Adsorption equilibria of CO2, CH4, N-2, O-2, and Ar were determined on three lab-synthesized ZSM-S adsorbents and four commercially available high silica zeolites including HiSiv-3000, HSZ-980HOA, HSZ-890HOA, and HSZ-390HUA. The synthesized ZSM-5 samples have a similar pore textural property (Brunauer-Emmett-Teller (BET) surface area and pore volume) as that of HiSiv-3000. The BET surface areas and total pore volume of the ZSM-5 sample were found to be similar to 300 m(2).g(-1) and 0.2 cm(3).g(-1), respectively. The synthesized materials have relatively higher adsorption capacities than those of HiSiv-3000 for the gases studied in this work. The order of adsorption capacities of CO2, CH4, N-2, Ar, and O-2 on each high silica zeolite follows the order of their polarizabilities. The selectivities of N-2/O-2 and Ar/O-2 pairs are close to 1.0, suggesting that it is very difficult to separate them by equilibrium-based adsorption processes. HSZ-890HOA and synthesized DT-100 showed higher equilibrium selectivities for CO2 over N-2 and CH4, implying that they are potential adsorbents for CO2 separation from flue gases as well as landfill gases.