The absorption of SO2 by morpholine cyclic amines with sulfolane as the solvent for flue gas

The absorption properties of N-(2-hydroxyethyl) morpholine (HEM), morpholine (MP) and N-(2-aminoethyl) morpholine (AEM) for SO2 were studied using sulfolane (SUL) as solvent in this work. Among these solvent combinations, HEM/SUL shows the best cyclic absorption performance, and the capacity of HEM-SUL-40 (40 wt% of HEM and 60 wt% of SUL) to absorb 8580 mg/m3 SO2 (the remainder is N2) is 192.18 mg/g at 293.15 K. The absorption capacity of the second cycle is 97.5% of the first absorption cycle, which is higher than 70% of the Cansolv amine solution in a commercial application with similar experimental conditions. However, MP/SUL is difficult to desorb at high temperature, and the absorption capacity of AEM/SUL is much lower than HEM/SUL and MP/SUL. According to the FTIR, 1H NMR and 13C NMR, all three cyclic amines have charge transfer effects with SO2. The structure of HEM/SUL can be recovered after heating, but MP cannot be recovered. ΔrGm° in the reaction against HEM with SO2 increases significantly with increasing temperature. The ΔrGm° of HEM-SO2 and MP-SO2 at 353.15 K is −12.56 kJ/mol and −16.29 kJ/mol, respectively, which further explains the easy desorption of HEM-SO2 and the difficult desorption of MP-SO2 at high temperature.