Synthesis and characterization of a high-performance bio-based Pebax membrane for gas separation applications

Abstract

Bio-based polymers with at least a portion of the polymer derived from renewable raw materials have been the subject of research due to the increasing worldwide inclination towards sustainability. The synthesis of bio-based polymeric membranes is required to reduce dependency on fossil fuels. Pebax® Rnew® 30R51 (Pebax Rnew) is a type of bio-based polymer consisting of polyether segments and polyamide segments, wherein the polyamide segments are obtained from renewable sources. This study focuses on synthesizing and characterizing Pebax Rnew membranes for gas separation applications. Pebax Rnew was dissolved in a solvent mixture of 1-butanol and 1-propanol and cast on a Petri dish, followed by complete solvent evaporation. Free-standing dense membranes of 2 wt%, 4 wt%, 6 wt% and 8 wt% polymer solution concentration were synthesized. Pure CO2, H2, CH4, N2 and O2 gas permeabilities were measured at ambient temperature and pressures varying from 2-10 bar, and the corresponding ideal selectivities were calculated. The synthesized membrane surface and cross-sectional morphologies were investigated by scanning electron microscopy. Thermogravimetric analysis, Fourier-transform infrared spectroscopy and X-ray diffraction studies were conducted to determine the thermal stability, intermolecular interactions and intersegment distance between the polymer chains. For a 6 wt% Pebax Rnew membrane, a high permeability of 205 Barrer was measured for CO2, whereas the CH4, O2 H2, and N2 permeabilities were 9.6, 8.1, 2.9 and 18.6 Barrer, respectively. With increasing pressure, the selectivity was enhanced from 65 to 91, 20 to 26 and 9.7 to 13.5 for CO2/N2, CO2/CH4 and CO2/H2 gas systems, respectively. This work provides scope for developing bio-based membranes comparable with existing membranes for different gas separation applications to achieve process targets.