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

Separation of N-2 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 Xray diffraction for the phase structure and BET for the pore textural properties. The adsorption equilibrium isotherms of CO2, N-2 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 N-2 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 N-2/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 N-2/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. (C) 2017 Elsevier B.V. All rights reserved.