Preparation of a swelling-resistant polyethyleneimine-based pervaporation membrane via surface gradient crosslinking for the separation of methanol/dimethyl carbonate

Dimethyl carbonate (DMC) was widely used as an environmentally friendly organic compound. However, the production process of DMC generated a methanol (MeOH)/DMC azeotrope, which increased the separation cost. Pervaporation technology was considered a promising method for the separation of MeOH/DMC. Based on the polarity differences between MeOH and DMC, polyethyleneimine (PEI) with abundant polar groups (NH₂) was selected as the membrane material for the separation of MeOH/DMC. We enhanced the organic solvent swelling resistance of PEI through in situ growth of SiO₂ and surface gradient crosslinking modifications. The results demonstrated that both the in-situ growth of SiO₂ and the surface gradient crosslinking modification significantly improved the membrane’s resistance to organic solvent swelling. However, the surface gradient crosslinking was the primary factor contributing to the enhancement. The membrane performance is optimized by adjusting the PEI concentration, TEOS concentration, TEOS reaction time, TMC concentration, and TMC crosslinking time. The prepared membrane achieved a flux of 0.9 kg·m⁻²·h⁻¹, with a separation factor of 54, and maintained stable operation for 50 h.