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  • 1.
    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.

  • 2.
    Lindmark, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Modification of MFI membranes for enhanced selectivity2009Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Zeolite membranes can potentially be used for separation of many types of mixtures. The membranes can be tailored by a number of methods to suit a specific separation application. In this work both traditional and new innovative methods were used to tailor the properties of zeolite membranes in order to enhance the selectivity for a given separation. In this work the traditional methods for tailoring of zeolite membranes by adjusting the Si/Al-ratio of, and exchanging the counterions in the zeolite have been used. In addition, two new methods have been developed: One where the impregnation concept often used in the catalysis field is adapted to tailor the properties of zeolite membranes for the first time, and another, where methylamine is used to modify the zeolite and form more and stronger basic sites. The polarity of a zeolite can be tailored by changing the Si/Al ratio in order to facilitate the separation of polar and non polar molecules. A low Si/Al ratio gives a more polar zeolite and vice versa. In the present work, separation of mixtures of water, hydrogen and n-hexane was investigated for membranes with two different Si/Al ratios (silicalite-1 and ZSM-5). The highest separation factors α-water/hydrogen were observed at 25 °C and were 14.3 and 19.7 for silicalite-1 and ZSM-5, respectively. Mixtures of methanol/ethanol, hydrogen, carbon dioxide and water were also investigated, and the highest measured methanol/hydrogen separation factor, 32, was achieved for a ZSM-5 membrane, while a silicalite-1 membrane was found to give the highest ethanol/hydrogen separation factor of 46. The polar ZSM-5 favours the separation of the polar methanol, whereas the less polar silicalite-1 is more favourable for separation of the less polar ethanol. These results confirm that the selectivity for these separations can be controlled by tailoring the polarity the zeolite. The effect of the counter ions in ZSM-5 was studied by preparing, silicalite-1 and ZSM-5 membranes with three different counter ions (Na+, Li+ and Ba2+) and evaluating these for separation of quadrupolar carbon dioxide from binary and ternary mixtures of carbon dioxide, hydrogen and water. The aim was to develop a membrane suitable for separation of carbon dioxide from synthesis gas. A separation factor α-carbon dioxide/hydrogen of 6.2 was achieved for a BaZSM-5 membrane at room temperature. In the BaZSM-5 membranes, the permeances of both carbon dioxide and hydrogen were decreased by the presence of the Ba2+counter ion, but due to enhanced adsorption of the more quadrupolar carbon dioxide the carbon dioxide permeance was decreased much less than the hydrogen permeance. By development of a new and innovative impregnation procedure, carbon dioxide selective membranes with high flux were prepared by impregnating the pores of a silicalite-1 membrane with calcium compounds to aid the adsorption of carbon dioxide. The separation experiments with mixtures of carbon dioxide and hydrogen showed that the separation factor α-carbon dioxide/hydrogen at 25 °C was drastically changed from 0.7 (hydrogen selective) to 3.7 (carbon dioxide selective) by this modification. A second new modification procedure was also developed, where MFI membranes with high Si/Al ratio were modified with methylamine to increase the carbon dioxide affinity and thus increase the carbon dioxide selectivity. These membranes were then evaluated for separation of carbon dioxide from various mixtures of carbon dioxide, hydrogen, methane and water. The modification had significant effects on both permeances and separation factors and the selectivity towards carbon dioxide was increased considerably for all the feed mixtures tested. The results of the different modifications were evaluated by techniques such as SEM, TEM, XRD, DRIFT spectroscopy and by single component permeation and mixture separation experiments. High quality membranes with few defects are critical to study the effects of membrane modification and throughout this thesis adsorption-branch permporometry is used as a standard tool to evaluate membrane quality. The permporometry technique was also studied more in detail. It is shown how the distribution of flow-through defects can be estimated from the permporometry pattern. The estimated defect distribution is supported by SEM observations. In addition the permporometry data 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.

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  • 3. Lindmark, Jonas
    Tailoring of MFI membranes for enhanced selectivity2006Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Zeolite membranes can potentially be used for the separation of many types of mixtures. The membranes can be tailored by a number of methods to suit a specific separation application. In this work both traditional and new innovative methods were used to tailor the properties of membranes in order to enhance the selectivity for a given separation. Traditional methods to tailor zeolite membranes include; choice of zeolite framework, adjustment of Si/Al ratio and choice of counterion. In zeolite catalysts the properties are often also tailored by incorporating metal or metal oxide clusters in the zeolite pores by impregnation. In this work the traditional methods for membrane tailoring by adjusting the Si/Al-ratio and exchanging the counterions have been used. In addition, a new method where the impregnation concept often used in catalyst preparation is adapted to tailor the properties of zeolite membranes, was used. The polarity of a zeolite can be tailored by changing the Si/Al ratio, and to facilitate the separation of polar and non polar molecure e.g. H2O and H2, the Si/Al ratio should be relatively low. In the present work, separation of mixtures of H2O, H2 and n-hexane was investigated for membranes with two different Si/Al ratios (silicalite-1 and ZSM-5), in the temperature range 25 to 350 C. The highest separation factors H2O/H2 were observed at 25 C and were 14.3 and 19.7 for silicalite-1 and ZSM-5, respectively. The membranes were selective also at 100 C and the separation factors were about 3.2 and 6 for silicalite-1 and ZSM-5, respectively. These results confirm that the selectivity for this separation can be controlled by changing the polarity the zeolite. The aim of the new and innovative modification procedure was to prepare CO2 selective membranes with high flux. The pores of a silicalite-1 membrane were impregnated with calcium compounds to aid the chemisorption of CO2, which is essential to achieve a membrane which is CO2 selective even at high temperatures. The result of the impregnation was evaluated by separation of CO2 and H2. Calcined membranes were impregnated with a solution of Ca(NO3)2 in methanol and heated to 600 to thermally decompose the Ca(NO3)2 Calcium compounds were evenly distributed in the pores of the silicalite-1 film and there were also some relatively large CaCO3 crystals on the surface. The separation experiments with of mixtures of CO2 and H2 showed that the separation factor CO2/H2 at 25C was drastically changed from 0.7 (H2 selective) to 3.7 (CO2 selective) by this modification. These results show that the properties of the H2 selective silicalite-1 membrane could be tailored by impregnation to prepare a CO2 selective membrane.

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  • 4. 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.

  • 5. Lindmark, Jonas
    et al.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Modification of MFI membranes with amine groups for enhanced CO2 selectivity2010In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 20, no 11, p. 2219-2225Article in journal (Refereed)
    Abstract [en]

    Much research on zeolite membranes has been devoted to MFI type zeolite and these membranes can be prepared reproducibly with high quality by our group. However, the MFI pores are too large for separation of small molecules such as CO2, H-2 CH4, and H2O by molecular sieving and the CO2 affinity is not sufficiently strong in our current membranes with quite high Si/Al ratio to achieve CO2 selective membranes. In the present work, existing MFI membranes with high Si/Al ratio are modified with methylamine to increase the CO2 affinity and thus increase the CO2 selectivity. To the best of our knowledge, this is the first time this type of modification is reported for zeolite membranes. These membranes were then evaluated for separation of CO2 from various mixtures of CO2, H-2, CH4 and H2O. The modification had significant effects on both permeances and separation factors and the selectivity towards CO2 was increased considerably for all the feed mixtures tested. The highest separation factor was observed for a CO2/CH4/H2O mixture and alpha-CO2/CH4 was 12 at about 40 degrees C. At the same time, the CO2 permeance was as high as 9 x 10(-7) mol m(-2) s(-1) Pa-1. The separation factor for the amine-modified silicalite-1 membranes was comparable to the highest reported separation factors for MFI membranes, while the CO2 permeance was higher than reported for other selective MFI membranes.

  • 6. Lindmark, Jonas
    et al.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Separation of CO2 and H2 with modified MFI membranes2007In: From Zeolites to Porous MOF Materials: The 40th Anniversary of International Zeolite Conference, Proceedings of the 15th International Zeolite Conference / [ed] Ruren Xu; Zi Gao; Jiesheng Chen; Wenfu Yan, Amsterdam: Elsevier, 2007, p. 975-980Conference paper (Refereed)
    Abstract [en]

    MFI membranes with equal film thickness were grown on graded alumina supports and modified by ion exchange or impregnation. Single gas permeances of CO2 and H2 were measured for all membranes. Both impregnation and ion exchange had a significant effect on the permeation properties of the membranes. The single gas CO2/H2 permeance ratios were 0.57, 0.82, 1.7 and 2.2 for silicalite-1, NaZSM-5, BaZSM-5 and silicalite-1 impregnated with Ca(NO3)2 , respectively. Selected membranes were tested for separation of a mixture of 90 kPa CO2 and 90 kPa H2 in the temperature range 25-400 °C. The separation factors at 25 °C were 0.7, 2.0 and 4.1 for silicalite-1, BaZSM-5 and impregnated silicalite-1, respectively and decreased with increasing temperature. The results show that the separation factor can be enhanced significantly by impregnation, lowering of the Si/Al ratio or ion exchange.

  • 7. 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.

  • 8.
    Lønstad, Bjørn-Tore
    et al.
    University of Oslo.
    Sjöberg, Erik
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Lindmark, Jonas
    Lillerud, Karl-Petter
    University of Oslo.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering.
    CO2 separation using amine modified MFI-membranes2010Conference paper (Other academic)
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  • 9.
    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.

  • 10.
    Rezai, Seyed Alireza Sadat
    et al.
    Catalysis Research Centre, University of Cape Town.
    Lindmark, Jonas
    Andersson, Charlotte
    Jareman, Fredrik
    Möller, Klaus
    Catalysis Research Group, University of Cape Town.
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Water/hydrogen/hexane multicomponent selectivity of thin MFI membranes with different Si/Al ratios2008In: Microporous and Mesoporous Materials, ISSN 1387-1811, E-ISSN 1873-3093, Vol. 108, no 1-3, p. 136-142Article in journal (Refereed)
    Abstract [en]

    MFI films with a thickness of about 550 nm were prepared on α-alumina substrates. The surface Si/Al ratios (XPS) were 157 and 62 for silicalite-1 and ZSM-5 films, respectively, and in accordance, XRD data indicated lower ratios for ZSM-5 films. Higher ratios were observed by ICP-AES for crystals grown in the bulk of the synthesis mixtures. Six membranes of each type were prepared. Porosimetry measurements showed that all membranes were of high and similar quality. Single gas permeances for H2, N2, He, CO2 and SF6 at 25 °C were very similar within each type of membranes. However, the average hydrogen permeance was 27% lower and the average H2/SF6 single gas permeance ratio was 67% higher for ZSM-5 membranes. These differences are attributed to a narrower effective pore diameter for the ZSM-5 membranes due to the sodium counter ions. Separation of mixtures of H2O, H2 and n-hexane (helium balance) was investigated in the temperature range 25-350 °C. The highest separation factors α-H2O/H2 were observed at 25 °C and were 14.3 and 19.7 for silicalite-1 and ZSM-5, respectively. The membranes were selective also at 100 °C and the separation factors were about 3.2 and 6 for silicalite-1 and ZSM-5, respectively. However, the selectivity decreased at elevated temperatures and the separation factor approached 1 at temperatures above 180 °C for both membrane types. The observed water selectivity was attributed to weak adsorption of water on polar sites. A low (1.5-3) α-H2O/n-C6 separation factor was observed for both membrane types for the entire investigated temperature range.

  • 11.
    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).

  • 12. Sandström, Linda
    et al.
    Lindmark, Jonas
    Hedlund, Jonas
    Luleå University of Technology, Department of Civil, Environmental and Natural Resources Engineering, Sustainable Process Engineering.
    Understanding and controlling carbon dioxide transport in zeolite membranes2010Conference paper (Refereed)
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  • 13. 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.

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