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A hybrid absorption-adsorption method to efficiently capture carbon.

Liu H, Liu B, Lin LC, Chen G, Wu Y, Wang J, Gao X, Lv Y, Pan Y, Zhang X, Zhang X, Yang L, Sun C, Smit B, Wang W - Nat Commun (2014)

Bottom Line: We show that this approach may give a more efficient technology to capture carbon dioxide compared to conventional technologies.Most importantly, the sorption enthalpy is only -29 kJ mol(-1), indicating that significantly less energy is required for sorbent regeneration.In addition, from a technological point of view, unlike solid adsorbents slurries can flow and be pumped.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102249, P. R. China.

ABSTRACT
Removal of carbon dioxide is an essential step in many energy-related processes. Here we report a novel slurry concept that combines specific advantages of metal-organic frameworks, ion liquids, amines and membranes by suspending zeolitic imidazolate framework-8 in glycol-2-methylimidazole solution. We show that this approach may give a more efficient technology to capture carbon dioxide compared to conventional technologies. The carbon dioxide sorption capacity of our slurry reaches 1.25 mol l(-1) at 1 bar and the selectivity of carbon dioxide/hydrogen, carbon dioxide/nitrogen and carbon dioxide/methane achieves 951, 394 and 144, respectively. We demonstrate that the slurry can efficiently remove carbon dioxide from gas mixtures at normal pressure/temperature through breakthrough experiments. Most importantly, the sorption enthalpy is only -29 kJ mol(-1), indicating that significantly less energy is required for sorbent regeneration. In addition, from a technological point of view, unlike solid adsorbents slurries can flow and be pumped. This allows us to use a continuous separation process with heat integration.

No MeSH data available.


Related in: MedlinePlus

Formation of ZIF-8/glycol slurries.Photographs of experimentally prepared slurries with solid ZIF-8 suspended in liquid glycol: (a) before mixing, (b) after mixing.
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f1: Formation of ZIF-8/glycol slurries.Photographs of experimentally prepared slurries with solid ZIF-8 suspended in liquid glycol: (a) before mixing, (b) after mixing.

Mentions: As a proof of concept, we first studied slurries of ZIF-8 (zeolitic imidazolate framework-8) suspended in liquid glycol (see Fig. 1). ZIFs are a sub-class of MOFs14, and generally possess excellent solution, chemical and thermal stability151617. ZIF-8 has narrow six-membered ring pore windows (3.4 Å), which are smaller than the kinetic diameter of glycol molecules (4.5 Å)18, and hence glycol is unlikely to influence the adsorption capacity of CO2 in suspended ZIF-8. To demonstrate that our ZIF-8/glycol slurry can separate different CO2 mixtures, we performed adsorption measurements on different CO2 gas mixtures (that is, CO2 with CH4, N2 or H2, see Supplementary Tables 1–5). Figure 2 shows the selectivity as a function of pressure for these three mixtures (that is, up to ~745 for CO2/H2, ~286 for CO2/N2 and ~37 for CO2/CH4), which are sufficiently large for an effective separation. No remarkable loss of separation ability was observed after several times of cycling use of the slurry (Supplementary Table 2), where the slurry was regenerated by applying vacuum. Further characterization of the solid ZIF-8, recovered from the slurry after these cycles showed that the ZIF-8 structure remained intact (see scanning electron microscopy images, X-ray diffraction (XRD) patterns, Fourier transform infrared spectra, Fourier transform Raman spectra and energy dispersive X-ray spectroscopy patterns in Supplementary Figs 1–5). In addition to glycol, other liquids such as ethanol, cyclohexane, normal hexane, methylbenzene, tetrachloromethane and triethylene glycol have been tested to form slurries with ZIF-8 to separate a CO2/N2 gas mixture (Supplementary Table 6). It was found that only triethylene glycol is effective with a selectivity higher than 50. Compared with triethylene glycol, the other studied liquids consist of smaller molecules that can enter into ZIF-8 frameworks. Note that, to provide a reference for showing the superiority of the slurry approach proposed in this work, absorption separation using pure glycol or water for the CO2/N2 and CO2/CH4 gas mixtures (Supplementary Table 7) and adsorption separation using solid ZIF-8 for the CO2/N2, CO2/H2 and CO2/CH4 gas mixtures (Fig. 2, Supplementary Tables 8–10) were also performed.


A hybrid absorption-adsorption method to efficiently capture carbon.

Liu H, Liu B, Lin LC, Chen G, Wu Y, Wang J, Gao X, Lv Y, Pan Y, Zhang X, Zhang X, Yang L, Sun C, Smit B, Wang W - Nat Commun (2014)

Formation of ZIF-8/glycol slurries.Photographs of experimentally prepared slurries with solid ZIF-8 suspended in liquid glycol: (a) before mixing, (b) after mixing.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4214418&req=5

f1: Formation of ZIF-8/glycol slurries.Photographs of experimentally prepared slurries with solid ZIF-8 suspended in liquid glycol: (a) before mixing, (b) after mixing.
Mentions: As a proof of concept, we first studied slurries of ZIF-8 (zeolitic imidazolate framework-8) suspended in liquid glycol (see Fig. 1). ZIFs are a sub-class of MOFs14, and generally possess excellent solution, chemical and thermal stability151617. ZIF-8 has narrow six-membered ring pore windows (3.4 Å), which are smaller than the kinetic diameter of glycol molecules (4.5 Å)18, and hence glycol is unlikely to influence the adsorption capacity of CO2 in suspended ZIF-8. To demonstrate that our ZIF-8/glycol slurry can separate different CO2 mixtures, we performed adsorption measurements on different CO2 gas mixtures (that is, CO2 with CH4, N2 or H2, see Supplementary Tables 1–5). Figure 2 shows the selectivity as a function of pressure for these three mixtures (that is, up to ~745 for CO2/H2, ~286 for CO2/N2 and ~37 for CO2/CH4), which are sufficiently large for an effective separation. No remarkable loss of separation ability was observed after several times of cycling use of the slurry (Supplementary Table 2), where the slurry was regenerated by applying vacuum. Further characterization of the solid ZIF-8, recovered from the slurry after these cycles showed that the ZIF-8 structure remained intact (see scanning electron microscopy images, X-ray diffraction (XRD) patterns, Fourier transform infrared spectra, Fourier transform Raman spectra and energy dispersive X-ray spectroscopy patterns in Supplementary Figs 1–5). In addition to glycol, other liquids such as ethanol, cyclohexane, normal hexane, methylbenzene, tetrachloromethane and triethylene glycol have been tested to form slurries with ZIF-8 to separate a CO2/N2 gas mixture (Supplementary Table 6). It was found that only triethylene glycol is effective with a selectivity higher than 50. Compared with triethylene glycol, the other studied liquids consist of smaller molecules that can enter into ZIF-8 frameworks. Note that, to provide a reference for showing the superiority of the slurry approach proposed in this work, absorption separation using pure glycol or water for the CO2/N2 and CO2/CH4 gas mixtures (Supplementary Table 7) and adsorption separation using solid ZIF-8 for the CO2/N2, CO2/H2 and CO2/CH4 gas mixtures (Fig. 2, Supplementary Tables 8–10) were also performed.

Bottom Line: We show that this approach may give a more efficient technology to capture carbon dioxide compared to conventional technologies.Most importantly, the sorption enthalpy is only -29 kJ mol(-1), indicating that significantly less energy is required for sorbent regeneration.In addition, from a technological point of view, unlike solid adsorbents slurries can flow and be pumped.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory of Heavy Oil Processing, China University of Petroleum, Beijing 102249, P. R. China.

ABSTRACT
Removal of carbon dioxide is an essential step in many energy-related processes. Here we report a novel slurry concept that combines specific advantages of metal-organic frameworks, ion liquids, amines and membranes by suspending zeolitic imidazolate framework-8 in glycol-2-methylimidazole solution. We show that this approach may give a more efficient technology to capture carbon dioxide compared to conventional technologies. The carbon dioxide sorption capacity of our slurry reaches 1.25 mol l(-1) at 1 bar and the selectivity of carbon dioxide/hydrogen, carbon dioxide/nitrogen and carbon dioxide/methane achieves 951, 394 and 144, respectively. We demonstrate that the slurry can efficiently remove carbon dioxide from gas mixtures at normal pressure/temperature through breakthrough experiments. Most importantly, the sorption enthalpy is only -29 kJ mol(-1), indicating that significantly less energy is required for sorbent regeneration. In addition, from a technological point of view, unlike solid adsorbents slurries can flow and be pumped. This allows us to use a continuous separation process with heat integration.

No MeSH data available.


Related in: MedlinePlus