13C MAS NMR mechanistic study of propane conversion into butanes over H-MFI catalyst

The mechanism of propane conversion into butanes over H-MFI as catalyst has been investigated using controlled atmosphere C-13 MAS NMR spectroscopy. The labelled reactant was propane 2-C-13 and the reactant loading was varied from 0.5 to 4 molecules per MFI unit cell. The nature of the primary labelled products was found to depend on the propane partial pressure. A high pressure of propane enhances its bimolecular disproportionation to ethane and both butane isomers. Al low pressure, the formation of i-butane only is favoured. A detailed mechanistic pathway is proposed to account for both high pressure and low pressure observations. The proposed mechanisms were ascertained by studying the effect of several additional probe molecules (C3H6 2-C-13, C6H6, H-2, H2O and CO). (C) 1999 Elsevier Science B.V. All rights reserved.