Ondřej Vopička

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

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/N2 separations.

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.

Evaluation of Two Methods for Measuring Vapor Sorption in Polymers

In this paper, two methods for measuring the equilibrium vapor sorption in polymers are critically compared and data on sorption of toluene, p-xylene, hexane, cyclohexane, and heptane in low density polyethylene are reported. The vapor phase calibration method (VPC) was used to measure vapor sorption at low vapor activities in air (below 0.01), and the gravimetric method was used to measure sorption over wide range of activities of pure vapors (0.1–0.9). The Flory-Huggins interaction parameter (in amorphous phase) varied between 1.00 for cyclohexane and 1.19 for toluene. The resulting confidence intervals are conjunctive, indicating that both methods provide consistent results.

Cyclopentyl methyl ether, tert -amyl methyl ether and tert -butyl methyl ether: density, dynamic viscosity, surface tension and refractive index

This work presents densities, dynamic viscosities, surface tensions, and refractive indices of three methyl ethereal solvents: cyclopentyl methyl ether (CPME), tert-amyl methyl ether (TAME), and tert-butyl methyl ether (MTBE). CPME and TAME were chosen as methyl alternatives of the common but environmentally problematic MTBE. The highest density, viscosity, surface tension, and refractive index were observed for CPME and the lowest for MTBE. The results are in good agreement with other authors’ data. Based on the experiments, the critical temperature and the critical pressure of CPME were estimated. The parachor, molar refraction, and critical compressibility factor were calculated from experimental data. Parameterisations of the experimental data using corresponding correlative models are presented.Graphical abstract