Abstract
The separation of C
2
H
2
/CO
2
is not only industrially important for acetylene purification but also scientifically challenging owing to their high similarities in physical properties and ...molecular sizes. Ultramicroporous metal-organic frameworks (MOFs) can exhibit a pore confinement effect to differentiate gas molecules of similar size. Herein, we report the fine-tuning of pore sizes in sub-nanometer scale on a series of isoreticular MOFs that can realize highly efficient C
2
H
2
/CO
2
separation. The subtle structural differences lead to remarkable adsorption performances enhancement. Among four MOF analogs, by integrating appropriate pore size and specific binding sites, Cu(dps)
2
(SiF
6
) (SIFSIX-dps-Cu, SIFSIX = SiF
6
2-
, dps = 4.4’-dipyridylsulfide, also termed as NCU-100) exhibits the highest C
2
H
2
uptake capacity and C
2
H
2
/CO
2
selectivity. At room temperature, the pore space of SIFSIX-dps-Cu significantly inhibits CO
2
molecules but takes up a large amount of C
2
H
2
(4.57 mmol g
−1
), resulting in a high IAST selectivity of 1787 for C
2
H
2
/CO
2
separation. The multiple host-guest interactions for C
2
H
2
in both inter- and intralayer cavities are further revealed by dispersion-corrected density functional theory and grand canonical Monte Carlo simulations. Dynamic breakthrough experiments show a clean C
2
H
2
/CO
2
separation with a high C
2
H
2
working capacity of 2.48 mmol g
−1
.
FT-IR spectra of pristine and ammonia exposed MOF-5 and MOF-177.
Ammonia adsorption equilibrium and kinetics on MOF-5 and MOF-177 were measured volumetrically at 298
K and ammonia pressures up to 800
...torr. This study allowed us to determine the ammonia adsorption properties and stability of both MOFs after exposure to ammonia. MOF-177 adsorbed more ammonia than MOF-5 at ammonia pressures below 150
torr and the ammonia adsorption capacity on both MOFs at 800
torr was about the same (12.2
mmol/g). It can be inferred from the adsorption results that physical adsorption of ammonia on both MOFs dominated at ammonia pressures below 150
torr after which chemical reactions between ammonia and MOF frameworks take place. After exposure to ammonia both MOFs lost majority of their pore textures as evidenced by a drastic decrease of specific surface area and pore volume. The X-ray diffraction study suggested a complete loss of crystallinity of both MOFs, and the FT-IR and Raman spectral analyses showed the generation of free organic ligands within both MOF-5 and MOF-177 after they were exposed to ammonia. Ammonia molecules are proposed to destroy the MOF frameworks by forming hydrogen bonds with Zn
4O clusters of MOFs.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Freshwater and energy are essential commodities for well being of mankind. Due to increasing population growth on the one hand, and rapid industrialization on the other, today's world is facing ...unprecedented challenge of meeting the current needs for these two commodities as well as ensuring the needs of future generations. One approach to this global crisis of water and energy supply is to utilize renewable energy sources to produce freshwater from impaired water sources by desalination. Sustainable practices and innovative desalination technologies for water reuse and energy recovery (staging, waste heat utilization, hybridization) have the potential to reduce the stress on the existing water and energy sources with a minimal impact to the environment. This paper discusses existing and emerging desalination technologies and possible combinations of renewable energy sources to drive them and associated desalination costs. It is suggested that a holistic approach of coupling renewable energy sources with technologies for recovery, reuse, and recycle of both energy and water can be a sustainable and environment friendly approach to meet the world's energy and water needs. High capital costs for renewable energy sources for small-scale applications suggest that a hybrid energy source comprising both grid-powered energy and renewable energy will reduce the desalination costs considering present economics of energy.
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The non-edible vegetable oils such as
Jatropha curcas and
Pongamia glabra (karanja) and edible oils such as corn and canola were found to be good viable sources for producing biodiesel. Biodiesel ...production from different edible and non-edible vegetable oils was compared in order to optimize the biodiesel production process. The analysis of different oil properties, fuel properties and process parameter optimization of non-edible and edible vegetable oils were investigated in detail. A two-step and single-step transesterification process was used to produce biodiesel from high free fatty acid (FFA) non-edible oils and edible vegetable oils, respectively. This process gives yields of about 90–95% for
J. curcas, 80–85% for
P. glabra, 80–95% for canola, and 85–96% for corn using potassium hydroxide (KOH) as a catalyst. The fuel properties of biodiesel produced were compared with ASTM standards for biodiesel.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Ordered mesoporous carbon was synthesized by a self-assembly technique and characterized with TEM, Raman spectroscopy, and nitrogen adsorption/desorption for its physical and pore textural ...properties. The high BET specific surface area (798 m(2)/g), uniform mesopore-size distribution with a median pore size of 62.6 Å, and large pore volume (0.87 cm(3)/g) make the ordered mesoporous carbon an ideal adsorbent for gas separation and purification applications. Adsorption equilibrium and kinetics of carbon dioxide, methane, nitrous oxide, and ammonia on the ordered mesoporous carbon were measured at 298 K and gas pressures up to 800 Torr. The adsorption equilibrium capacities on the ordered mesoporous carbon at 298 K and 800 Torr for ammonia, carbon dioxide, nitrous oxide, and methane were found to be 6.39, 2.39, 1.5, and 0.53 mmol/g, respectively. Higher adsorption uptakes of methane (3.26 mmol/g at 100 bar) and carbon dioxide (2.21 mmol/g at 13 bar) were also observed at 298 K and elevated pressures. Langmuir, Freundlich, and Toth adsorption equilibrium models were used to correlate all the adsorption isotherms, and a simplified gas diffusion model was applied to analyze the adsorption kinetics data collected at 298 K and four different gas pressures up to 800 Torr.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
A magnesium-based metal organic framework (MOF), also known as Mg-MOF-74, was successfully synthesized, characterized, and evaluated for adsorption equilibria and kinetics of CO₂ and CH₄. The ...Mg-MOF-74 crystals were characterized with scanning electron microscopy for crystal structure, powder X-ray diffraction for phase structure, and nitrogen adsorption for pore textural properties. Adsorption equilibrium and kinetics of CO₂ and CH₄ on the Mg-MOF-74 adsorbent were measured in a volumetric adsorption unit at 278, 298, and 318K and pressures up to 1bar. It was found that the Mg-MOF-74 adsorbent prepared in this work has a median pore width of 10.2Å, a BET specific surface area of 1174m²/g, CO₂ and CH₄ adsorption capacities of 8.61mmolg⁻¹ (37.8wt.%) and 1.05mmolg⁻¹ (1.7wt.%), respectively, at 298K and 1bar. Both CO₂ and CH₄ adsorption capacities are significantly higher than those of zeolite 13X under similar conditions. The pressure-dependent equilibrium selectivity of CO₂ over CH₄ (qCO₂/qCH₄) in the Mg-MOF-74 adsorbent showed a trend similar to that of zeolite 13X and the intrinsic selectivity of Mg-MOF-74 at zero adsorption loading is 283 at 298K. The initial heats of adsorption of CO₂ and CH₄ on the Mg-MOF-74 adsorbent were found to be 73.0 and 18.5kJmol⁻¹, respectively. The adsorption kinetic measurements suggest that the diffusivities of CO₂ and CH₄ on Mg-MOF-74 were comparable to those on zeolite 13X. CH₄ showed relatively faster adsorption kinetics than CO₂ in both adsorbents. The diffusion time constants of CO₂ and CH₄ in the Mg-MOF-74 adsorbent at 298K were estimated to be 8.11×10⁻³ and 4.05×10⁻²s⁻¹, respectively, showing a modest kinetic selectivity of about 5 for the separation CH₄ from CO₂.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Isoreticular principle has been employed to realize a flexible-robust metal–organic framework (MOF) with extended pore structure for the adsorptive removal of trace acetylene from ethylene under ...ambient conditions. The substitution from zinc(II) to copper(II) of high coordination distortion leads to elongated Cu–F bonds that expand the closed pore cavities in the prototypical MOF from 3.5 × 3.9 × 4.1 to 3.6 × 4.3 × 4.2 Å3. The optimal cavity size together with strong binding sites thus endows the new Cu analogue to possess open pore space accessible for trace C2H2 within a substantial low-pressure range while excluding C2H4 molecules, as validated by gas isotherms and single-crystal structure of its partially C2H2-loading phase. In contrast to the Zn prototype, at 298 K and 1.0 bar, the guest-free Cu analogue shows significant C2H2 uptake increase with a total capacity of 4.57 mmol g–1, and gains an over two orders of magnitude jump in IAST selectivity for C2H2/C2H4 (1/99, v/v). These results are higher than the benchmark MOFs for molecular sieving of C2H2/C2H4, leading a high C2H4 productivity of 14.9 mmol g–1. Crystallography studies, molecular modeling, selectivity evaluation, and breakthrough experiments have comprehensively demonstrated this flexible-robust MOF as an efficient adsorbent for C2H2/C2H4 separation.
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This work presents a facile and efficient one-pot melting-assisted and solvent-free method to prepare low-cost N-rich polymer SFRH. Furthermore, the polymer derived N-enriched porous carbon could be ...used for highly selective mixed-gas separation, CO2 storage and PSA.
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•Facile one-pot and solvent-free method to preparation.•N-doped porous carbons.•Outstanding gas mixture selectivity.•Excellent pressure/vacuum swing adsorption (P/VSA) working capacity.•10-fold scaled up production.
A facile one-pot melting-assisted and solvent-free method was successfully developed for the first time for preparing nitrogen-containing polymers. Followed by activation at temperatures ranging from 600 to 800 °C led to the formation of N-rich microporous carbons possessing narrow pore size distribution (ca. 0.5–3 nm), high specific surface area (ca. 1021.4–3657.0 m2 g−1), large pore volume (ca. 0.43–2.00 cm3 g−1) and high nitrogen content (ca. up to 5.11 wt%). Particularly, the porous carbons exhibited outstanding CO2 adsorption capacity of 2.65 and 7.38 mmol g−1 at 273 K and 0.15 and 1 bar, respectively; meanwhile, it also exhibited extremely large CO2 storage capacity of 22.06 mmol g−1 at 298 K and 20 bar. Moreover, the outstanding CO2/N2, CO2/CH4 and CH4/N2 selectivity up to 36.5, 6.9 and 5.1 at 298 K and 1 bar were achieved. The determinant factors on CO2 capture at 0.15, 1 and 20 bar were carefully investigated. Furthermore, this method could be 10-fold scaled up to produce almost identical high-performance carbons. For real-world applications, pressure/vacuum swing adsorption (P/VSA) working capacity, gas-mixture transit breakthrough experiment, and recycle feasibility are evaluated. Thus, these novel materials are promising candidates for CO2 capture from dilute gas mixtures.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Separation of CO2 and N2 from CH4 is significantly important in natural gas upgrading, and capture/removal of CO2, CH4 from air (N2) is essential to greenhouse gas emission control. Adsorption ...equilibrium and kinetics of CO2, CH4, and N2 on an ordered mesoporous carbon (OMC) sample were systematically investigated to evaluate its capability in the above two applications. The OMC was synthesized and characterized with TEM, TGA, small-angle XRD, and nitrogen adsorption/desorption measurements. Pure component adsorption isotherms of CO2, CH4, and N2 were measured at 278, 298, and 318 K and pressures up to 100 kPa, and correlated with the Langmuir model. These data were used to estimate the separation selectivities for CO2/CH4, CH4/N2, and CO2/N2 binary mixtures at different compositions and pressures according to the ideal adsorbed solution theory (IAST) model. At 278 K and 100 kPa, the predicted selectivities for equimolar CO2/CH4, CH4/N2, and CO2/N2 are 3.4, 3.7, and 12.8, respectively; and the adsorption capacities for CH4 and CO2 are 1.3 and 3.0 mmol/g, respectively. This is the first report of a versatile mesoporous material that displays both high selectivities and large adsorption capacities for separating CO2/CH4, CH4/N2, and CO2/N2 mixtures.
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Carbon monoxide adsorption equilibria and kinetics on zeolite 5A, 13X, MOF-5, and MOF-177 were measured volumetrically at (298, 237, and 194.5) K and carbon monoxide pressures up to 108 kPa. It was ...found that zeolite 5A had the highest adsorption capacity at ambient temperature (298 K) and ambient pressure (108 kPa), whereas MOF-177 was a better adsorbent at (194.5 and 237) K. Both the Langmuir and Freundlich isotherm models were used to correlate the adsorption isotherms. Diffusivities of carbon monoxide in these adsorbents were estimated from the adsorption uptake curves by a micropore diffusion model. The average carbon monoxide diffusivities at 298 K and carbon monoxide pressures below 108 kPa are 3.42·10−11 m2·s−1, 1.40·10−11 m2·s−1, 1.72·10−8 m2·s−1, and 5.01·10−9 m2·s−1 for zeolite 5A, 13X, MOF-5, and MOF-177, respectively. The heat of adsorption of carbon monoxide at low coverage on zeolite 5A and 13X is below 70 kJ·mol−1 and drops rapidly as the coverage increases, while the heat of adsorption of carbon monoxide in MOF-5 and MOF-177 is in the range of (16 to 22) kJ·mol−1.
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