As the impact of the greenhouse effect becomes increasingly severe, CO₂ generated from fossil fuel consumption must be captured and recycled. Carbon capture, utilization, and storage is a promising approach. A key technical challenge associated with sorption-enhanced water-gas shift is the identification and development of sorbents that can effectively capture CO₂. 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.
Research team from Taiyuan University of Technology has now addressed these problems through an advanced granulation method. As reported in a study published on July 1, 2025, in Frontiers of Chemical Science and Engineering, they incorporated four specific granulation promoters—sodium polyacrylate (SP) as an extrusion aid, pseudo-boehmite (PB) as a binder, nitric acid (NA) as a gum solvent, and microcrystalline cellulose (MC) as a pore-forming aid—during the pellet fabrication process combining ball milling and extrusion granulation methods.
Using the RSM-BBD model as a foundation, this study examined how the granulation promoters and their interactions impacted the initial CO₂ capture capacity. The interaction between PB and NA emerged as the primary variable. The optimal formulation was determined to be 1.01 wt% SP, 1.95 wt% PB, 15.08 wt% NA, and 10.05 wt% MC.
With this optimal formulation, the MgO-GA sorbent pellets achieved an initial CO₂ capture capacity of 11.46 mmol·g⁻¹, closely matching the model's predicted value of 11.47 mmol·g⁻¹. The mechanical strength reached 11.14 MPa, which was nearly three times greater than that of pellets prepared without any granulation promoters.
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.
The pellets demonstrated robust stability over multiple cycles. After 20 cycles, CO₂ capture capacity stabilized at 8.71 mmol·g⁻¹, while mechanical strength was maintained at 8.92 MPa.
This study provides an effective technological pathway to enhance the performance of the alkaline metal salt-promoted MgO sorbent pellets for industrial applications. By simultaneously improving capture capacity and mechanical durability, this granulation strategy represents a significant advancement toward the practical deployment of efficient CO₂ capture systems.
DOI
10.1007/s11705-025-2576-8