Gabriele Clarizia

Nanoporous Organic Polymer/Cage Composite Membranes

Organic?organic composite membranes are prepared by in?situ crystallization of cage molecules in a polymer of intrinsic microporosity. This allows a direct one-step route to mixed-matrix membranes, starting with a homogeneous molecular solution. Extremely high gas permeabilities are achieved, even after ageing for more than a year, coupled with good selectivity for applications such as CO2 recovery.

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.

Enhancement of CO2 Affinity in a Polymer of Intrinsic Microporosity by Amine Modification.

Nitrile groups in the polymer of intrinsic microporosity PIM-1 were reduced to primary amines using borane complexes. In adsorption experiments, the novel amine–PIM-1 showed higher CO2 uptake and higher CO2/N2 sorption selectivity than the parent polymer, with very evident dual-mode sorption behavior. In gas permeation with six light gases, the individual contributions of solubility and diffusion to the overall permeability was determined via time-lag analysis. The high CO2 affinity drastically restricts diffusion at low pressures and lowers CO2 permeability compared to the parent PIM-1. Furthermore, the size-sieving properties of the polymer are increased, which can be attributed to a higher stiffness of the system arising from hydrogen bonding of the amine groups. Thus, for the H2/CO2 gas pair, whereas PIM-1 favors CO2, amine–PIM-1 shows permselectivity toward H2, breaking the Robeson 2008 upper bound.

A study on a perfluoropolymer purification and its application to membrane formation

Abstract In this work, a study on a perfluoropolymer purification with crossflow MF and UF, using commercial membranes, has been carried out. Copolymers of tetrafluoroethylene (TFE) and 2,2,4trifluoro, 5trifluorometoxy 1,3 dioxide (TTD), known commercially as HYFLON® AD, are highly transparent to light from deep UV to near infrared, so they find applications in optic and electronic industries, such as plastic optical fibers (POF), anti-reflective coating and protective pellicles in manufacturing semi-conductor. For the above application, it is often crucial to avoid the presence of both suspended and dissolved contaminants in the polymer and polymeric solutions. Membranes made from this amorphous perfluoropolymer were prepared in flat sheet, tubular and hollow fiber forms. Tests of membrane hydrophobic character and of pure gas permeability were carried out. Experimental gas separation data obtained with membranes prepared with TTD–TFE co-polymers and data from the literature on membranes made with co-polymers of perfluoro2,2dimethyldioxide (PDD) and TFE, commercially known as TEFLON® AF, revealed an interesting linear relationship between permeation and glass transition temperature Tg. The voids volume fraction (Φv) of the above amorphous perfluoropolymers was also estimated from the difference between the experimental polymer density and a theoretical density obtained by simple calculations using the group contribution method.

Synthesis of cardo-polymers using Tröger's base formation

A series of novel cardo-polymers was prepared using a polymerisation reaction based on Trogers base formation. The precursor dianiline monomers are readily available from the reactions between appropriate anilines and cyclic ketones. One adamantyl-based cardo-polymer displays intrinsic microporosity with an apparent BET surface area of 615 m2 g−1. This polymer demonstrates a combination of good solubility and high molecular mass facilitating the solvent casting of robust films suitable for gas permeability measurements. The intrinsic microporosity of the polymer provides high gas permeabilities and moderate selectivities with particular promise for gas separations involving hydrogen.

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.

Membrane air separation for intensification of coal gasification process

Abstract High-ash and other low-quality coals are available in huge quantities in Russia and in other East European countries. Similar solid fuels can also be obtained as by-product of the enrichment process of coal. The aim of this work is the analysis of the possibility to use such low-quality coals as alternative energy sources in fluidised bed gasification process. In order to intensify gasification process in conditions where possible ash melting is avoided, it is proposed to use oxygen-enriched air (OEA) instead of air as a blow and gasification agent. The supply of OEA as fluidisation medium can be beneficial in other respects: it allows to burn at least a part of fly ash before they leave the furnace, thus improving energy efficiency and ecological impacts of the process. In this paper, the first successful example of combination of membrane air separation and coal gasification process is given. This paper summarises the performance of coal gasification in the presence of different oxygen/nitrogen mixtures as a blow for processing of low-quality (high moisture content) coal. The optimal content of O 2 in the blow is in the range 27–33% v/v. The heating value of synthesis gas obtained in optimal conditions was in the range 3.5–4.7 MJ/m 3 (STP). In second part of the paper, the performance of several membranes available for cheap and efficient air separation is analysed and, after comparing them, recommendations on appropriate selection of membrane type and module needed are given.

The influence of few-layer graphene on the gas permeability of the high-free-volume polymer PIM-1.

Gas permeability data are presented for mixed matrix membranes (MMMs) of few-layer graphene in the polymer of intrinsic microporosity PIM-1, and the results compared with previously reported data for two other nanofillers in PIM-1: multiwalled carbon nanotubes functionalized with poly(ethylene glycol) (f-MWCNTs) and fused silica. For few-layer graphene, a significant enhancement in permeability is observed at very low graphene content (0.05 vol.%), which may be attributed to the effect of the nanofiller on the packing of the polymer chains. At higher graphene content permeability decreases, as expected for the addition of an impermeable filler. Other nanofillers, reported in the literature, also give rise to enhancements in permeability, but at substantially higher loadings, the highest measured permeabilities being at 1 vol.% for f-MWCNTs and 24 vol.% for fused silica. These results are consistent with the hypothesis that packing of the polymer chains is influenced by the curvature of the nanofiller surface at the nanoscale, with an increasingly pronounced effect on moving from a more-or-less spherical nanoparticle morphology (fused silica) to a cylindrical morphology (f-MWCNT) to a planar morphology (graphene). While the permeability of a high-free-volume polymer such as PIM-1 decreases over time through physical ageing, for the PIM-1/graphene MMMs a significant permeability enhancement was retained after eight months storage.

Carbon nanotube- and carbon fiber-reinforcement of ethylene-octene copolymer membranes for gas and vapor separation.

Gas and vapor transport properties were studied in mixed matrix membranes containing elastomeric ethylene-octene copolymer (EOC or poly(ethylene-co-octene)) with three types of carbon fillers: virgin or oxidized multi-walled carbon nanotubes (CNTs) and carbon fibers (CFs). Helium, hydrogen, nitrogen, oxygen, methane, and carbon dioxide were used for gas permeation rate measurements. Vapor transport properties were studied for the aliphatic hydrocarbon (hexane), aromatic compound (toluene), alcohol (ethanol), as well as water for the representative samples. The mechanical properties and homogeneity of samples was checked by stress-strain tests. The addition of virgin CNTs and CFs improve mechanical properties. Gas permeability of EOC lies between that of the more permeable PDMS and the less permeable semi-crystalline polyethylene and polypropylene. Organic vapors are more permeable than permanent gases in the composite membranes, with toluene and hexane permeabilities being about two orders of magnitude higher than permanent gas permeability. The results of the carbon-filled membranes offer perspectives for application in gas/vapor separation with improved mechanical resistance.