Assessing Anhydrous Tertiary Alkanolamines for High-Pressure Gas Purifications

作者：Mathias Paul M^*; Jasperson Louis V; VonNiederhausern David; Bearden Mark D; Koech Phillip K; Freeman Charles J; Heldebrant David J

来源：Industrial & Engineering Chemistry Research, 2013, 52(49): 17562-17572.

DOI：10.1021/ie4020974

Anhydrous tertiary alkanolamines chemically react with CO2 and H2S, with greater selectivity for the latter. This is in direct contrast to aqueous amine-based solvent systems, which exhibit higher selectivity for CO2 over H2S. Anhydrous tertiary alkanolamines exhibit pressure-induced chemical fixation of CO2 to form zwitterionic ammonium alkylcarbonate ionic liquids, while the same tertiary alkanolamines react with H2S at atmospheric pressures to form hydrosulfide ionic liquids. This difference in capture pressure implies that certain anhydrous alkanolamines could be chemically selective for H2S over CO2. We present here the first published vapor liquid liquid equilibrium (VLLE) data of anhydrous ethyldiethanolamine (EDEA) with CH4, C3H8, H2S, and CO2 at 10-50 degrees 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 CO2 and H2S 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 CO2 and H2S (relative to physical solvents) and its selectivity for H2S over CO2 (relative to chemical solvents).

• 出版日期2013-12-11