Reaction kinetics of carbon dioxide and hydroxide in aqueous glycerol

Abstract

The reaction kinetics of carbon dioxide and sodium hydroxide (nominally 0.1N and 0.3N) in aqueous glycerol were measured in a wetted wall column (WWC) at 20, 30, and 40°C. Glycerol was added at 0–89wt% to achieve a liquid viscosity (μL) of 0.89–65cP. Compared to pure aqueous alkaline solution, the absorption rate (kg′) 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 (kAlk), which resulted from the competing effects of CO2/NaOH (kOH-) and CO2/glyceroxide (kGlycerol-) reactions. The kGlycerol- was 6–7 times faster than kOH-. The non-monotonic trend of kg′ was the combined effect of kAlk increasing and diffusivity (DCO2) 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 0.1N NaOH is 4% for water and 20% for 89wt% glycerol. Average depletion was less than 3% for 0.3N NaOH. The addition of 0.05N sodium carbonate has an insignificant effect on kg′.