Zn-promoted hydrogen exchange for methane and ethane on Zn/H-BEA zeolite: In situ 1H MAS NMR kinetic study

Hydrogen (H/D) exchange between Brønsted acid sites of both the acidic form of zeolite beta (H-BEA) and Zn-loaded zeolite beta (Zn/H-BEA) and small alkanes (methane and ethane) has been studied by monitoring the kinetics of the exchange in situ with 1H MAS NMR spectroscopy within the temperature range of 433–563 K. On Zn/H-BEA, the exchange has been found to be more than two orders of magnitude faster compared to that on H-BEA. The decrease of reaction temperature and activation energy of the exchange on Zn/H-BEA (86–88 kJ mol−1) compared to the acidic form of zeolite H-BEA (138 kJ mol−1) has been rationalized by the promoting effect of zinc. We propose that the mechanism of the H/D exchange on Zn/H-BEA involves Zn-alkyl species as intermediates.