Hydrogen storage in ion-exchanged zeolites

摘要

The hydrogen storage properties of zeolites X, Y, A and Rho containing various exchangeable cations have been investigated. All hydrogen storage capacities were measured at a temperature of -196 deg C and a pressure range of 0-15 bar, using a constant pressure thermogravimetric analyser. The results show that, zeolites exhibit diverse behaviour with respect to hydrogen uptake, dependent on both the framework structure and the nature of the cations present. A major factor influencing uptake is the available void space: in zeolites A and Rho pore blocking by large extraframework cations is a major factor restricting hydrogen uptake, but in zeolites X and Y, blocking does not occur. This study also suggests that cations may act as binding sites for hydrogen molecules. For zeolites X and Y, hydrogen uptake relates closely to the measured BET surface area. The highest gravimetric storage capacity of 2.19 wt. percent was obtained for CaX. Volumetric storage densities of up to 31.0 kg H_2/m~3 (143 H_2 molecules/unit cell) and 30.2kg H_2/m~3 (144 H_2 molecules/unit cell) were achieved for CaX and KX, respectively.