Development of CaO-based adsorbents loaded on charcoal for CO2 capture at high temperature

Abstract

CaO-based adsorbents have the potential to be used for CO2 capture at high temperature. However, CaO-based adsorbents exhibit a sharp decay in CO2 uptake capacity over multiple cycles, owing to the sintering of CaO particles. In this paper, a series of charcoal supported CaO-based adsorbents were developed to improve the CO2 capture performance of CaO using three different methods: physical mixing, wet impregnation and sol-gel method. The influences on CO2 capture of CaO loading and carbonation temperature are also included. The morphology and structural properties of the adsorbent were investigated by means of electron microscopy, nitrogen adsorption and XRD. It is found that the novel sorbent with an optimal mass ratio of CaO to charcoal of 4:1 prepared by the sol-gel method exhibits an initial capture capacity of 15.1 mmol g−1 and maintains a capacity of 8.0 mmol g−1 after 15 cycles of carbonation (600 °C) and calcination (650 °C), around 60% higher than that of sol-gel CaO. The CaC-4 possesses a porous stucture with a high surface area of 63.6 m2·g−1 and a pore volume of 0.166 cm3·g−1, making CO2 diffusion easier. The XRD analysis displays that crystalline size (26 nm) of the CaO phase in CaC-4 is much smaller than that of the reference bulk CaO (96 nm), reflecting that charcoal can effectively inhibit the growth of CaO crystalline. Furthermore, the introduction of charcoal derived from biomass pyrolysis will improve the economic viability of the CO2 capture process.