Solubilities of gases in physical solvents and absorption rates of carbon dioxide in a mixed solvent

The objective of this work is a search for the best solvents for natural gas sweetening that can be used in flue gas treatment. The study recommended using sulfolane or NFM in natural gas sweetening and PEGDME 250 (Selexol) or TTEGDME for flue gas treatment. The “analogy” between the solubilities of ethane and CO₂ in polar solvents should be investigated in a similar manner as the “N₂O analogy”. A simple model based on a modification of the Solubility Parameter Theory was used to predict reasonably well the absorption of CO₂, methane and ethane in glycol ethers. The model can also predict the solubility of CO₂ and methane in Selexol to within 3.0 and 1.6% respectively.; In order to select the best solvents, it is necessary to have a better understanding of the solute-solvent interactions. Results of the study indicate the possible formation of stable complexes in these solutions. A model was used to predict the viscosity of glycol ether if its density was known. Fifty-four data points could be correlated within 8% of error. The error falls to 2% if only ethylene and diethylene glycol ethers were correlated.; Carbon dioxide absorption by aqueous solutions of alkanolamines and mixed solvents occur by a process of mass transfer enhanced by chemical reactions in the boundary layer. The results of this study are confirmed by a solubility study of CO₂ in mixtures of MDEA + TEGMME and MDEA + methanol, where it was shown that the presence of the chemical solvent (MDEA) made the mixture absorb more CO₂ than the physical solvents alone (Henni and Mather, 1995). These results are in contradiction to what is generally acceptable in the literature. The absorption of carbon dioxide in an aqueous tertiary alkanolamine (methyldiethanolamine-MDEA) and in a mixed solvent of commercial importance (similar to Sulfinol M) made of aqueous MDEA and a physical solvent (sulfolane) were measured over a wide range of temperatures. It was concluded that the rate of absorption of CO₂ in the mixed solvent was greater than that of the equivalent aqueous alkanolamine at all temperatures. The density, viscosity, solubility and diffusivity involved in the model were measured. The study also shows that the modified Stokes-Einstein equation was not suitable for estimating the diffusivity of CO₂ in the aqueous MDEA-sulfolane solution. (Abstract shortened by UMI.)...