。通过两个反应证明了微反应器的可行性：1)在Pd - k边缘上，用operando XAS研究了2 wt% Pd/Al2O3上甲烷的燃烧；2)在1 wt% Pt/Al2O3催化剂上，用operando DRIFTS研究了CO的氧化。前者表明钯在250、300、350、400℃的温度下均处于氧化状态，后者表明铂表面存在线性吸附的CO。此外，还研究了甲烷对钯催化剂的温度分解还原和CO在铂催化剂上的氧化。在此基础上，讨论了催化剂结构和表面反应动力学，不仅证明了微反应器在XAS和DRIFTS联合研究中的适用性和通用性，而且说明了微反应器在高空间速度和瞬态响应实验中的独特优势。
Operando X-ray absorption spectroscopy (XAS), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and mass spectrometry (MS) provide complementary information on the catalyst structure, surface reaction mechanisms and activity relationships. The powerful combination of the techniques has been the driving force to design and engineer suitable spectroscopic operando reactors that can mitigate limitations inherent to conventional reaction cells and facilitate experiments under kinetic regimes. Microreactors have recently emerged as effective spectroscopic operando cells due to their plug-flow type operation with no dead volume and negligible mass and heat transfer resistances. Here we present a novel microfabricated reactor that can be used for both operando XAS and DRIFTS studies. The reactor has a glass–silicon–glass sandwich-like structure with a reaction channel (3000 μm × 600 μm; width × depth) packed with a catalyst bed (ca. 25 mg) and placed sideways to the X-ray beam, while the infrared beam illuminates the catalyst bed from the top. The outlet of the reactor is connected to MS for continuous monitoring of the reactor effluent. The feasibility of the microreactor is demonstrated by conducting two reactions: i) combustion of methane over 2 wt% Pd/Al2O3 studied by operando XAS at the Pd K-edge and ii) CO oxidation over 1 wt% Pt/Al2O3 catalyst studied by operando DRIFTS. The former shows that palladium is in an oxidised state at all studied temperatures, 250, 300, 350, 400 °C and the latter shows the presence of linearly adsorbed CO on the platinum surface. Furthermore, temperature-resolved reduction of palladium catalyst with methane and CO oxidation over platinum catalyst are also studied. Based on these results, the catalyst structure and surface reaction dynamics are discussed, which demonstrate not only the applicability and versatility of the microreactor for combined operando XAS and DRIFTS studies, but also illustrate the unique advantages of the microreactor for high space velocity and transient response experiments.