Adsorption of hydrogen and deuterium in MnO2 modified NaX zeolites

MnO2 modified NaX zeolites are prepared by dispersion of MnO2 on the surface of NaX in a calcination process. XRD, XPS and N2 adsorption tests confirm that the dispersed MnO2 is primarily monolayer and the calcination conditions affect the dispersion efficiency. The adsorption performances of hydrogen and deuterium of the modified zeolites are investigated at both 77 K and 295 K. A hydrogen adsorption capacity increase up to 30% is observed at 295 K for NaX with moderate MnO2 modification, but the corresponding adsorption at 77 K does not show much improvement, and even deteriorates for the samples with high MnO2 contents. NaX shows an adsorption capacity difference of 11% between hydrogen and deuterium at 9 bar and 77 K, higher than that of MnO2 modified samples (4%); while the difference is much smaller at 295 K for all samples. The effects of MnO2 modification on hydrogen adsorption properties are explained by the involvement of Kubas interaction, where Mn in MnO2 acts as a d-electron donor for the enhanced binding of hydrogen molecules.

Figure optionsDownload as PowerPoint slideHighlights
► MnO2 monolayer dispersion on surface of NaX zeolite.
► 30% increase of adsorption amount at 295 K by MnO2 modification.
► Involvement of Kubas interaction in enhancement of adsorption ability.
► Smaller difference between H2 and D2 adsorption after MnO2 modification.