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  • 1.
    Akhtar, Farid
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Sjöberg, Erik
    Korelskiy, Danil
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Rayson, Mark
    Department of Chemistry, The University of Surrey, Guildford.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Bergström, Lennart
    Department of Materials and Environmental Chemistry, Stockholm University.
    Preparation of graded silicalite-1 substrates for all-zeolite membranes with excellent CO2/H2 separation performance2015In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 493, p. 206-211Article in journal (Refereed)
    Abstract [en]

    raded silicalite-1 substrates with a high gas permeability and low surface roughness have been produced by pulsed current processing of a thin coating of a submicron silicalite-1 powder onto a powder body of coarser silicalite-1 crystals. Thin zeolite films have been hydrothermally grown onto the graded silicalite-1 support and the all-zeolite membranes display an excellent CO2/H2 separation factor of 12 at 0 °C and a CO2 permeance of 21.3×10-7 mol m-2 s-1 Pa-1 for an equimolar CO2/H2 feed at 505 kPa and 101 kPa helium sweep gas. Thermal cracking estimates based on calculated surface energies and measured thermal expansion coefficients suggest that all-zeolite membranes with a minimal thermal expansion mismatch between the graded substrate and the zeolite film should remain crack-free during thermal cycling and the critical calcination step.

  • 2. Andersson, Charlotte
    et al.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Effects of exposure to water and ethanol on silicalite-1 membranes2008In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 313, no 1-2, p. 120-126Article in journal (Refereed)
    Abstract [en]

    The effects of long exposures to ethanol, water and 0.1 M aqueous solutions of ammonia, sodium hydroxide, tetrapropylammonium hydroxide (TPAOH) and hydrochloric acid on thin TPA-silicalite-1 membranes were studied. Single gas permeation experiments, porosimetry and scanning electron microscopy were used to characterize the membranes. It was found that a short exposure (24 h) will only dissolve synthesis residues and will not affect membrane quality negatively. The only medium that had an effect after 24 h was sodium hydroxide, which almost dissolved the film completely. After exposing TPA-silicalite-1 membranes for 30 days in the various liquids, the membrane quality decreased in the order ethanol < 0.1 M hydrochloric acid < 0.1 M TPAOH < water < 0.1 M ammonia < 0.1 M sodium hydroxide due to dissolution of the silicalite-1 crystals. This study has shown that prolonged exposure to aqueous solutions will lead to dissolution of silicalite-1 crystals causing an increase in micro- and mesopores in the film. The amount and size of the pores will depend on the pH of the aqueous medium. Higher pH gives a higher dissolution and hence more non-zeolitic pores in the silicalite-1 film. Ethanol has no effect on the dissolution of the zeolite film even after 30 days. This finding has an effect in membrane preparation and in several membrane applications such as pervaporation and separation of hydrocarbons isomer mixtures.

  • 3.
    Butylina, Svetlana
    et al.
    Department of Chemical Technology, Lappeenranta University of Technology.
    Luque, Susana
    bDepartment of Chemical and Environmental Engineering, University of Oviedo.
    Nyström, Marianne
    Department of Chemical Technology, Lappeenranta University of Technology.
    Fractionation of whey-derived peptides using a combination of ultrafiltration and nanofiltration2006In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 280, no 1-2, p. 418-426Article in journal (Refereed)
    Abstract [en]

    This paper describes the fractionation and further isolation and characterisation of peptides and proteins present in sweet whey by means of ultrafiltration using a regenerated cellulose membrane with a nominal molar mass cut-off value of 10 kg/mol and nanofiltration through sulphonated polyether sulphone membrane with a cut-off of 1 kg/mol. The concentration of whey proteins was done below the critical flux. The sieving coefficients for the whey components (proteins, lactose and salts) were estimated. Whey proteins were completely rejected by the ultrafiltration membrane. Size exclusion chromatography (SEC) and matrix-assisted laser desorption ionisation time-of-flight (MALDI-TOF) mass spectrometry were used to evaluate the molar masses of the peptide fractions that were present in the whey permeates. Nanofiltration of whey permeates obtained after ultrafiltration was conducted at two pH values (9.5 and 3.0) that corresponded to the different charged states of the membrane and of the peptides. The transmission of peptides, amino acids and lactose was found to be mainly affected by the permeability of the fouling layer. The selectivity of the nanofiltration membranes toward peptides compared to lactose was calculated as 0.82 and 6.81 at pH 9.5 and 3.0, respectively.

  • 4.
    Cheng, Jie
    et al.
    School of Chemical and Petroleum Engineering, Dalian University of Technology, State Key Laboratory of Fine Chemicals.
    Yang, Guoqing
    School of Chemical and Petroleum Engineering, Dalian University of Technology, State Key Laboratory of Fine Chemicals.
    Zhang, Kuibu
    School of Chemical and Petroleum Engineering, Dalian University of Technology, State Key Laboratory of Fine Chemicals.
    He, Gaohong
    School of Chemical and Petroleum Engineering, Dalian University of Technology, State Key Laboratory of Fine Chemicals.
    Jia, Jia
    Division of Fuel Cells, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian.
    Yu, Hongmei
    Division of Fuel Cells, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, Dalian.
    Gai, Fangyuan
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Li, Lingdong
    School of Chemical and Petroleum Engineering, Dalian University of Technology, State Key Laboratory of Fine Chemicals.
    Hao, Ce
    School of Chemical and Petroleum Engineering, Dalian University of Technology, State Key Laboratory of Fine Chemicals.
    Zhang, Fengxiang
    School of Chemical and Petroleum Engineering, Dalian University of Technology, State Key Laboratory of Fine Chemicals.
    Guanidimidazole-quanternized and cross-linked alkaline polymer electrolyte membrane for fuel cell application2016In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 501, p. 100-108Article in journal (Refereed)
    Abstract [en]

    A modified imidazole, namely guanidimidazole (GIm) was designed and synthesized as a novel quaternizing- and cross-linking agent for alkaline polymer electrolyte membrane fabrication. The resulting membrane was more alkali tolerant and swelling resistant than that quaternized purely by 1-methylimidazole owing to the enhanced resonance and cross-linking ability of GIm, the former confirmed by a LUMO (lowest unoccupied molecular orbital) energy calculation. The membrane also showed good ionic conductivity, mechanical strength and thermal stability. A H2/O2 fuel cell using the synthesized membrane showed a peak power density of 39 mW cm−2 at 50 °C. This work preliminarily demonstrates the beneficial effect of imidazole modification by both experimental and computational investigation; it provides a new cation design strategy that may potentially achieve simultaneous improvement of alkali-stability and swelling resistance of alkaline electrolyte membranes.

  • 5.
    Goetz, Lee
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Jalvo, Bianca
    Department of Chemical Engineering, University of Alcalá.
    Rosal, Roberto
    Department of Chemical Engineering, University of Alcalá.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Superhydrophilic anti-fouling electrospun cellulose acetate membranes coated with chitin nanocrystals for water filtration2016In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 510, p. 238-248Article in journal (Refereed)
    Abstract [en]

    Electrospun cellulose acetate (CA) random mats were prepared and surface coated with chitin nanocrystals (ChNC) to obtain water filtration membranes with tailored surface characteristics. Chitin nanocrystals self-assembled on the surface of CA fibers into homogenous nanostructured networks during drying that stabilized via hydrogen bonding and formed webbed film-structures at the junctions of the electrospun fibers. Coating of CA random mats using 5% chitin nanocrystals increased the strength by 131% and stiffness by 340% accompanied by a decrease in strain. The flux through these membranes was as high as 14217 L m−2 h−1 at 0.5 bar. The chitin nanocrystal surface coating significantly impacted the surface properties of the membranes, producing a superhydrophilic membrane (contact angle 0°) from the original hydrophobic CA mats (contact angle 132°). The coated membranes also showed significant reduction in biofouling and biofilm formation as well as demonstrated improved resistance to fouling with bovine serum albumin and humic acid fouling solutions. The current approach opens up an easy, environmental friendly and efficient route to produce highly hydrophilic membranes with high water flux and low fouling for microfiltration water purification process wash water from food industry for biological contaminants.

  • 6.
    Grahn, Mattias
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Maxwell-Stefan modelling of High flux tubular silicalite-1 membranes for CO2 removal from CO2/H2 gas mixtures2014In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 471, p. 328-337Article in journal (Refereed)
    Abstract [en]

    In this work, a Maxwell-Stefan model for high flux tubular silicalite-1 membranes for separation of CO2 from a CO2/H2 mixture was developed. The model concerns tubular membranes operating in a counter flow module and includes transport through flow-through defects in the silicalite-1 film and pressure drop over the graded alumina support. Adsorption and diffusion parameters for perfect silicalite-1 crystals were taken from literature. The flux and selectivity predicted by the model were in reasonably good agreement with experimentally observed data for a ZSM-5 membrane without any fitting of the model. However, the CO2 flux and selectivity measured experimentally for the ZSM-5 membrane were higher than that predicted by the model for a silicalite-1 membrane.The model was used to investigate a case with a 20 000 Nm3/d feed comprised of a 50/50 mixture of CO2/H2 at pressure of 25 bar and a membrane temperature of 296 K. The permeate pressure was 1 bar and 90% of the CO2 permeated the membrane. In this case, the membrane permselectivity and CO2 flux varied along the length of the tubes between 20–26 and 950–396 kg/(m2 h), respectively. Further, both defects and pressure drop over the support were shown to have an adverse effect on the selectivity, which indicates that membrane selectivity can be improved by reducing the flow-through defects and/or by preparing supports with less flow resistance. For a one-stage process, the required membrane area is as small as ca 0.85 m2 and the hydrogen loss through the membrane was 12.4%. For a two-stage process the required membrane area almost doubled to 1.6 m2, however the hydrogen loss through the second membrane is reduced to as little as 2.5%. In summary, this work shows that high flux zeolite membranes may be an interesting option for CO2 removal from synthesis gas.

  • 7.
    Gualtieri, Magdalena Lassinantti
    et al.
    Luleå tekniska universitet.
    Andersson, Charlotte
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    Jareman, Fredrik
    Luleå tekniska universitet.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Gualtieri, Alessandro F.
    Dipartimento di Scienze della Terra, Universita di Modena e Reggio Emilia.
    Leoni, Matteo
    Dipartimento di Ingegneria dei Materiali, Università di Trento, I-38050 Mesiano.
    Meneghini, Carlo
    Dipartimento di Fisica ‘E. Amaldi’ Università di Roma Tre, Via della Vasca Navale 84, I-00146 Roma.
    Crack formation in α-alumina supported MFI zeolite membranes studied by in situ high temperature synchrotron powder diffraction2007In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 290, no 1-2, p. 95-104Article in journal (Refereed)
    Abstract [en]

    Cracks are frequently formed in α-alumina supported MFI membranes during calcination. To better understand crack formation, in situ powder diffraction data were collected during calcination of a type of MFI membrane (ca. 1800 nm thick) which is known to crack reproducibly. In addition, data for MFI powder and a blank support were also collected. Both a synchrotron radiation facility and an in-house instrument were used. The unit cell parameters were determined with the Rietveld method, and the strain in the direction perpendicular to the film surface was calculated for the film as well as for the support. The microstrain in the support was also estimated. Based on the results obtained here, a model for crack formation in this type of MFI membrane was proposed. The lack of cracks in other types of MFI membranes (ca. 500 nm) prepared in our laboratory is also explained by the model. In thicker MFI films, the crystals are well intergrown. During heating, the MFI crystals contract and the α-alumina support expands. Consequently, a thermal stress develops in the composite which eventually leads to formation of cracks in the film and structural defects in the support. In thinner films, the crystals are less well intergrown and the thermal expansion mismatch leads to opening of grain boundaries rather than cracks.

  • 8.
    Hedlund, Jonas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Korelskiy, Danil
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Rayson, Mark
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Öberg, Sven
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Mathematical Science.
    Briddon, Patrick R.
    School of Electrical, Electronic and Computer Engineering, University of Newcastle upon Tyne.
    Mass transport in porous media from first principles: an experimental and theoretical study2012In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 415-416, p. 271-277Article in journal (Refereed)
    Abstract [en]

    In the present work, the mass transport of helium through zeolite is experimentally determined by measuring the flow of helium through a zeolite membrane. By using a mathematical model, the mass transport through defects was accounted for to arrive at mass transport through zeolite pores. For the first time, we could thereby experimentally show that the mass transport of helium in zeolite pores is strongly controlled by the amount and location of hydrocarbons in the zeolite pores and varies several orders of magnitude. The mass transport of helium in ZSM-5 zeolite pores is first reduced gradually more than one order of magnitude when the loading of n-hexane is increased from 0 to 47% of saturation. As the loading of n-hexane is further increased to 54% of saturation, the mass transport of helium in the zeolite pores is further reduced abruptly by more than two orders of magnitude. This gradual decrease followed by an abrupt decrease of mass transport is caused by adsorption of n-hexane in the zeolite pores. In a similar yet different fashion, the mass transport of helium in the zeolite pores is reduced abruptly by almost two orders of magnitude when the loading of benzene is increased from 0 to 19% of saturation due to adsorption of benzene in the pore intersections. Effective medium approximation percolation models with parameters estimated using density functional theory employing the local density approximation, i.e. models with no adjustable parameters and the most sophisticated theory yet applied to this system, can adequately describe the experimental observations.

  • 9.
    Hedlund, Jonas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Jareman, Fredrik
    Luleå tekniska universitet.
    Bons, Anton-Jan
    ExxonMobil Chemical Europe Inc..
    Anthonis, Marc
    ExxonMobil Chemical Europe Inc..
    A masking technique for high quality MFI membranes2003In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 222, no 1-2, p. 163-179Article in journal (Refereed)
    Abstract [en]

    A procedure for the preparation of high quality zeolite membranes was developed. This procedure relies on a masking approach that fills all support pores with wax while leaving the top surface free for deposition of the zeolite film, thus, protecting the support from the synthesis mixture. Zeolite films of different thickness were grown on masked and non-masked supports using a seeded growth method. The zeolite-coated supports were calcined in order to remove the wax from the support and the template molecules from the zeolite. The membranes were characterized by SEM, XRD, single gas and multi-component permeation measurements. Support masking reduces the zeolite membrane thickness and the width of the cracks in the zeolite film. Thicker films, especially those prepared without masking, are defective. Masked membranes with a film thickness of 500 nm show no cracks or pinholes. These membranes have a H2 permeance of 220×10−7 mol/(s m2 Pa), an n-butane permeance of 9.8×10−7 mol/(s m2 Pa) and an n-butane/iso-butane separation factor of 9.0 at 25 °C. The separation factor for a mixture of n-hexane/2,2-dimethyl-butane was 227 at 400 °C and the n-hexane permeance was 5.6×10−7 mol/(s m2 Pa). The p-xylene permeance was 2.7×10−7 mol/(s m2 Pa) and the para/ortho separation factor was 17 at 400 °C for a mixture of xylenes.

  • 10.
    Hedlund, Jonas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Korelskiy, Danil
    Sandström, Linda
    Lindmark, Jonas
    Permporometry analysis of zeolite membranes2009In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 345, no 1-2, p. 276-287Article in journal (Refereed)
    Abstract [en]

    In permporometry analysis of zeolite membranes, the permeance of a non-adsorbing gas, such as helium, is measured as a function of pressure of a strongly adsorbing compound, such as n-hexane in the case of silicalite-1 membranes. The adsorbing compound effectively blocks the transport of the non-adsorbing gas already at very low activity of the adsorbing compound. The plot of the permeance of the non-adsorbing gas as a function of relative pressure of the adsorbing compound is denoted a permporometry pattern. The present work is based on experimental data for a number of thin MFI membranes with a film thickness ranging from 300 to 1800 nm. An adsorption-branch permporometry experiment is simple and straightforward and after activation of the membrane by removing adsorbed species at 300 °C in a flow of dry gas, a full permporometry pattern is recorded within about 7 h for such membranes. It is shown how the distribution of flow-through defects can be estimated from the permporometry pattern using a simple model for permeation based on Knudsen diffusion. The estimated defect distribution is supported by SEM observations. In addition, the permeance of the non-adsorbing gas through defects measured in permporometry can be used to predict the permeance of molecules diffusing through defects in the membrane in mixture separation experiments and also indicate the separation factor. For instance, the helium permeance through defects in an MFI membrane measured by helium/n-hexane permporometry at room temperature can be used to estimate the permeance of 2,2-dimethylbutane (DMB) in a mixture separation experiment at a higher temperature with a feed containing both DMB and n-hexane by assuming Knudsen diffusion for both helium and DMB in the defects. Also, the separation factor αn-hexane/DMB in a mixture separation experiment at a certain temperature with an MFI membrane with a given defect distribution can be estimated from n-hexane/helium permporometry data recorded at the same temperature through an empirical correlation. In summary, adsorption-branch permporometry is a very effective tool for analysis of thin zeolite membranes, that in short time gives data that can be used to estimate the distribution of flow-through defects in the membrane and to estimate the transport of large molecules through defects in separation experiments and also estimate separation performance.

  • 11.
    Hedlund, Jonas
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Noack, M.
    Institute of Applied Chemistry e.V., Rudower Chaussee 5, D-12489, Berlin.
    Kölsch, P.
    Institute of Applied Chemistry e.V., Rudower Chaussee 5, D-12489, Berlin.
    Creaser, Derek
    Luleå tekniska universitet.
    Sterte, Johan
    Caro, J.
    Institute of Applied Chemistry e.V., Rudower Chaussee 5, D-12489, Berlin.
    ZSM-5 membranes synthesized without organic templates using a seeding technique1999In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 159, no 1-2, p. 263-273Article in journal (Refereed)
    Abstract [en]

    Porous α-alumina supports were seeded with colloidal TPA-silicalite-1 crystals and calcined. The supports were treated in a synthesis solution to grow the seed crystals into ZSM-5 films. The synthesis solution was free from organic template molecules in order to avoid the calcination step which often introduces cracks in the synthesized zeolite film. An SEM investigation indicated that the zeolite films on the supports were defect free and that the film thickness was approximately 1.5 μm. XRD data showed that the film consisted of well-crystallized ZSM-5. The permeance in single gas experiments decreased in the order H2O, H2, CO2, O2, N2 and CH4. The difference in permeance between each molecular species in the series was almost one order of magnitude which indicated that the membranes were of a high quality. Molecules larger than CH4 permeated with similar and low rates, independent of their kinetic diameters, indicating a non-selective permeation path through defects in the zeolite films. However, the permeance of these larger molecules was less than 1/10 000 of that for H2O. The highest measured separation factors for binary mixtures of N2/SF6 and H2/i-C4 were 110 and 99.

  • 12.
    Jalvo, Blanca
    et al.
    Department of Chemical Engineering, University of Alcalá.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Rosal, Roberto
    Department of Chemical Engineering, University of Alcalá.
    Coaxial poly(lactic acid) electrospun composite membranes incorporating cellulose and chitin nanocrystals2017In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 544, p. 261-271Article in journal (Refereed)
    Abstract [en]

    In this study, we used electrospinning to produce core-shell nanofibers of poly(lactic acid) as core and polyacrylonitrile/cellulose nanocrystals (CNC) or polyacrylonitrile/chitin nanocrystals (ChNC) as shell. Electrospun materials prepared at different nanocrystal concentrations were tested and assayed as microfiltration membranes. The coaxial membranes presented a maximum pore size in the 1.2–2.6 μm range and rejections > 85% for bacterial cells (0.5 × 2.0 μm) and > 99% for fungal spores (> 2 μm). The morphological and mechanical properties and the water permeability of the nanocomposite membranes were studied. The morphological characterization showed random fibers of beadless and well-defined core/shell structured fibers with diameter generally below the micron size with presence of secondary ultrafine nanofibers. Tensile strength and Young's modulus of elasticity improved with respect to coaxial membranes without nanocrystals with best mechanical properties achieved at 5 wt% CNC and 15 wt% ChNC loadings. The enhancement was attributed to the reinforcing effect of the percolating network of cellulose nanocrystals. Water permeability increased for all membranes loaded with nanocrystals with respect to the coaxial fibers without nanocrystals, the highest corresponding to ChNC composites with up to a 240% increase over non-loaded membranes. Composite membranes prepared with CNC in their shell were hydrophilic, in contrast with the hydrophobic PLA core, while coaxial fibers with ChNC were superhydrophilic. CNC membranes were negatively charged but ChNC originated neutral or positively charged membranes due to the contribution of deacetylated chitin structural units. Upon exposure to E. coli cultures, composite membranes containing ChNC showed a high antimicrobial action and were essentially free of bacterial colonization under strong biofilm formation conditions.

  • 13.
    Jareman, Fredrik
    et al.
    Luleå tekniska universitet.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Creaser, Derek
    Chalmers University of Technology.
    Sterte, Johan
    Modelling of single gas permeation in real MFI membranes2004In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 236, no 1-2, p. 81-89Article in journal (Refereed)
    Abstract [en]

    A novel permeation model for flow through defects and zeolite pores in real MFI membranes, also accounting for substrate effects has been developed. Defect distributions for two types of MFI membranes were determined from porosimetry data using the model, which incorporated the Horvath Kawazoe (micropores) or the Kelvin equation (mesopores). The narrowest (1.08 nm) and also most common defects were found to be separated with a distance of 10–40 μm according to the model. Diffusion coefficients for hydrogen, helium, nitrogen and SF6 in the zeolite were further determined from single gas permeation data using the model using the independently determined defect distribution. The coefficients are consistent with values previously reported in the literature.

  • 14.
    Kangas, Jani
    et al.
    University of Oulu.
    Sandström, Linda
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Malinen, Ilkka
    University of Oulu.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Tanskanen, Juha
    University of Oulu.
    Maxwell-Stefan modeling of the separation of H2 and CO2 at high pressure in an MFI membrane2013In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 435, p. 186-206Article in journal (Refereed)
    Abstract [en]

    In the present study, a Maxwell-Stefan based model was developed for the separation of CO2 from H2 at high pressure in an MFI membrane. The usage of the Vignes interpolation formula for mixture surface diffusivities together with the IAST (ideal adsorbed solution theory) using bulk gas phase fugacities for mixture adsorption proved to be a feasible combination for this case. Both the effects of defects in the zeolite film and the mass transfer resistance caused by the support layers were studied and included in the model. Only pure component experimental data was used in the model building to predict the gas mixture permeation. The fitted diffusion parameters were in line with the literature values. The occupancy fraction dependence of CO2 surface diffusivity was utilized for the first time in the prediction of binary separation of H2/CO2 at high pressure on a real MFI membrane. Usage of an occupancy fraction dependence for CO2 surface diffusivity improved the model predictions. The adsorption parameter fitting for hydrogen based on the permeation measurements resulted in a feasible adsorption model, but should be used with caution. The model predicts binary separation measurement results relatively well. Both defects and support have a noticeable impact on the overall performance of the membrane.

  • 15.
    Karim, Zoheb
    et al.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science. Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Claudpierre, Simon
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Oksman, Kristiina
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Mathew, Aji P.
    Luleå University of Technology, Department of Engineering Sciences and Mathematics, Material Science.
    Nanocellulose based functional membranes for water cleaning: Tailoring of mechanical properties, porosity and metal ion capture2016In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 514, p. 418-428Article in journal (Refereed)
    Abstract [en]

    Multi-layered nanocellulose membranes were prepared using vacuum-filtration of cellulose nanofibers (CNF) suspensions followed by dip coating with cellulose nanocrystals having sulphate (CNCSL) or carboxyl surface groups (CNCBE). It was possible to tailor the specific surface area, pore structure, water flux and wet strength of the membranes based on drying conditions and acetone treatment. CNF coated with CNCBE showed the highest a tensile strength (95 MPa), which decreased in wet conditions (≈3.7 MPa) and with acetone (2.7 MPa) treatment. The water dried membranes showed pore sizes in nanofiltration range (74 Å) from liquid nitrogen adsorption/desorption data and the acetone treatment increased the average pore sizes to tight ultrafiltration range (194Å) with a concomitant increase (7000%) of the BET surface area. The water flux, also increased from zero to 25 Lm-2h-1 at a pressure differential of 0.45 MPa, for acetone treated ones. The membranes irrespective of the surface functionality showed exceptional capability (≈100%) to remove Ag+, Cu2+ and Fe3+ ions from mirror industry effluents. Surface adsorption followed by microprecipitation was considered as the possible mechanism of ion removal, which opens up a new generation of ultrafiltration membranes with high selectivity towards ions and low-pressure demands.

  • 16.
    Karimi, Somayeh
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Korelskiy, Danil
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Mortazavi, Yadollah
    Catalysis and Nanostructured Materials Research Laboratory, College of Engineering, School of Chemical Engineering, University of Tehran.
    Khodadadi, Abbas Ali
    Catalysis and Nanostructured Materials Research Laboratory, College of Engineering, School of Chemical Engineering, University of Tehran.
    Sardari, Kaymar
    Catalysis and Nanostructured Materials Research Laboratory, College of Engineering, School of Chemical Engineering, University of Tehran.
    Esmaeili, Mohammad
    Catalysis and Nanostructured Materials Research Laboratory, College of Engineering, School of Chemical Engineering, University of Tehran.
    Antzutkin, Oleg
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Shah, Faiz Ullah
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    High flux acetate functionalized silica membranes based on in-situ co-condensation for CO2/N2 separation2016In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 520, p. 574-582Article in journal (Refereed)
    Abstract [en]

    Acetate-functionalized silica membranes were prepared via co-condensation. The molar ratio of functional groups in the silica matrix was varied in the range of 0–0.6, denoted by x. The presence of functional groups bonded to the silica network was revealed by FTIR and 29Si and 13C solid-state NMR analysis. The stability of the groups was studied by TG analysis. The membranes were evaluated for CO2/N2 mixture separation in a temperature range of 253–373 K using a feed pressure of 9 bar and a sweep gas kept at atmospheric pressure on the permeate side. The membranes were found to be CO2-selective at all the conditions studied. The highest observed selectivity was 16 for x=0.4, with a CO2 permeance of 5.12×10−7 mol s−1 m−2 Pa−1. For x=0.2, a permeance of as high as 20.74×10−7 mol s−1 m−2 Pa−1 with a CO2/N2 selectivity of 7.5 was obtained. This permeance is the highest reported for CO2/N2 separation using functionalized silica membranes. It is proposed that the separation mechanism between CO2 and N2 was the preferential adsorption of CO2, which inhibited adsorption and permeation of N2 through the silica pore network. Permporometry results revealed that as the loading of functional groups increased, the He permeance decreased. It was also indicated that the quantity of micropores in the functionalized membrane was higher than that in the parent silica membrane.

  • 17.
    Karimi, Somayeh
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering. Catalysis and Nanostructured Materials Research Laboratory, College of Engineering, School of Chemical Engineering, University of Tehran.
    Korelskiy, Danil
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Yu, Liang
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Khodadadi, Abbas Ali
    Catalysis and Nanostructured Materials Research Laboratory, College of Engineering, School of Chemical Engineering, University of Tehran.
    Mortazavi, Yadollah
    Catalysis and Nanostructured Materials Research Laboratory, College of Engineering, School of Chemical Engineering, University of Tehran.
    Esmaeili, Mohammad
    Catalysis and Nanostructured Materials Research Laboratory, College of Engineering, School of Chemical Engineering, University of Tehran.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    A simple method for blocking defects in zeolite membranes2015In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 489, p. 270-274Article in journal (Refereed)
    Abstract [en]

    The abatement of defects in zeolite membranes is essential for achieving high selectivity. In the present work, a simple and effective method for blocking defects in ultra-thin (ca. 0.5 μm) MFI zeolite membranes has been developed. The method is based on deposition of an ultra-thin (∼15 nm) layer of amorphous silica on the top surface of the membrane. Permporometry data indicated that the amount of defects, especially defects larger than 4 nm, in the membranes was significantly reduced after the modification. In mixture separation experiments, the CO2/H2 separation factor increased dramatically after blocking the defects in a defective membrane that was selected for the experiments. For instance, at 263 K and 9 bar feed pressure, the CO2/H2 separation factor increased from 8.5 to 36 after modification of the membrane, whereas the CO2 flux only decreased by ca. 40%.

  • 18.
    Korelskiy, Danil
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Mouzon, Johanne
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Characterization of flow-through micropores in MFI membranes by permporometry2012In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 417-418, p. 183-192Article in journal (Refereed)
    Abstract [en]

    Permporometry was used for the first time to characterize flow-through micropore defects down to 0.7 nm in size in MFI zeolite membranes. Helium was used as the non-adsorbing gas and n-hexane or benzene was used as the adsorbate. The helium flow through zeolite pores was estimated using percolation theory and the remaining flow was assigned to flow-through defects. The area distribution of flow-through defects was estimated from the data using a simple model and similar results were obtained using both adsorbates. The total area of defects determined using n-hexane as the adsorbate was as low as about 0.7% of the membrane area and defects with a width below 1 nm constituted 97% of the total defect area for the best membrane. The permporometry results were supported by n-hexane/1,3,5-trimethylbenzene separation experiments. The permporometry data were also consistent with HR-SEM observations indicating the presence of narrow open grain boundaries, and absence of large cracks and pinholes

  • 19.
    Korelskiy, Danil
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Leppäjärvi, Tiina
    Department of Process and Environmental Engineering, University of Oulu.
    Zhou, Han
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Tanskanen, Juha
    Department of Process and Environmental Engineering, University of Oulu.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    High flux MFI membranes for pervaporation2013In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 427, p. 381-389Article in journal (Refereed)
    Abstract [en]

    MFI membranes with a thickness of 0.5 μm prepared on a graded α-alumina support were evaluated for separation of feed mixtures of 3 wt.% n-butanol/water and 10 wt.% ethanol/water by pervaporation. The membranes were selective to n-butanol and ethanol. The flux observed in the present work was about 100 times higher than that previously reported for n-butanol/water separation by pervaporation and about 5 times higher than that for ethanol/water separation by pervaporation. At 60 °C, the observed n-butanol/water flux was about 4 kg m−2 h−1 and the n-butanol/water separation factor was about 10 for the best membrane. At the same temperature, the membrane displayed an ethanol/water flux of ca. 9 kg m−2 h−1 and an ethanol/water separation factor of ca. 5. A mathematical model indicated significant mass transfer resistance in the support, which reduced the flux and the selectivity of the membranes.

  • 20. Lindmark, Jonas
    et al.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Carbon dioxide removal from synthesis gas using MFI membranes2010In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 360, no 1-2, p. 284-291Article in journal (Refereed)
    Abstract [en]

    A membrane processes may represent a more effective alternative compared to current technology for separation of CO2 from synthesis gas. In the present work, MFI membranes were prepared and the separation performance was evaluated. The Si/Al ratio and the counter ions in the membrane had a significant effect on both single gas permeation and mixture separation by modifying both the effective pore size and the adsorption properties of the membranes. The membranes were relatively unselective for binary mixtures of carbon dioxide and hydrogen, but when the feed also contained water, a CO2/H2 separation factor of 6.2 was achieved for a BaZSM-5 membrane at room temperature. The CO2 permeance for this membrane was as high as 13·10-7 mol · m-2 · s-1 · Pa-1. A suitable terminology for this effect, that a third component, in this case water, enhanced the separation of two other components, in this case CO2 and H2, is sorption enhanced separation. Due to the reduced adsorption of both CO2 and water at higher temperature, the CO2/H2 separation factor was always reduced as the temperature was increased. This work clearly shows that MFI membranes are promising candidates for CO2 separation from synthesis gas.

  • 21. Lindmark, Jonas
    et al.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Wirawan, Sang Kompiang
    Creaser, Derek
    Chalmers University of Technology, Department of Chemical and Biological Engineering.
    Li, Mingrun
    Department of Materials and Environmental Chemistry, Berzelii Center EXSELENT on Porous Materials, Stockholm University.
    Zhang, Daliang
    Department of Materials and Environmental Chemistry, Berzelii Center EXSELENT on Porous Materials, Stockholm University.
    Zou, Xiaodong
    Department of Materials and Environmental Chemistry, Berzelii Center EXSELENT on Porous Materials, Stockholm University.
    Impregnation of zeolite membranes for enhanced selectivity2010In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 365, no 1-2, p. 188-197Article in journal (Refereed)
    Abstract [en]

    A new method to enhance the selectivity of zeolite membranes for alternative separation tasks has been developed. Calcined MFI membranes were impregnated with a solution of Ca(NO3)2 in methanol and calcined at 600 °C to thermally decompose the nitrate. SEM and EDS data indicated that calcium compounds were evenly distributed in the entire MFI film and in addition, a few crystals of a calcium compound were observed on top of the film in some locations. A HR-TEM investigation showed that calcium compounds were present in low concentration in the sample and that the interiors of the MFI crystals remained fully crystalline after impregnation and calcination. However, the HR-TEM investigation could neither confirm nor rule out the occurrence of calcium compounds in the pores in the interiors of the crystals. In accordance with the SEM and TEM observations, XRD data showed that calcium compounds on top of the film were relatively large CaCO3 crystals and that the zeolite film remained crystalline after impregnation. However, eventual calcium compounds in the pores of the zeolite could not be studied by XRD since these would probably generate a very weak signal of amorphous material. FTIR data indicated that impregnation increased the amount of both physisorbed and chemisorbed CO2, the latter resulting in carbonate species in the film. n-Hexane/helium adsorption branch permporometry showed that the high quality of the membranes remained after modification. The single component permeance ratio CO2/H2 increased from 0.6 to 1.5 after impregnation. Calculations indicated that the increased CO2/H2 single component permeance ratios were both an effect of increased adsorption of CO2 in the film and reduced pressure drop in the support. The dual component separation factor α CO2/H2 at room temperature increased drastically from 0.7 (H2 selective) to 3.4 (CO2 selective) after impregnation. This work shows for the first time that impregnation procedures can be used to tailor the diffusion properties of zeolite membranes in a similar way as impregnation procedures are used to tailor the catalytic performance of catalysts.

  • 22. Mathew, Aji P.
    et al.
    Packirisamy, S.
    Vikram Sarabhai Space Centre.
    Stephen, Ranimol
    Mahatma Gandhi University.
    Thomas, Sabu
    Mahatma Gandhi University.
    Transport of aromatic solvents through natural rubber/polystyrene (NR/PS) interpenetrating polymer network membranes2002In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 20, no 1-2, p. 213-227Article in journal (Refereed)
    Abstract [en]

    A series of interpenetrating polymer network membranes have been synthesised from natural rubber and polystyrene by the sequential polymerisation technique. The transport of aromatic hydrocarbons through semi- and full-interpenetrating polymer network membranes (IPNs) have been studied in detail by tracing the solvent uptake up to equilibrium. The sorption was carried out in a series of aromatic solvents viz. benzene, toluene and xylene. The effect of temperature on swelling is studied by carrying out the experiments in toluene in the temperature range of 30-75 °C. The effects of blend ratio, crosslinker content and nature of initiator on the diffusion of various solvents were analysed. It was found that in all cases, the uptake value increased by about 50% as the PS content decreased from 70-30%. The diffusion, sorption and permeation coefficients were evaluated. As the crosslink density was increased, the uptake decreased by 40%. Kinetic and thermodynamic parameters were evaluated from diffusion experiments. The diffusion profiles were compared with theoretical predictions. The influence of swelling on the mechanical performance of the membranes has been investigated by conducting tensile testing of swollen specimens.

  • 23.
    Perdana, Indra
    et al.
    Chalmers University of Technology, Department of Chemical and Biological Engineering.
    Creaser, Derek
    Chalmers University of Technology, Department of Chemical and Biological Engineering.
    Lindmark, Jonas
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Influence of NOx adsorbed species on component permeation through ZSM-5 membranes2010In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 349, no 1-2, p. 83-89Article in journal (Refereed)
    Abstract [en]

    A thin ZSM-5 film was grown on an α-alumina support, resulting in a composite membrane. The membranes were characterized by SEM and adsorption branch n-hexane/helium permporometry. In addition, the permeation of gas mixtures containing NO2, NO, N2 and argon was evaluated. The effect of temperature and gas mixture composition on the component permeation and selectivity was investigated. It was found that NOx permeation through the ZSM-5 membrane was partially surface concentration dependent and was thermally activated. However, transport by gas translational diffusion seemed to dominate at the conditions studied. The presence of various NOx adsorbed species appeared to influence diffusion of NO2 in ZSM-5 and reduced transport of other inert and weakly adsorbed components over a wide temperature range (20 to 400 °C). Strongly adsorbed surface nitrate species formed in the presence of gas phase NOx should be responsible for the reduced transport of these components at the elevated temperature. The findings are of interest for possible applications of ZSM-5 membranes for component separation at high temperature.

  • 24.
    Sandström, Linda
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Lindmark, Jonas
    Hedlund, Jonas
    Separation of methanol and ethanol from synthesis gas using MFI membranes2010In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 360, no 2, p. 265-275Article in journal (Refereed)
    Abstract [en]

    Methanol or ethanol production from synthesis gas is limited by thermodynamic equilibrium and separation of the alcohol product in or near the reactor at reaction conditions (about 250° C and 50 bar) could improve the process. Separation of methanol and ethanol from synthesis gas by MFI membranes with two different Si/Al ratios has therefore been evaluated in the present work. The synthesis gas was represented by hydrogen, carbon dioxide and water, and membrane separation performance was evaluated at atmospheric pressure and varying temperatures.The highest measured methanol/hydrogen separation factor, 32, was observed for the more polar membrane type with the lowest Si/Al ratio, while the highest ethanol/hydrogen separation factor, 46, was observed for the less polar membrane type with the highest Si/Al ratio, both at room temperature. The separation was controlled by adsorption, and consequently, the separation factors were reduced as the temperature increased, since the feed composition was kept constant.The methanol and ethanol permeances were about 10x10-7 mol m-2 s-1 Pa-1 independent of feed composition, membrane type or temperature, which is more than three times higher than previously reported for gas phase separation using zeolite membranes.A simple mathematical model was successfully fitted to the experimental data. The model suggests that membrane selectivity is temperature dependent, as also observed experimentally, but independent of feed pressure. Experimental data and mathematical modelling thus suggest that the membranes would be alcohol selective at reaction pressure (50 bar) and room temperature, but not at reaction temperature (250°C).

  • 25. Sandström, Linda
    et al.
    Palomino, Miguel
    Instituto de Tecnologia Quımica, Universidad Politecnica de Valencia.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    High flux zeolite X membranes2010In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 354, no 1-2, p. 171-177Article in journal (Refereed)
    Abstract [en]

    Methanol synthesis from synthesis gas is equilibrium limited and selective removal of products could improve the process. In the present work, zeolite X membranes with a film thickness of about 1 μm were evaluated for this separation. A maximum methanol/carbon dioxide separation factor of about 140 and a maximum methanol/hydrogen separation factor of about 8 were observed in the temperature range 50 to 100 °C. In the same temperature range, the maximum water/carbon dioxide and water/hydrogen separation factors were about 250 and 15, respectively.The membranes were also evaluated for room temperature drying of synthesis gas and natural gas. The observed water/carbon dioxide separation factors were 482 and 252 for carbon dioxide/hydrogen/water and carbon dioxide/methane/water feed mixtures, respectively.In all separation experiments performed in the present work, the observed water and methanol permeances were very high. The water permeance was in the range 15-24 10−7 mol m−2 s−1 Pa−1 for all evaluated feed mixtures and temperatures, while the methanol permeance in the methanol/synthesis gas feed mixture was 12-14 10−7 mol m−2 s−1 Pa−1 in the temperature range 100 to 150 °C. To the best knowledge of the authors, the observed methanol and water permeances are several times higher than previously reported in the open literature for gas phase separations using FAU membranes.In summary, the membranes were found to be selective for the most polar components in a feed mixture, and the observed permeances were high.

  • 26.
    Sandström, Linda
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Sjöberg, Erik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Very high flux MFI membrane for CO2 separation2011In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 380, no 1-2, p. 232-240Article in journal (Refereed)
    Abstract [en]

    Membrane separation of CO2 from synthesis gas, natural gas or biogas may be a simple and energy-efficient alternative to other separation techniques. In this work, membranes comprised of an about 0.7 μm thick MFI film on a graded alumina support was used to separate mixtures of CO2/H2, CO2/CO/H2 and CO2/CH4 gas at high pressure. The membranes were prepared on masked supports.The single gas permeance of H2 was larger than that of CO2, but for a binary CO2/H2 mixture, the H2 permeability was blocked and the membrane was CO2 selective. A CO2 flux as high as 657 kg m−2 h−1 was observed at room temperature, 3000 kPa feed pressure and 600 kPa permeate pressure. Under these conditions, the CO2/H2 separation factor was 16.2. The maximum CO2/H2 separation factor was 32.1, and was observed at 1000 kPa feed pressure, a permeate pressure of 200 kPa and a temperature of 275 K. Under these conditions, the CO2 flux was still as high as 332 kg m−2 h−1. The highest measured CO2 permeance for the binary CO2/H2 mixture was 93 10−7 mol m−2 s−1 Pa−1. The membrane was also CO2 selective for a CO2/CO/H2 mixture. However, both the CO2 flux and the CO2/H2 separation factor were reduced slightly in the presence of CO, probably as a result of competing adsorption between CO and CO2. The CO2/CH4 separation factor was much lower than the CO2/H2 separation factor, probably as a result of competing adsorption between CO2 and CH4 in the first case. The highest measured CO2/CH4 separation factor was 4.5.The results show that MFI membranes are promising candidates for separation of CO2 from synthesis gas, natural gas or biogas. The very high CO2 fluxes likely result from a combination of several factors such as: low film thickness, a fully open graded support, high CO2 pressure in the feed resulting in saturation of the zeolite at the feed side, relatively high CO2 diffusivity in MFI pores, relatively high molecular weight, and high pressure drop. The separation is likely caused by efficient blocking of H2 transport by CO2 adsorption.

  • 27. Sjöberg, Erik
    et al.
    Barnes, Simon
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Korelskiy, Danil
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    MFI membranes for separation of carbon dioxide from synthesis gas at high pressures2015In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 486, p. 132-137Article in journal (Refereed)
    Abstract [en]

    Membranes are considered to be one of the most promising technologies for simple and energy efficient removal of carbon dioxide from gas mixtures. In the present work, MFI membranes with different Si/Al ratios and counter-ions were evaluated for separation of carbon dioxide from synthesis gas, i.e. a mixture of carbon dioxide and hydrogen. Single gas permeation experiments were also carried out. These membranes consisted of a 0.5 µm thick MFI film grown on graded alumina supports. The feed pressure was varied between 3 and 8 bar and the permeate pressure was kept constant at 1 bar, while the temperature was varied in a range of 273–350 K. The silicalite-1 membrane showed the best overall carbon dioxide separation performance, in terms of flux and separation factor, when compared with NaZSM-5 and BaZSM-5 membranes. The silicalite-1 membrane displayed a CO2/H2 separation factor of 31, with a carbon dioxide flux of ca. 560 kg m−2 h−1 at 8 bar feed pressure and a temperature of 273 K. The higher performance of the silicalite-1 membrane was attributed to a more suitable CO2 adsorption isotherm, which resulted in larger difference in fractional surface loading of CO2 between the feed and permeate side for this type of membrane, and consequently higher CO2 flux and CO2/H2 separation factor. Accordingly, the difference in membrane performance was larger at low temperature (273 K), while at elevated temperatures, the CO2/H2 separation factor decreased for all membranes and the difference between the membrane types diminished, as a result of decreased carbon dioxide adsorption.

  • 28.
    Sjöberg, Erik
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Sandström, Linda
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Öhrman, Olov
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Separation of CO2 from black liquor derived syngas using an MFI membrane2013In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 443, p. 131-137Article in journal (Refereed)
    Abstract [en]

    Membrane separation of CO2 from synthesis gas could be an energy efficient and simple alternative to other separation techniques. In this work, a membrane comprised of an about 0.7 µm thick MFI film on a graded alumina support was used to separate CO2 from synthesis gas produced by pilot scale gasification of black liquor. The separation of CO2 from the synthesis gas was carried out at a feed pressure of 2.25 MPa, a permeate pressure of 0.3 MPa and room temperature. In the beginning of the experiment, when the H2S concentration in the feed was 0.5% and the concentration of water in the feed was 0.07%, a CO2/H2 separation factor of 10.4 and a CO2 flux of 67.0 kg m-2 h-1 were observed. However, as the H2S concentration in the feed to the membrane increased to 1.7%, the CO2/H2 separation factor and the CO2 flux decreased to 5 and 61.4 kg m-2 h-1, respectively. The results suggest that MFI membranes are promising candidates for the separation of CO2 from synthesis gas.

  • 29.
    Tantekin-Ersolmaz, B.
    et al.
    Istanbul Technical University.
    Atalay-Oral, C.
    Istanbul Technical University.
    Tather, M.
    Istanbul Technical University.
    Erdem-Senatalar, A.
    Istanbul Technical University.
    Schoeman, Brian
    Sterte, Johan
    Effect of zeolite particle size on the performance of polymer–zeolite mixed matrix membranes2000In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 175, no 2, p. 285-288Article in journal (Refereed)
    Abstract [en]

    The effect of zeolite particle size on the performance of silicalite–PDMS mixed matrix membranes is investigated at two different zeolite loadings. The separation properties of the membranes prepared are characterized by permeability measurements for O2, N2 and CO2 gases. The permeabilities of the silicalite–PDMS mixed matrix membranes are determined to increase with increasing particle size. The variations occurring in the permeability values with changes made in the particle size are much more pronounced at the higher zeolite loading. The ideal selectivity values corresponding to the mixed matrix membranes, on the other hand, generally seem to be less affected by the changes made in the particle size. The permeability values corresponding to the mixed matrix membranes exceed those pertaining to the original polymer membrane only at relatively higher zeolite loadings and/or for relatively larger particle sizes. The variations occurring in the permeabilities and selectivities with changes made in the zeolite particle size may be responsible for the different values of these parameters reported in the literature for the same types of zeolite filled polymeric membranes.

  • 30. Wirawan, Kompiang
    et al.
    Creaser, Derek
    Lindmark, Jonas
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Bendiyasa, I Made
    Gadjah Mada University, Yogyakarta.
    Sediawan, Wahyudi Budi
    Gadjah Mada University, Yogyakarta.
    H2/CO2 permeation through a silicalite-1 composite membrane2011In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 375, no 1-2, p. 313-322Article in journal (Refereed)
    Abstract [en]

    Single and binary H2/CO2 gas permeation was studied through a silicalite-1 composite membrane consisting of a thin zeolite film (< 1 μm) supported on α-alumina. The temperature range for permeation measurements was 25 to 300 °C. To determine the quality of the membrane, i.e the quantity and size of defects, n-hexane/helium permporometry measurements were performed. In general, single component fluxes decreased with increasing temperature whereas binary component fluxes showed a maximum value followed by a continuous decrease. A mass transport model that takes into account the surface diffusion and gas translational diffusion in the zeolite pores, Knudsen diffusion in defects, as well as viscous flow and Knudsen diffusion in the support material was developed to simulate the single and binary gas permeation measurements. Simulation results show that the surface diffusion was the dominant mass transport mechanism in the membrane. In addition, the transport resistance of the support material was not negligible and it was found to influence the permeation selectivity. The model adequately described the experimental results for both single and binary permeation. The model predictions indicated that a CO2/H2 separation factor exceeding 9.8 and a CO2 flux exceeding 4 mol/(m2·s) could be obtained at 0 °C and a feed pressure of 10 bar and atmospheric permeate pressure.

  • 31.
    Ye, Pengcheng
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Korelskiy, Danil
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Cryogenic air separation at low pressure using MFI membranes2015In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 487, p. 135-140Article in journal (Refereed)
    Abstract [en]

    Ultra-thin MFI membranes were for the first time evaluated for air separation at low feed pressures ranging from 100 to 1000 mbar at cryogenic temperature. The membrane separation performance at optimum temperature at all investigated feed pressures was well above the Robeson upper bound for polymeric membranes at near room temperature. The O2/N2 separation factor at optimum temperature increased as the feed pressure was decreased and reached 5.0 at 100 mbar feed pressure and a membrane temperature of 67 K. The corresponding membrane selectivity was 6.3, and the O2 permeance was as high as 8.6×10−7 mol m−2 s−1 Pa−1. This permeance was about 100 times higher than that reported for promising polymeric membranes. The membrane selectivity and high O2 permeance was most likely a result of O2/N2 adsorption selectivity. The increase in O2/N2 separation factor with decreasing pressure and temperature was probably due to increased adsorption selectivity at reduced temperature. This work has demonstrated the potential of MFI zeolite membranes for O2/N2 separations at cryogenic temperature.

  • 32.
    Yu, Liang
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Ultra-thin MFI membranes for removal of C3+ hydrocarbons from methane2018In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 551, p. 254-260Article in journal (Refereed)
    Abstract [en]

    The removal of propane and heavier hydrocarbons (C3+) from natural gas is an important part of natural gas upgrading. In the present work, ultra-thin MFI zeolite membranes with a thickness of 400 nm and an estimated Si/Al ratio of 152 were evaluated for separation of C3H8 and n-C4H10 from binary and ternary mixtures with CH4. The membranes were selective towards the heavier hydrocarbons and showed high permeance at all investigated temperatures. At room temperature, the n-C4H10/CH4 separation selectivity was 25, coupled with an n-C4H10 permeance of 31 × 10−7 mol m−2 s−1 Pa−1 for a 10/90 n-C4H10/CH4 binary feed mixture. As the temperature was decreased to 281 K, the separation selectivity increased to as high as 55 with an n-C4H10 permeance of 25 × 10−7 mol m−2 s−1 Pa−1. The separation selectivities for a 10/90 C3H8/CH4 binary mixture were 9.5 and 19, with C3H8 permeances as high as 54 and 37 × 10−7 mol m−2 s−1 Pa−1 at 297 and 271 K, respectively. The higher selectivities observed for n-C4H10 containing mixtures was ascribed to stronger adsorption of n-C4H10 than C3H8 in MFI, thus resulting in higher adsorption selectivities of the n-C4H10 containing mixtures over CH4. For a 10/10/80 n-C4H10/C3H8/CH4 ternary mixture, the highest sum selectivity of (n-C4H10 + C3H8)/CH4 was 48 and the corresponding sum permance of (n-C4H10 + C3H8) was 26 × 10−7 mol m−2s−1 Pa−1 at 283 K, which were similar to the separation results of n-C4H10/CH4 binary mixture at the same conditions. The n-C4H10/CH4 and C3H8/CH4 separation selectivities from the ternary mixture were of course lower, but still as high as 32 and 16 at 283 K, with n-C4H10 and C3H8 permeances of 17 and 8 × 10−7 mol m−2 s−1 Pa−1, respectively. The results show that ultra-thin MFI zeolite membranes are promising candidates for separation of C3+ hydrocarbons from natural gas. 

  • 33.
    Yu, Liang
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Ye, Pengcheng
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Ultra-thin MFI membranes for olefin/nitrogen separation2017In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 524, p. 428-435Article in journal (Refereed)
    Abstract [en]

    The recovery of light hydrocarbons such as propylene and ethylene from vent streams in polymer plants is desirable since it opens up for more efficient conversion of the monomers with high economic value. Consequently, polymer membrane vapour-gas separation systems have been used for this purpose for decades [1,2]. However, an alternative is zeolite membranes. In this work, ultra-thin MFI zeolite membranes (0.5 µm) were used to separate propylene or ethylene from binary 20/80 olefin/nitrogen mixtures at different temperatures. The membranes were olefin selective with high permeance at all investigated temperatures. At room temperature, the permeance of propylene was 22×10-7 mol m-2 s-1 Pa-1 and the separation factor was 43, which corresponds to a separation selectivity of around 80. For a mixture of 20 mol.% ethylene in nitrogen, the maximum separation factor was 6 (corresponds to a separation selectivity of 8.4) at 277 K with an ethylene permeance of 57×10-7 mol m-2 s-1 Pa-1. The membrane selectivity was governed by more extensive adsorption of olefin, especially propylene, as compared to nitrogen. Comparing with ethylene, propylene has higher heat of adsorption, which probably caused the higher propylene/nitrogen selectivity compared to ethylene/nitrogen selectivity. The permeance and the selectivity for propylene were much higher than for commercial polymeric membranes. For ethylene, the permeance was much higher, and the selectivity was comparable to commercial polymeric membranes. Modelling showed that the pressure drop over the support limited the flux through the membranes especially at higher temperatures and in particular for the ethylene/nitrogen system with high flux. Further, modelling indicated that the result obtained at high temperatures, where the flux was high, was also affected by concentration polarization. However, for the propylene/nitrogen system at the optimum separation temperature, the pressure drop over the support and the concentration polarisation were small. The results show that ultra-thin MFI zeolite membranes are promising candidates for light olefins/nitrogen separation in polymer plants.

  • 34.
    Yu, Liang
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Nobandegani, Mojtaba Sinaei
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Holmgren, Allan
    ZeoMem Sweden AB, Luleå, Sweden.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Chemical Engineering.
    Highly permeable and selective tubular zeolite CHA membranes2019In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 588, article id 117224Article in journal (Refereed)
    Abstract [en]

    Highly permeable and selective tubular zeolite CHA membranes with a thickness of about 450 nm and a length of 100 mm and an inner diameter of 7 mm were evaluated by single gas permeation experiments and for separation of an equimolar CO2/CH4 mixture. The membranes displayed high H2 and CO2 single gas permeances of 55 × 10−7 mol m−2 s−1 Pa−1 and 94 × 10−7 mol m−2 s−1 Pa−1, respectively, and a very low SF6 permeance of 3 × 10−9 mol m−2 s−1 Pa−1. The highest observed mixture separation factor was 99 with CO2 permeance of 60 × 10−7 mol m−2 s−1 Pa−1 at a feed pressure of 5 bar and permeate pressure of 0.12 bar. The corresponding CO2flux was 1.46 mol m−2 s−1. The highest observed flux was 1.98 mol m−2 s−1 with a separation factor of 52 at a feed pressure of 10 bar and permeate pressure of 0.12 bar at room temperature. To the best of our knowledge, this is the first report describing highly permeable and selective tubular CHA membranes. The results indicate that the membranes have a great potential for industrial separation of CO2from natural gas and biogas.

  • 35.
    Zhou, Han
    et al.
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Korelskiy, Danil
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Leppäjärvi, Tiina
    Department of Process and Environmental Engineering, University of Oulu.
    Grahn, Mattias
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Tanskanen, Juha
    Department of Process and Environmental Engineering, University of Oulu.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Ultrathin zeolite X membranes for pervaporation dehydration of ethanol2012In: Journal of Membrane Science, ISSN 0376-7388, E-ISSN 1873-3123, Vol. 399–400, p. 106-111Article in journal (Refereed)
    Abstract [en]

    Discrete Faujasite zeolite nanocrystals with an average size of about 60 nm were attached as a well-defined monolayer on the surface of porous graded alumina supports. Ultrathin zeolite X films with a total thickness of about 1 μm were grown from the seed monolayers by hydrothermal treatment in clear synthesis solutions. One of the membranes showed a total flux of 3.37 ± 0.08 kg m -2 h -1 and a separation factor of 296 ± 4 for dehydration of a 90/10 wt.% ethanol/water mixture by pervaporation at 65 °C. Moreover, the membranes displayed stable performance during pervaporation for 5.5 h operation. A mathematical model indicated that the flux and selectivity of the membranes were limited by pressure drop in the supports. Therefore, in order to obtain higher flux, the permeability of the support must be improved.

1 - 35 of 35
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