铌插入 αII-VOPO4：调整选择性氧化的催化性能,ACS Catalysis

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铌插入 αII-VOPO4：调整选择性氧化的催化性能
ACS Catalysis ( IF 11.3 ) Pub Date : 2023-02-20 , DOI: 10.1021/acscatal.2c06209
Frederik Rüther ₁ , Rhea Machado ₁ , Esteban Gioria ₁ , Sylvia L. Kunz ₂ , Knut Wittich ₃ , Patricia Löser ₃ , Michael Geske ₁ , Stephan A. Schunk _{3,

4} , Robert Glaum ₂ , Frank Rosowski _{1,

5}

Affiliation

对焦磷酸氧钒 (IV) 的关键催化特性的全面了解使正丁烷氧化中的马来酸酐 (MAN) 产率更高，这引发了一场自发现催化剂以来一直在持续的争论。在反应条件下，在催化剂表面检测到钒（V）正磷酸结构碎片。然而，单相 α _II - 和 β-V ^V OPO ₄显示出低得多的催化性能。该研究表明，将 Nb 引入 α _II -VOPO ₄中形成固溶体 (V _{1 -x} Nb _x )OPO ₄会产生具有可调催化性能的块状材料。的选择性在 (V _0.1 Nb _0.9 )OPO _4上X_正_丁烷= 30 % 的转化率下S _MAN = 48%显示与表面 V 位点的隔离有关，这远远超过已知的 VOPO _{4催化剂。}_{(V 1-}_x Nb _x )OPO ₄的另一个特征是在富含烷烃的进料条件下整体正丁烷消耗量和 MAN 选择性的提高，从而大大提高了 MAN 的生产力。XPS 研究表明，用 Nb 逐步替代 V 会导致近表面 V 的平均氧化态从 +4.7 降低到 +4.3，这一发现与 MAN 选择性的提高呈线性相关。这项研究通过实验证实了近表面 V 物种的位点隔离和电子环境是关键的催化特性，从中推导出催化剂设计规则以优化部分氧化反应。

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Niobium Insertion into αII-VOPO4: Tuning the Catalytic Properties for Selective Oxidation

A holistic understanding of the key catalytic features of vanadyl(IV) pyrophosphate enabling high maleic anhydride (MAN) yields in n-butane oxidation has fostered a debate which has continued since the finding of the catalyst. Under reaction conditions, vanadium(V) orthophosphate structure fragments were detected on the surface of the catalyst. However, single-phase α_II- and β-V^VOPO₄ reveal a much lower catalytic performance. This study shows that introducing Nb into α_II-VOPO₄ forming a solid solution (V_1-xNb_x)OPO₄ yields a bulk material with tunable catalytic properties. Selectivities of S_MAN = 48% at a conversion of X_n-butane = 30% on (V_0.1Nb_0.9)OPO₄ are shown to be related to the isolation of surface V-sites, which surpass known VOPO₄ catalysts by far. A boost in the overall n-butane consumption and MAN selectivity under alkane-rich feed conditions is shown to be another characteristic of (V_1-xNb_x)OPO₄, leading to a highly increased MAN productivity. XPS studies reveal that a progressive replacement of V by Nb induces a reduction of the averaged oxidation state of near-surface V from +4.7 to +4.3, a finding that correlates linearly with an elevated MAN selectivity. This study experimentally confirms site isolation and electronic environment of the near-surface V-species as the key catalytic properties, from which catalyst design rules are derived to optimize partial oxidation reactions.

更新日期：2023-02-20

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