Catalytic desorption of CO₂-loaded solutions of diethylethanolamine using bentonite catalyst

The absorption of CO2 gas into aqueous alkanolamine solutions is the most advanced CO(2 )separation technology and a key challenge in this technique is the energy-intensive process of solvent regeneration. The tertiary amine N,N ' -diethylethanolamine (or DEEA) is a candidate CO2-capturing solvent with potential. To improve the energy efficiency of regeneration of DEEA, several catalysts were used for desorbing CO2 from loaded solutions of DEEA (2.5 M) at T = 363 K. Desorption trials were conducted in batch mode. The initial CO2 loading varied in the 0.3-0.35 mol CO2/mol DEEA range. The performance was analyzed by calculating the rate of CO(2 )desorption, cyclic capacity, and reduction in sensible energy. The amount of thermal energy needed for amine regeneration was significantly lowered by using nine transition metal oxide catalysts and the hierarchy was as follows: Al2O3 < MoO3 < V2O5 < TiO2 < MnO2 < ZnO < Cr2O3 < SiO2 < ZrO2. Among the metal oxides, Al2O3 increased desorption efficiency compared to blank runs by 89%. A clay-based powder bentonite was also used as catalyst and its efficacy was compared with the metal oxides. This cheap and easily available bentonite catalyst was tuned through simple ion-exchange with four acids (HCl, H3PO4, HNO3, and H2SO4). Upon treatment with H2SO4, bentonite remarkably increased desorption efficiency by 100%. Furthermore, bentonite catalyst treated with sulphuric acid (denoted here as Bt/H2SO4) was characterized by Brunauer-Emmett-Teller (BET), scanning electron microscopy (SEM), Fourier transform infrared spectrometery (FTIR), X-ray diffraction (XRD), and ammonia temperature-programmed desorption (NH3-TPD). In this way, a comprehensive study on catalytic desorption of DEEA was performed.