Low-cost DETA impregnation of acid-activated sepiolite for CO2 capture

Abstract In this paper, a low-cost sepiolite-based adsorbent for CO 2 capture was obtained by impregnating DETA into the acid-modified sepiolite. Thermogravimetric analysis, nitrogen adsorption-desorption isotherm, Fourier transform infrared spectroscopy and X-ray diffraction were used for the characterization of the sepiolite supports before and after DETA impregnation. Thermogravimetric analysis was also employed to evaluate the CO 2 adsorption performances of the adsorbents. The characterization methods revealed that DETA impregnated into the acid-modified sepiolite effectively. The CO 2 adsorption experimental results indicated that acid-activation and amine-loading simultaneously improved the CO 2 adsorption capacities of sorbents. For amine-loaded acid-modified sepiolite, low dosage of impregnated amine decreased the CO 2 adsorption capacities of sorbents at 35 °C due to the restrictions imposed in the transport and reaction of CO 2 due to pore blockage by amines. The highest CO 2 adsorption performance attained 1.65 mmol/g with the acid-modified sepiolite with 0.8 g-DETA loading. 95.2% of the adsorption capacity of 0.8-DETA/SH-18 maintains after 4 adsorption-desorption cycles, and the sorbent can be almost fully recovered at 75 °C, pure N 2 . The kinetic studies showed that for low amine loadings the CO 2 adsorption is controlled by micropore blocking. For higher loadings a more complex diffusion and reaction process leads to a two-step adsorption kinetics. By contrast, it can be found that Avrami model is in good accordance with the adsorption kinetics of CO 2 on amine-functionalized sepiolite. A cost evaluation indicated that DETA-impregnated sepiolites are cheap adsorbents for CO 2 capture.