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

• Published in: Solid state nuclear magnetic resonance 2009-04, Vol.35 (2), p.130-137
• Main Authors: Frey, Jörg, Sang Ooi, Yean, Thomas, Bejoy, Reddy Marthala, V.R., Bressel, Arne, Schölkopf, Thomas, Schleid, Thomas, Hunger, Michael
• Format: Article
• Language: English
• Subjects: Butanes - chemistry; Catalysis; Computer Simulation; Heterogeneous catalysis; Local structure; Magnetic Resonance Spectroscopy - methods; Mars-van-Krevelen mechanism; Models, Chemical; Models, Molecular; Molecular Conformation; Oxidation-Reduction; Phosphates - chemistry; Porosity; Powders; Selective oxidation; Solid-state NMR; Vanadium Compounds - chemistry; Vanadyl orthophosphate; VPO catalysts
• ISSN: 0926-2040; 1527-3326
• DOI: 10.1016/j.ssnmr.2009.02.005

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 Q 2 (Si(2Si,2OH)) and Q 3 (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-VOPO 4 phases could be identified. Upon conversion of n-butane- 13C 4, a strong decrease of the 31P MAS NMR signals characteristic for the δ-VOPO 4 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-VOPO 4 phase in the selective oxidation of n-butane on VPO/SBA-15 catalysts.