Search

1,3‐Butadiene (BD) is a petrochemical‐based volatile organic compound, extensively used for the manufacture of synthetic rubber. There is no method reported for its recovery from nitrogen mixture. Herein, for the first time, BD is efficiently recovered by gas separation through facile and novel mixed‐metal ZIF‐8 based mixed matrix membranes (MMMs). Addition of Ni‐ZIF‐8 nanoparticles in PDMS matrix, significantly improved the penetrant‐membrane interactions and the solution‐diffusion properties of BD. Positron annihilation lifetime spectroscopy analysis showed that the well dispersion of Ni‐ZIF‐8 in PDMS enhanced the free volume of membrane and created efficient continuous paths for BD diffusion. Then, 15 wt% Ni‐ZIF‐8 MMM exhibited the BD permeance of 323 GPU and the BD/N2 ideal selectivity of 19.5, which were 60 and 81% higher than pure PDMS membrane, respectively. The simultaneous enhancement of BD permeance and BD/N2 ideal selectivity indicated that Ni‐ZIF‐8 was an effective filler applied in MMMs for efficient BD recovery. [ABSTRACT FROM AUTHOR]

High porosity and large pore volume of MIL-101 MOF makes it a potential material to be used in membrane separation technology. However, the extra-large pore size and natural hydrophilicity restrict its application in the organic perm-selective pervaporation process. To overcome this issue, Herein, we successfully synthesized ILs@MOFs composite by modifying MIL-101 via coordinative covalent grafting of designed hydrophobic ionic liquids (ILs). Later on, synthesized ILs-modified MIL-101 was embedded into poly (ether-block-amide) (PEBA) polymer to fabricate mixed matrix membranes (MMMs) for ethyl acetate perm-selective pervaporation. Incorporation of ILs within the cages and over the surface of MIL-101 not only successfully tuned the pore structure and surface properties of MIL-101 but also inhibits the formation larger aggregates with no obvious defects in resultant MMMs. Moreover, molecular simulation verified that the grafted ILs endowed MIL-101 with better adsorption ability for ethyl acetate and improved interfacial compatibility with PEBA. The optimized MMMs exhibited outstanding separation performance for 5 wt% feed solution at 30 °C, with a separation factor of 207.6 and normalized total flux of 51.8 kg·μm·m−2·h−1. Compared with the pure PEBA membrane, the separation factor and ethyl acetate flux increased by 205.7% and 129.5%, respectively, while the MMMs embedding original MIL-101 showed a decrease in separation factor. This study may inspire the design and construction of high-performance MMMs by employing modification in porous nanomaterial microstructure. Image 1 • Grafting of hydrophobic ILs into MIL-101 via coordination covalent bonds. • Precisely regulating of MIL-101 pore structure and surface properties. • Molecular simulation verified the better adsorption ability of ILs modified MIL-101. • Ameliorative interfacial compatibility between ILs modified MIL-101 and PEBA. • Resultant membranes with superior ethyl acetate perm-selective performance. [ABSTRACT FROM AUTHOR]

With the help of density functional theory calculations, a unique MOF-capped nanotube architecture was initially conceived in this study based on the solution-diffusion mechanism. Then, the novel ZIF-8-capped halloysite nanotubes (ZHNTs) were prepared and incorporated in the polydimethylsiloxane (PDMS) bulk to achieve the mixed matrix membranes (MMMs) for n -butanol permselective pervaporation. The remarkable characteristic of this membrane was that the HNT lumen (∼25 nm) in ZHNTs provided the exquisite diffusion highway for the penetrants that were first selected through the capping ZIF-8 layer. Simultaneously, the close connection of ZIF-8 layer on external surface of ZHNTs created the relatively continuous pathways for molecular permeation. As expected, the embedding ZHNTs significantly improved the separation performances of the membranes. Impressively, the as-obtained membrane acquired a high separation factor of 61.3 (58.7% higher than that of PDMS control membrane) with a comparable flux of 683 g m-2 h-1 (2.43-fold as much as that of PDMS control membrane) at 40 °C in the separation of 1 wt% n -butanol aqueous solution. Moreover, the presence of ZHNTs conferred excellent interfacial compatibility, mechanical properties, and good long-term stability on the resultant membranes. This study may shed light on the rational design of high-performance MMMs for biofuels recovery from fermentation broths. Image 1 • Novel MOF-capped tubular architecture was conceived relying on DFT calculations. • ZIF-8-capped HNTs nanotubes (ZHNTs) were incorporated in PDMS bulk to prepare MMMs. • ZHNTs constructed relatively continuous permeation pathways for penetrants. • Trade-off in PV membrane was facilely addressed by incorporating ZHNTs. • Embedding ZHNTs notably reduced permeation energy barriers for penetrants. [ABSTRACT FROM AUTHOR]

Polymeric membrane separations have been used for hydrocarbon recovery in some polyolefin plants due to the low energy consumption and easy operation, but the relatively low separation factor and hydrocarbon permeance block their ways to popularization. In this study, membranes with high propylene permeance and sufficient separation factor for propylene/nitrogen separation were prepared by direct incorporating 2-methylimidazole (MIM) into polydimethylsiloxane (PDMS), which manifested simultaneous promotion of separation factor and propylene permeance. Interestingly, MIM simultaneously acted in promoting the crosslinking process of PDMS and tetraethyl orthosilicate. A series of tests and characterizations were conducted to investigate the microstructure, morphology, thermal property, and mass transfer property of the membranes. The gas separation performance of the MIM-incorporated PDMS membrane with a separation factor of 20.2 and propylene permeance of 440.9 GPU outperformed many other propylene-selective membranes reported in the literature. Molecular dynamics simulations revealed that MIM had a preferential affinity for propylene rather than nitrogen, which was similar to PDMS, but the propylene-affinity of MIM was significantly higher than that of PDMS, accounting for the promoted separation of propylene/nitrogen upon the incorporation of MIM. The MIM-incorporated PDMS membranes with readily available, cheap materials and straightforward manufacturing procedures should be a promising alternative for hydrocarbon recovery. It is also enlightening for the study and design of membrane materials for gas separation. [Display omitted] • 2-Methylimidazole (MIM) was directly incorporated into PDMS membranes. • MIM accelerated the crosslinking reaction of PDMS prepolymer. • Separation factor and permeance of C 3 H 6 were simultaneously promoted by MIM. • MD simulation reveals MIM has a higher preferential propylene-affinity than PDMS. [ABSTRACT FROM AUTHOR]