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Abstract
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A static, volumetric method has been used to determine the adsorption equilibrium of CH4and CO2andtheir binary mixtures on 13X molecular sieves at various temperatures between 273 and 343 K. Pressuresfor the pure component data extend up to 10 bar, while all binary data were obtained at 4 bar and 6 bar. Themeasured pure isotherms were regressed using different isotherm equations and the regressed param-eters were applied to different thermodynamic models such as ideal adsorbed solution theory (IAST),vacancy solution theory (VST) and real adsorbed solution theory (RAST). CH4/CO2system that deviatefrom ideality is not well represented by IAST and VST, whereas RAST which include activity coefficientin the adsorbed phase as characterizing parameter for non-ideality, show a much better representationof the binary equilibria. Experimental selectivities CO2/CH4range from 26 to 2 at different pressure andtemperatures. It is concluded that zeolite 13X suitable for natural gas industrial separation with yCO2< 0.2at 303 K and 4 bar. For landfill gas upgrading, where yCO2< 0.45, zeolite 13X can be successfully appliedat 303 K, 4 bar and 303 K, 6 bar and 323 K, 4 bar.
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