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Title: Reversible Acid Gas Capture Using CO2-Binding Organic Liquids

Abstract

Acid gas scrubbing technology is predominantly aqueous alkanolamine based. Of the acid gases, CO2, H2S and SO2 have been shown to be reversible, however there are serious disadvantages with corrosion and high regeneration costs. The primary scrubbing system composed of monoethanolamine is limited to 30% by weight because of the highly corrosive solution. This gravimetric limitation limits the CO2 volumetric (≤108 g/L) and gravimetric capacity (≤7 wt%) of the system. Furthermore the scrubbing system has a large energy penalty from pumping and heating the excess water required to dissolve the MEA bicarbonate salt. Considering the high specific heat of water (4 j/g-1K-1), low capacities and the high corrosion we set out to design a fully organic solvent that can chemically bind all acid gases i.e. CO2 as reversible alkylcarbonate ionic liquids or analogues thereof. Having a liquid acid gas carrier improves process economics because there is no need for excess solvent to pump and to heat. We have demonstrated illustrated in Figure 1, that CO2-binding organic liquids (CO2BOLs) have a high CO2 solubility paired with a much lower specific heat (<1.5 J/g-1K-1) than aqueous systems. CO2BOLs are a subsection of a larger class of materials known as Binding Organic Liquidsmore » (BOLs). Our BOLs have been shown to reversibly bind and release COS, CS2, and SO2, which we denote COSBOLS, CS2BOLs and SO2BOLs. Our BOLs are highly tunable and can be designed for post or pre-combustion gas capture. The design and testing of the next generation zwitterionic CO2BOLs and SO2BOLs are presented.« less

Authors:
; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
989440
Report Number(s):
PNNL-SA-69452
TRN: US201019%%492
DOE Contract Number:
AC05-76RL01830
Resource Type:
Conference
Resource Relation:
Conference: Preprints of Symposia - American Chemical Society Fuel Chemistry Division, 55(1):81-82
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ACID CARBONATES; CAPACITY; CORROSION; DESIGN; ECONOMICS; GASES; HEATING; ORGANIC SOLVENTS; PUMPING; REGENERATION; SCRUBBING; SOLUBILITY; SOLVENTS; SPECIFIC HEAT; TESTING; WATER; CO2BOL, CO2, ionic liquid

Citation Formats

Heldebrant, David J., Koech, Phillip K., Yonker, Clement R., Rainbolt, James E., and Zheng, Feng. Reversible Acid Gas Capture Using CO2-Binding Organic Liquids. United States: N. p., 2010. Web.
Heldebrant, David J., Koech, Phillip K., Yonker, Clement R., Rainbolt, James E., & Zheng, Feng. Reversible Acid Gas Capture Using CO2-Binding Organic Liquids. United States.
Heldebrant, David J., Koech, Phillip K., Yonker, Clement R., Rainbolt, James E., and Zheng, Feng. 2010. "Reversible Acid Gas Capture Using CO2-Binding Organic Liquids". United States. doi:.
@article{osti_989440,
title = {Reversible Acid Gas Capture Using CO2-Binding Organic Liquids},
author = {Heldebrant, David J. and Koech, Phillip K. and Yonker, Clement R. and Rainbolt, James E. and Zheng, Feng},
abstractNote = {Acid gas scrubbing technology is predominantly aqueous alkanolamine based. Of the acid gases, CO2, H2S and SO2 have been shown to be reversible, however there are serious disadvantages with corrosion and high regeneration costs. The primary scrubbing system composed of monoethanolamine is limited to 30% by weight because of the highly corrosive solution. This gravimetric limitation limits the CO2 volumetric (≤108 g/L) and gravimetric capacity (≤7 wt%) of the system. Furthermore the scrubbing system has a large energy penalty from pumping and heating the excess water required to dissolve the MEA bicarbonate salt. Considering the high specific heat of water (4 j/g-1K-1), low capacities and the high corrosion we set out to design a fully organic solvent that can chemically bind all acid gases i.e. CO2 as reversible alkylcarbonate ionic liquids or analogues thereof. Having a liquid acid gas carrier improves process economics because there is no need for excess solvent to pump and to heat. We have demonstrated illustrated in Figure 1, that CO2-binding organic liquids (CO2BOLs) have a high CO2 solubility paired with a much lower specific heat (<1.5 J/g-1K-1) than aqueous systems. CO2BOLs are a subsection of a larger class of materials known as Binding Organic Liquids (BOLs). Our BOLs have been shown to reversibly bind and release COS, CS2, and SO2, which we denote COSBOLS, CS2BOLs and SO2BOLs. Our BOLs are highly tunable and can be designed for post or pre-combustion gas capture. The design and testing of the next generation zwitterionic CO2BOLs and SO2BOLs are presented.},
doi = {},
journal = {},
number = ,
volume = ,
place = {United States},
year = 2010,
month = 8
}

Conference:
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  • Current chemical CO2 scrubbing technology is primarily aqueous alkanolamine based. These systems rapidly bind CO2 (forming water-soluble carbamate and bicarbonate salts) however, the process has serious disadvantages. The concentration of monoethanolamine rarely exceeds 30 wt % due to the corrosive nature of the solution, and this reduces the maximum CO2 volumetric (≤108 g/L) and gravimetric capacity (≤7 wt%) of the CO2 scrubber. The ≤30 wt % loading of ethanolamine also means that a large excess of water must be pumped and heated during CO2 capture and release, and this greatly increases the energy requirements especially considering the high specific heatmore » of water (4 j/g-1K-1). Our approach is to switch to organic systems that chemically bind CO2 as liquid alkylcarbonate salts. Our CO2-binding organic liquids have higher CO2 solubility, lower specific heats, potential for less corrosion and lower binding energies for CO2 than aqueous systems. CO2BOLs also reversibly bind and release mixed sulfur oxides. Furthermore the CO2BOL system can be direct solvent replacements for any solvent based CO2 capture systems because they are commercially available reagents and because they are fluids they would not require extensive process re-engineering.« less
  • CO2-binding organic liquids (CO2BOLs) chemically bind and release CO2 more energetically and efficiently than aqueous alkanolamine systems. CO2BOLs are comprised of alcohols and organic amidine or guanidine bases, which bind CO2 chemically as liquid amidinium / guanidinium alkylcarbonate salts. CO2BOLs have high CO2 capacities (19% by weight, 147 g CO2/L) compared to 30% monoethanolamine solution in water (7% by weight, 108 g CO2/L) because they are liquid with or without CO2 and do not require any added solvent such as water. The dissolution of CO2 into and out of the liquid phase limits the rate of CO2 capture and release.more » Absorption of CO2 is selective over nitrogen in both concentrated and dilute gas streams making these systems applicable to post and pre-combustion CO2 capture. The free energy of CO2 binding in these systems is small and is independent on choice of alcohol. The free energies of these systems are however dependent on the choice of base; -9 kJ/mol for diazabicyclo[5.4.0]unced-7-ene (DBU) and Barton’s base and +2 kJ/mol for 1,1,3,3-tetramethylguanidine. The specific heats of the organic CO2BOLs are over 50% lower than that of water, resulting in a 50% reduction in energy to strip out CO2 as compared to aqueous alkanolamine solutions. CO2BOLs have been recycled for five cycles without losing activity or selectivity towards CO2.« less
  • Carbon dioxide (CO2) emission to the atmosphere will increase significantly with the shift to coal powered plants for energy generation. This increase in CO2 emission will contribute to climate change. There is need to capture and sequester large amounts of CO2 emitted from these coal power plants in order to mitigate the environmental effects. Here we report the synthesis, characterization and system performance of multiple third generation CO2 binding organic liquids (CO2BOLs) as a solvent system for post combustion gas capture. Alkanolguanidines and alkanolamidines are single component CO2BOLs that reversibly bind CO2 chemically as liquid zwitterionic amidinium / guanidinium alkylcarbonates.more » Three different alkanolguanidines and alkanolamidines were synthesized and studied for CO2 capacity and binding energetics. Solvent performance of these three CO2BOLs was evaluated by batch-wise CO2 uptake and release over multiple cycles. Synthesis of CO2BOLs, characterization, CO2 uptake, selectivity towards CO2 as well as solvent tolerance to water will be discussed.« less
  • Reversible acid-gas binding organic liquid systems that permit separation and capture of one or more of several acid gases from a mixed gas stream, transport of the liquid, release of the acid gases from the ionic liquid and reuse of the liquid to bind more acid gas with significant energy savings compared to current aqueous systems. These systems utilize acid gas capture compounds made up of strong bases and weak acids that form salts when reacted with a selected acid gas, and which release these gases when a preselected triggering event occurs. The various new materials that make up thismore » system can also be included in various other applications such as chemical sensors, chemical reactants, scrubbers, and separators that allow for the specific and separate removal of desired materials from a gas stream such as flue gas.« less
  • Amine systems are effective for CO 2 capture, but they are still inefficient because the solvent regeneration energy is largely defined by the amount of water in the process. Most amines form heat-stable salts with SO 2 and COS resulting in parasitic solvent loss and degradation. Stripping the CO 2-rich solvent is energy intensive it requires temperatures above 100 °C due to the high specific heat and heat of vaporization of water. CO 2-capture processes could be much more energy efficient in a water free amine process. In addition, if the capture-material is chemically compatible with other acid gases, lessmore » solvent would be lost to heat-stable salts and the process economics would be further improved. One such system that can address these concerns is Binding Organic Liquids (BOLs), a class of switchable ionic liquids.« less