CO 2 Adsorption from Biogas Using Amine-Functionalized MgO

Abstract

Biogas is a renewable fuel source of methane (CH 4 ), and its utilization as a natural gas substitute or transport fuel has received much interest. However, apart from CH 4 , biogas also contains carbon dioxide (CO 2 ) which is noncombustible, thus reducing the biogas heating value. Therefore, upgrading biogas by removing CO 2 is needed for most biogas applications. In this study, an amine-functionalized adsorbent for CO 2 capture from biogas was developed. Mesoporous MgO was synthesized and functionalized with different tetraethylenepentamine (TEPA) loadings by wet impregnation technique. The prepared adsorbents (MgO-TEPA) were characterized by X-ray diffraction (XRD) and N 2 adsorption-desorption. The CO 2 adsorption performance of the prepared MgO-TEPA was tested using simulated biogas as feed gas stream. The results show that the CO 2 adsorption capacities of the adsorbents increase with increasing TEPA loading. The optimum TEPA loading is 40 wt.%, which gives the highest CO 2 adsorption capacity of 4.98 mmol/g. A further increase in TEPA loading to 50 wt.% significantly reduces the CO 2 adsorption capacity. Furthermore, the stability and regenerability of the adsorbent with 40% TEPA loading (MgO-TEPA-40) were studied by performing ten adsorption-desorption cycles under simulated biogas and real biogas conditions. After ten adsorption-desorption cycles, MgO-TEPA-40 shows slight decreases of only 5.42 and 5.75% of CO 2 adsorption capacity for the simulated biogas and biogas, respectively. The results demonstrate that MgO-TEPA-40 possesses good stability and regenerability which are important for the potential application of this amine-based adsorbent.