Dual effects of long-chain alcohols in phase change capture of SO2: Increasing mutual solubility and decreasing product viscosity

Abstract To realize the goal of energy-saving SO2 capture process, a series of novel SO2 phase change absorbents (SPCAs) composed of 2-[2-(Dimethylamino)ethoxy]ethanol (DMEE)/long-chain alcohols/hexadecane were investigated in this work. The long-chain alcohols had dual effects in SPCAs, i.e., increasing mutual solubility of DMEE and hexadecane, and decreasing viscosity of the absorption products. Three alcohols, including butyl, hexyl and decyl alcohol, could turn the immiscible mixture of DMEE and hexadecane into homogeneous solution to form SPCAs. The decyl alcohol in absorption product could efficiently decrease the viscosity from 2338.1 mPa·s to 362.02 mPa·s, which is beneficial to gas-liquid mass transfer and fluid transport process. Meanwhile, the NMR and FTIR results indicated that DMEE chemically absorbed SO2, forming a zwitterionic alkyl sulfite compound. The long-chain alcohol formed hydrogen bonds with the alkyl sulfite and it didn't change the reaction mechanism. Noteworthy, the SPCA can absorb 0.823 mol SO2/mol DMEE (0.396 g SO2/g DMEE) at 293.15 K and 0.002 atm, which was exceptionally attractive. Furthermore, the absorbed SO2 could be partly released under vacuum at 110 °C and the net cycle capacity can reach 73% ~ 74% of the maximum capacity, which indicated the SPCAs have a promising application prospect.