A greener route to prepare PEBAX®1074 membranes for gas separation processes

Abstract

The solvent used in membrane fabrication is crucial for a potential industrial application, with a direct effect on its safety, environmental and economic impact. Thus, in the last years, the search for greener and safer solvents became of utmost importance aiming for a sustainable fabrication of highly performing membranes, since that also affects the final membrane morphology. Typically, solvent evaporation-based methods are used for the preparation of membranes for gas separation processes, such as dip-coating and spray coating methods. The advantage of this approach relies on the possibility of using greener non-toxic solvents, such as water and ethanol. However, an alternative route might involve the use of phase inversion methods. In this procedure, the selection of the solvent will play an even more important role, with an impact on the gas separation membrane properties. Small defects or structural changes will decisively alter the final membrane performance.In this work, it is presented for the first time the alternative use of a non-toxic and eco-friendly solvent, Rhodiasolv®Polarclean, for the preparation of CO2-selective PEBAX®-based membranes using a hybrid phase inversion method. This preliminary study evaluates the relationship between the fabrication protocol, with the resulting structural, thermal, and mechanical membrane properties for self-standing membranes. The gas separation performance was tested for different gases: H2, N2, O2, CO2 and CH4. This analysis also includes a comparison with the commonly used, although strongly restricted and hazardous, solvent N-Methyl-2-Pyrrolidone (NMP).