Mechanism study on the effect of SO2 on CO2 adsorption performance of potassium-based adsorbent

Abstract

After desulphurization, the trace amount of SO2 in the tail gas of coal-fired power plant will lead to the deterioration of CO2 adsorption performance of potassium-based adsorbent. Using crystalline aluminum chloride as precursor, the solid adsorbent K2CO3/Al2O3 was prepared by sol-gel method. The adsorption characteristics of CO2 in SO2 (0, 150, 250 and 400 mg/m3) atmosphere were simulated by fixed bed reaction system. Combined with the BET and XRD characterization methods, the pore structure and material composition of the adsorbent were analyzed. The influence of SO2 on the surface adsorption of CO2 by K2CO3/Al2O3(0001) was studied by using the DFT theory. The results showed that in the ideal atmosphere, the cumulative adsorption capacity of CO2 of potassium adsorbent is 1.72 mmol/g. In the presence of 150 mg/m3 SO2 in the reaction atmosphere, the potassium adsorbent reacts with SO2 to form K2SO3, resulting in a 19.77% decrease in adsorption capacity (1.38 mmol/g). When the concentration of SO2 increases to 400 mg/m3, the cumulative adsorption capacity of CO2 of potassium-based adsorbent gradually decreases to 1.26 mmol/g, the adsorption performance of CO2 of the adsorbent is deteriorated. The adsorption capacity of potassium-based adsorbent decreases to 1.1 mmol/g after seven cycles, and the cycle performance is deteriorated. The adsorption sites of CO2 and SO2 on the surface of K2CO3/Al2O3(0001) are Al-O bridge sites, and the H2O molecules are O top sites. The adsorption of SO2 on K2CO3/Al2O3(0001) surface is greater than that on H2O and CO2. When H2O and CO2 are co-adsorbed, the O-s orbitals and H-s orbitals overlap in the CO2 molecules, so that the two can promote each other during surface adsorption. Due to the active p orbitals of S and O atoms, the SO2 molecules preferentially preempt the adsorption site of CO2 and inhibit the adsorption of CO2 on the surface when co-adsorbed with CO2. The catalytic effect of H2O molecules on the adsorption of SO2 on the surface of K2CO3/Al2O3(0001) is greater than that of CO2. The presence of H2O will accelerate the reaction between SO2 and the surface, leading to the deterioration of the adsorption capacity of CO2 on the surface of the adsorbent. When CO2 and H2O are co-adsorbed on K2CO3/Al2O3(0001) surface, the carbonation mechanism is H+ and OH− in H2O molecules, which forms \begin{document}${\mathrm{HCO}}_3^- $\end{document} with \begin{document}${\mathrm{CO}}_3^{2-} $\end{document} and CO2 respectively. The reaction energy barrier is 1.12 eV, and the reaction heat is −1.47 eV.

Keywords

• co2 capture
• potassium-based adsorbent
• so2 influence
• aerogel
• dft