Ceramic-zeolite composite membranes and their application for separation of vapor/gas mixtures (original) (raw)
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STUDY OF PERMEATION OF GASES THROUGH CERAMIC SUPPORTED POLYMERIC AND ZEOLITE MEMBRANES
2 from various effluent gas mixtures. Membrane operations are recognized as feasible and economical operations over conventional technologies for gas separation due to a higher flexibility to tolerate fluctuations in feed composition and flow rate. In this present work Hydroxy Ethyl Cellulose (HEC) membrane prepared on Silicon carbide (SiC) tube and ZSM-5 membrane casted on α-Al 2 O 3 tube support is used to study the permeation characteristics of various gases. Pour and decanting technique is used to coat HEC membrane on SiC tube whereas seed growth hydrothermal technique is used to prepare ZSM-5 zeolite membrane. Scanning electron microscope (SEM) and X-ray diffraction techniques (XRD) are used to characterize the membranes. Single component permeation experiments are conducted for measurement of permeability coefficients which are essential for understanding and designing the membrane modules. Both the membranes have shown good permeation characteristics for all the gases. Ideal selectivity values are calculated from the pure component permeances.
Preparation and separation properties of silicalite composite membranes
Journal of Membrane Science, 1995
Silicalite-alumina composite membranes were prepared by an in situ zeolite synthesis method using an alumina membrane tube with a 5-nm pore diameter, T-alumina layer as a substrate. Single gas permeances of H2, Ar, n-C4H~o, i-C4H~o, and SF 6 were measured and mixtures of H2/i-C4Hmo and H2/SF6 were separated to characterize the silicalite membrane. These measurements were made from 300 to 737 K, and are compared to an alumina membrane without a silicalite layer. Permeances were lower in the silicalite membrane (a factor of 8 for Ar at 298 K). Permeances for the alumina membrane decreased as the temperature increased, and separation selectivities were lower than values expected for Knudsen diffusion. Transport through the alumina membrane was by Knudsen flow and surface diffusion. The silicalite membrane showed dramatically different behavior, and transport appeared to be controlled by molecular size and adsorption properties. Permeances of all components studied were activated in the silicalite membrane, and activation energies ranged from 8.5 to 16.2 kJ/mol. The ratio of single gas permeances was as high as 136 for H2 to SF6 and 1100 for H2 to i-C4HIo at 298 K. Separation selectivities at elevated temperatures were significantly above Knudsen diffusion selectivity for the silicalite membrane and were larger than ratios of pure gas permeances at the same temperature. The largest permeance ratio for the separation of mixtures was 12.8 for H2/SF 6 at 583 K. Separation selectivities for both membranes were higher when a pressure drop was maintained across the membrane than when an inert sweep gas was used because of counter diffusion of the sweep gas.
Synthesis and Characterization of Ceramic Membranes (W-Type Zeolite Membranes)
International Journal of Applied Ceramic Technology, 2012
In this article, effects of synthesis parameters (synthesis temperature, synthesis time, and number of layers) on W-type zeolite membranes synthesized over flat SUS supports for O 2 /SF 6 gas separation were experimentally investigated. Experiments were carried out at these levels of synthesis temperature: 165°C, 185°C, and 200°C; synthesis time: 6, 12, and 18 h and number of layers: 1 and 2. Permeation measurements, XRD and SEM analysis were used for characterization of the synthesized membranes. The results showed that increasing synthesis temperature from 165°C up to 185°C increases separation factor of O 2 /SF 6 , however, further increasing decreases the separation performance. The same trend was observed for synthesis time for the single layer synthesized zeolite W membrane, although for the double layer synthesized zeolite W membrane, separation factor increased with increasing synthesis time. Repetition of layering has a net positive effect on separation factor of O 2 /SF 6 , and negative effect on permeation flux through the membranes. This behavior was attributed to the dual effect of synthesis temperature and synthesis time on selectivity. More zeolite crystals are deposited and larger crystals are formed at higher synthesis temperatures and longer synthesis times. Well W-type zeolite membrane was synthesized at 185°C for 18 h with two repeating layers with a high separation factor of 20.1.
A route to MFI zeolite-α-alumina composite membranes for separation of light paraffins
Desalination, 2008
Zeolites are microporous crystalline materials used as catalysts, ion-exchangers, adsorbents and molecular sieves. Several industrial separation processes, e.g. dehydration of alcohols, have been developed based on zeolite membranes. It is also of great interest the separation of light paraffins. Silicalite-1 crystal layers were synthesised on the surface of asymmetric α-alumina planar supports. A molar ratio of synthesis mixture was 100 SiO 2 :42.9 TPAOH: 2229 H 2 O with Aerosil 380 (Degussa) used as a silica source. Permeation and separation characteristics of the membranes were measured using steady state apparatus MEMFIS. Separation factor of ceramic silicalite-1 composite membrane, which was synthesised for 24 h using a synthesis mixture aged for 7 days, was studied by an equimolar mixture of butane isomers as a function of temperature. High separation factor for n-butane (> 10) in the mixture with isobutane showed good quality of the composite membrane. The results showed that the separation performance of the membrane could be tailored to find suitable compromise between permeation and separation.
Silicalite-1 Membranes Synthesis, Characterization, CO2/N2 Separation and Modeling
2014
Zeolite membranes are considered to be a promising alternative to polymeric membranes and they have the potential to separate gases under harsh conditions. Silicalite-1 membranes in particular are easy to prepare and suitable for several industrial applications. In this research project, silicalite-1/ceramic composite membranes were prepared using the pore plugging hydrothermal synthesis method and supports with zirconium oxide and/or titanium oxide as active layers. The effect of the support’s pore size on the morphology and permeation performance of the prepared membranes was investigated using five supports with different active layer pore sizes in the range of 0.14 – 1.4 m. The prepared membranes were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), electron diffraction spectrometer (EDS), single gas and binary gas mixtures permeation tests. The results confirmed the presence of a typical silicalite-1 zeolite structure with a high internal crystalli...
Zeolite LTA/carbon membranes for air separation
Microporous and Mesoporous Materials, 2008
Zeolite LTA membranes with few defects have been successfully synthesized on a carbon support by the secondary growth method, in which hydrothermal synthesis is preceded by the seeding of the carbon support with colloidal LTA zeolite crystals (about 100 nm) by means of the ElectroPhoretic Deposition (EPD) method. The effect of different synthesis parameters, such as pre-treatments of the carbon support, and different synthesis times and temperatures, on the quality of the zeolite LTA/carbon composite, were analysed by means of XRD, SEM, EDS, and TG-DTA-MS. In addition, in order to analyse the permeation characteristics of the composite materials, they were mounted in a permeation cell, and single gas components or binary mixtures of N 2 /O 2 (in a ratio of 79:21) were fed to the zeolite side. The best zeolite LTA/carbon membrane was obtained using a pre-oxidised and EPD seeded support which then underwent hydrothermal treatment at 373 K for 4.5 h. This final composite, upon reaching the steady state, separates air with a high permeance (about 2.7 Â 10 À7 mol s À1 Pa À1 m À2) and possesses a good separation factor (about 2.7).
Journal of Membrane Science, 2001
Faujasite type zeolite membranes were synthesized on porous ceramic alumina supports by using direct (in situ) and secondary (seeded) growth methods. In the secondary growth method a seed layer of ZSM-2 nanocrystals (prepared according to a report by Schoeman et al. J. Colloid Interface Sci. 1995, 170, 449-456) was deposited on the surface of the support before the hydrothermal growth. For both in situ and secondary growth, the mixture composition was 4.17 Na 2 O:1.0 Al 2 O 3 :10 TEA (triethanol ammonium):1.87 SiO 2 :460 H 2 O. X-ray diffraction (XRD), scanning electron microscopy (SEM), and electron microprobe analysis (EPMA), indicate well intergrown 5-30 m thick FAU films with Si/Al ∼1-1.5. The separation of saturated/unsaturated hydrocarbon mixtures is demonstrated over a range of temperatures (40-160 • C). The mixtures examined (and the corresponding equimolar mixture separation factors) are benzene/cyclohexane (160), benzene/n-hexane (144), toluene/n-heptane (45), propylene/propane (6.2), and ethylene/methane (8.4). In all cases, the membranes are unsaturated hydrocarbon permselective. With equimolar feed mixtures (5 kPa/5 kPa benzene/cyclohexane) and in the temperature range 65-160 • C, the membranes exhibit separation factor of 20-160 with the benzene flux in the range 10 −4 -10 −3 mol m −2 s −1 . Decreasing the total feed partial pressure (0.31/0.31 kPa benzene/cyclohexane) reduces both separation factor (12) and benzene flux. Similar trend is observed when the benzene/cyclohexane ratio in the feed mixture (0.5/9.5 kPa benzene/cyclohexane) is reduced. A sorption diffusion model based on the Stefan-Maxwell formulation has also been employed to show that the benzene/cyclohexane separation can mainly be attributed to differences of their adsorption properties.
Novel Zeolite-polyurethane membrane for environmental applications and gas separations
Matériaux & Techniques
This research work investigates the effect of polyurethane polymer on the separation of CO2, CH4 and C3H8 through a zeolite/polyurethane mixed matrix membrane. A methodology based on the modification of porous ceramic inorganic support with the aim to achieve high selectivity for the hydrocarbons has been developed. Polyurethane-zeolite nanoparticles were prepared by combined blending and casting method. The physical properties of the zeolite/polyurethane mixed matrix membrane were investigated by Scanning Electron Microscope (SEM), Fourier Transform Infra-Red spectroscopy (FTIR) and Nitrogen physisorption (BET). These confirmed the homogenous and nanoscale distribution of zeolite particles in the polyurethane-zeolite membrane. The Nitrogen physisorption measurements showed the hysteresis isotherm of the membrane corresponding to type IV and V that is indicative of a mesoporous membrane. The surface area and the pore size determined using the Barrett, Joyner, Halenda (BJH) desorption method showed a pore diameter of 3.320 nm, a pore volume of 0.31 ccg-1 and surface area of 43.583 m 2 g-1. Single gas permeation tests were carried out at a pressure range of 0.01 to 0.1 MPa. The membrane showed the permeance of CH4 to be in the range of 5.189 x 10-7 to 1.78 x 10-5 mol s-1 m-2 Pa-1 and a CH4/C3H8 selectivity of 3.5 at 293 K. On the basis of the results obtained it can be concluded that for the recovery of volatile organic compounds the addition of polyurethane polymer to the zeolite membrane did not increase the performance of the membrane.