Vanadium phosphates on mesoporous supports: model catalysts for solid-state NMR studies of the selective oxidation of n

详细信息    查看全文

• 作者：Jö ; rg Frey ; Yean Sang Ooi ; Bejoy Thomas ; V.R. Reddy Marthala ; Arne Bressel ; Thomas Schö ; lkopf ; Thomas Schleid ; Michael Hunger
• 关键词：Solid-state NMR ; Local structure ; Heterogeneous catalysis ; VPO catalysts ; Vanadyl orthophosphate ; Selective oxidation ; Mars-van-Krevelen mechanism
• 刊名：Solid State Nuclear Magnetic Resonance
• 出版年：2009
• 出版时间：April 2009
• 年：2009
• 卷：35
• 期：2
• 页码：130-137
• 全文大小：438 K

文摘

SBA-15 was utilized as mesoporous support for the dispersion of vanadium phosphate (VPO) compounds. Loading of SBA-15 with VPO compounds was found to be accompanied by decreasing ²⁹Si MAS NMR signals of Q² (Si(2Si,2OH)) and Q³ (Si(3Si,1OH)) silicon species, which indicates coverage of the mesoporous support by the guest compounds. The ⁵¹V MAS NNR spectra of the activated VPO/SBA-15 catalysts consist of patterns typical for the α_II- and β-phases of vanadyl orthophosphate. In the ³¹P MAS NMR spectra of the activated VPO/SBA-15 catalysts, signals of β-, δ-, and α_II-VOPO₄ phases could be identified. Upon conversion of n-butane-¹³C₄, a strong decrease of the ³¹P MAS NMR signals characteristic for the δ-VOPO₄ phase occurred, while by ¹³C MAS NMR spectroscopy the formation of maleic anhydride, carbon monoxide, and carbon dioxide was observed. This finding supports the active role of the δ-VOPO₄ phase in the selective oxidation of n-butane on VPO/SBA-15 catalysts.