Adsorption of carbon dioxide, nitrogen and methane on modified titanosilicate type molecular sieves

Separation of N2 and CO2 from methane is a vital step in natural gas refining processes. The adsorption of carbon dioxide, nitrogen and methane was studied and compared on modified titanosilicate molecular sieves ETS-10 (cation exchanged forms of ETS-10 involving Na-ETS-10, Ag-ETS-10 and Ba-ETS-10) as a packed bed adsorbent. The synthesized ETS-10 was characterized by SEM for crystal structure, powder X-ray diffraction for the phase structure and BET for the pore textural properties. The adsorption equilibrium isotherms of CO2, N2 and CH4 on the adsorbents were measured at 277, 298, and 310 K and pressures up to 10 bar. The experimental adsorption equilibrium isotherms were well described by the UNILAN equation. Breakthrough curves were measured for the fixed bed. Na-ETS-10 is found to have selectivity 5.72 for CO2 over methane and 1.09 for N2 over methane at 277 K and 1000 kPa in Henry's law regime. For Ag-ETS-10 selectivity of CO2/CH4 is 4.86 and for N2/CH4 is 1.49. Finally, Ba-ETS-10 has been found to be a better adsorbent for the removal of impurity from methane with selectivity 8.37 for CO2/CH4 and 1.24 for N2/CH4. The selectivity increased with pressure in all cases studied, especially for Barium exchanged form. The packing efficiency of the bed was increased through granule size decrease from 4 mm to 2 mm.