CO2 high-temperature sorbent (Al, Fe, Ti) CO-doped Li4SiO4 from fly ash-derived SiO2 aerogel: In-situ synthesis, enhanced capture ability and long cycle stability

Abstract

Lithium silicate (Li4SiO4), an efficient CO2 high-temperature sorbent, has become the research hotspot in CO2 capture due to its large theoretical adsorption capacity and fast rate. How to further reduce production cost while ensuring the adsorption performance has become the key to industrial application. In this work, using Al, Fe, Ti co-doped SiO2 aerogel synthesized from fly ash as silicon source, Li4SiO4 sorbents were achieved through solid-state calcination method. The influences of preparing conditions on the microstructure and CO2 capture property were systematically investigated. Under the optimum conditions, the as-prepared Li4SiO4 demonstrated the best CO2 adsorption capacity of 33.24 wt% within 7.0 min. Particularly, the CO2 capture capacity remained 23.38 wt% (>70% of the first value) after 35 cycles, indicative of long cycle stability. Moreover, the kinetic characteristics of CO2 adsorption process could be well simulated by the double exponential model, and the diffusion process of Li+/O2− ions was the decisive step of the whole adsorption reaction. Compared with Li4SiO4 by pure reagents, the sorbent from fly ash-based aerogel exhibited competitive adsorption capacity, which provides a new cost-effective way to synthesize CO2 high-temperature sorbent with super capture performance and good cycle stability.