Green solvents for Novolac-based carbon membranes production

Over the last three decades, carbon membranes (CMs) have gained attention as technology for gas separation. However, their fabrication often involves toxic and hazardous solvents with significant environmental impact, like N-methyl-2-pyrrolidone (NMP). In this work, Novolac-based CMs were developed using two greener and safer organic solvents, Cyrene™ and γ-valerolactone (GVL). Single gas permeation tests with He, H₂, N₂ and CH₄ were conducted at temperatures from 20 °C to 200 °C and pressure differences (ΔP) between 1 and 5 bar. GVL led to the best performing CM, achieving an ideal selectivity of 340 the H₂/CH₄ system at 20 °C. The GVL-derived CM exhibited a pore size distribution similar to that of the NMP-derived one, with 85.6 % ultra-micropores, 13.7 % micropores and 0.7 % mesopores. Raman spectroscopy, organic elemental analysis (OEA) and perm-porometry confirmed structural and chemical differences among the CMs fabricated with different solvent. This study highlights the potential of GVL as a safer and greener solvent for fabricating H₂-selective Novolac-based CMs, representing a step forward towards a more sustainable CMs production.