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CO2 Adsorption Behavior of Activated Coal Char Modified with Tetraethylenepentamine

Wang, Xia, Guo, Qingjie
Energy & Fuels 2016 v.30 no.4 pp. 3281-3288
adsorption, carbon dioxide, climate, coal, greenhouse gas emissions, hydrochloric acid, industrial applications, models, power plants, silica gel, sorbents, temperature, water vapor
The climate deterioration problem mainly caused by excessive CO₂ emission from coal-fired power plants has led to heightened concerns, and the reduction of the separation cost of CO₂ is essential to realize the industrial application of adsorption technology. The activated char was obtained by passing water vapor through a reactor while pyrolyzing coal at 650 °C, which was further pore-expanded using HCl. Then, the pore-expanded activated char was impregnated with tetraethylenepentamine (TEPA) for the preparation of amine-modified solid sorbents for CO₂ capture. The effects of the HCl concentration, coal type, adsorption temperature, and activation time of water vapor on CO₂ adsorption were investigated in a fixed-bed reactor, and the regenerability, kinetics, and deactivation rate during the adsorption process for sorbents were also studied. The saturated adsorption capacity of 3.38 mmol/g was obtained for 10 wt % TEPA-modified Ordos coal activated char (PE6-E120-TEPA10%) at 60 °C. After 10 adsorption–desorption cycles, the adsorption capacity for PE6-E120-TEPA10% was 3.19 mmol/g, which was a drop of 5.6%. The experimental breakthrough curve for PE6-E120-TEPA10% was well-fitted by the Avrami–Erofeyev deactivation model, the deactivation rate of which was significantly slower than that of TEPA-modified MCM-41 and silica gel (Gel). At the initial breakthrough adsorption stage, the CO₂ adsorption rate for PE6-E120-TEPA10% was rapid and then the rate significantly decreased; the external diffusion adsorption was the rate-controlling step. PE6-E120-TEPA10% not only realized effective CO₂ capture from coal-fired power plants but also reduced the CO₂ separation cost.