Dynamic restructuring of silver catalysts during the industrial conversion of methanol to formaldehyde leads to surface faceting and pinhole formation. Subsequent sintering under reaction conditions, followed by increased pressure drop and decreased catalyst activity requires catalyst bed replacement after several months of operation. This necessitates a comprehensive understanding of the bulk catalyst restructuring under exposure to different gas environments. In this work, Ag restructuring was studied at elevated temperatures under different reactive and inert gas environments. Bubble formation within catalysts of 5–8 μm thickness was visualized in real-time using in situ X-ray ptychography. Stepwise heating up to 650 °C in combination with imaging was used to determine the effect of temperature on silver restructuring. Dynamic changes within the catalyst were further quantified in terms of relative changes in mass on selected regions at a constant temperature of 500 °C. Quantitative assessment of dynamic changes in the catalyst resulting from bubble growth and movement revealed the influence of temperature, time, and gas environment on the degree of restructuring. Post-mortem scanning electron microscopy with energy-dispersive X-ray spectroscopy mapping confirmed the redistribution of material as a consequence of bubble rupture and collapse. The formation of pores and cavities under different gas environments was additionally confirmed using a fixed bed reactor, and subsequent examination using focused-ion beam milling, providing detailed analysis of the surface structure. This study demonstrates the unique advantage of correlative hard X-ray and electron microscopy for quantitative morphological studies of industrial catalysts.

中文翻译：

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使用原位 X 射线叠层照相术和电子显微镜研究用于甲醇转化为甲醛的银催化剂的重构


在甲醇工业转化为甲醛的过程中，银催化剂的动态重组导致表面刻面和针孔形成。随后在反应条件下烧结，随之而来的是压降增加和催化剂活性降低，需要在运行几个月后更换催化剂床。这就需要全面了解暴露于不同气体环境下的本体催化剂重组。在这项工作中，研究了在不同反应性和惰性气体环境下的高温下银的重组。使用原位X 射线叠层成像技术实时可视化厚度为 5-8 μm 的催化剂内气泡的形成。逐步加热至 650 °C 并结合成像来确定温度对银重组的影响。催化剂内的动态变化进一步量化为 500 °C 恒温下选定区域的质量相对变化。对气泡生​​长和运动引起的催化剂动态变化的定量评估揭示了温度、时间和气体环境对重组程度的影响。尸检扫描电子显微镜和能量色散 X 射线光谱图证实了气泡破裂和崩溃导致材料的重新分布。使用固定床反应器进一步确认了不同气体环境下孔隙和空腔的形成，并使用聚焦离子束铣削进行了后续检查，提供了表面结构的详细分析。这项研究证明了相关硬 X 射线和电子显微镜在工业催化剂定量形态研究中的独特优势。