Preparation And CO₂ Adsorption Performance Of Amine-functionalized Porous Materials

Global warming has become one of the major environmental problems in face of mankind nowadays. Carbon dioxide emission from fossil fuels combustion is the main cause of global warming, which has contributed to more than 60% of the global climate change. In China, coal supplies primary energy in energy structure, and more than 70% of the electricity is produced by coal-fired power plants. Therefore, CO₂ capture, separation and storage（CCSS） from the flue gas of a coal-fired power plant is of great concern.Solid amine adsorbents with high adsorption performance, high selectivity, low corrosion resistance and low energy consumption during the regeneration, have received increasing interest among researchers, and also made great progress. However,there are still many weaknesses on the diffusion of CO₂ in the pore of adsorbents and the further improvement of CO₂ adsorption performance. Therefore, to solve the above-mentioned challenges, a series of solid amine adsorbents were developed for CO₂ capture in this paper. The main research conclusions are as follows:1 HZSM-5 and MCM-41 were physically mixed to act as supports.Tetraethylenepentamine（TEPA） was used to modify the mixed supports to prepare the sorbents by the impregnation method. The saturated adsorption capacity of 3.57mmol?g-1 was obtained at the adsorption temperature of 55 °C, influent velocity of 30 m L?min-1and 15 vol.% CO₂ / 85 vol.% N2 when the weight ratio of HZSM-5 and MCM-41 was 1:1 and the TEPA loading was 30 wt.%. When the CO₂ concentration was 12%¹5%, the saturated adsorption capacity of HZSM-5/MCM-41-30%TEPAwas more than 2 mmol?g-1. After ten adsorption-desorption cycles, the adsorption capacity decreased by 8.1 wt.%.2 The CO₂ adsorption kinetics and thermodynamics of TEPA modified HZSM-5/MCM-41 were investigated. The CO₂ adsorption process for HZSM-5/MCM-41-30%TEPA appeared to be a two-stage process, included a fast breakthrough adsorption and a gradual approaching saturated stage. Moreover, the breakthrough adsorption capacity obtained in the initial stage accounted for approximately 80% of the saturated adsorption capacity. The Avrami model fit well with the whole CO₂ adsorption process. The isosteric heat of CO₂ adsorption calculated from the adsorption isotherms using the Clausius-Clapeyron equations on HZSM-5/MCM-41-30%TEPA was 20 k J·mol-1⁴0 k J·mol-1, ranging from the physisorption to chemisorption heats. The above results indicated that the adsorption mechanism was dominated by physical and chemical adsorption.3 A mixture of TEPA and 2-amino-2-methyl-l-propanol（AMP） modified mesoporous silica gel（SG） sorbents were prepared by the wet impregnation method.The hydrogen bonding interactions among AMP, TEPA and SG may facilitate the dispersion of TEPA and AMP, reduce the diffusion resistance of CO₂ in the sorbents,and improve the thermal stability and adsorption kinetics of the prepared sorbents. The results showed that the maximum CO₂ adsorption capacity was 2.83 mmol?g-1 of SG-20%TEPA-20%AMP at the adsorption temperature of 70 °C and influent velocity of 30 m L?min-1. After a ten-cycle, the CO₂ adsorption capacity only decreased by 4.6wt.%. It illustrated that SG-20%TEPA-20%AMP had excellent regenerability.