Unravelling the pore templating effect on CO2 adsorption performance of alkali metal nitrates promoted MgO pellets.

• Alkali metal salts promoted MgO pellets were prepared for CO 2 capture. • Sacrificial pore-forming templates were employed to improve CO 2 uptakes. • Template modification improved pore structure and facilitated CO 2 bulk diffusion. • Structure-performance relationships of AMS-MgO-P were unraveled. • AMS-MgO-P-MC exhibited high CO 2 uptake and desirable mechanical property. Alkali metal salts (AMS) promoted MgO with high CO 2 uptakes represents a promising adsorbent candidate for CO 2 capture. The AMS-MgO composite adsorbents are facing the challenges of increased pressure drop or elutriation when employed in dual fixed-bed reactor or twin circulating fluidized-bed configurations. Granulation by the extrusion-spheronization technique represents an effective problem-solving strategy. However, textural properties and CO 2 uptakes of MgO-based adsorbent pellets might be adversely affected by the granulation process. In this work, AMS-MgO composite adsorbent pellets were prepared by the extrusion-spheronization method. Citric acid (CA), ammonium bicarbonate (AB), urea (UA) and microcrystalline cellulose (MC) were employed as pore-forming templates to improve the porous structures and CO 2 uptakes of the AMS-MgO pellets. CO 2 uptakes and adsorption kinetics of the adsorbent pellets were studied using a fixed-bed reactor. Effects of granulation and pore templating on the structure-performance relationships of the AMS-MgO pellets were unraveled. Granulation had resulted in the remarkable decrease in CO 2 uptake from 10.87 to 4.24 mmol CO 2 /g due to the impaired textural parameters. The employed sacrificial templates endowed the AMS-MgO pellets with enhanced CO 2 uptakes and improved carbonation kinetics. This was associated with extended surface area and expanded pore structures due to gas liberation in the pyrolysis of templates, which had facilitated the kinetics of CO 2 bulk diffusion. The desired AMS-MgO-MC pellet modified with MC template showed a high CO 2 uptake of 7.54 mmol CO 2 /g in 50%CO 2 at 340 °C, and its CO 2 uptake was stabilized around 5.0 mmol CO 2 /g within 20 cycles. Besides, the AMS-MgO-MC pellet also exhibited good mechanical properties. The results will guide the rational design of highly efficient and robust MgO-based adsorbent pellets for CO 2 capture applications. [ABSTRACT FROM AUTHOR]