Ag–exchanged X–type zeolite membrane has been developed for olefin/paraffin mixture separation. Preparation method, separation property, and separation mechanism of Ag–X membrane were investigated. Olefins preferentially adsorb on and penetrate through Ag–X membrane through the contribution of strong interaction between Ag cation and olefins’π–electron. Paraffin permeation is inhibited due to the occupation of micropores by adsorbed olefins. Ag–X membrane exhibited the maximum propylene selectivity of 70 with the permeance of 4.5 × 10^–8 mol m^–2 s^–1 Pa^–1 at 353 K for a propylene/propane (50 : 50) mixture. Ag–X membrane also showed stable permselectivity over 7000 h for propylene/propane separation.

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A hydrogen permselective membrane reactor was developed by using a counter diffusion CVD (chemical vapor deposition) method. The deposition mechanism was investigated to improve hydrogen permeance through the silica membrane. Nitrogen was introduced into the outer side of the porous substrate and the diffusion of the nitrogen through the pores of the porous substrate during the silica deposition was measured with a quadrupole mass spectrometer. The deposition reaction was found to be a primary reaction and the rate determining step must be the decomposition of the alkoxide of the silica precursor. The influence of organic groups such as alkyl groups in the silica precursors on the decomposition rate was not significant. The organic groups at the deposited silica decomposed and the pore size became larger after vapor deposition. By increasing the pore size, the hydrogen permeance can be improved. The hydrogen and propane permeances through the deposited silica membrane were the similar between the single component permeation and the mixed gas permeation. The propane was separated by a molecular sieving mechanism, and the effect of the adsorption of propane to the membrane was negligible at high temperature permeation tests. This silica membrane was applied to the propane dehydrogenation reaction. Both the propane conversion and selectivity were improved by the hydrogen extraction through the membrane. However, the coke deposition on the catalyst and the cold spots in the reactor must be solved for the improvement of the reactor.

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Hydrocarbon gases permeation properties through amorphous silica membrane via sol–gel method was reviewed. Pore size tuning for the formation of loose structure in comparison with conventional dense silica membranes was possible to apply for propylene/propane separation system. Here, effect of membrane fabrication parameter such as calcination temperature, cation, and anion doping into silica structure on propylene/propane permeation and adsorption properties was introduced.

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We aim to develop high–performance carbon hollow fiber membranes derived from sulfonated poly(phenylene oxide) (SPPO) for hydrogen separation from light hydrocarbons such as ethylene and propylene. After optimization of the preparation conditions, the high hydrogen selectivity was successfully obtained. In addition, we also improved the hydrogen permeance by the addition of cross–linkers into the precursor polymer and achieved the targeted value for hydrogen/propylene mixed gas separation.

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Metal–Oorganic Framework (MOF) represents the largest class of materials among the crystalline porous materials ever developed. Their extremely uniform pore aperture and nearly unlimited structural and chemical characteristics have attracted great interest and promise in applying MOF to adsorptive and membrane–based separations. This review presents the recent progress in continuous MOF membranes for hydrocarbon separation, especially, olefin/paraffin separation. The contributions of the underlying mechanism to separation performances, and the adopted strategies and membrane processing technologies for breaking the selectivity/permeability trade–off are discussed.

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Mixed Matrix Membranes (MMMs) are composite membranes composed of continuous polymer matrix and dispersed fillers. MMMs exhibit the synergetic effects from both components: cost effectiveness and high processability from polymer, and high permeability and high selectivity from fillers. In recent years, MMMs became an active area following the development of various novel porous materials. Metal–organic frameworks (MOFs) are especially focused as a candidate material for fillers for MMMs. Among various kinds of MOFs, zeolitic imidazolate frameworks– 8 (ZIF–8) is currently recognized as a promising material for propylene/propane separation. This literature review provides a brief summary of recent progress on hydrocarbon separation using MMMs and future perspectives.

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Zeolite membranes represent one of the most significant developments in the inorganic membranes field. This review of zeolite membranes includes on preparation, permeation properties and industrial application in pervaporation and vapor permeation for water–organics separation. The past two decades have seen considerable progress in these areas. However, commercialization of the membrane in reaction processes such as esterification reaction and methanol synthesis remains a big challenge.

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The sensing of biomolecules is essential for the early detection of diseases. While target molecules and receptors for various diseases have been investigated for medical diagnosis, the detection system is also important. Enzymelinked immunosorbent assay (ELISA) is a current technique with high sensitivity; however, this method is timer–consuming and labor–intensive (need hours to days) because the diffusion of substances to the reaction site inside the well is slow. Thus, a rapid and sensitive detection system is still required for application of point–of–care testing (POCT). To solve this problem, we developed a new rapid and sensitive biosensing device using the pore space of a porous membrane as the reaction space. Porous membranes have a unique morphology (nano–microscale pores) and a large available surface area, and efficient utilization of the pore space will lead to a promising material for POCT. Although the idea using small pores as the recognition space is also seen in microfluidic devices, the use of membrane pores can achieve further miniaturization of the flow channel. In our membrane–based sensor, receptor molecule is densely immobilized inside the pores by using the plasma graft polymerization technique, which enables uniform grafting in the membrane thickness direction. Also, the detection time required for molecular recognition can be shortened by using solution flow through the membrane pores. This system is demonstrated via antigen (target molecule)–antibody (receptor) system, and it achieves superior signal characteristics to conventional ELISA with a detection time of 35 min. We expect that this new system aids the design of biosensing devices, and could be applied to various diagnostic areas including POCT.

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Microfiltration membranes of polyhydroxyalkanoate (PHA), a biodegradable biomass plastic, were prepared via nonsolvent–induced phase separation methods. Dimethylformamide (DMF) was found to be the best solvent for the preparation among the four solvents examined (DMF, 1,4–dioxane, N–methyl–2–pyrrolidone, and dimethylsulfoxide); water at 25 ℃ was used as a nonsolvent. The polymer concentrations and casting temperatures were examined at 10% ～ 20% and 40 ～ 60 ℃, respectively. The surface pore size of the top surface of the asymmetric structure was found to depend on the polymer concentration and casting temperature. When the membrane was prepared at a polymer concentration of 18% and a casting temperature of 50 ℃, the membrane resistance and retention toward 0.3–m latex beads were 4.0 × 109 m–1 and 99%, respectively. The PHA membrane was stable at 25 ℃ even under wet conditions and degraded at 60 ℃ under wet conditions. The membranes developed from biodegradable biomass plastics will be useful as degradable filters to reduce filter media waste in food and biochemical industries by composting membranes containing foulants after filtration.

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Poly(vinylidene difluoride) (PVDF) is the main stream material for water treatment membrane. Thermally induced phase separation (TIPS) is frequently used as a manufacturing technology to produce a porous membrane. In phase separation technology, polymeric additives can be added to control the pore structure of the porous membranes. In this study, in order to clarify the functions of the polymeric additives such as Poly(ethylene glycol) (PEG) and Poly(vinyl pyrrolidone) (PVP) in the PVDF TIPS process, phase diagrams were prepared on TIPS process. In addition, cast films were prepared using dopes whose phase diagrams were prepared, and their surface structures were observed by SEM analysis. As a result, we clarified the mechanisms for controlling the pore structures of PVDF by selection of polymeric additives.

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Brine concentration is becoming quite important and high–in–demand due to increased strict regulations and environmental concerns. Current technologies available for brine concentration are thermal–based technologies and membrane–based ones like reverse osmosis (RO). Thermal–based technologies can theoretically concentrate solutions up to saturated concentration, but the energy consumption is too high due to a phase change from liquid to gas. On the other hand, RO can concentrate solutions up to 7 w/w% with far less energy consumption than thermal–based ones thanks to its non–phase change process. Thus, current available brine concentration technologies can’t achieve both high concentration and low energy consumption at the same time. In this paper, we wish to introduce Toyobo’s newly developed hollow fiber “Brine Concentration Membrane” which can concentrate solutions up to 20 w/w% with far less energy than current available technologies. Also, we have developed a laboratory testing unit for brine concentration membrane recently.

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