Hydrogen uptake in palladium and ruthenium exchanged zeolite X

The hydrogen adsorption properties and uptake capacities of NaX and its palladium and ruthenium exchanged forms were investigated at 77 K in a static volumetric adsorption setup up to 1 bar, and at 303 K and 333 K in a gravimetric adsorption system up to 5 bar. All the hydrogen adsorption isotherms were of Type I with a maximum adsorption capacity shown in NaX at 77 K temperature. Hydrogen adsorption capacities at 77 K were found to be decreasing as palladium and ruthenium exchange levels increases. Chemisorption of hydrogen was observed at 303 K and 333 K and was due to the chemical interaction between the transition metal cations and the hydrogen molecules. The maximum hydrogen uptake at 303 K and 5 bar was observed for palladium exchanged zeolite X with a value of around 85 cm(3)/g. Grand canonical Monte Carlo simulations were also performed to study the adsorption of H, in these zeolites at 77 K as well as 303 K and 333 K. The simulation studies are suitable for establishing a correlation between the microscopic behavior of the zeolite and adsorbate system with the macroscopic properties which are measured experimentally, such as adsorption isotherms. (C) 2007 Elsevier B.V. All rights reserved.