DBU-based CO_2 absorption–mineralization system: Reaction process,feasibility and process intensification

Amine-based carbon dioxide(CO_2) capture is still limited by high desorption energy consumption. Fixing CO_2 into carbonate is a safer and more permanent method. In this work, calcium oxide(CaO) is introduced to perform chemical desorption instead of thermal desorption on 1,8-diazabicyclo [5.4.0] undec-7-ene(DBU) aqueous solution after CO_2 absorption. The X-ray diffraction(XRD) patterns of solid products show the formation of calcite calcium carbonate(CaCO_3), which prove the feasibility of this method. The effects of reaction temperature, reaction time and Ca~(2+)/CO_3~(2-) molar ratios on the related reactions in CO_2 absorption–mineralization process and CaCO_3 precipitation are discussed, and purer CaCO_3 is obtained by ultrasonic treatment. The CaCO_3 content can be increased to 95.8% and the CO_2 desorption ratio can achieve 80% by 30 min ultrasonic dispersion treatment under the conditions(40℃, 180 min, Ca~(2+)/CO_3~(2-) molar ratio = 1.0). After five cycles, DBU aqueous solution shows stable CO_2 absorption and mineralization ability. Fourier transform infrared spectroscopy(FT-IR) spectra of the reaction process also indicate the regeneration of the solvent. Compared with thermal desorption, this process is exothermic, almost without no additional heat.

DBU-based CO2 absorption-mineralization system: Reaction process,feasibility and process intensification

Amine-based carbon dioxide (CO₂) capture is still limited by high desorption energy consumption. Fixing CO₂ into carbonate is a safer and more permanent method. In this work, calcium oxide (CaO) is introduced to perform chemical desorption instead of thermal desorption on 1,8-diazabicyclo [5.4.0] undec-7-ene (DBU) aqueous solution after CO₂ absorption. The X-ray diffraction (XRD) patterns of solid products show the formation of calcite calcium carbonate (CaCO₃), which prove the feasibility of this method. The effects of reaction temperature, reaction time and Ca²⁺/CO₃^2- molar ratios on the related reactions in CO₂ absorption-mineralization process and CaCO₃ precipitation are discussed, and purer CaCO₃ is obtained by ultrasonic treatment. The CaCO₃ content can be increased to 95.8% and the CO₂ desorption ratio can achieve 80% by 30 min ultrasonic dispersion treatment under the conditions (40 ℃, 180 min, Ca²⁺/CO₃^2- molar ratio = 1.0). After five cycles, DBU aqueous solution shows stable CO₂ absorption and mineralization ability. Fourier transform infrared spectroscopy (FT-IR) spectra of the reaction process also indicate the regeneration of the solvent. Compared with thermal desorption, this process is exothermic, almost without no additional heat.