A diverse collection of 14 metal−organic frameworks (MOFs) was screened for CO2 capture from flue gas using a combined experimental and modeling approach. Adsorption measurements are reported for the ...screened MOFs at room temperature up to 1 bar. These data are used to validate a generalized strategy for molecular modeling of CO2 and other small molecules in MOFs. MOFs possessing a high density of open metal sites are found to adsorb significant amounts of CO2 even at low pressure. An excellent correlation is found between the heat of adsorption and the amount of CO2 adsorbed below 1 bar. Molecular modeling can aid in selection of adsorbents for CO2 capture from flue gas by screening a large number of MOFs.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
Adsorption isotherms are reported for pure carbon dioxide and water vapor on 5A and 13X zeolite beads and silica gel granules. These data were obtained using a volumetric method and cover the ...temperature ranges of (−45 to 175) °C for carbon dioxide and (0 to 100) °C for water. Also, pure carbon dioxide isotherms on silica gel at temperatures from (10 to 55) °C were measured using a gravimetric apparatus. All pure component equilibria are described well by Toth isotherms with parameters having temperature dependence. For carbon dioxide adsorption, zeolites 5A and 13X have similar loadings and show a much higher capacity than silica gel. However, for water vapor, zeolite 13X has a slightly higher capacity than zeolite 5A. Both zeolites have very good adsorption capacities for water vapor at low pressures but lose their advantages to silica gel when water pressures are high.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
Metal−organic frameworks (MOFs) have recently attracted intense research interest because of their permanent porous structures, huge surface areas, and potential applications as novel adsorbents and ...catalysts. In order to provide a basis for consideration of MOFs for removal of carbon dioxide from gases containing water vapor, such as flue gas, we have studied adsorption equilibrium of CO2, H2O vapor, and their mixtures and also rates of CO2 adsorption in two MOFs: HKUST-1 (CuBTC) and Ni/DOBDC (CPO-27-Ni or Ni/MOF-74). The MOFs were synthesized via solvothermal methods, and the as-synthesized products were solvent exchanged and regenerated before experiments. Pure component adsorption equilibria and CO2/H2O binary adsorption equilibria were studied using a volumetric system. The effects of H2O adsorption on CO2 adsorption for both MOF samples were determined, and the results for 5A and NaX zeolites were included for comparison. The hydrothermal stabilities for the two MOFs over the course of repetitive measurements of H2O and CO2/H2O mixture equilibria were also studied. CO2 adsorption rates from helium for the MOF samples were investigated by using a unique concentration-swing frequency response (CSFR) system. Mass transfer into the MOFs is rapid with the controlling resistance found to be macropore diffusion, and rate parameters were established for the mechanism.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
Metal–organic frameworks with unsaturated metal centers in their crystal structures, such as Ni/DOBDC and Mg/DOBDC, are promising adsorbents for carbon dioxide capture from flue gas due to their high ...CO2 capacities at subatmospheric pressures. However, stability is a critical issue for their application. In this paper, the stabilities of Ni/DOBDC and Mg/DOBDC are investigated. Effects of steam conditioning, simulated flue gas conditioning, and long-term storage on CO2 adsorption capacities are considered. Results show that Ni/DOBDC can maintain its CO2 capacity after steam conditioning and long-term storage, whereas Mg/DOBDC does not. Nitrogen isotherms for Mg/DOBDC show a drop in surface area after steaming, corresponding to the decrease in CO2 adsorption, which may be caused by a reduction of unsaturated metal centers in its structure. Conditioning with dry simulated flue gas at room temperature only slightly affects CO2 adsorption in Ni/DOBDC. However, introducing water vapor into the simulated flue gas further reduces the CO2 capacity of Ni/DOBDC.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
Carbon dioxide adsorption in metal–organic frameworks has been widely studied for applications in carbon capture and sequestration. A critical component that has been largely overlooked is the ...measurement of diffusion rates. This paper describes a new reproducible procedure to synthesize millimeter-scale Cu-BTC single crystals using concentrated reactants and an acetic acid modulator. Microscopic images, X-ray diffraction patterns, Brunauer–Emmett–Teller surface areas, and thermogravimetric analysis results all confirm the high quality of these Cu-BTC single crystals. The large crystal size aids in the accurate measurement of micropore diffusion coefficients. Concentration-swing frequency response performed at varying gas-phase concentrations gives diffusion coefficients that show very little dependence on the loading up to pressures of 0.1 bar. The measured micropore diffusion coefficient for CO2 in Cu-BTC is 1.7 × 10–9 m2/s.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
7.
Metal-Organic Frameworks for Oxygen Storage DeCoste, Jared B.; Weston, Mitchell H.; Fuller, Patrick E. ...
Angewandte Chemie (International ed.),
December 15, 2014, Volume:
53, Issue:
51
Journal Article
Peer reviewed
We present a systematic study of metal–organic frameworks (MOFs) for the storage of oxygen. The study starts with grand canonical Monte Carlo simulations on a suite of 10 000 MOFs for the adsorption ...of oxygen. From these data, the MOFs were down selected to the prime candidates of HKUST‐1 (Cu‐BTC) and NU‐125, both with coordinatively unsaturated Cu sites. Oxygen isotherms up to 30 bar were measured at multiple temperatures to determine the isosteric heat of adsorption for oxygen on each MOF by fitting to a Toth isotherm model. High pressure (up to 140 bar) oxygen isotherms were measured for HKUST‐1 and NU‐125 to determine the working capacity of each MOF. Compared to the zeolite NaX and Norit activated carbon, NU‐125 has an increased excess capacity for oxygen of 237 % and 98 %, respectively. These materials could ultimately prove useful for oxygen storage in medical, military, and aerospace applications.
MOFs store oxygen too: Two metal–organic frameworks with open metal sites store oxygen at capacities far greater than that of an empty cylinder and are comparable to the state‐of‐the‐art oxygen storage materials. Self‐assembled materials allow for rational design of materials for adsorption of specific gases.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
This work examined in detail the a priori prediction of the axial dispersion coefficient from available correlations versus obtaining both it and mass transfer information from experimental ...breakthrough data and the consequences that may arise when doing so based on using a 1-D axially dispersed plug flow model and its associated Danckwerts outlet boundary condition. These consequences mainly included determining the potential for erroneous extraction of the axial dispersion coefficient and/or the LDF mass transfer coefficient from experimental data, especially when nonplug flow conditions prevailed in the bed. Two adsorbent/adsorbate cases were considered, i.e., CO2 and H2O vapor in zeolite 5A, because they both experimentally exhibited significant nonplug flow behavior, and the H2O-zeolite 5A system exhibited unusual concentration front sharpening that destroyed the expected constant pattern behavior (CPB) when modeled with the 1-D axially dispersed plug flow model. Overall, this work showed that it was possible to extract accurate mass transfer and dispersion information from experimental breakthrough curves using a 1-D axial dispersed plug flow model when they were measured both inside and outside the bed. To ensure the extracted information was accurate, the inside the bed breakthrough curves and their derivatives from the model were plotted to confirm whether or not the adsorbate/adsorbent system was exhibiting CPB or any concentration front sharpening near the bed exit. Even when concentration front sharpening was occurring with the H2O-zeolite 5A system, it was still possible to use the experimental inside and outside the bed breakthrough curves to extract fundamental mass transfer and dispersion information from the 1-D axial dispersed plug flow model based on the systematic methodology developed in this work.
Full text
Available for:
IJS, KILJ, NUK, PNG, UL, UM
A highly porous adsorbent capable of broad spectrum filtration of toxic industrial chemicals (TICs) is necessary for many civilian and military applications. To promote the gas adsorption of TICs ...such as NH 3 and SO 2 , a biphasic carbon silica composite (CSC) and other single phase carbonaceous and siliceous materials functionalized with sparingly soluble ZnCO 3 are considered. The adsorption capacities of these substrates functionalized via both in-pore synthesis and a wet impregnation have been measured with very low concentrations of both TICs in a balance of helium. Along with capacity performance, the functionalized materials have been characterized using X-ray diffraction, microscopy, and porosimetry techniques. Results show successful incorporation of a well dispersed ZnCO 3 phase when incorporated via in-pore synthesis. All ZnCO 3 functionalized materials enhance adsorption capacities compared to impregnant-free substrates. Characterization results show reduced pore volumes and surface areas of functionalized materials while maintaining structural integrity. In order to target both adsorbates effectively, in-pore synthesis of ZnCO 3 on CSC provides high adsorption performance with NH 3 and SO 2 capacities of 4.2 and 0.59 mol/kg, respectively.
Full text
Available for:
EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Adsorption equilibrium data for oxygen and argon are needed for design of adsorptive separation processes to produce pure oxygen from air and also for adsorptive gas storage applications. Carbon ...molecular sieves may be used to accomplish a rate-based separation of oxygen and argon and, as we show, may also be useful for gas storage. Given the limited data available, particularly at high pressures, volumetric methods are applied in this paper to measure surface excess isotherms of oxygen and argon on a carbon molecular sieve, Shirasagi MSC-3R Type 172. Temperatures are considered from 25 to 100°C with pressures as high as 100bar. Isotherms are compared at 25°C, including new data measured for nitrogen. Adsorbed-phase excess loadings are high, approaching 10mol/kg at 100bar. The oxygen capacity of the carbon molecular sieve at high pressure is comparable to that of a superactivated carbon on a mass basis, and it is higher on a volumetric basis. The excess adsorption isotherms are modeled using a multi-temperature Toth equation, which provides an excellent description. A carbon molecular sieve is shown to be a promising adsorbent for oxygen storage.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
PDF
