Equilibrium adsorption and kinetic study of CO2 and N2 on synthesized carbon Black–Zeolite composite

Abstract

In this study, the preparation of a composite of zeolite-carbon black (CB) for enhancing the CO2 adsorption capacity of zeolites has been investigated. The composites were prepared by adding 5 wt% CB to zeolite 13X crystals via a hydrothermal synthesis method. The standard instrumental analysis techniques, including X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, differential thermal analysis, and obtaining N2 adsorption/desorption isotherms at 77 K, were used to characterize the as-prepared composite. The adsorption isotherms of CO2 and N2 on the composite were measured by a volumetric method at 283, 303, and 323 K and up to 2.2 bar. Employing the Sips and Toth isotherm models, it was found that the Toth model has the best adaptability to the experimental isotherms data. The isosteric heats of adsorption were evaluated with the Clausius-Clapeyron equation. The binary adsorption isotherm and selectivity of CO2 over N2 were predicted using the ideal adsorbed solution theory. The adsorption kinetics of CO2 and N2 on the composite were determined by the non-isothermal kinetic model. The microporous diffusional time constants obtained from correlating the kinetic model with the experimental uptake curves were also compared with those of zeolite 13X. The results show the significant improvements in the adsorption capacity and rate by adding around 5 wt% CB to zeolite 13X.