In situ 1H MAS NMR studies of the H/D exchange of deuterated propane adsorbed on zeolite H‐ZSM‐5

The hydrogen exchange in the propane‐d 8 loaded zeolite H‐ZSM‐5 was monitored by in situ 1H MAS NMR spectroscopy within the temperature range 457–543 K. Measurements of the H/D exchange between the acidic hydroxyl groups of the zeolite and the adsorbed deuterated propane molecules show that both methyl and methylene groups of alkane are involved in the exchange. The comparison of the experimentally obtained apparent activation energies for the exchange in methyl groups (108 ± 7 kJ mol-1) and methylene groups (117 ± 7 kJ mol-1) with theoretical values for methane and ethane supports the assumption that the H/D exchange for methyl and methylene groups takes place via a pentavalent transition state.