Formulation, adsorption performance, and mechanical integrity of triamine grafted binder-based mesoporous silica pellets for CO₂ capture

This work explored the formation of mesoporous silicas pellets using a range of bentonite and colloidal silica (LUDOX) fractions, aiming to optimise the binder composition that minimises any deteriorating effects on adsorption performance, while providing adequate mechanical integrity. Thermogravimetric analysis, scanning electron microscopy, and dynamic mechanical analysis were used to structurally characterise the pellets. Further, CO₂ adsorption isotherms of synthesised pellets, pre and post triamine grafting, were measured. Bentonite was found to be an effective single binder that forms mechanically strong pellets and retains up to 85% of CO₂ capacity of the base adsorbent. In the presence of LUDOX, pellet hardness was lower, and led to the largest decrease in CO₂ capacity. Formulation with 25% bentonite was found to provide pellets with post triamine functionalisation CO₂ capacity equivalent to powder SBA-15, at an amine efficiency of 0.41 mol CO₂/mol, while minimising pore blockage and maintaining a compressive strength of 1.5 MPa.