Binder free novel synthesis of structured hybrid mixed metal oxides (MMOs) for high temperature CO₂ capture

Here we report a novel, binder free simple post synthesis modification of layered double hydroxides (LDHs) to develop structured CO₂ capture sorbents. The method involves the modification of LDHs with an organic modifier, melamine, to create the porosity and provide support for enhanced CO₂ capture properties. The modified LDHs were pelletized (2 mm) to overcome the particle size issues associated with powder samples when used in the relevant process, e.g. in fixed bed reactors. The organic modifier, melamine, played a significant role in creating the porosity and providing support for the mixed metal oxides (MMOs) pellets. The CO₂ capture capacity of the resultant hybrid pellets directly correlates with the amount of modifier used. The hybrid MMOs pellets captured 1.34 mmol of CO₂ per g of sorbent at 200 °C and 1 bar, and they significantly outperformed their unmodified counterparts (0.35 mmol/g) and commercial (Pural MG70, SASOL) MMOs pellets (0.33 mmol/g). They also showed excellent cycling behaviour over 20 carbonation/regeneration cycles. This novel post synthesis modification method shows promise to develop LDH based MMOs structured sorbents that are suitable for industrial scale CO₂ capture applications.