High temperature CO2 capture performance and kinetic analysis of Na4SiO4 ceramics

Abstract

Alkali silicate-based ceramics sorbents were regarded as particularly suitable materials for CO2 capture at high temperatures, however, the CO2 capture behaviors of Na4SiO4 had been seldom investigated. In this work, the Na4SiO4 ceramics samples were prepared using the one-step synthesized method, and the CO2 sorption/desorption performances at high temperatures, the thermal stability, and the cycling stability of Na4SiO4 were systematically investigated. It was demonstrated that the maximum CO2 sorption capacity of SO-3 sample reached 19.4 wt% at 725 °C, and the optimal condition of cycling tests were 750 °C for sorption and 800 °C for desorption based on the sorption/desorption capacity and rate, which exhibited good thermal stability and high cyclic stability. Besides, the kinetic analysis results showed that the diffusion process was the rate-determining step of CO2 adsorption, which was more dependent on temperature than the chemisorption process. The structure and surface morphology variations were also investigated, it was interesting that there was a special “fish scale” surface structure after the sorption process, revealing that the melting phenomenon happened during the chemisorption reaction process. By comparing with common sorbent Li4SiO4, the material and CO2 capture costs of Na4SiO4 were much lower. These results proved that Na4SiO4 was expected to be a suitable high temperature CO2 capture material as a good supplement to alkali silicate-based ceramics sorbents.