Marek Lanč

Triptycene Induced Enhancement of Membrane Gas Selectivity for Microporous Tröger's Base Polymers

A highly gas permeable polymer with exceptional size selectivity is prepared by fusing triptycene units together via a poly-merization reaction involving Trögers base formation. The extreme rigidity of this polymer of intrinsic microporosity (PIM-Trip-TB) facilitates gas permeability data that lie well above the benchmark 2008 Robeson upper bounds for the important O2 /N2 and H2 /N2 gas pairs.

A highly permeable polyimide with enhanced selectivity for membrane gas separations

A highly gas permeable polyimide with improved molecular sieving properties is produced by using a bisanhydride monomer based on the rigid ethanoanthracene unit. The polymer (PIM-PI-EA) demonstrates enhanced selectivity for gas separations so that its gas permeability data lie above the 2008 Robeson upper bounds for the important O2–N2, H2–N2, CO2–CH4 and CO2–N2 gas pairs.

A highly rigid and gas selective methanopentacene-based polymer of intrinsic microporosity derived from Tröger's base polymerization

Polymers of intrinsic microporosity (PIMs) have been identified as potential next generation membrane materials for the separation of gas mixtures of industrial and environmental relevance. Based on the exceptionally rigid methanopentacene (MP) structural unit, a Polymer of Intrinsic Microporosity (PIM-MP-TB) was designed to demonstrate high selectivity for gas separations. PIM-MP-TB was prepared using a polymerisation reaction involving the formation of Trogers base linking groups and demonstrated an apparent BET surface area of 743 m2 g−1 as a powder. The microporosity of PIM-MP-TB was also characterized by chain packing simulations. PIM-MP-TB proved soluble in chlorinated solvents and was cast as a robust, free-standing film suitable for gas permeation measurements. Despite lower gas permeability as compared to previously reported PIMs, high selectivities for industrially relevant gas pairs were obtained, surpassing the 2008 Robeson upper bound for H2/CH4 and O2/N2, (e.g., PO2 = 999 Barrer; αO2/N2 = 5.0) and demonstrating a clear link between polymer rigidity and selectivity. Upon aging, the permeability data move parallel to the Robeson upper bounds with a decrease of permeability, compensated by a related increase in selectivity. Mixed gas permeation measurement for CO2/CH4 and CO2/N2 mixtures confirmed the excellent selectivity of PIM-MP-TB for potentially relevant separations such as biogas upgrading and CO2 capture from flue gas. Importantly, unlike other high performing PIMs, PIM-MP-TB is prepared in four simple steps from a cheap starting material.

Thin high flux self-standing graphene oxide membranes for efficient hydrogen separation from gas mixtures

The preparation and gas-separation performance of self-standing, high-flux, graphene oxide (GO) membranes is reported. Defect-free, 15-20 μm thick, mechanically stable, unsupported GO membranes exhibited outstanding gas-separation performance towards H2 /CO2 that far exceeded the corresponding 2008 Robeson upper bound. Remarkable separation efficiency of GO membranes for H2 and bulky C3 or C4 hydrocarbons was achieved with high flux and good selectivity at the same time. On the contrary, N2 and CH4 molecules, with larger kinetic diameter and simultaneously lower molecular weight, relative to that of CO2 , remained far from the corresponding H2 /N2 or H2 /CH4 upper bounds. Pore size distribution analysis revealed that the most abundant pores in GO material were those with an effective pore diameter of 4 nm; therefore, gas transport is not exclusively governed by size sieving and/or Knudsen diffusion, but in the case of CO2 was supplemented by specific interactions through 1) hydrogen bonding with carboxyl or hydroxyl functional groups and 2) the quadrupole moment. The self-standing GO membranes presented herein demonstrate a promising route towards the large-scale fabrication of high-flux, hydrogen-selective gas membranes intended for the separation of H2 /CO2 or H2 /alkanes.

Poly(imide-siloxane)s based on hyperbranched polyimides

Abstract Poly(imide-siloxane)s differing in their composition were prepared and characterized. The starting polymer (control) was the hyperbranched polyimide based on 4,4′-oxydiphthalic anhydride and 4,4′,4″-triaminotriphenylmethane. In the poly(imide-siloxane)s, 10 or 40–50 mol% of the 4,4′,4″-triaminotriphenylmethane was theoretically substituted for by amine-terminated siloxane dimer or oligomers. 1,3-Bis(3-aminopropyl)-1,1,3,3-tetramethyldisiloxane, bis(3-aminopropyl)-terminated poly(dimethylsiloxane) with a theoretical number-average molar mass of 1000 g·mol−1 and bis(3-aminopropyl)-terminated poly(dimethylsiloxane) with a theoretical number-average molar mass of 2500 g·mol−1 were used for this purpose. The thermo-mechanical properties and gas separation characteristics for hydrogen, carbon dioxide and methane of these polymeric products were shown to be dependent on their composition.

A Novel Time Lag Method for the Analysis of Mixed Gas Diffusion in Polymeric Membranes by On-Line Mass Spectrometry: Pressure Dependence of Transport Parameters

This paper presents a novel method for transient and steady state mixed gas permeation measurements, using a quadrupole residual gas analyser for the on-line determination of the permeate composition. The on-line analysis provides sufficiently quick response times to follow even fast transient phenomena, enabling the unique determination of the diffusion coefficient of the individual gases in a gas mixture. Following earlier work, the method is further optimised for higher gas pressures, using a thin film composite and a thick dense styrene-butadiene-styrene (SBS) block copolymer membrane. Finally, the method is used to calculate the CO2/CH4 mixed gas diffusion coefficients of the spirobisfluorene-based polymer of intrinsic microporosity, PIM-SBF-1. It is shown that the modest pressure dependence of the PIM-SBF-1 permeability can be ascribed to a much stronger pressure dependence of the diffusion coefficient, which partially compensates the decreasing solubility of CO2 with increasing pressure, typical for the strong sorption behaviour in PIMs. The characteristics of the instrument are discussed and suggestions are given for even more versatile measurements under stepwise increasing pressure conditions. This is the first report on mixed gas diffusion coefficients at different pressures in a polymer of intrinsic microporosity.