Salt Hydrates: New Reversible Absorbents for Carbon Dioxide

Quinn, R.; Appleby, John; Pez, Guido P.

doi:10.1021/ja00106a035

Cited by 60 publications

(44 citation statements)

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“…Although ILs (molten salts) have been known to be used as CO 2 absorbents, [7] only in the past decade have IL-CO 2 systems been extensively studied. Brennecke et al reported that supercritical CO 2 is highly soluble in ILs, whereas ILs do not dissolve in supercritical CO 2 .…”

Section: Il-co 2 Systemsmentioning

confidence: 99%

“…[3,7] The very few examples studied contained substantial amounts of water, up to almost 2 mol per mol IL. ii Chinn et al reported that [bmim][acetate] + 14 wt-% H 2 O has a CO 2 absorption profile (CO 2 loading versus pressure) typical for a chemical absorption process with an initial steep rise and a subsequent plateau at higher pressures.…”

Section: Carboxylate Functionalitymentioning

confidence: 99%

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Why are Ionic Liquids Attractive for CO2 Absorption? An Overview

2009

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As the climate debate is hotting up, so is the (re)search for finding powerful new materials for the efficient and cost-effective removal of CO2 from flue-gas streams from power plants and other emission sources. Ionic liquids (ILs), exhibiting higher CO2 solubility than conventional organic solvents, have received considerable interest as new CO2 absorbents. The present paper evaluates the advantages and disadvantages of ILs, and provides an overview of the recent developments of ILs for CO2 capture. In conventional ILs, CO2 is absorbed by occupying the free space between the ions through physical absorption mechanisms. As another promising strategy, task-specific ILs have been studied that, by attaching functional groups to the ions, allow the formation of chemical bonds to improve the overall absorption capacity during the CO2 capture process. Other strategies include using ILs as reaction media or as selective absorption materials.

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Section: Il-co 2 Systemsmentioning

confidence: 99%

Section: Carboxylate Functionalitymentioning

confidence: 99%

Why are Ionic Liquids Attractive for CO2 Absorption? An Overview

2009

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“…For example, Quinn et al (1994Quinn et al ( , 1995aQuinn et al ( ,b, 1997 showed that composite membranes prepared from PVBTAF (poly(vinylbenzyltrimethyl ammonium fluoride)) exhibited a CO 2 /H 2 selectivity value of 87. Also, a composite membrane of PDMS/PDADMAF/PDMS has an H 2 S/H 2 selectivity of 260.…”

Section: Facilitated Transport/solid Polymer Electrolytesmentioning

confidence: 99%

Novel Technologies for Gaseous Contaminants Control

Turk¹,

Merkel²,

López-Ortíz³

et al. 2001

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The overall objective of this project is to develop technologies for cleaning/conditioning the syngas from an integrated gasification combined cycle (IGCC) system to meet the tolerance limits for contaminants such as H 2 S, COS, NH 3 , HCN, HCl, and alkali for fuel cell and chemical production applications. RTI's approach is to develop a modular system that (1) removes reduced sulfur species to sub-ppm levels using a hybrid process consisting of a polymer membrane and a regenerable ZnO-coated monolith or a mixed metal oxide sorbent; (2) removes hydrogen chloride vapors to sub-ppm levels using an inexpensive, high-surface area material; and (3) removes NH 3 with acidic adsorbents.RTI is working with MEDAL, Inc., and North Carolina State University (NCSU) to develop polymer membrane technology for bulk removal of H 2 S from syngas. These membranes are being engineered to remove the acid gas components (H 2 S, CO 2 , NH 3 , and H 2 O) from syngas by focusing on the "solubility selectivity" of the novel polymer compositions. The desirable components of the syngas (H 2 and CO) are maintained at high-pressure conditions as a non-permeate stream while the impurities are transported across the membrane to the low pressure side. RTI tested commercially available and novel materials from MEDAL using a high-temperature, high-pressure (HTHP) permeation apparatus. H 2 S/H 2 selectivities >30 were achieved, although there was a strong negative dependence with temperature. MEDAL believes that all the polymer compositions tested so far can be prepared as hollow fiber membrane modules using the existing manufacturing technology.For fuel cell and chemical applications, additional sulfur removal (beyond that achievable with the membranes) is required. To overcome limitations of conventional ZnO pellets, RTI is testing a monolith with a thin coating of high surface area zinc-oxide based materials. Alternatively, a regenerable sorbent developed by DOE/NETL (RVS-1) is being evaluated for this application. A multi-cycle test of 2-in. (5-cm) diameter monolith samples demonstrated that <0.5 ppm sulfur can be achieved.Removal of HCl vapors is being accomplished by low-cost materials that combine the known effectiveness of sodium carbonate as an active matrix used with enhanced surface area supports for greater reactivity and capacity at the required operating temperatures. RTI is working with SRI International on this task. Sorbents prepared using diatomaceous earth and sepiolite, impregnated with sodium carbonate achieved steady-state HCl level <100 ppb (target is 10 ppb). Research is continuing to optimize the impregnation and calcination procedures to provide an optimum pore size distribution and other properties.RTI and SRI International have established the feasibility of a process to selectively chemisorb NH 3 from syngas on high surface area molecular sieve adsorbents at high temperatures by conducting a series of temperature-programmed reactions at 225C (437F). Significant levels of NH 3 were adsorbed on highly acidic ads...

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“…(5) with an equilibrium constant of 2.76 Â 10 24 kPa 21 mol CO 2 per mole of salt (6). A comparison of the …”

Section: Resultsmentioning

confidence: 99%

“…Salt hydrates which reversibly absorb large amounts of CO 2 have relatively basic anions, fluoride or carboxylate, coupled with monovalent cations, and fewer than about six moles of bound water per mole of cation. For example, tetramethylammonium fluoride tetrahydrate, [(CH 3 ) 4 N]F : 4H 2 O, at 508C and 100 kPa absorbs 0.28 mol CO 2 per mole of salt (6). Salt hydrates such as [(CH 3 ) 4 N]F : 4H 2 O proved useful in the development of immobilized liquid membranes which selectively permeate CO 2 from H 2 and CH 4 -containing gas mixtures (3 -5).…”

Section: Introductionmentioning

confidence: 99%

Hydrogen sulfide separation from gas streams using salt hydrate chemical absorbents and immobilized liquid membranes

Quinn

Appleby

Pez

2002

Separation Science and Technology

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The salt hydrate tetramethylammonium fluoride tetrahydrate, [(CH 3 ) 4 N]F : 4H 2 O, in the liquid state reversibly absorbs large quantities of hydrogen sulfide, for example 0.30 mol H 2 S per mole of salt at 508C and 100 kPa. Gas absorption likely occurs by deprotonation of H 2 S to form bisulfide, HS 2 , and bifluoride, HF 2 2 . The equilibrium constant for the reaction of H 2 S with [(CH 3 ) 4 N]F : 4H 2 O is 1.4 Â 10 22 kPa 21 at 508C as determined from absorption/desorption data. The heat of H 2 S absorption was surprisingly low, 20.78 kcal mol 21 . A second salt hydrate, tetraethylammonium acetate tetrahydrate, [(C 2 H 5 ) 4 N]CH 3 CO 2 : 4H 2 O, also reversibly absorbs H 2 S but with a lower affinity. However, at higher pressures, its H 2 S capacity increases more than does that of [(CH 3 ) 4 N]F : 4H 2 O making it more suitable for use as a pressure swing absorbent. Absorption/desorption data are consistent with reaction of one mole of [(C 2 H 5 ) 4 N]CH 3-CO 2 : 4H 2 O for each mole of H 2 S and an equilibrium constant of 6.4 Â 10 24 kPa 21 mol H 2 S per mole of salt. Membranes 627

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Salt Hydrates: New Reversible Absorbents for Carbon Dioxide

Cited by 60 publications

References 0 publications

Why are Ionic Liquids Attractive for CO2 Absorption? An Overview

Why are Ionic Liquids Attractive for CO2 Absorption? An Overview

Novel Technologies for Gaseous Contaminants Control

Hydrogen sulfide separation from gas streams using salt hydrate chemical absorbents and immobilized liquid membranes

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