•A new method of using a platinum agent to pre-polymerize PDMS polymer is employed.•A thin silicalite-1-PDMS hybrid membrane with a selective layer of 5 µm is developed.•As much as 67 wt% silicalite-1 is incorporated in the thin composite membrane.•The thin composite membrane exhibits a PSI of 80.04 for PV of an ethanol–water mixture.•The composite membrane shows a strong interfacial binding force.Sedimentation of silicalite-1 occurs in the fabrication of thin silicalite-1 filled polydimethylsiloxane (PDMS) hybrid composite membranes if the viscosity of membrane solution is low, which makes this preparation challenging. In this work, a new method that use a platinum catalytic agent to assist the pre-polymerization of PDMS polymer to increase the viscosity of the membrane solution was studied. With this method, supported silicalite-1 filled PDMS hybrid composite membranes were fabricated and applied in the pervaporative separation of a 5 wt% dilute ethanol aqueous solution. The effect of the concentration of platinum catalytic agent on the membrane properties was first investigated using CRM, DSC and extraction experiment. Optimum of viscosity of the composite membrane solution was then conducted and a selective layer of as thin as 5 µm thickness was obtained with a flux of 5.52 kg/m2h in combination with a separation factor of 15.5 at 50 °C. After that the separation performances of different thick membranes, interfacial adhesion properties of hybrid membranes, comparisons with other reported results and membrane stability were investigated. Results showed homemade silicalite-1-PDMS hybrid composite membrane offers relatively high separation performance, indicating a potential industrial application for the separation of ethanol from aqueous solutions.

AbstractMicroporous polymer membranes continue to receive tremendous attention for energy-efficient gas separation processes owing to their high separation performances. A new network microporous polyamide membrane with good molecular-sieving performance for the separation of N2 from a volatile organic compound (VOC) mixture is described. Triple-substituted triptycene was used as the main monomer to form a fisherman's net-shaped polymer, which readily forms a composite membrane by solution casting. This membrane exhibited outstanding separation performance and good stability for the molecular-sieving separation of N2 over VOCs such as cyclohexane. The rejection rate of the membrane reached 99.2 % with 2098 Barrer N2 permeability at 24 °C under 4 kPa. This approach promotes development of microporous membranes for separation of condensable gases.

AbstractMicroporous polymer membranes continue to receive tremendous attention for energy-efficient gas separation processes owing to their high separation performances. A new network microporous polyamide membrane with good molecular-sieving performance for the separation of N2 from a volatile organic compound (VOC) mixture is described. Triple-substituted triptycene was used as the main monomer to form a fisherman's net-shaped polymer, which readily forms a composite membrane by solution casting. This membrane exhibited outstanding separation performance and good stability for the molecular-sieving separation of N2 over VOCs such as cyclohexane. The rejection rate of the membrane reached 99.2 % with 2098 Barrer N2 permeability at 24 °C under 4 kPa. This approach promotes development of microporous membranes for separation of condensable gases.

•A thin PDMS/PVDF composite membrane with a thickness of 6 μm is developed.•The thin composite membrane shows high performance for PV of a DMC–methanol mixture.•The more permeable DMC can increase the permeability of the less permeable methanol.In this paper, polydimethylsiloxane (PDMS) composite membranes that were supported using polyvinylidene fluoride (PVDF) microfiltration membrane were developed for the pervaporation (PV) of dimethyl carbonate (DMC) from a methanol solution. Experimental studies on the solubility and the diffusivity of pure DMC and methanol in the membrane were first measured. Higher DMC uptake indicates that the sorption step is the rate-limiting step in the selective transport through the membrane. By controlling the fabricating parameters such as the concentration of the casting membrane solution, composite membranes with different thicknesses from 3 to 160 μm were fabricated. When the composite membrane is defect-free, the separation factor is independent of its thickness. The composite membrane with a thickness of 6 μm exhibited a separation factor of 3.95 and a normalized total flux of 0.4872 kg/m2 h in the pervaporation of 28 wt% DMC–methanol mixture at 40 °C. In addition, the membrane swelling effects, pervaporation performance, and stability were investigated. The results of the PDMS composite membrane exhibited higher and more stable performance in separating DMC from the methanol solution. The PDMS composite membrane can be a suitable PV membrane to separate DMC from a methanol solution.

•Phase separation in the permeate during the pervaporation of an ABE–water solution was studied.•Approximately 68 wt% ABE in the organic phase was obtained when phase separation occurred.•Ethanol and acetone hindered the phase separation in the permeate.•Phase separation more easily occurred at higher temperatures in the ABE–water solution.When butanol and water are mixed at a proper ratio, phase separation can occur because of the immiscibility of butanol with water. A highly concentrated aqueous butanol solution in the organic phase can be obtained. Thus, in this study, the phase separation of the permeate was examined during pervaporation (PV) of an acetone–butanol–ethanol–water solution (ABE–water solution) to obtain a high permeate organic concentration. The effects of feed composition and operating temperatures on the phase separation of the permeate obtained during pervaporation of acetone–butanol–water and ethanol–butanol–water solutions were first evaluated with different membranes. Acetone and ethanol both hindered the phase separation of the permeate because of their miscibility with water and butanol. In the separation of the acetone–butanol–water solution, higher temperatures and lower acetone concentrations in the feed solution favored phase separation in the permeate, whereas for the ethanol–butanol–water solution, lower temperatures and lower ethanol concentrations in the feed solution led to relatively facile phase separation in the permeate. Pervaporation of a 1.5 wt% ABE–water solution with different membranes at different temperatures was also performed. When phase separation in the permeate occurred under proper conditions, the ABE concentration in the organic phase reached approximately 68 wt%.