Granulation mechanism and CO2 capture performance of alkaline metal salt-promoted MgO sorbents

Alkaline metal salt-promoted MgO sorbents are effective for CO₂ capture, but they face challenges with decreased CO₂ capture performance and powder elutriation in practical applications, arising due to the loss of pore structures and poor mechanical strength of alkaline metal salt-promoted MgO sorbent powder. Herein, granulation technology was employed to resolve the above problem. The optimized alkaline metal salt-promoted MgO sorbent pellets exhibited a CO₂ capture capacity of 11.46 mmol·g⁻¹ and a mechanical strength of 11.14 MPa. This mechanical strength was nearly three times greater than that of alkaline metal salt-promoted MgO sorbent pellets without granulation promoters. After 20 cycles, CO₂ capture capacity stabilized at 8.71 mmol·g⁻¹, while mechanical strength was maintained at 8.92 MPa. Through characterization, it was revealed that the pore structure generated by the pyrolysis of the granulation promoters notably increased the specific surface area, leading to high CO₂ capture capacity. Meanwhile, the strengthened mechanical strength of the alkaline metal salt-promoted MgO sorbent pellets was primarily due to the in situ formation of a γ-AlOOH sol-gel cluster skeleton. Thus, this study provides an effective technological pathway to enhance the performance of the alkaline metal salt-promoted MgO sorbent pellets for industrial applications.