CO2 Capture Performance of CaO-Based Sorbents Prepared by a Sol-Gel Method

The CaO-based sorbents are considered to be promising candidates for capturing CO2 from postcombustion of fossil fuels, and how to improve the sintering-resistant performance of the sorbents at high temperature is a challenge for researchers. In this paper, a series of CaO-based sorbents, which consisted of active CaO and inert Ca9Al6O18 acting as the support matrix, was synthesized by a sol-gel method with various calcium precursors. The structural properties of the resulting sorbents were characterized by N-2 physisorption, X-ray diffraction (XRD), field emission scanning electron microscope (FESEM), and energy dispersive spectrometry (EDS) techniques, showing that the sorbents prepared by the sol-gel method possessed small grains, interconnected pore network as well as uniform distribution of CaO and Ca9Al6O18. These features gave rise to enhanced CO2 capture performance of the synthetic sorbents compared to pure CaO. In particular, the sorbent with a CaO content of 90 wt % (weight fraction) derived from calcium lactate displayed the best performance for CO2 capture during a long-term cyclic operation, whose CO2 capture capacity remained as high as 0.59 gco(2)/g(sorbent) at the 35th carbonation-calcination cycle. Finally, this sorbent was applied to the sorption-enhanced steam methane reforming process for hydrogen production, and all the conversion or concentration profiles obtained in 10 consecutive reforming-regeneration cycles almost overlapped, further demonstrating the excellent performance of the sol-gel-derived CaO-based sorbent.