Influence of framework Si/Al ratio on the Na+/mordenite interaction energy

A direct synthesis of Na-mordenite, characterized by Si/Al ratios ranged from 5.5 to 12, without introducing any organic compounds, is reported. The effect of aluminium concentration and alkalinity of the synthesis system on the composition of the zeolite are discussed. The crystallinity, and the microporosity of the samples are also studied. The effects of the starting raw materials, stirring time and reaction temperature on the crystallization are discussed. The evolution of thermally stimulated currents (TSC) measured on these Na-mordenite compounds is examined as a function of the Si/Al ratio. The TSC signal analysis leads to an evaluation of the interaction energies between the hopping Na+ ions and the zeolitic network. According to the ratio Si/Al and the nature of the occupied Na+ sites, a quantitative and qualitative characterization of each site is given.