Vapour permeation and sorption in fluoropolymer gel membrane based on ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulphonyl)imide

Abstract

The emissions of hydrocarbons from fossil fuels into atmosphere entail both an economic loss and an environmental pollution. Membrane separations can be used for vapour recovery and/or vapour removal from the permanent gas stream, given that the appropriate membrane is identified. A neat poly(vinylidene fluoride-co-hexafluoropropylene) membrane is impermeable to both the representatives of aliphatic hydrocarbons and branched hydrocarbons, namely hexane and isooctane, whereas the permeation flux is enhanced by the presence of 80 mass % of the ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulphonyl)imide in the membrane, as detailed in this work. The permeabilities of hydrocarbon vapours were determined from the binary mixture containing hydrocarbon and nitrogen to simulate the real input of an air stream containing a condensable hydrocarbon. The diffusion coefficient determined from sorption measurements was higher for hexane, as would be expected for a smaller molecule, whereas both the sorption isotherms and permeabilities of the hydrocarbons studied were found to be almost identical. It is possible that the sorption effect predominates in the transport mechanism for VOCs/N 2 separations.

Ethanol sorption and permeation in fluoropolymer gel membrane containing 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ionic liquid

“…The sorption uptakes of ethanol vapor in the IL membrane exceed the sorption uptakes in the neat polymer membrane at the same vapor activities about ten times. The sorption uptakes of ethanol in the IL membrane exceed those of hexane and isooctane [21] vapors about ten times, showing an apparently high affinity of ethanol to the ionic liquid. The ethanol uptake in the IL membrane increases with temperature, which occurs presumably due to the endothermic mixing of ethanol with the ionic liquid.…”

“…Ethanol permeation experiments were carried out at three temperatures, namely 25 C, 35 C, and 45 C. The test stand apparatus was described in detail in the previous work [21]. Circle membrane samples had the area of 40.72 cm 2 and the weight of IL membrane was 1.2581 g. The samples laid on a disc of sintered steel (1.6 mm thick) in a membrane cell.…”

“…However, the risk of the ionic liquid leakage has to be minimalized [15]. It can be achieved either by making a membrane from polymerizable ionic liquids or by immobilization of the ionic liquid in a polymeric material [16][17][18][19][20][21].…”

Comparison of Hexane Vapour Permeation in Two Different Polymeric Membranes via an Innovative In-line FID Detection Method

“…The basic test apparatus ( Figure 1) was described previously 10,11 , but has been significantly modified to extend the set of experimental data. The significant modification was based on the necessity of mass balance check.…”

“…Each membrane sample was placed on a disc of sintered stainless steel in a cross-flow membrane cell. The custom-made cell has a special design that allows radial flow profiles in co-current and counter-current mode, and has been described elsewhere 10,11,12 . The appropriate mixture of nitrogen with VOC vapour is prepared by bubbling nitrogen through a tempered glass one-stage custom made saturator until complete saturation of this stream, and subsequent mixing of this stream with a known amount of dry nitrogen until the desired activity.…”