Mixed matrix membranes based on torlon® and ZIF-8 for high-temperature, size-selective gas separations

Torlon® is a thermally and plasticization-resistant polyamide imide characterized by low gas permeability at room temperature. In this work, we aimed at improving the polymer performance in the thermally-enhanced He/CO2 and H2/CO2 separations, by compounding Torlon® with a highly permeable filler, ZIF-8, to fabricate Mixed Matrix Membranes (MMMs). The effect of filler loading, gas size, and temperature on the MMMs permeability, diffusivity, and selectivity was investigated. The He permeability increased by a factor of 3, while the He/CO2 selectivity decreased by a factor of 2, when adding 25 wt % of ZIF-8 at 65◦C to Torlon®; similar trends were observed for the case of H2. The MMMs permeability and size-selectivity were both enhanced by temperature. The behavior of MMMs is intermediate between the pure polymer and pure filler ones, and can be described with models for composites, indicating that such materials have a good polymer/filler adhesion and their performance could be tailored by acting on the formulation. The behavior observed is in line with previous investigations on MMMs based on glassy polymers and ZIF-8, in similar conditions, and indicates that ZIF-8 can be used as a polymer additive when the permeability is a controlling aspect, with a proper choice of loading and operative temperature

Polymer ultrapermeability from the inefficient packing of 2D chains

The promise of ultrapermeable polymers, such as poly(trimethylsilylpropyne) (PTMSP), for reducing the size and increasing the efficiency of membranes for gas separations remains unfulfilled due to their poor selectivity. We report an ultrapermeable polymer of intrinsic microporosity (PIM-TMN-Trip) that is substantially more selective than PTMSP. From molecular simulations and experimental measurement we find that the inefficient packing of the two-dimensional (2D) chains of PIM-TMN-Trip generates a high concentration of both small (<0.7 nm) and large (0.7–1.0 nm) micropores, the former enhancing selectivity and the latter permeability. Gas permeability data for PIM-TMN-Trip surpass the 2008 Robeson upper bounds for O2/N2, H2/N2, CO2/N2, H2/CH4 and CO2/CH4, with the potential for biogas purification and carbon capture demonstrated for relevant gas mixtures. Comparisons between PIM-TMN-Trip and structurally similar polymers with three-dimensional (3D) contorted chains confirm that its additional intrinsic microporosity is generated from the awkward packing of its 2D polymer chains in a 3D amorphous solid. This strategy of shape-directed packing of chains of microporous polymers may be applied to other rigid polymers for gas separations

Ageing of membrane contactors for post-combustion carbon dioxide capture in amine solvents : comparison between microporous and composite hollow fibers

International audienc

Optimization of the fabrication of amidoxime modified PIM-1 electrospun fibres for use as breathable and reactive materials

This study reports the preparation of waterproof/breathable films based on amidoxime functionalized PIM-1, which were processed into fibrous membrane using the electrospinning process with a green solvent, i.e. dimethyl sulfoxide. The influence of the feed solution (polymer concentration, solvent nature, presence of salt) and the electrospinning process conditions (flow rate, distance between the tip and the collector and voltage) has been investigated in order to obtain bead-free, thin fibres with regular structure and low porosity. The addition of salt allowed the production of nanofibres at low polymer concentration, resulting in the fabrication of fibrous mats with 1.5 μm diameter fibres and porosity below 10 μm. These fibre mats possess a hydrophobic character with a contact angle superior to 90°. Moreover, they are breathable, but not permeable to liquid water, which is essential for use within protective gear (i.e. gas masks or protective clothing)

Contacteurs membranaires pour le captage de CO2

International audienc