The promotion of silica-supported vanadyl species [VO₄]/SiO₂ (1) by α-NaVO₃ or β-NaVO₃ enhances the specific rate of the propene formation in oxidative dehydrogenation of propane (ODP) by, respectively, 30 and 125% at 450 °C and ca. 1 V nm⁻² nominal coverage. The increased rate of propene formation is offset only moderately by a decreased selectivity to propene, which declines by 10 and 15% relative to 1 (74%) in α-NaVO₃/1 and β-NaVO₃/1, at 5.8 and 8.2% propane conversion. The structural characterization of the promoted catalysts by Raman mapping, X-ray absorption near edge structure (XANES), transmission electron microscopy (TEM) and solid-state nuclear magnetic resonance (⁵¹V and ²³Na MAS NMR) allowed for associating the higher specific activity of β-NaVO₃/1 with a higher dispersion of vanadium sites on the silica support, while the agglomeration of these sites with the concomitant formation of a poorly dispersed Na_1+xV₃O₈ phase is related to a decreased catalytic activity. Surprisingly, solid-state ⁵¹V NMR and Raman spectroscopies reveal that the α-NaVO₃/1 and β-NaVO₃/1 catalysts contain the metastable β-NaVO₃ phase, explained by a more favorable interaction of Na_1+xV₃O₈/SiO₂, formed after calcination in both materials, with β-NaVO₃ than with α-NaVO₃.

中文翻译：

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偏钒酸钠促进的二氧化硅负载的钒基位上丙烷的氧化脱氢

促进二氧化硅负载氧钒物种的[VO ₄ ] /的SiO ₂（1）由α-NAVO ₃或β-NAVO _3个增强了丙烷（ODP）的氧化脱氢的丙烯形成的特定速率被分别30和在450°C时约为125％1 V nm ^-2标称覆盖率。的丙烯形成的速率增加偏移仅适度通过选择性降低到丙烯，其通过相对于10和15％的下降1（74％）的α-NAVO ₃ / 1和β-NAVO ₃ / 1，丙烷转化率分别为5.8％和8.2％。通过拉曼作图，近边缘结构的X射线吸收（XANES），透射电子显微镜（TEM）和固态核磁共振（⁵¹ V和²³ Na MAS NMR）对助催化剂的结构进行表征，从而可以关联更高的比的活性β-NAVO ₃ / 1与在二氧化硅载体上的钒位点的较高的分散体，而这些位点的与伴随形成分散不良的Na的团聚_{1+ X} V ₃ ö ₈相涉及一种降低的催化活性。令人惊讶的是，固态⁵¹V NMR和拉曼光谱揭示出α-NAVO ₃ / 1和β-NAVO ₃ / 1催化剂含有亚稳态的β-NAVO ₃相，被Na的更有利的相互作用解释_{1+ X} V ₃ ö ₈ /二氧化硅₂，在这两种材料在煅烧后形成的，与β-NAVO ₃比用α-NAVO ₃。