Adsorption of Co2 and N2 on Bimetallic Mg-Al Hydrotalcites and Z-13x Zeolites Under High Pressure and Moderate Temperatures

Abstract

The adsorption of carbon dioxide on a commercial hydrotalcite (HT) was investigated using gravimetric analysis at 473 K, 573 K and 673 K and pressures up to 10 bar. The CO 2 adsorption performance of HT was correlated with a wide range of physicochemical characterisation techniques. For further understanding and comparative purposes, the same adsorption and characterisation measurements are reported for a commercial zeolite 13X (Z-13X). The HT exhibited higher adsorption capacities per unit mass of sorbent at relatively low pressures and per unit surface area over the whole range of pressures analysed, compared to zeolite 13X. However, HT showed adsorption-desorption isotherms with a hysteresis loop indicating a stronger binding energy. The HT also presented deactivation upon cycling (up to ~ 10%, depending on conditions) suggesting the need for future studies focused on improvement of its regenerability. The same performance regarding hysteresis and deactivation was observed in the presence of N 2 . The CO 2 adsorption isotherms of HT were successfully fitted to the Freundlich model. The values of heat of adsorption calculated -56 and -84 kJ mol -1 for the 1 st and 5 th cycle, are indicative of a chemisorption process. The data of this work provide information regarding fundamentals of CO 2 adsorption of the materials that is useful in the design of realistic adsorption units in conventional and novel H 2 -Carbon Dioxide Capture processes, especially in the sorption-enhanced H 2 reaction process.

Keywords: HydrotalcitesCO2 adsorptionFreundlichZeolite 13XN2 adsorptionheat of adsorption