Screening of Solvents for Carbon Dioxide Capture: Kinetics, Solubility and Calorimetric Studies.

摘要

The scope of this work is to investigate potential solvents to be used in gas sweetening operations. Following an initial screening study, it was concluded that polyamines and cyclic amines have higher reaction rates than linear amines. Six aqueous cyclic polyamine solutions were studied using the stopped-flow technique. The reaction of CO2 in a non-aqueous piperazine system (ethanol and triethylene glycol) was also measured and compared to other amines.;High pressure solubilities for CO2 in 1.45 M and 2.89 M aqueous 1-methyl piperazine (1-MPZ) solutions were measured. The E-NRTL model was used to correlate the solubility of CO2 in aqueous solutions of 1-MPZ with an average pressure deviation of 1% and 6% in loading. Nuclear Magnetic Resonance studies were conducted to identify the species present.;Molar heat capacities of thirty eight pure solvents are also reported. Existing structural similarities between the compounds were explored using group additivity analysis and molecular connectivity principles.;The heat of absorption values in aqueous tertiary amines (methyldiethanolamine, dimethylpropanolamine and dimethylisopropanolamine, DMIPA) were measured at different temperatures, pressures, and compositions. Heat of absorption values were measured for DMIPA at 5 MPa for different temperatures. Data were correlated using a rigorous thermodynamic model developed in this work. DMPA was found to have a lower heat of absorption and a higher CO2 loading capacity than other popular tertiary amines.;High pressure equilibrium solubilities of CO2, CH4 and C2H6 in a widely used mixture of polyethylene glycol dimethyl ethers (Genosorb 1753) were measured and compared to other physical solvents. Genosorb 1753 was found to have the highest absorption capacity for CO2 and a low absorption capacity for CH4, along with a high absorption capacity for C2H6.;Molar excess enthalpies of five amines (monoethylethanolamine, ethyldiethanolamine, n-butyldiethanolamine, tert-butyldiethanolamine, triethylamine and morpholine) were measured. The pKas of forteen amines were measured using potentiometric titration. The influence of steric hindrance, the number of --OH groups and the alkyl chain lengths of the molecules on the basicity of the aqueous solution was investigated. Densities, viscosities and refractive indices are reported for aqueous solutions of 1-amino propanol and 1-methylpiperazine, in addition to the surface tensions of an aqueous 1-methylpiperazine solution.