Re‐carbonation by recycling NaOH‐dissolved ethanol solution for carbon dioxide fixation

Abstract

AbstractRe‐carbonation is investigated using NaOH‐dissolved ethanol. Five hundred mL of recycled filtrates is obtained from a previous carbonation in which 3 g of NaOH has been replenished and dissolved. CO2 is physically absorbed at each re‐carbonation, and the amount decreases with increasing numbers of re‐carbonation repetitions. However, the amount of CO2 chemically absorbed that was consumed in the production of precipitates, such as sodium ethyl carbonates (SEC) and NaHCO3, slightly increases. This is due to the slight water that accumulates with repeated re‐carbonation, which increases the generation of NaHCO3 and the reaction time. The amount of precipitates and SEC composition decrease from the initial carbonation to the 22nd re‐carbonation, and the amount of CO2 fixed in the precipitates is calculated as a maximum of 0.92 g of CO2/g of NaOH at the initial carbonation, which then decreases linearly to 0.56 g of CO2/g of NaOH at the 22nd re‐carbonation. However, 3.16 g of NaHCO3 precipitates is repeatedly obtained from the 23rd re‐carbonation, maintaining an ethanol concentration of 90.33 wt.%. Thus, 0.55 g of CO2/g of NaOH is fixed in this region. Therefore, CO2 can be fixed in the SEC and NaHCO3 precipitates via re‐carbonation using NaOH‐dissolved ethanol.