High-temperature CO2 capture by Li4SiO4 adsorbents: Effects of pyroligneous acid (PA) modification and existence of CO2 at desorption stage

摘要

Li4SiO4 has been demonstrated as a promising adsorbent for CO2 capture. However, Li4SiO4 adsorbents from the conventional solid-state method usually exhibit dense microstructures and, thus, poor CO2 capture performance. Treating Li4SiO4 with organic acids has been proved effective to improve the microstructures. The commonly used acids such as acetic acid, citric acid and gluconic acid are too expensive, restricting the application of this modification technique. In addition, in the typical Li4SiO4-based CO2 capture looping system, CO2 usually exists in the desorption reactor. However, the effect of the existence of CO2 at the desorption stage on adsorption performance has been rarely studied. Focusing on these two issues, this work employed pyroligneous acid (PA), a low-cost by-product of the fast pyrolysis of biomass, to modify the microstructures of Li4SiO4. It was found that modification by pyroligneous acid (PA) successfully improved the microstructures and enhanced the surface area of Li4SiO4 adsorbent. As a result, the obviously improved CO2 adsorption performance was achieved. In addition, the test results under CO2-containing desorption atmospheres indicated that the existence of CO2 at the desorption stage decreased the adsorption performance due to the severe sintering caused by the existence of CO2 at the desorption stage.