Preparation of a morph-genetic CaO-based sorbent using paper fibre as a biotemplate for enhanced CO2 capture

Calcium looping is regarded as an effective and viable way to address CO2 emissions. To overcome the loss-in-capacity problems of calcium-based sorbents with the number of calcium looping cycles, a novel CaO/Ca12Al14O33 sorbent with a microtube-like structure was prepared from carbide slag and Al(NO3)3·9H2O using paper fibre as a biotemplate. The CO2 capture performance and microstructure of the novel synthetic sorbent under calcium looping conditions were investigated. The results show that the utilization of the biotemplate is good to retain the high cyclic CO2 capture reactivity of the synthetic sorbent. Due to the unique hollow porous structure, the CO2 capture capacity of the synthetic sorbent containing 7.5 wt% Al2O3 retains 0.56 and 0.33 g/g after 30 cycles under mild and severe calcination conditions, respectively, which are 2.56 and 2.11 times higher than those of carbide slag under the same respective calcination conditions. With the presence of 10% steam in the carbonation atmosphere, the CO2 capture capacity of the synthetic sorbent retains 0.55 g/g under the severe calcination conditions after 10 cycles. The native hierarchical biostructure of paper fibre is preserved in the synthetic sorbent. CaO and Ca12Al14O33 are uniformly distributed in the synthetic sorbent, resulting in a high sintering resistance during multiple CO2 capture cycles. CO2 can penetrate through the microtube-like structure of the synthetic sorbent from two directions, i.e., from the outer surface and inner surface. This phenomenon effectively enlarges the contact area between CO2 and CaO. The CaO/Ca12Al14O33 sorbent with a hollow porous structure by means of a biotemplate appears promising in the calcium looping technology for CO2 capture.