Anhydrous tertiary alkanolamines chemically react with CO 2 and H 2 S, with greater selectivity for the latter. This is in direct contrast to aqueous amine-based solvent systems, which exhibit higher selectivity for CO 2 over H 2 S. Anhydrous tertiary alkanolamines exhibit pressure-induced chemical fixation of CO 2 to form zwitterionic ammonium alkylcarbonate ionic liquids, while the same tertiary alkanolamines react with H 2 S at atmospheric pressures to form hydrosulfide ionic liquids. This difference in capture pressure implies that certain anhydrous alkanolamines could be chemically selective for H 2 S over CO 2 . We present here the first published vapor−liquid−liquid equilibrium (VLLE) data of anhydrous ethyldiethanolamine (EDEA) with CH 4 , C 3 H 8 , H 2 S, and CO 2 at 10−50°C measured by the TPx and TPxy methods. The data are modeled in Aspen Plus using an NRTL-with-solvation model. Data trends and the underlying phenomena are discussed for each gas. We also present process simulations that compare anhydrous EDEA's performance for CO 2 and H 2 S high-pressure separations to other solvents such as Fluor Solvent (propylene carbonate), Selexol, and aqueous methyldiethanolamine (MDEA) for a representative gas-purification absorber. This work indicates that a niche for anhydrous EDEA in high-pressure gas purifications may be its stronger absorption for CO 2 and H 2 S (relative to physical solvents) and its selectivity for H 2 S over CO 2 (relative to chemical solvents). ■ INTRODUCTIONChemical solvents such as alkanolamines are well-suited for gastreating applications, such as natural gas purification and CO 2 capture, because they provide high selectivity for acid-gas components (e.g., CO 2 and H 2 S) over nonpolar species. 1,2 More than 80 years ago Bottoms 3 first recognized amines as chemical solvents, and also invented the absorption-stripping process used today. Amine scrubbing is widely expected to be the dominant technology for the low-pressure CO 2 capture from power plants, particularly for coal-fired plants. 4 Amine scrubbing is also widely used for higher-pressure gas purifications associated with gas processing. 1,2 However, chemical solvents have the disadvantage of relatively high enthalpies of solution, and in cases where the acid-gas impurities are at a significant composition of the total gas stream, the energy penalty of regenerating the solvent by application of heat may be out of proportion to the value of the treated gas. This has provided an opportunity for physical solvents, in which nonreactive organic agents are used. Here, solvent regeneration can often be accomplished by a simple reduction in pressure, without the need for heat to increase the temperature. Examples of physical solvents for gas-purification processes are Rectisol (methanol), Fluor Solvent (propylene carbonate), and Selexol (mixture of propylene glycol dimethyl ethers). 1 In this work, we present a preliminary evaluation of the niche for anhydrous tertiary alkanolamines such as EDEA (ethyldiethanolamine) for high-press...
Quantitative understanding of the water content of pipeline fluids in equilibrium with hydrates is critically important to ensure pipeline flow without hindrance from solid precipitation. This paper focuses on pipelines with CO 2 -rich fluids in cold environments (such as those in Alaska) and generally in CO 2 capture. Since there is considerable question about the available data for the water solubility in CO 2 at these conditions, a round-robin testing program was structured by Fluor/Worley Parsons Arctic Solutions to quantitatively establish the water solubility. The goal of the data program was to determine the water solubility in CO 2 -rich mixtures to estimated uncertainty. This paper presents the data program and evaluates its results through thermodynamic analysis and comparison to available literature data.
Experimentally determined critical temperatures (T c ) and critical pressures (P c ) are reported for 64 compounds. In addition, the critical volume (V c ) has been experimentally determined for 14 of these compounds. The compounds in this study are of industrial interest in process design, simulation, and safety. These data also extend our understanding of and ability to predict these properties from group contribution methods.
We report liquid−liquid mutual solubilities for binary aqueous mixtures involving 2-, 3-, and 4-ethylphenol, 2-, 3-, and 4-methoxyphenol, benzofuran, and 1H-indene for the temperature range (300 < T/K < 360). Measurements in the waterrich phase for (2-ethylphenol + water) and (4-ethylphenol + water) were extended to T = 440 K and T = 380 K, respectively, to facilitate comparison with literature values. Liquid−liquid equilibrium tie-line determinations were made for four ternary systems involving (water + toluene) mixed with a third component: phenol, 3-ethylphenol, 4-methoxyphenol, or 2,4-dimethylphenol. Literature values at higher temperatures are available for the three (ethylphenol + water) systems, and in general, good agreement is seen. The ternary system (water + toluene + phenol) has been studied previously with inconsistent results reported in the literature, and one report is shown to be anomalous. All systems are modeled with the predictive methods NIST-modified-UNIFAC and NIST-COSMO-SAC, with generally good success (i.e., within 0.05 mole fraction) in the temperature range of interest (300 < T/K < 360). This work is part of a larger project on the testing and development of predictive phase equilibrium models for compound types occurring in catalytic fast pyrolysis of biomass, and background information for that project is provided.
Vapor−liquid equilibrium (VLE) measurements have been performed on several binary systems incorporating chemicals of interest to the biofuels industry. Systems were chosen based on two criteria: (1) similarity to measurement requests received by Wiltec and (2) suitability of using the Wilson Equation to model the activity coefficients for the VLE data. The Wilson Equation is a good choice for modeling fully miscible solutions of moderately polar compounds. With these two ideas in mind, systems were chosen incorporating the following compounds: 1-methoxy-2-propanol, 2-furaldehyde, allyl alcohol, butyl acetate, carbon dioxide, carbon disulfide, carbonyl sulfide, ethanolamine, ethyl acetate, n-butanol, pentane, and tert-butanol. Measurement temperatures ranged from −25 °C to +200 °C.
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