Absorption rates of carbon dioxide in aqueous and non-aqueous amine solutions and solubility of carbon dioxide in aqueous piperazine solution

• Main Author: Kadiwala, Salim
• Format: Dissertation
• Language: English
• Subjects: engineering, chemical; engineering, environmental
• ISBN: 0494550368; 9780494550366

Aqueous and non-aqueous alkanolamine solutions have been widely studied for acid gas removal processes. Research interest has recently shifted towards non-alkanolamines in search for adequate solvents. In this comprehensive study, the kinetic rates of absorption of carbon dioxide in various alkanolamines and non-alkanolamine solutions, in aqueous or non-aqueous media, have been measured using a stop-flow instrument. Absorption rates of carbon dioxide (CO2) in non-aqueous solutions of ethylenediamine (FDA) and 3-amino, 1-propanol (3AP) were studied in a concentration range of 20-120 mol/m3 and a temperature range of 293-313 K. The results were compared with 2-((2-aminoethyl) amino) ethanol (AEEA). The present study shows that the second order reaction rate constants in non-aqueous solutions of ethylenediamine (FDA) in methanol and ethanol are higher than that of 2-((2-Aminoethyl) amino) ethanol (AEEA). Reaction kinetics for this solvent increase in the following order: EDA>AEEA>3AP. 3AP, a primary amine, is kinetically faster than the "industry standard" monoethanolamine (MEA) in aqueous and non-aqueous solutions. Two novel tertiary amines, 3-dimethylamino-1-propanol (3DMA1P) and 1-dimethylamino-2-propanol, were introduced and the absorption rates of CO2 were measured using the stop flow technique in a concentration range of 100-1000 mol/m3 and a temperature range of 298-313 K. Both amines were found to react almost 10 times faster with CO2 than the "industry standard" N-methyldiethanolamine (MDEA).
The kinetics of CO2 in an aqueous solution of piperazine were also studied using the stop flow technique in a concentration range of 20-50 mol/m3 and a temperature range or 298-313 K. The reaction rate constant found with the stop-flow technique was in agreement with those found by indirect methods.
The solubility of CO2 in aqueous solutions of piperazine at low concentrations is required in view of its application as a promoter to slower reacting tertiary amines. Therefore, the solubility or CO2 in an aqueous solution of piperazine was measured at temperatures of 313 K and 343 K, over concentrations of 3 mass % and 10 mass % piperazine. The Electrolyte-NRTL model was used to correlate and predict the solubility of CO2 in an aqueous solution of piperazine, using the data obtained in this study. Electrolyte NRTL model gave good fit for both concentrations (3 mass% and 10 mass% piperazine) except above 4000 kPa pressure at high temperature in the case of 10 mass% piperazine.