Solubility of carbon dioxide in aqueous diethanolamine blended with 1-butyl-1-methylpyrrolidinium dicyanamide and 1-butyl-1-methylpyrrolidinium trifluoromethanesulfonate at high pressure / Siti Nabihah Jamaludin

Removing of CO2 gases is very important process in many chemical industries today. Alkanolamines are mature in technology for efficiently capturing CO2. However, even if the reaction between CO2 and these amines is significantly fast, their potential application in CO2 capture encounters several drawbacks. Alternatively, ionic liquids (ILs) seem very attractive with a great advantage. However, gas dissolution into ILs is a physical phenomenon with no chemical reaction and the absorption rate is quite slow. To achieve better performance, some special groups were introduced to the anion. In recent years, the mixed solutions consisted of amine and ILs have received particular interest. Generally, CO2 capture with amine-ILs mixture have been reported having low capability of CO2 loading. However, by tuning the ILs may increase the capacity of CO2 absorption. Hence, the studies on the potential of different types of ionic liquid toward CO2 absorption performance is necessary. Most of CO2 capture with amine-ILs mixture also focused on absorption ability at ambient pressures, while seldom research was concerned at high pressure. This not only limits the CO2 absorption application at high pressure, but also the determination of the operation condition. This work mainly reported CO2 solubilities in aqueous Diethanolamine (DEA) mixed with pyrrolidinium based ILs; 1 -Butyl-1-Methylpyrrolidinium Dicyanamide [BmPyrr][DCA] and 1-Butyl 1-Methylpyrrolidinium Trifiuoromethanesulfonate [BmPyrr][OTf] at various operating temperatures (303.15K-333.15K), pressures (500psi - 700 psi) with 0-10wt% concentration of ILs and 30-40wt% of DEA concentration. 1-Butyl-1- Methylpyrrolidinium Dicyanamide [BmPyrr][DCA] and 1-Butyl-1- Methylpyrrolidinium Trifiuoromethanesulfonate [BmPyrr][OTf] were selected as physical absorbents for capturing CO2. The absorption performance was investigated by conducting the experiment using high pressure reactor. The absorption capacities were calculated based on pressure change until the equilibrium phase were achieved by the system. The results of CO2 solubility in liquid are expressed as Dto2 (mol CCVmol amine) for all the experimental. From the results of this research, it was found that the CO2 solubility performance reduced when [BmPyrr][DCA] is added to the aqueous DEA solution at all temperatures measured and with addition of [BmPyrr][OTfJ at temperatures of 303.15K and 313.15K. However, the absorption capacities for aqueous DEA-[BmPyrr][OTf] mixture exhibits good absorption performance at temperature condition of 323.15K-333.15K. Similar reducing trend of CO2 absorption was observed for aqueous DEA for all measured temperatures. This shows that DEA-[BmPyrr][OTfJ system has better performance compared to DEA-[BmPyrr][DCA], indicating that OTf anion has great potential for capturing CO2 in future application. In term of pressure, the CO2 absorption increases as pressure increases for both DEA-[BmPyrr][DCA] and DEA-[BmPyrr][OTfJ systems. A solubility model was developed to predict the CO2 solubility data as a function operating variables in the studied range in aqueous blends of DEA and ILs. There is an acceptable degree of agreement between experimental data and prediction by Jou and Mather model with an average absolute deviation of 5.165%. Therefore, it can be concluded that this work has achieved the objectives of this research.