Selective aerobic oxidation of n-butane is one of the most complex selective aerobic oxidation reactions but is of great importance in producing maleic anhydride (MA) as a versatile chemical intermediate/platform in the chemical industry. Supported VO_x catalysts are extensively used in the selective oxidation of alkanes. However, the identification of active sites is quite challenging since various VO_x structures (single sites, clusters, nanoparticles, and crystals) and the related surface functional groups (V = O, V-O-V, and V-OH) can be formed on the surface. By simply tuning the V/Al ratios of V/Al₂O₃ catalysts, we prepared various VO_x structures using flame-spray pyrolysis and investigated their activities in the selective oxidation of n-butane to MA. The presence of single-site VO_x (SSV), polymeric VO₄ species, crystalline AlVO₄ clusters, and vanadium oxide is probed by systematic studies using ⁵¹V and ²⁷Al solid-state NMR spectroscopy and confirmed by XRD, HRTEM, Raman, and UV–vis spectroscopies. VO_x single-sites interacting with surface penta-coordinated Al (Al^V) sites are identified as active sites promoting the conversion of n-butane to MA. V/Al₂O₃ with a high population of SSV-Al^V pairs in the amorphous Al₂O₃ network provides the best performance compared to other V/Al₂O₃ catalysts and those reported in the literature. Finally, a reaction mechanism based on the concerted action of SSV-Al^V pairs is proposed.

正丁烷的选择性好氧氧化是最复杂的选择性好氧氧化反应之一，但对于生产马来酸酐 (MA) 作为化学工业中的通用化学中间体/平台具有重要意义。负载型VO _x催化剂广泛用于烷烃的选择性氧化。然而，活性位点的识别非常具有挑战性，因为可以在表面上形成各种 VO _x结构（单个位点、簇、纳米颗粒和晶体）和相关的表面官能团（V = O、VOV 和 V-OH） . 通过简单地调整 V/Al ₂ O ₃催化剂的 V/Al 比，我们制备了各种 VO _x使用火焰喷雾热解的结构，并研究了它们在正丁烷选择性氧化为 MA 中的活性。通过使用⁵¹ V 和₂₇ Al 固态 NMR 光谱的系统研究探测^并通过XRD 、 _HRTEM、_Raman 、和紫外可见分光光度计。与表面五配位 Al (Al ^V ) 位点相互作用的VO _x单位点被确定为促进正丁烷转化为 MA 的活性位点。V/Al ₂ O _{3与其他 V/Al 2} O ₃催化剂和文献中报道的催化剂相比，在无定形 Al ₂ O ₃网络中具有高数量的 SSV-Al ^V对可提供最佳性能。最后，提出了一种基于SSV-Al ^V对协同作用的反应机理。