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

Li 4 SiO 4 has been demonstrated as a promising adsorbent for CO 2 capture. However, Li 4 SiO 4 adsorbents from the conventional solid-state method usually exhibit dense microstructures and, thus, poor CO 2 capture performance. Treating Li 4 SiO 4 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 Li 4 SiO 4 -based CO 2 capture looping system, CO 2 usually exists in the desorption reactor. However, the effect of the existence of CO 2 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 Li 4 SiO 4 . It was found that modification by pyroligneous acid (PA) successfully improved the microstructures and enhanced the surface area of Li 4 SiO 4 adsorbent. As a result, the obviously improved CO 2 adsorption performance was achieved. In addition, the test results under CO 2 -containing desorption atmospheres indicated that the existence of CO 2 at the desorption stage decreased the adsorption performance due to the severe sintering caused by the existence of CO 2 at the desorption stage.