CO2 Capture using Organic Nonaqueous Solvents

Abstract

Aqueous amines are suggested as good mechanism for post-combustion CO2 capture, however, these solvents are known for their high energy requirements. This requirement is reported to come majorly from the solvent regeneration step other than the complications expected during operation. Equipment corrosion is one of the drawbacks brought by the aqueous amines and that is due to their water component. To eliminate these issues faced with aqueous amines, studies suggest the usage of nonaqueous organic solvents as an alternative. It is reported that this class of solvents require less energy for regeneration in comparison with aqueous based solvents. Furthermore, due to their non-aqueous medium, problems related to corrosion and contamination production are minimized. However, literature reveals that non-aqueous organic solvents are highly viscous when CO2 is fully absorbed. In relation to that, up to date, there is a lack of studies regarding the effect ofCO2 loading on the physical properties of organic non-aqueous solvents. Therefore, the objective that is reported in this study is analogous to the investigation of the influence of the CO2 loading on the physical properties of these solvent systems. The studied systems consisted of 4 amines and 2 solvents. As a representitive of primary, secondary and tertairy amines, MEA, DEA and MDEA were chosen respectively. TMG was also a tested amine in this study as literature showed its potential in non-aqueous enviroment. These amines were studied in 1-propanol and 1-hexanol. The amine concentrations were varied for each solvent and the results were reported in terms of viscosity, density and CO2 loading. From these systems it was found that the amine amounts in non-aqueous organic solvents are lower than those for aqueous systems. For the primary amine MEA in 1-PrOH, best results were obtained for the 3.5M concentration in which viscosity was reported to be 17 cP with 55 (mg CO2/g sample) loading. The secondary amine DEA in 1-PrOH, showed leading results with the 3.5M system in which its viscosity was 35.68 cP for 74 (mg CO2/g sample) as a loading. Furthermore, the tertiary MDEA systems in 1-PrOH exhibited only physical absorption in which it was in agreement with the literature. Lastly, the TMG in 1-propanol showed the best performance with the 2M system in which it exhibited 16 cP viscosity and 60 (mg CO2/g sample) loading where unlike other systems, 2M TMG in 1-PrOH did not show any solvent losses. In addition to that the 2M TMG in 1-PrOH was found to have a similar CO2 capacity to the 30wt.% aqueous MEA for a lower amount of amine in 1- PrOH. In relation to 1-hexanol systesm, analysis was limited by the equipment available, hence it is considered part of the future work.

Date of Award	Dec 2017
Original language	American English