Adsorption equilibria and kinetics of six pure gases on pelletized zeolite 13X up to 1.0 MPa: CO2, CO, N2, CH4, Ar and H2

Abstract

The adsorption equilibria and kinetics of CO2, CO, N2, CH4, Ar and H2 on zeolite 13X were measured via the volumetric method at 293, 308 and 323K and up to 1.0MPa. Adsorption isotherms and the heat of adsorption were analyzed over a full range of pressures. Each experimental isotherm was correlated with Langmuir, Sips and temperature-dependent Sips models, with the deviations for each model being evaluated. The Sips model showed a smaller degree of deviation from the experimental data than the Langmuir model. The isosteric heat of adsorption sequence was H2<Ar<CH4≒N2<CO<CO2 along with surface loading. The experimental uptake curves were correlated with a non-isothermal kinetic model because the adsorption kinetics was controlled via heat generation and transfer. Adsorption rates of the gases on zeolite 13X were affected by the isosteric heat of adsorption, heat transfer rate and adsorption affinity. At the same temperature and pressure, the sequence of reciprocal of the effective diffusional time constant (D/RP2) revealed the following sequence: CH4≒N2<CO<CO2, showing pressure and temperature dependency. While the diffusion rates of CO and N2 were controlled via micropore diffusion, CO2 and CH4 were significantly affected by macropore diffusion due to high heat transfer resistance. Compared to experimental results between the powder and pellet forms of zeolite 13X, the zeolite pellet binders led to a reduction in adsorption capacity and heat of adsorption. However, the difference in adsorption kinetics was relatively minute.