The oxidative dehydrogenation (ODH) of propane over supported vanadia catalysts is an attractive route toward propene (propylene) with the potential of industrial application and has been extensively studied over decades. Despite numerous mechanistic studies, the active vanadyl site of the reaction has not been elucidated. In this work, we unravel the ODH reaction mechanism, including the nuclearity-dependent vanadyl and surface dynamics, over ceria-supported vanadia (VO_x/CeO₂) catalysts by applying (isotopic) modulation excitation IR spectroscopy supported by operando Raman and UV–vis spectroscopies. Based on our loading-dependent analysis, we were able to identify two different mechanisms leading to propylene, which are characterized by isopropyl- and acrylate-like intermediates. The modulation excitation IR approach also allows for the determination of the time evolution of the vanadia, hydroxyl, and adsorbate dynamics, underlining the intimate interplay between the surface vanadia species and the ceria support. Our results highlight the potential of transient IR spectroscopy to provide a detailed understanding of reaction mechanisms in oxidation catalysis and the dynamics of surface catalytic processes in general.

中文翻译：

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使用瞬态红外光谱揭示 VOx/CeO2 氧化催化剂中的活性钒位点和吸附动力学

丙烷在负载型钒催化剂上的氧化脱氢 (ODH) 是获得具有工业应用潜力的丙烯 (丙烯) 的有吸引力的途径，并且已被广泛研究了数十年。尽管进行了大量的机理研究，但尚未阐明反应的活性氧钒位点。在这项工作中，我们通过应用操作支持的（同位素）调制激发红外光谱，揭示了 ODH 反应机制，包括依赖于核的钒基和表面动力学，在二氧化铈负载的氧化钒 (VO _x /CeO _{2 ) 催化剂}上拉曼光谱和紫外可见光谱。基于我们的负载相关分析，我们能够确定导致丙烯的两种不同机制，其特征在于异丙基和丙烯酸类中间体。调制激发 IR 方法还允许确定氧化钒、羟基和吸附物动力学的时间演化，强调表面钒物质和二氧化铈载体之间的密切相互作用。我们的结果突出了瞬态红外光谱的潜力，可以详细了解氧化催化中的反应机制和一般表面催化过程的动力学。