Preparation and Characterization of High-Performance Perfluorosulfonic Acid/SiO₂ Nanofibers with Catalytic Property via Electrospinning

Polymer nanofiber-supported perfluorosulfonic acid (PFSA)/SiO₂ catalysts are successfully fabricated by electrospinning method from polymer/nanoparticle suspensions. This kind of catalyst has a large number of active acid sites and high specific surface area up to 85.6 m²/g. Scanning electron microscope images reveal that the catalysts present high porosity and inner-connected porous structure which varies much with SiO₂ loading. Nitrogen adsorption–desorption measurements demonstrate a wide distribution of pore sizes inside the composites. Catalysts of different compositions are evaluated in esterification in a batch reactor under various conditions, and the results indicate that those of 20 wt % PFSA loading have the best activity of unit PFSA. Supporting PFSA by a nanofibrous matrix enhances liquid holdups inside the catalysts and offers accessibility of the acid sites, and therefore improves the activity of the catalysts. Moreover, these catalysts allow recovery at high percentages and regeneration with high activity

Processing–Structure–Property Correlations of Polyethersulfone/Perfluorosulfonic Acid Nanofibers Fabricated via Electrospinning from Polymer–Nanoparticle Suspensions

Polyethersulfone (PES)/perfluorosulfonic acid (PFSA) nanofiber membranes were successfully fabricated via electrospinning method from polymer solutions containing dispersed calcium carbonate (CaCO₃) nanoparticles. ATR-FTIR spectra indicated that the nanoparticles mainly existed on the external surface of the nanofibers and could be removed completely by acid treatment. Surface roughness of both the nanofibers and the nanofiber membranes increased with the CaCO₃ loading. Although FTIR spectra showed no special interaction between sulfonic acid (−SO₃) groups and CaCO₃ nanoparticles, XPS measurement demonstrated that the content of −SO₃ groups on external surface of the acid-treated nanofibers was enhanced by increasing CaCO₃ loading in solution. Besides, the acid-treated nanofiber membranes were performed in esterification reactions, and exhibited acceptable catalytic performance due to the activity of −SO₃H groups on the nanofiber surface. More importantly, this type of membrane was very easy to separate and recover, which made it a potential substitution for traditional liquid acid catalysts

Preparation and Characterization of Perfluorosulfonic Acid Nanofiber Membranes for Pervaporation-Assisted Esterification

Multilayer membranes were prepared by the combination of perfluorosulfonic acid/SiO₂ nanofibers and a poly­(vinyl alcohol) (PVA) pervaporation layer and were used to enhance the esterification of acetic acid (HAc) and ethanol (EtOH). The esterification–pervaporation experiments were carried out in a continuous membrane contactor. The effects of the temperature, the ratio of HAc to EtOH, and the ratio of membrane area to reaction volume were investigated. The results demonstrated that the membranes had good catalytic activities even at low temperature because of the nanofibrous structure of the catalysis layer. The conversion of HAc at 60 °C after 10 h was 10–15% more than the equilibrium conversion and by improved about 45% with respect to the equilibrium conversion after 55 h. The yield of EtAc was higher than 90%, which demonstrates that the difunctional membrane could enhance the esterification process greatly through the in situ removal of water