Influence of regeneration conditions on cyclic CO2 adsorption on NaA zeolite at high pressures

Abstract

This work aimed to determine the influence of different regeneration conditions on CO2 adsorption on NaA zeolite at high pressures through cyclic processes. To reach this goal, NaA characterization, high-pressure adsorption isotherms, heat of adsorption and working capacities for CO2/NaA system were performed. NaA zeolite characterization showed a high crystalline and stable microporous structure with 0.43 nm pore diameter and 247 m² g-1 specific area. CO2 adsorption isotherms are strongly favorable, showing adsorption uptakes equal to 4.73, 4.54 and 4.44 mol kg-1 (c.a. 20 wt%) at 40 bar and 20, 30 and 40 °C, respectively. Jensen-Seaton model fits experimental data and was used to determine CO2/NaA heats of adsorption from 10 to 40 kJ mol-1, which are characteristic of physisorption process. This was corroborated by constant working capacity for all regeneration processes, reaching 1.44, 3.27, and 4.27 mol kg-1 for REG-1 (1 bar, 30 °C), REG-2 (vacuum, 30 °C) and REG-3 (vacuum, 150 °C) regeneration processes, respectively. The working capacity simulation showed a strong influence of pressure and practically insensitive to adsorption temperature from 20° to 40°C. Therefore, NaA zeolite is a regenerative material showing a high potential for utilization in high pressure cyclic adsorption processes, such as fixed and fluidized beds, for CO2 separation when pressure and temperature are changed in blowdown/regeneration step.