Assessing Anhydrous Tertiary Alkanolamines for High-Pressure Gas Purifications

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• 作者：Paul M. Mathias ; Louis V. Jasperson ; David VonNiederhausern ; Mark D. Bearden ; Phillip K. Koech ; Charles J. Freeman ; David J. Heldebrant
• 刊名：Industrial & Engineering Chemistry Research
• 出版年：2013
• 出版时间：December 11, 2013
• 年：2013
• 卷：52
• 期：49
• 页码：17562-17572
• 全文大小：596K
• 年卷期：v.52,no.49(December 11, 2013)
• ISSN：1520-5045

文摘

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鈥搇iquid鈥搇iquid equilibrium (VLLE) data of anhydrous ethyldiethanolamine (EDEA) with CH₄, C₃H₈, H₂S, and CO₂ at 10鈥?0 掳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鈥檚 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).