LAUSR

Abstract A novel Li 4 SiO 4 -based high-temperature CO 2 sorbent was prepared directly from the expanded vermiculite (EXVMT) for the first time. Due to the separating effect by the existing impurity phases in EXVMT, this new CO 2 sorbent Li 4 SiO 4 -(EXVMT)-4 possesses better dispersion of Li 4 SiO 4 nanoparticles and higher porosity, which resulted in a much enhanced CO 2 sorption/desorption cycling stability. Elemental mapping revealed the homogeneous dispersion of Li 4 SiO 4 with the other co-existing phases and XRD analyses indicates the crystal size of Li 4 SiO 4 in Li 4 SiO 4 -(EXVMT)-4 kept almost unchanged even after 10 cycles. In addition, this sorbent exhibited much higher CO 2 sorption capacity and faster sorption rate at relatively lower sorption temperature (550 °C). We also demonstrated that this sorbent possesses lower activation energies for both the chemisorption and the diffusion processes, enabling it to be much less affected by CO 2 concentration. By decreasing the CO 2 concentration from 100 to 20 vol%, the CO 2 sorption capacity of Li 4 SiO 4 -(EXVMT)-4 only slightly decreased from 19.4 to 18.6 wt%, but the capacity for Li 4 SiO 4 synthesized from pure SiO 2 decreased significantly from 22.0 to 11.3 wt%. Thanks to its high CO 2 sorption capacity, excellent cycling stability, fast sorption rate, low cost, and scalable synthesis, the VMT derived Li 4 SiO 4 -based high-temperature CO 2 sorbent is very promising for practical applications.