• Energy Research

AbstractFour pure amines were tested in a rapid screening apparatus to study hydroxyl and amine functionalities. The apparatus was validated with an aqueous 30 mass % MEA solution. The result shows that a viscous loaded solvent was the main challenge. The initial absorption rate for pure MEA was significantly higher than that of MEA in 30 mass % aqueous solutions. Pure DEA showed the lowest initial absorption rate while polyamines such as MAPA and DETA gave the highest absorption rates. The equilibrium CO2 capacity of amine was shown to correspond to the number of amine functionalities. The hydroxyl functionality might contribute by maintaining the interfacial tension of the gas/liquid during the process. The carbamate and bicarbonate formation are the main reaction products in the systems as seen in the NMR results.

AbstractQualitative NMR spectroscopy was used to study the species formed during CO2 absorption in aqueous solution of diamines. Three different systems, consisting of primary (ethylenediamine), primary/secondary (3-(Methylamino) propylamine) and secondary (piperazine) diamines were studied by 13C NMR and the main products were identified based on various 1D and 2D NMR techniques. The main compounds were observed and assigned to (primary/ secondary) carbamate, dicarbamate and carbonate/bicarbonate. The highest concentration of carbonate/bicarbonate and dicarbamate were observed in the PZ/CO2/H2O followed by MAPA/CO2/H2O and EDA/CO2/H2O. Both 1H and 13C NMR spectroscopy was used to quantitatively determine the speciation of amines but 13C-NMR, although slower, has the potential of being more accurate than the 1H-NMR. The diamines studied in the present work were found to have high CO2 absorption capacity compared to other amines described in the literature. This indicates that they are interesting for the further investigation.

AbstractAn extension of the Debye-Hückel model was used to re-evaluate the MDEA protonation constant as a function of temperature and ionic strength. The Debye-Hückel limiting slope was estimated and the suggested parameters are successfully representing the data. The ionic strength was calculated by the speciation generated in the system and not only from the salt background concentration. Correlations for the protonation constant of MDEA were proposed for infinite dilution and high ionic strength and the standard thermodynamic properties for protonated MDEA were calculated.

AbstractQualitative 13C-NMR experiments were performed at 298 K and for different loadings to investigate the liquid speciation in amino acid neutralized by both strong inorganic and weak organic bases. The two different systems, potassiumsarcosinate(KSAR) and sarcosine blended with equinormal quantities of 3-(methylamino)propylamine (MAPA-SAR) were studied. In presence of CO2, the spectra of the MAPA-SAR system showed more species than that of the K-SAR system due to the presence of carbamates from the primary, secondary and amino acid amine groups even at very low loadings. This means that complete neutralization of sarcosine with MAPA does not occur since carbamates of the primary and secondary amine group of MAPA were formed in the system. In order to quantify the percentage of carbamate formed on the amine group of sarcosine compared to carbamates formed on MAPA, a quantitative 13C-NMR experiment is needed as a future work.

Abstract Effect of different promoters on performance of two bicarbonate forming solvents (HS1 and HS2) was studied in this work and results compared with the performance of 30 wt% MEA and CESAR1 solvents. Based on the results from rapid screening experiments (absorption at 40oC, desorption at 80oC), one promoter was selected for further study. Vapor-liquid equilibrium (VLE) and heat of absorption were measured for two solvent systems promoted with the selected promoter.

AbstractQualitative and quantitative NMR experiments were performed on 5M aqueous solutions of monoethanolamine (MEA) loaded with CO2 (α = 0.4) and in presence of 1mM FeSO4 x 7H2O as a catalyst. The main degradation products were identified and quantified by 1D and 2D NMR Spectroscopy as: N-(2-hydroxyethyl) imidazole (HEI), 2-oxazolidone (OZD), N-(2-hydroxyethyl) formamide (HEF). There are also some other signals not quantified yet because of the low intensity. The NMR results were compared with GC/LC-MS results of the same solution.

AbstractThe kinetics of the reactions of the primary and secondary amine groups in aqueous DETA solution were measured in a string of discs contactor at different concentrations and temperatures. The reaction rates of the primary amine group were performed at very low loading and for the secondary amine group H2SO4 was used to neutralize the primary amine groups. The reaction rates increase with increasing DETA concentration and temperature. The reaction order is found to be a broken-order and to vary slightly with the temperature. Both the termolecular and the zwitterion mechanisms were applied to interpret the experimental data and gave identical result. Both DETA and water contribute to the carbamate formation in the primary and secondary amine groups. The rate of CO2 absorbed in the primary amine group is faster than the secondary amine group and about 100 times higher.