Reaction kinetics of carbon dioxide and hydroxide in aqueous glycerolby Song, D; Rochelle, GT
The reaction kinetics of carbon dioxide and sodium hydroxide (nominally 0.1 N and 0.3 N) in aqueous glycerol were measured in a wetted wall column (WWC) at 20, 30, and 40 degrees C. Glycerol was added at 0-89 wt% to achieve a liquid viscosity (mu(L)) of 0.89-65 cP. Compared to pure aqueous alkaline solution, the absorption rate (k(g)’) initially increased by 30% and then decreased rapidly by 75% with increasing glycerol. Based on the measured kg, a model was developed to calculate the overall reaction rate constant (k(Alk)), which resulted from the competing effects of CO2/NaOH (k(OH-)) and CO2/glyceroxide (k(Glycerol-)) reactions. The k(Glycerol-) was 6-7 times faster than k(OH-). The non-monotonic trend of kg! was the combined effect of k(Alk) increasing and diffusivity (D-co2) decreasing when glycerol increased. The effect of alkalinity depletion at the gas/liquid interface has been included in the kinetic model. The average depletion for 0.1 N NaOH is 4% for water and 20% for 89 wt% glycerol. Average depletion was less than 3% for 0.3 N NaOH. The addition of 0.05 N sodium carbonate has an insignificant effect on k(g)’. (C) 2016 Elsevier Ltd. All rights reserved.