| 1. |
- Berezovsky, Vladimir, 1978-, et al.
(författare)
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Computational study of the CO adsorption and diffusion in zeolites : validating the Reed–Ehrlich model
- 2018
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Ingår i: Adsorption. - : Springer. - 0929-5607 .- 1572-8757. ; 24:4, s. 403-413
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Tidskriftsartikel (refereegranskat)abstract
- Molecular simulations have been employed to explore at the microscopic scale the adsorption of CO in zeolites (MFI, CHA and DDR). On the basis of classical force fields, grand canonical Monte Carlo simulations are performed to predict the adsorption properties (isotherms) of these types of zeolites up to high pressure. Subsequent careful analysis yields details the microscopic mechanism in play, along the whole adsorption process, together with a considering of the arrangements of CO in MFI at high pressure. This work also summarizes an approach which uses single component diffusion data in prediction of multicomponent diffusion.
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| 2. |
- Faisal, Abrar, et al.
(författare)
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MFI zeolite as adsorbent for selective recovery of hydrocarbons from ABE fermentation broths
- 2014
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Ingår i: Adsorption. - : Springer Science and Business Media LLC. - 0929-5607 .- 1572-8757. ; 20:2-3, s. 465-470
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Tidskriftsartikel (refereegranskat)abstract
- 1-Butanol and butyric acid are two interesting compounds that may be produced by acetone, butanol, and ethanol fermentation using e.g. Clostridium acetobutylicum. The main drawback, restricting the commercialization potential of this process, is the toxicity of butanol for the cell culture resulting in low concentrations of this compound in the broth. To make this process economically viable, an efficient recovery process has to be developed. In this work, a hydrophobic MFI type zeolite with high silica to alumina ratio was evaluated as adsorbent for the recovery of butanol and butyric acid from model solutions. Dual component adsorption experiments revealed that both butanol and butyric acid showed a high affinity for the hydrophobic MFI zeolite when adsorbed from aqueous model solutions. Multicomponent adsorption experiments using model solutions, mimicking real fermentation broths, revealed that the adsorbent was very selective to the target compounds. Further, the adsorption of butyric and acetic acid was found to be pH dependent with high adsorption below, and low adsorption above, the respective pKa values of the acids. Thermal desorption of butanol from MFI type zeolite was also studied and a suitable desorption temperature was identified.
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| 3. |
- Faisal, Abrar, et al.
(författare)
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Recovery of butanol from model ABE fermentation broths using MFI adsorbent: a comparison between traditional beads and a structured adsorbent in the form of a film
- 2016
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Ingår i: Adsorption. - : Springer Science and Business Media LLC. - 0929-5607 .- 1572-8757. ; 22:2, s. 205-214
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Tidskriftsartikel (refereegranskat)abstract
- Butanol, a promising biofuel, can be produced by ABE (acetone, butanol and ethanol) fermentation using e.g. Clostridium acetobutylicum. However, the butanol concentration in the resulting broth is limited to only ca. 20 g/L due to the toxicity for the microorganisms. This low product concentration demands an efficient recovery process for successful commercialization of this process. In this study, a structured adsorbent in the form of steel monolith coated with a silicalite-1 film was prepared using the in situ growth method. The adsorbent was carefully characterized by SEM and XRD. The performance of the adsorbent was evaluated by performing breakthrough experiments at room temperature using model ABE fermentation broths and the performance was compared with that of traditional adsorbents in the form of beads. The structured silicalite-1 adsorbent showed less saturation loading time as compared to commercial binder free silicalite-1 beads, reflecting the different dimensions of the columns used, set by experimental constraints. Studies of the desorption process showed that by operating at appropriate conditions, butanol with high concentration i.e. up to 95.2 wt% for butanol–water model system and 88.5 wt% for ABE fermentation broth can be obtained using the structured silicalite-1 adsorbent. Commercial silicalite-1 beads also showed good selectivity but the concentration of butanol in the desorbed product was limited to 70 % for the butanol–water model system and 69 % for ABE fermentation broth, probably as a result of entrained liquid between the beads.
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| 4. |
- Henry, Christophe, et al.
(författare)
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A refined algorithm to simulate latex colloid agglomeration at high ionic strength
- 2016
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Ingår i: Adsorption. - : Springer Netherlands. - 0929-5607 .- 1572-8757. ; 22:4-6, s. 503-515
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Tidskriftsartikel (refereegranskat)abstract
- This study is focussed on the simulation of particle agglomeration at relatively high ionic strength using a refined stochastic algorithm developed in the context of parcel-tracking approaches. For that purpose, experimental data of both diffusion-limited and reaction-limited aggregation of latex particles were obtained using dynamic light scattering techniques for different initial particle sizes (diameters ranging from 24 to 495 nm) and at various chemical conditions (ionic strength between 0.5 and 2 M with NaCl or CaCl2 solutions). The experimental data collected have been compared to numerical results obtained with the refined parcel-tracking algorithm for particle agglomeration which has been developed. Results show that the evolution of the aggregate diameters over time can be properly captured by the present model with the value of the aggregate fractal dimension that is extracted from experimental data.
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| 5. |
- Jansson, Mats, et al.
(författare)
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Kinetic evaluation of sorption and desorption
- 2010
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Ingår i: Adsorption. - : Springer Science and Business Media LLC. - 0929-5607 .- 1572-8757. ; 16:3, s. 155-159
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Tidskriftsartikel (refereegranskat)abstract
- Sorption is often quantified by a distribution coefficient, K-d, which is the equilibrium ratio between species sorbed to the rock and species in solution. Traditionally K-d-values are determined in batch experiments from equilibrium concentrations. In this work we describe an approach to determine rate constants for sorption and desorption from data obtained in ordinary batch sorption experiments. By varying the surface area to solution volume ratio in experiments where the dynamics for sorption equilibration is monitored, the rate constants (and consequently the K-d-value, which is the quota between forward and backward reactions) can be determined. To demonstrate the method, sorption of strontium to crushed granite was studied. The K-d-value obtained with the kinetic approach was in good agreement with that obtained from equilibrium concentrations.
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| 6. |
- Mosca, Alessandra, et al.
(författare)
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Optimization of synthesis procedures for structured PSA adsorbents
- 2008
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Ingår i: Adsorption. - : Springer Science and Business Media LLC. - 0929-5607 .- 1572-8757. ; 14:4-5, s. 687-693
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Tidskriftsartikel (refereegranskat)abstract
- Structured adsorbents in the form of supported thin zeolite films may represent a competitive alternative to traditional zeolite adsorbents in form of beads or pellets used in PSA processes, due to the reduction of mass- and heat-transfer limitations typical of packed beds. Thin NaX films were grown by hydrothermal treatment using a clear solution on cordierite monoliths. Films grown by a multiple synthesis procedure were dense and uniform with a very small amount of sediments adjacent to the film, which may be an advantage in PSA applications. The CO2 adsorption capacity and the pressure drop for the supported films were compared to those of a packed NaX bed. Although the adsorption capacity of the column filled with the structured adsorbents was 67 times lower than when the column was filled with zeolite beads, the pressure drop was 100 times lower for the structured adsorbent. The adsorption capacity can be increased by increasing the film thickness or the cell density of the monoliths without increasing the pressure drop significantly, indicating the potential advantage of structured adsorbents in PSA processes. Further investigations are needed in order to prove this hypothesis.
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| 7. |
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| 8. |
- Twumasi, Ebenezer, et al.
(författare)
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Preparation and characterization of double metal-silica sorbent for gas filtration
- 2013
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Ingår i: Adsorption. - : Springer Science and Business Media LLC. - 0929-5607 .- 1572-8757. ; 19:1, s. 49-61
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the preparation of a porous (Mg, Ca) silicate structure, which could be employed as sorbent filter media. The sorbents have been prepared using sodium silicate precipitated with various ratios of magnesium and calcium salts. The sorbents obtained were characterized using scanning electron microscope (SEM), X-ray diffraction (XRD) and nitrogen physisorption isotherm. Further, the applicability and performance of the sorbent impregnate with potassium hydroxide for removal of sulphur dioxide (SO2) has been demonstrated. From the isotherms, specific surface area, pore diameter and volume of pores were estimated. Results show that the chemical composition and textural properties of the resultant sorbents were highly dependent on Mg/Ca molar ratio. It was found that sorbents made with 68 mol% Mg and 32 mol% Ca (PSS-MgCa-68/32); and 75 mol% Mg and 25 mol% Ca (PSS-MgCa-75/25) exhibited even higher specific surface area and pore volume than the sorbents containing a single metal. The Mg/Ca-silica sorbents obtained contains interconnected bimodal porosity with large portions being mesopores of varied sizes. The pore size distribution (PSD) results further indicate that PSS-MgCa-68/32 sorbent exhibits wide PSD of interconnected pores in the size range of 1 to 32 nm while PSS-MgCa-50/50 and PSS-MgCa-75/25 exhibits narrow PSD of 1 to 5 nm. Using SO2 as model contaminate gas, it was shown that the dynamic adsorption performance of the PSS-MgCa-sorbents impregnated with 8 wt% KOH exhibits SO2 uptake, with impregnated PSS-MgCa-68/32 showing better performance. This shows that the materials prepared can be used as adsorbent for gas filtration.
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| 9. |
- Zelinka, Samuel L., et al.
(författare)
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Interlaboratory study of the operational stability of automated sorption balances
- 2024
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Ingår i: Adsorption. - 0929-5607.
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Tidskriftsartikel (refereegranskat)abstract
- Automated sorption balances are widely used for characterizing the interaction of water vapor with hygroscopic materials. These instruments provide an efficient way to collect sorption isotherm data and kinetic data. A typical method for defining equilibrium after a step change in relative humidity (RH) is using a particular threshold value for the rate of change in mass with time. Recent studies indicate that commonly used threshold values yield substantial errors and that further measurements are needed at extended hold times as a basis to assess the accuracy of abbreviated equilibration criteria. However, the mass measurement accuracy at extended times depends on the operational stability of the instrument. Published data on the stability of automated sorption balances are rare. An interlaboratory study was undertaken to investigate equilibration criteria for automated sorption balances. This paper focuses on the mass, temperature, and RH stability and includes data from 25 laboratories throughout the world. An initial target for instrument mass stability was met on the first attempt in many cases, but several instruments were found to have unexpectedly large instabilities. The sources of these instabilities were investigated and greatly reduced. This paper highlights the importance of verifying operational mass stability of automated sorption balances, gives a method to perform stability checks, and provides guidance on identifying and correcting common sources of mass instability.
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