Prospect of oxyplus hollow fibre membrane with dense polymethylpentene (PMP) skin as support-gutter layer of thin film composite (TFC) for biogas upgrading

Abstract

High selective polymers are bound to exhibit low intrinsic permeability. To mitigate this issue, thin film composite (TFC) membrane has been proposed whereby high selectivity, low permeability thin polymer layers are deposited on top of a thicker, highly permeable (even porous) materials. Nevertheless, deposition of thin film can be complicated on these structures due to limitation of fabrication methods (pore intrusion and support resistance to thin film solvent) and/or reduction of permeation efficiency (lateral diffusion). In this work, the potential of commercial Oxyplus® hollow fibre membrane as support-gutter layer was studied. Polymethylpentene (PMP), the material of the dense skin in Oxyplus has high gas permeability yet glassy enough to be selfstanding, making it a possible candidate as a combined support-gutter layer. Ten fibres were potted together, assembled into a module, and tested in dead-end mode under 1-5 bar transmembrane pressure for CO2, CH4 and N2 gases. The permeances were registered at 607.3 ± 31.3 GPU, 156.0 ± 13.1 GPU, and 84.6 ± 6.2 GPU, respectively, equivalent to a separation factor of 7.4 ± 0.4 (CO2/N2), 4.0 ± 0.2 (CO2/CH4) and 0.6 ± 0.1 (N2 /CH4). With dense skin layer thickness of 0.1 ± 0.1 μm, these values are comparable to the PMP results in literatures and are suitable as support-gutter layer for low permeability polymers such as P84® polyimide.