Quantitative solid-state NMR investigation of V⁵⁺ species in VPO catalysts upon sequential selective oxidation of n-butane

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• 作者：Jö ; rg Frey ; Christian Lieder ; Thomas Schö ; lkopf ; Thomas Schleid ; Ulrich Nieken ; Elias Klemm ; Michael Hunger
• 关键词：Selective n-butane oxidation ; VPO catalysts ; Mars– ; van-Krevelen mechanism ; V⁵⁺ species ; Solid-state NMR spectroscopy
• 刊名：Journal of Catalysis
• 出版年：2010
• 出版时间：25 May 2010
• 年：2010
• 卷：272
• 期：1
• 页码：131-139
• 全文大小：2299 K

文摘

Bulk VPO catalysts (VPO/bulk) and VPO catalysts supported on mesoporous SBA-15 material (VPO/SBA-15) were treated sequentially in a flow of nitrogen loaded with n-butane and of synthetic air loaded with n-butane in order to reach a complete reduction and reoxidation, respectively, of the catalyst surface. The V⁵⁺ species on these VPO catalysts were quantitatively investigated by solid-state NMR spectroscopy and correlated with the catalytic activities of the corresponding materials in the selective oxidation of n-butane to maleic anhydride. By ³¹P{¹H} cross-polarization MAS NMR experiments on the n-butane-loaded VPO/SBA-15 catalyst was evidenced that n-butane is preferentially adsorbed at surface sites of δ-VOPO₄-like phases. Based on the number of P/V⁵⁺ species in δ-VOPO₄-like phases as determined by MAS NMR spectroscopy, the turnover frequency of the surface sites on the VPO/SBA-15 catalyst was estimated to be about 0.2 s⁻¹.