Post-Combustion CO2 Capture Using Diethanolamine in 1-Propanol

Abstract

In order to study the effect of CO2 loading on the physical properties of non-aqueous organic solvents, the secondary amine diethanolamine (DEA) was studied in 1-Propanol. The effect was reported in terms of viscosity, density and CO2 loading; their trends were obtained based on timely basis. Three different concentrations of DEA in 1-Propanol were tested to show the effect of amine concentration on the measured properties. The considered concentrations were of 2, 3.5 and 5M at room conditions. All three concentrations showed solid formation beyond their maximum CO2 capacity where a biphasic behaviour was observed for 3.5 M and 5 M. Furthermore, the trend for the measured properties were of increasing pattern for all concentrations until the solid formation point, where after this point the readings fluctuated. All of the investigated concentrations showed losses that were ~11 w.t% of 1-Propanol. For comparison reasons, also 30 w.t% of aqueous DEA was studied in the same manner and better CO2 loadings were obtained for all the studied non-aqueous systems. The aqueous secondary amine showed a maximum loading of 31 (mg CO2/g sample) where the 2 M DEA in 1-Proponol showed a comparable maximum capacity of 35 (mg CO2/g sample) with the viscosity and density of 9.28 cP and 0.91 g/mL, respectively. It is noteworthy that this loading in the non-aqueous medium was obtained using a lower amount of DEA than in aqueous solution. Out of the three studied concentrations, the secondary amine DEA in 1-Propanol, showed leading results with the 3.5 M concentration, in which its viscosity was 35.68 cP for 74 (mg CO2/g sample) as a loading and 0.93 g/mL of density. It was observed that flowing CO2 beyond this point leads to solid formation within the 3.5 M solvent system; biphasic behaviour. With this, the 3.5 M system can be advised to be further studied for post-combustion CO2 capture.