Layered Double Hydroxides-Based Mixed Metal Oxides: Development of Novel Structured Sorbents for CO2 Capture Applications

Layered double hydroxide (LDHs)-based mixed metal oxides (MMOs) are widely studied as the medium to high temperature (200-400 degrees C) CO2 capture sorbents. However, most of the studies are carried out using the powdered samples. To upgrade these sorbents for industrial-scale CO2 capture, it is important to move away from the powdered form and develop structured sorbents. Moreover, the CO2 capture properties of these sorbents need to be improved in terms of capture capacity and cycling stability. Here we are utilizing a modified amide hydrolysis method to improve the CO2 capture capacities of LDHs-based MMOs. Subsequently, aqueous exfoliation coupled with the freeze-drying technique was utilized to develop LDHs-based novel MMOs. Exfoliated LDH nano sheets were pelletized (2 mm) to circumvent the challenges associated with powder samples when used in industrial-scale applications. The obtained pellets have an average crushing load of 11.1 N and 4.3 MPa of compressive strength, which indicate their good mechanical stability. The MMOs pellets showed a narrow distribution of pores (8-10 nm) with very good surface area (264 m(2)/g) and pore volume (1.27 cm(3)/g). They also had much improved CO2 capture capacities at ambient pressure and both low (2.17 mmol/g, 30 degrees C) and medium temperature (1.43 mmol/g, 200 degrees C), as compared to previously reported pristine MMOs powder samples. The pelletized structured sorbents also outperformed commercial LDH-based pellets by several fold.

Automated summary

The study focuses on improving the CO2 capture capacities of LDHs-based MMOs through a modified amide hydrolysis method and aqueous exfoliation technique, leading to the development of pelletized structured sorbents. These structured sorbents exhibit good mechanical stability, high surface area, pore volume, and significantly improved CO2 capture capacities at different temperatures. The pellets outperformed commercially available LDH-based pellets by several fold.