Synthesis, characterization and adsorption capacities of microporous titanosilicate EMS-3

A titanosilicate, named EMS-3, has been synthesized using the organic base TMAOH (tetramethylammonium hydroxide) and Na ion, as structure directing agents, under hydrothermal conditions. The XRD pattern of EMS-3 contains sharp and broad reflections typical of a partially disordered structure. EMS-3 has low thermal stability, indeed XRD pattern shows a decreased resolution after thermal treatment at 300 °C. An amorphous phase is observed at 500 °C. EMS-3 has a high cationic exchange capacity. A small amount of TMA cation has been detected in all the exchanged forms of EMS-3, as showed by IR spectroscopy and thermogravimetric analyses. Cation exchanged EMS-3’s show higher thermal stability than as-synthesized EMS-3. In particular, the typical features of EMS-3 are maintained, although Sr-EMS-3 exhibits poorly resolved XRD pattern after thermal treatment at 500 °C. Divalent cation exchanged EMS-3’s have higher specific surface area than as-synthesized EMS-3, due to a lower amount of extra-framework atoms inside the porous structure. CO2 adsorption capacity is higher than both CH4 and N2. Both the charge and the ionic radius of the exchanged cations affect the adsorption properties. Ca-EMS-3 has the highest adsorption capacity for all the adsorbates.