Ionic liquid membranes for carbon dioxide-methane separation

The transport of carbon dioxide and methane in polymer containing ionic liquid was studied by a dynamic gas permeation method. Poly(vinylidene fluoride-co-hexafluoropropylene) polymeric membrane (Viton) and two ionic liquids 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [hmim][Tf(2)N]) and 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide [emim][Tf(2)N]) were used for preparation of ionic liquid membranes (ILM) with different ionic liquid amounts (from 0 to 80 wt%). For the better understanding of transport mechanism through ionic liquid membranes it is very useful to know also transport properties of pure ionic liquids and pure polymeric material. The gas transport through pure ionic liquid was determined indirectly, by means of the gas transport measurement through two special types of membranes: "sandwich arrangement" and "support arrangement". The dependencies of the separation factor and gas fluxes on the ionic liquid amounts in ionic liquid membranes were determined. The gas permeability increased with the ionic liquid [emim][Tf(2)N] content in the membrane, the permeability for the membranes with [hmim][Tf(2)N] exhibits the maximum for IL concentration of 70 wt%. Ideal separation factor CO(2)/CH(4) was low for small contents of ILs in membranes (0-15 wt%), around 7 for [emim][Tf(2)N] and 8 for [hmim][Tf(2)N] but for higher contents (30-75 wt%) it was approximately constant, 15 for [emimj[Tf(2)N] and 12 for [hmim][Tf(2)N]. Very interesting is the comparison of carbon dioxide permeability, it increases in the series: polymer, ionic liquid and ionic liquid membrane. Although the transport properties values of ILM were expected to be in the middle of the ionic liquid and the polymer from which were formed, surprisingly the obtained transport properties of ILM are much better than those for the pure components. For example, the carbon dioxide permeability for the ionic liquid membrane with 70 wt% of [hmim][Tf(2)N] is almost thousand times higher than for the pure polymer, and hundred times higher than for the ionic liquid. This fact indicates that the mechanism of the transport in ionic liquid membranes has to be different from the transport mechanisms in an ionic liquid. An explanation could be that "new transport pores" are created between polymer chains and an ionic liquid. (C) 2011 Elsevier BM. All rights reserved

Interfacial interaction between CMS layer and substrate: Critical factors affecting membrane microstructure and H-2 and CO2 separation performance from CH4

The claim that quality of membrane fabrication is based on surface smoothness of substrate has been known since the 1960s. In this study, we propose a concept based on the interfacial interaction between the carbon molecular sieving (CMS) selective layer and the Al2O3 substrate to understand the development of the CMS membrane's micro-structure at the molecular level, especially for natural gas purification. We further compare the results with those of our previous work to determine the dominant influence on the structural development of CMS membranes, and discover a remarkable enhancement in H2/CH4 and CO2/CH4 gas pair separation performances that surpass the upper limit for polymer membranes proposed by Robeson. Permselectivity performance was found to be strongly related to substrate properties, and especially to the surface roughness. When TiO2 intermediately layer and polishing technology was used to modify the roughness of the substrate, the supported CMS membrane displayed an improvement of 364% and 144% (or 720.1 ± 16.0 and 86.3 ± 5.1) in H2/CH4 and CO2/CH4 selectivities, respectively, when compared to bare alumina-supported membranes prepared under the same conditions; the H2 permeability also increased from 537.5 to 566.1 Barrer. These results indicated an important connection between the substrate structure and the performance of the CMS membranes, providing a new understanding of the influence of each preparation parameter and a route to tailoring the structure of CMS membranes that benefit gas separation applications

Polymer Nanocomposite Membranes

Based on the results of research works reflected in the scientific literature, the main examples, methods and approaches to the development of polymer inorganic nanocomposite materials for target membranes are considered. The focus is on membranes for critical technologies with improved mechanical, thermal properties that have the necessary capabilities to solve the problems of a selective pervaporation. For the purpose of directional changes in the parameters of membranes, effects on their properties of the type, amount and conditions of nanoparticle incorporation into the polymer matrix were analyzed. An influence of nanoparticles on the structural and morphological characteristics of the nanocomposite film is considered, as well as possibilities of forming transport channels for separated liquids are analyzed. Particular attention is paid to a correlation of nanocomposite structure-transport properties of membranes, whose separation characteristics are usually considered within the framework of the diffusion-sorption mechanism

Synthesis, Characterization, and Gas Adsorption Performance of Amine-Functionalized Styrene-Based Porous Polymers

In recent years, porous materials have been extensively studied by the scientific community owing to their excellent properties and potential use in many different areas, such as gas separation and adsorption. Hyper-crosslinked porous polymers (HCLPs) have gained attention because of their high surface area and porosity, low density, high chemical and thermal stability, and excellent adsorption capabilities in comparison to other porous materials. Herein, we report the synthesis, characterization, and gas (particularly CO2) adsorption performance of a series of novel styrene-based HCLPs. The materials were prepared in two steps. The first step involved radical copolymerization of divinylbenzene (DVB) and 4-vinylbenzyl chloride (VBC), a non-porous gel-type polymer, which was then modified by hyper-crosslinking, generating micropores with a high surface area of more than 700 m2 g−1. In the following step, the polymer was impregnated with various polyamines that reacted with residual alkyl chloride groups on the pore walls. This impregnation substantially improved the CO2/N2 and CO2/CH4 adsorption selectivity