Thermodynamics and regeneration studies of CO₂ adsorption on activated carbon

Abstract

The kinetic and thermodynamic studies of CO2 adsorption on activated carbon were carried out in a fixed bed. Six different CO2 concentrations (from 5% up to 18 vol.%) and four temperatures (303 K, 313 K, 323 K, and 333 K) were applied to investigate dynamic adsorption behaviors. It showed that the increase in temperature led to faster adsorption kinetics, but also reduced the adsorption capacity. An isotherms modeling was made by the Langmuir isotherm model. The experimental isotherms data were well fitted. Then, based on the adsorption isotherms, the isosteric heats of CO2 adsorption were determined by Clausius‐Clapeyron equation. The calculated isosteric heat declined slightly with the adsorbed amount on activated carbon, and had an average value of 16.09 kJ/mol, which is much lower than the actual heat of adsorption measured by calorimeter. Moreover, regeneration experiments by vacuum evacuation (<10 kPa) were conducted to assess the regeneration efficiency (RE) of activated carbon. Regeneration efficiency increased with the reduction of vacuum pressure and reached over 90% at the vacuum of 4 kPa. A temperature swing integrated into the vacuum evacuation process resulted in a remarkable increase of RE with an increase in regeneration temperature, which confirmed the favorable effect of temperature on regeneration of activated carbon and providing almost full regeneration. © 2016 Society of Chemical Industry and John Wiley & Sons, Ltd

Electrochemical carbon dioxide capture to close the carbon cycle

“…Among the available methods, most research focus has been given to the post-combustion methods as they can be retrofitted more easily to the existing industrial units, compared to the Oxy-fuel and Pre-combustion methods [229]. Traditional post-combustion capture methods are absorption [18,19,[231][232][233][234][235][236], adsorption [13,18,[237][238][239], membrane gas separation [240][241][242][243][244][245][246], calcium looping [19,[247][248][249] and mineral carbonation [110,[250][251][252][253][254][255][256][257][258][259][260], see Table (4).…”

“…• Limited CO 2 absorbing capacity resulted from the reaction stoichiometry and dependent on the absorbent type (e.g., low capacity as 0.4 kg CO 2 /kg-MEA or higher as 1.2 kg CO 2 /kg-NH 3 [18,269]) • High absorbent regeneration (i.e., CO 2 desorption) energy • Solvent losses caused by volatility or thermal/chemical degradation, the subsequent equipment corrosion & negative environmental impacts of solvent emissions • High sensitivity to flue gas temperature, pressure and presence of impurities, such as NOx, SOx and oxygen (i.e., oxidative degradation) [270] ( Adsorption [13,18,[237][238][239] CO 2 (g) is adsorbed on solid materials and will be recovered through temperature, pressure or vacuum swing desorption…”

Transforming Plastic Waste into Porous Carbon for Capturing Carbon Dioxide: A Review

“…For chemical activation, KOH reacted with char to convert some carbon and oxygen from char into organic species (K 2 CO 3 ). Meanwhile, at higher temperatures (800-1100 • C), certain oxygen and K metals from KOH were released to become gas or bio-oil by-products [19,90]. It can be concluded that if the activation temperature is too high, the micropore structure will be destroyed, thus decreasing the char yield.…”

A review of N-functionalized solid adsorbents for post-combustion CO2 capture

“…Adsorbents are the cornerstones for all adsorption processes, and numerous porous solid adsorbents have been developed for CO2 adsorption in post-combustion gas conditions. However, these materials suffer either from low CO2 affinity or low moisture toleration, and more importantly, are primarily used at low temperatures (under 30 °C) due to their rapid decline in capture capacity at higher temperatures [17][18][19]. N-functionalized solid adsorbents (NFSAs) are a group of adsorbents that have shown stronger CO2 affinity than bare, porous adsorbents and have better moisture tolerance.…”