Separação CO2/N2 usando membranas de matriz mista de sílica/PMDS: efeito do método sol-gel, teor de sílica e pressão do desempenho

Abstract

This study investigated CO2/N2 separation using mixed-matrix membranes (MMMs) produced by incorporating commercial silica (SC) particles or sol–gel-derived silica (LI05) into polydimethylsiloxane (PDMS), aiming to evaluate the impact of the silica synthesis route, filler loading, and feed pressure on transport properties and separation performance. MMMs were prepared with loadings between 1 and 15 wt% and evaluated through pure-gas permeation tests at 1 and/or 2 bar, using the time-lag method to estimate transport parameters. The membranes were also characterized to discuss dispersion and material properties, including microscopy, thermal analyses, and spectroscopy. The results showed that commercial silica simultaneously increased permeability and selectivity up to 10 wt%, with the 10 wt% SC membrane standing out by achieving a CO2 permeability of 2974 Barrer and a CO2/N2 selectivity of 11, corresponding to gains of 43% and 70%, respectively, relative to neat PDMS. For the sol–gel silica, an increase in permeability with a tendency toward selectivity loss at higher loadings was observed; the best performance was achieved by the 5 wt% membrane, with increases relative to the polymer of approximately 60% in permeability and 25% in selectivity. As silica loading increased, a trend of increasing diffusion coefficient and decreasing sorption coefficient was observed using the time-lag method. Comparisons with the Maxwell model indicated deviations from ideal behavior, suggesting a relevant interfacial contribution, potentially related to interfacial voids and their effects on transport.