Nonideal adsorption from multicomponent gas mixtures at elevated pressures on a 5A molecular sieve

Single component adsorption isotherms for H₂, CH₄, CO and CO₂ at pressures upto 800 psia, and multicomponent adsorption equilibria for various mixtures of these gases at 214 and 314 psia were measured on a 5A molecular sieve at 298 and 373 K. The extended Langmuir (EL) and ideal adsorbed solution (IAS) models were tested against the data. The predictions from these models were very similar. The IAS model also showed that the binary data exhibited considerable nonideal adsorbed solution (NAS) behavior which was further demonstrated from the experimental adsorbed phase activity coefficients and from the correlation with the spreading pressure-dependent (SPD) NAS model. Strong negative deviations from Raoult's law were generally exhibited; however, moderate positive deviations from Raoult's law also occurred from one of the components in some systems. In addition, the effects of gas phase nonidealities on the experimental adsorbed phase activity coefficients, and on the component loadings and adsorbed phase activity coefficients obtained from the SPD-NAS models, were studied. In both cases, the effects were significant only for the activity coefficients of systems which exhibited markedly different single component isotherms.